Jaycar Dual battery isolator

I noticed that but it's speced. at full load of 70 amps - I doubt any dual battery switcher could do better than that at 70 amps - despite what their specs. may say, after all it would require an "ON" resistance of less than 0.0129 ohms! Even a large contactor would struggle to do that, let alone any semiconductor device! Any switch device is far from perfect.

Mike Harding

By the size of the heatsink I would say it is a diode type not a switching type. It will have a 0.6 V drop at low currents. Steer clear.

PeterD

I don't know what a "diode type" is but would you please explain to me how you would switch 70A through a resistance of less than 0.0129 ohms?

Are you suggesting that most other dual battery systems use a switch mode DC to DC converter method?

70 amps is _always_ going to dissipate a significant amount of heat.

Damned if I know why I seem to be defending Jaycar - bloody hobbyists shop! :)

Mike Harding

Right on the money Peter, it doesn’t exactly say that but as there is a voltage drop and there is no indication of a cut in or cut out voltage, this is most likely a diode isolator and as diode isolators are proven to be unable to charge batteries properly, buyers beware.

Mike

A diode is a one way valve - it allows current to flow through itself in one direction only. They are formed by a junction between two pieces of silicon or germanium. When current flows through this junction there is at least a 0.6 V drop it silicon is used or 0.3 V if germanium is used - germanium is only used for very small current devices.

A diode isolator consists of two diodes, one feeds the starting battery and the other the auxiliary battery. Current will pass through to the batteries when the alternator's output is high enough but does not flow back through the isolator but not back when the motor is stopped. These diodes are mounted in heat sinks to dissipate the lost power that is the product of the current passing through the diodes and the voltage drop across them (power = current * voltage.) With the known voltage drop through these isolators and the availability of isolators employing solenoids controlled by simple logic devices it is disappointing to see people still peddling these devices. I classify these as not much better than snake oil devices. Batteries are not charged to near their maximum capacity if you only use a vehicle alternator without suppressing its output by 0.6 to 0.9 volts with your isolator.

PeterD

Hi guys

Your standard garden variety automotive mosfets are around 3 milliohms( 0.003) these days at 75amps

Robin Miller

Hi Peter

Thanks for the lecture on diodes :)

>Batteries are not charged to near their maximum capacity
>if you only use a vehicle alternator without suppressing
>its output by 0.6 to 0.9 volts with your isolator.

Why do you say this? A lead acid 6 cell battery has a nominal voltage of 12V6. Therefore any charging source with a voltage greater than 12V6 will force current into the battery. The average vehicle alternator will produce about 14V3; if one deducts 0V7 for diode drop 13V6 will still provide a charging current will it not?

The only negative is that such a system will take rather longer to bring the battery to full charge. I don't think there is any question that 13V6 will overcome the internal losses of the battery.

Energy is energy - it's just a case of adjusting the time.

Mike Harding

Mike

The nominal voltage of a 12 V battery is actually 12 V – this is the voltage that is used by most texts when they do power calculations. The voltage of my battery measures 12.8 V after using the lights for the night and taking the reading immediately before any solar charge takes place the next morning. Years ago there was a magical figure of 2.2 V/cell – this was the voltage you had to exceed before the battery would accept any charge – that was the days before calcium was added to batteries so the figure of 2.2 should be increased a tad for modern batteries. Another figure oft quoted is 13.8 V – this is a maintenance charge or in other words the voltage you apply to a battery to overcome the self discharge currents. The voltage needed by most batteries to give them a good absorption charge ranges between 14.2 and 14.6 V.

These voltages apply to a reasonably charged battery. However with a diode in series you need 13.8 plus 0.6 equals 14.4 V - you are going to have to exceed 14.4 V if you are going to recharge a battery in a days driving between camping stops. Looking at the first paragraph it should be obvious that the relationship between increasing voltage and the resultant increased in in current is non-linear. If your alternator is putting out 14.4 V and you are charging through a diode isolator then you will get reasonable charging for a start but the charging will taper off well short of fully charging your battery if you are on a trip, running a car fridge and travelling for more than a couple of nights. If your trip is a week or more you will either over flogging your battery or finding your fridge is not running in the morning. If you are running like this you may as well buy starting batteries, you will not get the value out of deep cycle ones.

PeterD

>You get what you pay for

No, frequently you don't.

Mike Harding

PS. How much was your roof top box?

Richard,
'frequently' you do get what you are prepared to pay for!

I've used Redarc, then Piranha and recently changed to Rotronics, all in the same vehicle, and not because I enjoy spending money.

However if I said each one worked better than the previous one, some-one (who has never owned a Rotronics Electronic battery isolator) would make some inane comment, so I will not print anything detrimental about the lack of battery charging performance with mechanical solenoids here, lol

Check out the specs on the Piranha DBE 150S MK II ELECTRONIC model
Site Link

150 Amp unit.

Hey Derek
You may be able to answer this. Most reasonably sophisticated battery isolators, as far as I can tell, charge either the main battery until it reaches a particular voltage and then switches to charge both auxillary and main together. Would there be any advantage in the isolator charging each battery separately instead of a bank of two?
I would imagine that this would allow for faster charging of a deficient auxillary battery. If this is the case why don't they design them to do this?
Look forward to your response.

Derek,

In the isolated state, auxilary loads appear to be able draw current of the main battery via the diodes???

