Caravan Power Supply

Hi
Many only supp;y 12v & are not suitable for charging, does it have a manual?
One means of determining if is suitable is to, as above, connect a volt meter across battery, then turn on a heavy load , all 12v lights etc.
The volt reading should initially drop to approx 12.6 then start climbing again when the charger ? starts up. Switch all load "off"
It should then climb to about 14.2to 14.5v, then switch "off"& the voltage should slowly fall to about 12.7v [indicating a fully charged battery]
If under no load the voltage remains steady @ about 13. 6 volts it is not a charger but will only keep a fully charged bat floating.

Ok Derek, I give up, where is it on your web site. Looks nice. 30 A too.

link

Thanks Wazzaaaa

This is a n interesting development Derek. For years you have been flogging your battery isolators as devices that will properly charge auxiliary batteries. In fact on the same link that Wazzaaaa gave you have a new "Ultimate Isolator" - in the description it says "Ensures Batteries are FULLY charged." These devices are cheaper than the "DC-DC 4 Stage Smart Charger" so if they will truly fully charge a battery and are not akin to snake oil devices then why are you introducing the new DC - DC Smart Charger?

PeterD

Peter perhaps I can have a go on Dereks behalf. Usual disclaimers etc etc other than I have bought 1 or 2 products from him.

The application I have is for a battery in a camper. I have the usual dual battery / isolator set up in the vehicle which works fine for me. BUT the batteries in the van are connected by about 8m of cable, and I want to put AGM's in. The voltage drop across that distance inevitably means the van's charger never gets fully charged.This will be worse when I have SLA's which I am pretty sure will need a higher voltage still. Hence the DC - DC charger. Another application I can think of is charging one 12v battery from another.

I don't know too much about Derek's other product but it sounds to me like it charges one battery at a time, hence optimising the charge for each battery. If this is right then it woud be a great solution if you had a clean sheet.

I can't see snake oil. Just smarter ways of doing things based on good knowledge and better electronics these days.

Sorry to elaborate on the battery to battery charging application.

When I have my camper parked for a while, obviously the battery goes flat. My second battery in the car charges as I drive around. When I get back to the camp site I could use the DC - DC charger to charge the camper's batteries from the freshly charged aux in the vehicle. I reckon that's pretty cool.

Hi Peter

You already know the answers to these questions but to clarify for others here are the basics.

Some people are trying to charge a battery at distance and may not want to fit heavy cables and isolators. The object of the battery to battery charger is to overcome voltage drop over distance and to charge batteries that require higher voltage than some alternators can produce for these types of batteries (AGM and Calcium). The battery to battery charger is a 30A device.

Isolators are great high current devices and work very effectively with heavy cable and will charge at a very fast rate and can charge multiple batteries and still power accessories with power from the alternator. We all know that joining the batteries with an isolator in parallel slows down the charge rate slightly, also the alternators regulator at operating temperature will bring the charge voltage down to 13.5V in some cases, this means that a battery 8m away in the caravan will still charge but many not be 100% charged and will require a top up when you get home with a mains charger, if this is done correctly isolators and mains chargers are still the preferred method. The alternator is a 80A to 120A 'approx' device.

The 'Ultimate Isolator' is a non-parallel type isolator. It directs the alternator charge directly to a battery. The battery not connected to the alternator receives a 'top up' via an isolated charge circuit. Cost of this isolator will be more than the battery to battery charger as it has effectively 3 electronic isolators in it + a booster and digital monitor.

So a quick comparison.

Battery to Battery Charger: 30A – 14.8V Max (Adjustable) No voltage drop.

Smart Isolators: *100A – 13.8V (Less at full temp) Aux battery charge rate affected by main battery. Voltage drop over distance. Parallel type isolator.

Ultimate Isolator: *100A – 13.8V (Less at full temp) Each battery is independently charged. Proper Isolation, non-parallel.

*100A used as a base for the average 4wd Alternator.

Regards

Derek from ABR

Derek
For anyone to believe the above you need to state what the acceptance voltage is that the DC /DC charger will operate from.

To make a statement that smaller cables will run it leaves a lot to be desired and further information is needed to justify your claim.

I am not saying this to knock the product it is in your interest to get it right.

Ian

Here is a bit of info.



Note: They are 90% efficient so you would need cables rated at approx 40A continuous to run 30A on the output side.

Regards

Derek from ABR

Here is a picture from Sterling who make a similar product. I think Ian may sell these units.



Regards

Derek from ABR

Derek

Pretty pictures do not answer the question asked.