Hi Michael

Our new Bisolator does this. There are a few wiring configurations. The unit in our 4wd situations will be wired with the ALT on the center pin and the MAIN & AUX batteries on the two outer pins. This allows for what you are asking.

Hi Frshn

The Bisolator needs 13.3v to activate current flow from the center pin.

For faster charging of batteries the Bisolator will be wired with the ALT on the center pin and the MAIN & AUX batteries on the two outer pins. The drawing on my website is for a 3 bank system. The Bisolator has many wiring configurations.

Regards

Derek.

Derek,

Because I am slow, could you just confirm the following for me. With the bisolater installed as you suggest above, when the cranking battery reaches 13.3v will the alternator provide a full charge to the aux battery?

I ask this because I have received disappointing results with my current set up which is a Redarc isolator downstream of the cranking battery. I have upgraded the wiring to something approaching overhead but am still not happy with the rate at which my aux batteries charge when driving (my 70W solar panel performs the job better).

With my limited knowledge I assume this is because the cranking battery acts as a 'buffer' between the alternator and the aux batteries, ie the regulator only really responds to the state of charge of the cranking battery which does not much more than trickle charge the aux batteries. Am I way off the mark here?

If the bisolater does do a better job than my current arrangement, then consider one sold when they arrive.

Matt.

Hi Matt

Yes you are right that the main battery acts as a buffer when the Redarc or similar controller joins the two batteries at a preset voltage. This only becomes a problem when the auxiliary battery reaches around 80% charge and then the buffer action of the main battery will cause the auxiliary battery to only trickle charge slowly. They are still quite effective up to 75% to 80% capacity. It is that last 20% that is quite important because if you don’t charge to 100% you will build up sulphation and decrease battery life and its capacity.

Our new Bisolator if wired as mentioned will allow the auxiliary battery to charge to maximum capacity as if it was the only battery in the system.

Regards

Derek.

Righto, I'll buy one then. Thanks for that.

Matt.

Matt M, There is no such thing as a buffer action caused by the main battery or the auxiliary battery or anything else.

This is nothing more than total fantasy, once the motor is running and the alternator is supplying power to your vehicle’s electrics, there is no effect from one battery on any other battery.

The highest voltage in the system controls the system and once your motor is started, the alternator is supplying the highest voltage by a long margin and is there fore the controlling device.

If your auxiliary battery is not charging properly then start by checking how high your vehicle’s operating voltage is.

It should be somewhere between 14 and 14.2 on average and if it is then there is no reason why you can not charge your batteries, ALL YOUR BATTERIES to at least 95%.

This crap about not being able to charge automotive batteries to better that 80% is usually posted by people who either have no idea of what they are talking about or have something to sell that looks better if they can convince people that unless you buy their product, you won’t be able to charge your batteries properly and again this is nothing but total fiction, particularly where 4x4s are concerned.

Matt, if your vehicle’s voltage is at or above 14 volts and you are doing sufficient driving to charge the batteries, try getting a voltage reading at your cranking battery and then take another one at your auxiliary. If you have a voltage drop then start taking measurements at different places along you dual battery set up’s wiring until you find the point where the biggest drop occurs.

If you find the fault is at your Redarc, give them a call, they have excellent back service.

Wow ! 'drivesafe'

I think I have seen some of your similar posts on msn caravan forum. You sure have issues - You seem realy 'charged up' :-)

One thing you said is true. Redarc have fantastic back up service. Paul down there is always willing to help.

Hi Drivesafe

I think this is more a terminology thing than anything else.
Its reasonable to use the terms "Buffer" and to say that battery
doesn't normally charge above 70-80%.

Technically we agree that if you drive long enough you should get close
to a practical full charge on both but for the average use of driving to work
and trips under a couple of hours the battery doesn't fully charge.

The analogy of a buffer is generally reasonable because a typical installation
sees longer leads to the auxillary and hence an uneven current distribution.
So starter battery usually "soaks up" more charge than the aux and is
in this sense a "Buffer"

Robin Miller

Let us look at a few things in these follow ups.

Quote from Mat “With my limited knowledge I assume this is because the cranking battery acts as a 'buffer' between the alternator and the aux batteries, ie the regulator only really responds to the state of charge of the cranking battery which does not much more than trickle charge the aux batteries. Am I way off the mark here?”

First things first – The alternator responds to nothing. There is only two wires coming from the common alternator (the earth has direct connection to the alternator frame.) One of these is a wire from the ignition switch to provide the power to the field to start the charge when starting from rest (Alternators are not self starting like the old generators.) The other is the output to the battery. There is no other wire to sense anything. There is also no monitor in the regulator to limit current output (like in generators.) Alternators simply run out of magnetic flux before their wiring self destructs – or in other words alternators are self limiting in regards to their current output. Therefore alternator regulators respond to nothing other than the voltage at the alternator output terminal. (this only applies to standard alternators – there are after market regulators with extra wires that sense the battery voltage and temperature.)

With this in mind we can see that all the batteries can do is accept what is offered to them by the alternator. With a “smart isolator” this offering to the auxiliary battery is delayed until the starting battery has reached a pre-set value – there is no smart monitoring to determine whether sufficient current has been accepted by the battery to “fully charge it” before the power is switched to the auxiliary battery. (I know this was not mentioned in this thread but some suppliers claim that smart isolators make sure the starting battery is fully charged before the other is switched in.)

The current accepted by the batteries is governed by a factor of the batteries size, construction and condition of charge in conjunction with the voltage of the system. A battery will rarely accept all the current an alternator can offer. A dead flat battery will mostly draw less than 1A until a fair amount of charge is restored. During the bulk charge time the current will rise to its maximum and then taper off as the absorption stage is reached. The charge current cannot be simply measured at one point and assumed to be that value for the whole time.

Quote from Mat “I have upgraded the wiring to something approaching overhead but am still not happy with the rate at which my aux batteries charge when driving (my 70W solar panel performs the job better).”

Of course the Solar panel will do a better job. Solar regulators are set to a higher voltage than auto alternators. Alternators have built in temperature compensation so the starting battery is not overcharged whilst it is at an elevated temperature when the motor has been running for a while. Your experience with a solar panel of only 70 W giving better battery charging than an alternator demonstrates how little current a battery accepts from a standard vehicle alternator.

Quote from MichaelR “Would there be any advantage in the isolator charging each battery separately instead of a bank of two?”

Generally not. Mostly your recoverage charging after a nights camping will be carried out without running headlights and with the starting battery in good condition. You will have seen from the above that an alternator will supply ample output when you are not using heaavy current drawing accessories to charge an auxiliary battery. If your starting battery is in good condition and you do not have trouble starting the engine then the starting battery will recharge in a few minutes and will thus be drawing very little current from the system. I suggest that if your starting battery is drawing large amounts of current for a long period of time then you are in deeper potential trouble than not having a charged battery for your fridge.

PeterD

Once again Peter, right on the money and I’ll take this even further.

Matt and Robin, if this theory of buffing and the main battery soaking up the power was correct, then as it takes about 5 minutes for a cranking battery to replace the current that is used during starting, every time you started your vehicle at night, because your battery was “ Soaking up “ the power your headlights would be so dimm as to be next to useless.

Now we all know this does not happen and as Peter has already pointed out and putting this crudely, the alternator in conjunction with the regulator is designed to turn out a given voltage. If a load of an form is applied anywhere in the vehicle, whether it be a battery ( or 2 ) or headlights being turned on or a sound system being turned on or just your fridge cutting in, as any or all of these devices connect to the electrical system, they will cause a voltage drop.

The alternator/regulator senses this voltage drop but has absolutely no idea what caused it, the alternator just simply increases it current output until the vehicles voltage rises to the regulators pre-set level.

If on the other hand something is turned off ( or in the case of charging batteries, the current reduces as the battery charges ) there will be an increase in the vehicles voltage and this time the alternators current output reduces accordingly until again the regulator’s pre-set voltage is reached.

There’s nothing secretive or special to how a vehicle’s charging system work, it’s as simple as what Peter and I posted.

If there is sufficient current available, and it is very VERY rear that there isn’t, your vehicle can easily handle all it’s normal current requirements AND charge at least 2 batteries at the same time.

There are people who have worked in this industry for decades, designing and manufacturing gear for the RV trade and then there are Jonny-come-laterlys that are nothing more than salesmen with no real idea of vehicle electrics, it’s up to the individual to go and check what is factual and what is nothing more than total fiction.

What he said.

Drivesafe,

As I said, I am not coming at this from at this from a particular point of view, just trying to understand what goes on. As for your last paragraph, checking up is exactly what I am trying to do. Not sure who you are aiming at here, but I would have thought that your last paragraph is somewhat nugatory as these types of people exist in just about any industry.

I'm not sure that you get what I mean by 'buffering' and perhaps a poor choice of terms on my part. I don't mean 'soaking up' but that by having the isolator downstream of the cranking battery that the process you describe by which the alternator and regulator output power, is driven largely by the cranking battery not the aux battery. As you point out the cranking battery returns to full fairly quickly, so does the second battery apply the demand to the alternator or is this demand attenuated by the now full cranking battery?

Again, not wedded to any particular idea, just trying to understand.

Matt.

Hi matt M, my post, while primarily posted for yours and Robins benefit, was not meant as a dressing down but as a more accurate explanation of how vehicle electrics work and nothing more.

The last paragraph is self explanatory and NOT aimed at you or Robin.

Now back to subject, it makes no difference as to the state of the cranking battery as to how much current is going to be available for other devices, including the auxiliary battery, the vehicle’s electrics just don’t work that way.

Very simply put, alternators do no more than provide power on demand and each individual device sets the amount of current it will require, independently of any and every other device that may also require power at the same time.

Cheers

Hi Drivesafe

That statement of yours as per below really is nonesense, the concept of the buffering as put in my post (not anothers intrepretation) is readily proveable based on the relative impedances placed across the battery.
Year 1 basic in any electrical engineering degree.

( Hold on - did I pass ? ..........yep.....ok lets continue)

If you would like to show me your equations (or even in logical format) I will do my best to show you where the errors are.

Robin Miller



"Matt and Robin, if this theory of buffing and the main battery soaking up the power was correct, then as it takes about 5 minutes for a cranking battery to replace the current that is used during starting, every time you started your vehicle at night, because your battery was “ Soaking up “ the power your headlights would be so dimm as to be next to useless.

Hi Disco

Love your line ->

"First things first – The alternator responds to nothing."

Try disconnecting it from your battery and putting a short across the terminals , this will soon sort out that statement.

Robin Miller

Hi Robin.

If you do the math you will quickly see that the full charging of two batteries, even when these batteries are at different states of charge ( SoC ), as the alternator’s voltage is higher than either of the batteries, no matter what state of charge they may be at, means the alternator can charge both batteries to a full ( at least 95% ) SoC.

I’ll put it another way, if you have battery A, say just under full charge, at an SoC of 90% which is about 12.5 volts and battery B with an SoC of 40%, which is about 11.9 volts and the alternator is capable of turning out 85 amps at 14 volts.

Now as the current for any battery will vary for different reasons, for simplicity sake say the battery A requires that you will need around 7 amps to maintain it’s charging rate based on the SoC of battery A and the alternators voltage and that battery B requires that you will need around 25 amps to maintain it’s charging rate.

This means the alternator is going to have to be producing around 32 amps to maintain both batteries at 14 volt. It can do this and still more that half it’s capacity available for the rest of the vehicle’s electrical requirements.

Now how does one battery effect the other when the alternator is easily maintaining 14 volts at both batteries and it makes no difference which battery is first in line after the alternator as long as the cables are thick enough, both batteries will be supplied with the same voltage even though they will be consuming different current rates.

As I started with, do the math, if one battery has an SoC of 11,9 volts, the second battery has an SoC of 12.5 volts and the alternator is easily maintaining 14 volts then the highest voltage controls the whole circuit and this is obviously the alternator.

Cheers

Robin,

What 'drivesafe' is saying is a well tuned system with perfect cables, super absorbent batteries of the same type and age and a perfect alternator you will have charging 'Utopia'. Much like an exhaust system on a race car where each extractor is the same size and length to ensure equal volumes and power to all cylinders.

When charging a add on auxiliary battery of differing age and size to the battery that the alternator is connected to and there are differing cable sizes, fuses, plugs and distance added to the equation then things start to change.

This is why there are large manufacturers in a growing market producing battery combiners and each one using modern technology and electronics to make them better. The days of a simple battery switch are over and with less space under the bonnets of cars the auxiliary batteries are moving further away from the alternator.

I know 'drivesafe' is pushing his point and he is not altogether wrong. He has his SOC % and voltages correct and if used in a 'Utopia' system you will be very happy with the result.

Thank You for you input Robin you have valid points.

Regards

Derek.

Stick to being a salesman Derek, if you had the slightest clew about this subject, you would know that the information I just supplied would be as relevant for a brand new vehicle with new batteries as it would for an old vehicle with near clapped out batteries. The operating principals are the same.

Robin – re follow up 17. - Yes I stuffed that line up beautifully didn't I. What I was trying to say is that the regulator responds to nothing outside the alternator. Its only reference is to the the output voltage of the alternator. There is no monitoring of anything else in the system. The regulator attempts to provide a constant output voltage. It does so very well up to the point where the current draw from the alternator approaches it maximum current. When this point is reached the the alternator can not supply much current and its output voltage commences to drop. This rarely happens in practice. The regulator does not monitor the output current – the alternator self regulates the output current due to the fact that the field reaches a limit in the amount of magnetic flux it can produce – nothing to do with the regulator.

On the subject of the starting battery buffering the auxiliary battery. - From Wickepedia “In general, to buffer is to isolate or minimize the effects of one thing on another”

The starting battery does not minimise or isolate the current to the auxiliary battery – the isolator does that. After starting the motor there is a delay until the electrical system reaches a predetermined voltage (assuming a smart isolator) and then the isolator switches the auxiliary battery on line. When this happens both batteries gain equal access to the current available from the alternator. Assuming there is sufficient gauge of wire used the batteries will have the same voltage applied to them. The current they will draw from the system will be dependent solely on their characteristics and not the regulator as there is no monitoring fed back from them to the regulator. This state will continue until you switch enough accessories on and the alternator commences to overload – then when the voltage drops sufficiently the isolator will disconnect the auxiliary battery.

Mat – your statement “that by having the isolator downstream of the cranking battery that the process you describe by which the alternator and regulator output power, is driven largely by the cranking battery not the aux battery.” has been answered above. Until the alternator goes into overload neither battery has any influence on the regulator.

Derek – No matter what electronics are in the isolator box I have only seen isolators do two things

1. Keep the batteries electrically isolated when the motor is not running
2 Give the starting battery some time to charge before the auxiliary battery is connected.

The second thing may be accomplished by simply using a voltage sensing comparator or by employing a time delay circuit (or both.) As soon as the solenoid is closed the batteries are connected in parallel. The things that will determine the current draw for any particular alternator voltage output is the battery characteristics and the resistance of the wiring.

Diode isolators only do the first thing, not the second

PeterD

'drivesafe' and 'disco'

Electric Principles are one thing and practical testing is another. Yes they go hand in hand but I have seen practical examples of improved charging and higher current flow by simply moving the alternator feed wire to the isolator. This increases voltage to the auxiliary battery and reduces charge time. I have seen and tested this. Try it before knocking it.

"1. Keep the batteries electrically isolated when the motor is not running"

This is only partly true. Most electronic isolators will stay engaged until the main battery drops down to a preset voltage allowing the accessories on the auxiliary battery to use some of the power from the main battery. There are even some manufacturers that advertise this advantage. I have seen this take up to 2 hours to disengage in some cases.

“2 Give the starting battery some time to charge before the auxiliary battery is connected.”

This is only partly true. Traditional isolators will do this but our new Bisolator will actually engage before start up if needed and may even stay engaged after the engine is running depending on system demands, I have extracted this sentence from the description below but read the whole description for your own information. “if the main battery’s voltage falls below 9.0V for ½ second and the auxiliary battery is above 9.0V, both batteries are connected to provide a powerful boost start.”

“The things that will determine the current draw for any particular alternator voltage output is the battery characteristics and the resistance of the wiring.”

Disco here you are very correct in saying wiring resistance will effect current. This is what I have been saying all along “differing cable sizes, fuses, plugs and distance” will affect current flow, voltages and charge times.

Lastly I am more than a salesman and I am proud of my inventions, designs, future new products and our business. We are designing, sourcing, manufacturing and introducing new technology to the automotive and recreational market.

Working Principle Of BiSolator M-Series:-

The BiS M-Series performs well in two important fields: firstly to provides a reliable and efficient method of both charging and isolating dual batteries, secondly if the main battery’s voltage falls below 9.0V for ½ second and the auxiliary battery is above 9.0V, both batteries are connected to provide a powerful boost start.

With BiSolator’s electronic voltage and load sensing design on the main 12V system, when the voltage rises above 13.3V for at least 12 seconds, as happens when the engine is running normally, the BiSolator will close the isolating system, providing charging current to the auxiliary battery and overcomes those eficiencies that allow other battery isolators, splitters or combiners to discharge the main battery.

When the system is in the status of charging the auxiliary battery or when auxiliary charging from solar or mains charger is being performed the featured LED indicator then turn “GREEN” to show the exact operating diagnostics of battery system. This can be extended to a remote status lamp.

Forced override is possible with a remote switch.

Derek, you have been in the field for what, a little over 12 months, you are nothing more than a self proclaimed expert that in truth knows very little about this field and on many occasions you have not only posted incorrect info, on a number of occasions your posts were so incorrect as to be a danger to anyone who might be unfortunately mislead into thinking you knew what you were posting and tried it.

You are nothing more than a salesman and good luck to you in that business but don’t try and palm yourself off as an expert in this field while you are trying to drum up business for your self.

I’m not particularly interested in what you are peddling but this much I will point out, tampering with the alternator/battery cabling in most vehicles WILL void the vehicles warranty.

And even if it doesn’t, how do you increase the voltage to a battery without either altering the vehicle’s voltage regulator or by adding a step up inverter.

It sounds like some Chinese company has found itself one dumb sucker and have feed you a line that you have taken, hook, line and sinker.

ALL vehicles are designed to have the alternator feed directly to the battery and then all power for the vehicle is then sourced from the battery.

This is done to allow the battery to both filter the alternators output and to protect the alternator from sudden heavy current discharges.

Dear drivesafe

In reply to your last post.

I have been in the trade for almost 25 years. ABR was established in 1992 and was one of the 3 businesses I purchased when I migrated to Australia in 1996.

Your line “sounds like some Chinese company has found itself one dumb sucker and have feed you a line that you have taken, hook, line and sinker” appears to show you are not aware of similar products on the market, some are even made right here in Australia.

There are numerous battery charge systems that use this basic system of alternator management. We have just improved on it and taken the best features from them and incorporated them into one unit.

Just for your information I have included a few examples below.

1) Rotronics
2) Blue Sea Systems
3) Projecta

Regards

Derek.

From the Rotronics website. Rotronics

RBT12 Operation :
The Main battery is recharged first. The voltage is monitored at the Main battery by the RBT12 and when the Main battery is "On Charge", the RBT12 connects the Vehicle Auxiliary battery for recharging and isolates the Main battery from the Alternator and Vehicle Electrical System. This ensures the Maximum Recharge Current is supplied to the auxiliary battery, during the Auxiliary battery recharge cycle. The Main battery is also tested by the RBT12 for state of charge, when isolated [ during the auxiliary battery recharge cycle ] and reconnected, for further recharging as required. to maintain full charge of the Main battery. The Main battery and the Vehicle Auxiliary battery, are isolated, when the engine is "Off". The RBT12 Monitor [ 2STM ] Displays which battery bank is "On Charge".

From Blue Sea Systems. Blue Sea Systems

In multiple battery bank systems, Charge Management Devices (CMD's) automate charging. These devices provide a means for combining two battery banks when a charge source is present, while keeping the battery banks isolated from each other when no charge source is present. This assures that even if one battery bank is depleted, there will always be a charged battery bank available for engine starting. Some devices also provide a manual means of connecting both battery banks together for additional power while starting engines. There are many types of CDM's that fulfill this role. The two main categories are battery isolators, and Automatic Charge Relays (ACR's).



From Projecta Australia.

(Look at the instructions pdf at the bottom of the page. Here is the picture from those instructions)

Projecta

I am well aware of them and of the problems they can cause, but more to the point, there are very few places where these products will give you any real form of advantage over simply paralleling batteries while charging and in many cases and if your were as experienced in this field as you try to make out then you would know this type of charging will actually take longer to charge multiple battery set ups than just paralleling the batteries and letting the alternator do what it’s designed to do.

I again emphases, you nothing more than a salesman that is trying to make out you are an expert in this field for no other reason then to sell products.

Hi Drivesafe

Actually this post is getting a little long and convoluted , and people are discussing different points.

I think though that you are now agreeing with the buffer effect of a battery as I replied to intial post but hat you have a different time span on it.

And I'm not sure were we disagree now , however if have this wrong and you have a specific disaggrement with anything I have said please come back and highlight it and my offer to explain anything I have said in detail and with proper maths to back it up still remains.

If we can isolate a disagreement it will probably be worth starting a new post..

Robin Miller

Derek - comments on followup 22

First paragraph. As I understand it (working with European systems) the alternator regulator takes its sense wire from the out put terminal. Yes you can disconnect this from its internal connection and route it out of the alternator frame and connect it to the starting batteries terminal. However I would not recommend that the average punter attempt this – it can produce expensive results if you make a slight slip up. Also what do you mean by “the feed wire?” Is it the wire from the output terminal to the battery or is it the wire that follows a convoluted path from the ignition switch through the alternator indicator light to the alternator for the purpose of giving the field winding some starting current?

As to the next few paragraphs – I concur that there are some not so basic types that I have not seen the circuitry for. The models that delay the isolation of the auxiliary battery until the batteries drop to a very low voltage or perhaps incorporate switch off time delay, are few in number. When we make these general statements we have to consider the general case equipment. You go then on to quote the DiSolator isolators as they are indicative of the equipment on the market today but in reply-6 you stated they are not available until late April.

I still stand by my beliefs that basically all your isolators are built to do the job that I outlined in Followup 21. That is parallel the batteries for charging and disconnect the auxiliary battery after the alternator ceases charging. None of them boost the voltage supplied to the auxiliary battery to the same maximum voltage that a solar regulator outputs, but some poor installations will introduce a voltage drop in the system.

There are a couple of facts we should acknowledge. The first is that we can not fully charge a deep cycle battery quickly unless we can supply it the level of voltage that the manufacturer deems to be the absorption voltage. Secondly if we keep applying that level of voltage after it has fully charged then we will boil the electrolyte out of the battery – a somewhat disastrous situation for sealed batteries. If your battery will sit under under the bonnet of your truck happily without being boiled dry then your alternator is not supplying sufficient voltage to quickly recharge it on a camping trip.

The only way I know of that can achieve an output equal to the absorption voltage of a battery and then suppress the output to a float voltage when the battery is charged, is to use an inverter to drive a three stage battery charger. Just wire the input of the inverter through a relay controlled from the accessory position of the ignition switch. The cost of providing this will certainly be cheaper than the Rotronics system that you quoted in Followup-24 (unless there has been a considerable price drop from the $800 odd price I was quoted some years ago.)

The newer “smarter” isolators still provide the same basic functions as the basic models. The “smart” models still only provide the same steady state function that the basic models do – that is parallel the two batteries across the alternator. I only classify the additional features as just that, additional, not smart. You can become orgasmic over these additional features if you like, you will not start exciting me until you start offering some form of battery boost feature in your boxes with its output characteristics the same as the commercial three stage battery chargers.

Derek, are you familiar with the company Victron Energy and in particular their publication “Energy Unlimited?” If you read it you will have a better understanding of where I am coming from. Take particular note of sections 5.2.2 and 5.2.3.1. You can download it from http://www.victronenergy.com/upload/documents/Book-EN-EnergyUnlimited.pdf This company does supply simple isolators (for those who don't understand) but most of their equipment is more sophistocated. It is written for marine folk but batteries operate the same on land as they do on the water.

PeterD

Robin

As I explained in my earlier posts - nothing buffers anything else. When you have two batteries connected in parallel (via the solenoid in the isolator) connected to an alternator output with a good constant voltage output, one can not control the other. The regulator in the alternator does not get any signal from the starting battery only the output terminal of that alternator (this applies to a standard automotive setup.)

PeterD

Hi Peter

I knew I'd get lost in this long post , I assume you are referring to my followup (3 of 7) posted against wrong reply.

I have no disagreement with most of whats posted apart from the "nothing buffers anything part" which I maintain is a terminology usage difference.

I think your followup 28 avoids talking about what buffering is, as per your posted
definition.

It, or I haven't referred to "control the other" , nor refer to "getting any signal", it is simply minimizing the effect on another device and as two batteries in parallel share in the current, "Buffering" at some level is taking place by definition.

Robin Miller

P.S. What do you reckon, we have both put our opinions and this post is becoming a waste of time and settle with an appreciation of each others point of view albiet we still disagree.

Thank you Adrian for a very kind offer. However I have access to the sorts of components which are used in these things but someone else may be glad of your unit - thanks again.

Mike Harding

This has certainly been a most informative and lively post. I did ask a question earlier and would like to thank those that contributed. I have a dual battery system controlled in the past by a mechanical, switched rellay and now by an electronic 'smart' relay. Still I do feel I am missing something, despite some of the above assertions. The present system I would regard as adequate but probably not optimal

We now have 4 stage battery chargers that purport to charge more fully and safely. They are comprised of complex electronics to achive this. They certainly do not model themselves on a vehicles alternator/regulator system

It seems highly likely that a vehicle regulator designed around similar lines could deliver a battery a more appropriate charge taking into consideration variables such as state of charge, type of battery, temperature (battery and alternator), wiring losses etc.

Further charging batteries separately rather than in parallel does appear to shorten the time to full charge. According to the Rotronics site charging in this way may shorten charge time by a quarter. So the presence of another battery in the parralel system, even if it is fully charged, will affect the process even if it is not by way of 'buffering'.

There must be some recognition that a alternator's charging system, a design many years old is probably not optimal although for most it may be adequate. Modern electronic regulators that consider many variables would most likely be superior even if at this stage they are expensive.

Hi MichaelR, I would agree that most modern alternator/regulator set ups have not changed much in the last few decades but if you want to see what the future is going to be in this area, take a look at a Discovery 3 or Range Rover Sports.

Their electrical system is nothing short of incredible and makes most multi stage chargers look feeble in comparison and you can be assured that these are just a taste of whats to come.

Cheers

Agreed. I thought Drivesafe's attack on Derek was less than merited. I have found the best way to interact with people who I believe are incorrect on a technical matter is to ask them to explain their position, usually they either cannot or you can point out an error. Although even we professionals in these areas can be wrong sometimes so it's always worth listening.

Having said that; as a professional with qualifications and very wide and long experience in some of the most complex areas of electronic/electrical/software design it does get frustrating when you have to, time after time, correct false information from people who know little about the field - although often think they do - if we had a medical doctor frequently posting medical advice on here I wonder how many people with a First Aid badge would be telling him he was wrong? But with electrical stuff, especially simple stuff like 12 volt DC, everyone seems to be an expert :)

Mike Harding

My late father used to say 'If you can't say something nice then say something intelligent, but say it nicely. If you can't do that, then say nothing at all'.
Always sounded reasonable to me.

Hi Disco (followup 21)

Sorry I missed your handle PeterD in this long thread so Hi Peter.

Actually you didn't stuff it up to badly as thats a reasonable approximation statement re the issue, and in the same vein I defended Matts statment on the buffering effect.

RE the definition you supplied about buffering as one device minimizing the effect on the other , this is just how the dual parallel battery works.

Consider the following very trim explanation of how one battery reduces the efect on another.

When you have two parallel batteries and you turn on a load connecting across them then current for the load comes from 2 sources not 1 - hence effect on any 1 is reduced from what it would be if it were the only battery.
I.E. Mimimized as per buffer definition.

This effect can be a factor of not 1/2 as it might seem but up to several times in the case of starter battery just having started a car, as it gulps up current from the alternaor in the first few minutes as its effective resistance is dropped.

The depth of the efect is directly that of the two different effective resistances to ground (including the typically longer leads to aux batt).

(apologies to other engineers for not using the capacitive battery model)

Robin Miller

P.S. I have been waiting for someone to pick me up on followup 17 , as it has what could be construedas a error but really isn't.

Hi Norm C, just a little clarifying needed here, Derek as with Collyn Rivers, will say anything he can to sell a product. While their posting stay within the bounds of being correct and in Collyn Rivers, truthful, I will not argue the point.

But if you care to do a search, you will find that on the occasion that I called Collyn Rivers a liar, not only had HE started the slanging match but if you read the whole thread you would have to be blind freddy to think that he was not lying.

That thread ended for me, when one of the moderators on this site sent me an E-mail requesting that I not pick on Collyn and although the E-mail was polite, I still took offence to it because as I have pointed out, I was one of the protagonists but NOT the instigator of the slanging or nor did I once lie which could not be said about collyn.

After receiving the E-mail I did as the moderator requested but further by not bothering with this site at all.

Four or so months later, a regular on this site sent me an E-mail and told me to have a look at a posting on this site.

I responded that I couldn’t be bothered. He returned and stated that I had been vindicated and that I should take a look.

When I went to the link E-mailed to me I found a posting by one of this site’s moderators, in which the moderator specifically branded Collyn Rivers as a liar.

It is at this point that Collyn Rivers left this site and it had absolutely nothing to do with anything I had posted.

So please Norm, could you also stick to the facts and for the benefit of those who did not see the other debate just recently on the 4WD Monthly forum, again, an individual with the sole intention of deliberately set out to mislead other forum readers got his wings clipped.

Now Norm and Mike, if you think it’s OK for others, with the intention of nothing more that making a dollar by deliberately deceiving unsuspecting readers on this or any other forum, then you obviously don’t care too much about anybody but yourselves.

I, on the other hand think it’s the responsibility of EVERY forum member to protect other forum users from such Snake oil pedlars, BUT I will apologies for my over the top response.

Cheers.

>Now Norm and Mike, if you think it’s OK for others, with the
>intention of nothing more that making a dollar by deliberately
>deceiving unsuspecting readers on this or any other forum,
>then you obviously don’t care too much about anybody but
>yourselves.

Emmmmm.... This is part of the problem Drivesafe, it's not so much what you say but the way you say it although you did apologise, so that's good.

I have been posting electrical advice to this forum for a few years and believe I have established my credentials here in that area and I don't think anyone would accuse me of having any kind of financial interest.

In my opinion Derek would not try to deliberately mislead people for the sake of making a sale. His technical knowledge in the electrical field may not be as comprehensive as your's or mine but he's no fool and does have a decent grasp of 12 volt stuff. Of course he has an interest in sales and in his early days was, certainly, a little emmm... eager :) for which I (amongst others) chided him on a number of occasions. In recent times his thrust has been much more directed towards offering knowledge and hoping to make sales through being helpful - which is fair enough in my book - especially as he is both a member and sponsor of this site.

The people who read this forum are not stupid and soon work out who _really_ knows what they're talking and who doesn't I wouldn't worry too much about protecting them.

Mike Harding

Hi Drivesafe, last thing I want to do is start yet another debate, so this will be my last post on this matter.

I certainly respect your technical knowledge and your willingness to freely share that knowledge. Although you often mention your products, you don't push them or seek to sell them on the forums. For that I commend you.

But a couple of simple examples from just one of your posts (immediatly above):

'Derek as with Collyn Rivers, will say anything he can to sell a product.'
Also this quote from the same post:

'Now Norm and Mike, if you think it’s OK for others, with the INTENTION of nothing more that making a dollar by DELIBERATELY DECEIVING unsuspecting readers on this or any other forum, then you obviously don’t care too much about anybody but yourselves.' (my emphasis).

Apart from the (in my view outrageous) statement about the intention and actions of others, when read in it's entirety, this para is an attack on Mike and me. Unwarranted, but if that's how you feel.......

If you think these are reasonable statement to make about anybody on a forum like this, then that's the difference between you an me.

See my post above which I repeat again (with emphasis):
My late father used to say 'If you can't say something nice, then say something intelligent, BUT SAY IT NICELY. IF YOU CAN"T DO THAT, THEN SAY NOTHING AT ALL.

Mike to my recollections, I’ve not criticised any of your posts but to say that Derek would not deliberately mislead anyone, only a few months back Derek was pushing Redarcs as the ants pants, now, that he has another product coming along, suddenly the Redarcs aren’t all that good, read back through this thread and you’ll see what I mean.

Norm, I’m not out to argue with anyone but I will most definitely stand up against whose who attempt to profit by deceiving the less informed.

Your father’s saying is good but there is one I prefer to try and live by and from memory it goes something like this

Evil can only succeed when honest men stand by and do nothing.

Cheers

Hi Drivesafe

>Mike to my recollections, I’ve not criticised any of your posts

Noooo... I don't think you have but, as for any of us who stick our heads up, we're always fair game :)

>but to say that Derek would not deliberately mislead anyone,

I did say it was opinion....

>only a few months back Derek was pushing Redarcs as the ants
>pants, now, that he has another product coming along, suddenly
>the Redarcs aren’t all that good, read back through this thread
>and you’ll see what I mean.

Drivesafe... Derek is a salesman, as you mentioned, and I have _never_ known _any_ salesman who didn't propose that his current product was the best thing since sliced bread :) That doesn't make him a liar... it just makes him a salesman and most of us understand that and make the appropriate, credibility, allowance.

Mike Harding

PS. That 10% still OK with you Derek? :)

If a product is good, it will stand on it’s own and as far as I’m concerned, anyone, salesman or otherwise who needs to try to improve a product they are pushing by deceptively implying that some other product suffers from a mythical drawback or implied non existent fault then that person should be exposed for what they are.

Call it what you will, lying, poetic salesmanship, whatever, the point is this site like any other, regularly has people coming here to try to get honest replies to technical issues that they may have.

As I have posted time and time again, it is the responsibility of every member of any forum to at least attempt to see that the information that a person may be enquiring about, is not only correct but should not be tainted in any way, particularly if it is being tainted for no other reason than to line someone else’s pocket.

Failure of members of any forum to do this usually ends up in that particular site, as a whole gaining a reputation for being an exploited forum or worst still, for being next to useless.

I’m not a paid member of this site but it surprises me that paid members don’t seem to mind the site being used as a market place rather than place of information.

But this is just my opinion.

Cheers.

Ive loved reading all of this thread and fronm it I can assume the following.
Technoloy has changed considerably in the last fifteen years and multi stage smart charging is the way to go.
Smart charging is one that every time the ignition is turned on a charger eplaced the cranking battery start up power and then checks the condition of the aux battery and calculates the boost time and then smart charges the aux battery but in doing so has the capacity to charge all types of batteries at the relevent voltage necessary to maximise the charge in the shortest possible time and has thermal compensation to safeguard both the battery and the alternator.

Sterling Power Products do just that and have capacities up to 210A in 12V and 100A in 24V.

No Bull.
Ian

To view view these Sterling chargers look at http://www.sterling-power.com/pdf/bbc121245e.pdf - This is the type of equipment I would like to have here. The closest th their 'battery to battery chargers we have here is the Arrid twin charge (which has a constant 14.4V OP and boils batteries dry if used for too long.)

The Sterling home page is www.sterling-power.com/ . If you go to the 'Download' tab on the LHS you can download the instruction manuals for the the individual types of equipment. Very interesting reading - but you have to look carefully as some of the words did not translate correctly from the original German. The FAQ section is interesting but refers to battery types we don't get here - apparently they have 'leisure batteries' and cheap deep cycle ones are not readily available as they are here.

PeterD

I forgot one thing that brings this thread back on track and is relevent to the first post.
Sterling also has splitters with a low voltage drop in 70A 90A and 130A and if you read the literature when used with Sterling Smart chargers the charger compensates the loss to guarantee the charge to the batteries.
Sterling is also on the verge of releasing water proof Battery to Battery units in 12/12V and 12/24V to charge batteries off outboards for electric trolling motors.
Ian

Would Sterling Power Products perhaps be involved in the second coming of The Lord too? Would you, Ian, have any... you know vague.. connection with Sterling Power Products...?

Mike Harding

This is possible but more to a coming of age in improved technology and yes I may have a vague interest but the information was offered out of enthusiasm for a good product and I believe I read where a good product will sell inself so now Ill shut up and follow NormC,s advise.
BTW How could Sterling be involved in the second coming of the Lord when it appears he is already here preaching on this forum.
Ian.

Oh dear... no good getting grumpy because you've been rumbled Ian :)