"What is the input acceptance voltage of your B/B charger ".

There is no way that you can claim a comparison of product as I would not recommend in any situation where the appropriate wire size to minimise voltage drop is not used.

Quoting a theoretical efficiency percentage and an output cable expectancy is avoiding the question.

The Sterling can compensate for voltage drop but why encourage people to create voltage deficiency and make the charger work harder to do its job than necessary.
Ian

Dear Ian

Perhaps this link can answer your questions.

DC-DC_50A

This company promotes a similar product for $780.00, perhaps you know them. They are also a bit vague on their specs and simply refer you to the UK website. (Where the pretty picture comes from)

Note: Customers will generally ask what cable and fuse sizes they need for their application. Your questions are not relevant and yes the picture shows input voltage of 8V to 15V. There would be many variations to amps drawn at a certain voltage and output. I could post a graph but you may not like it. I have said that if you allow for 40A max and use suitable cable for the distance involved you will be fine. This too would vary depending on where the charger is mounted.


Regards

Derek

"They are 90% efficient so you would need cables rated at approx 40A continuous to run 30A on the output side"


The current drawn in the cable needs to be based on a worst-case situation - assume the supply battery is down to 11 volts when supplying 30 amps - to the load. (No, this does not mean the battery has been discharged to 0% remaining capacity)

So to supply 14.4 volts at 30 amps (432 watts), the input power needs to be 11.0 volts at 39 amps (432 watts).

At this high voltage conversion ratio (with voltage drop in long wiring, the voltage at the Converter is going to be closer to 10 volts) the efficiency is going to be closer to 80%, so the current flowing in the cable will be closer to 49 amps.

Hi Mike

Yes you understand it perfectly. Did you work on 8m of 6mm2 cable with a chassis return ?

Regards

Derek

Mike

Like the original poster said enough “gobble gobble”.

Now something that a layman may understand.

Using the device in an automotive application.

What alternator in a car would charge a battery at 8Volt so no benefit is gained while travelling that would enhanse the use of the product.

When stationary most batteries that you draw from are cranking batteries and cranking batteries do not have the capacity to recover continually from deep discharge and 11 Volts may represent 80% Depth of Discharge in extended use of the device so who recommends that.

In a lot of applications the battery being charged by the device will be a deep cycle and will not be satisfied with a short duration charge from a lesser value battery.

Ian

I thought you would be able to understand "the current flowing in the cable will be closer to 49 amps."

"What alternator in a car would charge a battery at 8Volt so no benefit is gained while travelling that would enhanse the use of the product. "


The main reason for getting a DC-DC charger is to compensate for the voltage drop in long thin wiring runs to a trailer. Even if the Alternator is putting 15 volts into the battery, you might still end up with 8 volts in the trailer.

Then why suffer voltage drop by using suffient cable in the first place to offset voltage drop then the alternator can do its own job of supply.

If you have an alternator that can produce greater than 30A why strangle it and then use something supposedly to compensate for an initial poor wiring practice.

The biggest problem we have in Australia is undersized cabling so why promote a product that compounds that use.
Ian

Derek,
You say:
" Ultimate Isolator: *100A – 13.8V ( Less at full temp ) "

I believe the "less at full temp" would be far more often than not

what are the relevant numbers supplied when "at full temp" ??

Maîneÿ . . .

Ian,
Yes, you've stated it as I was going to above, but I've chosen to create a new post to give it the prominence it definitely deserves.

Why suffer from voltage drop, by using sufficiently sized cable in the first place, to offset voltage drop, the alternator can then do its job.
If you have an alternator that produces greater than 30 Amps why strangle it, then have to use another device to compensate for the initial poor wiring practice.

I use a Rotronics Electronic battery isolator, all batteries are connected together by 2B&S ( 32 mm² ) cable that does deliver 14.4 Volts at the two AGM's, which is the same Voltage delivered to the Cranking battery.

If I had used thinner (cheaper) battery connection cable I would have Voltage drop at the AGM's and then would need another 'device' to again increase the Voltage delivered to the AGM's.

If the Alternator regulator supplies 14.4 Volts why not have it ALL delivered to ALL the batteries ?

Maîneÿ . . .

Iam / Mainey said

"If you have an alternator that can produce greater than 30A why strangle it and then use something supposedly to compensate for an initial poor wiring practice. "

Not sure where the 30 A alternator comes in, but here are some good reasons to buy the product.

1)Regardless of what cable you have, you get a voltage drop, across the cable, connectors, fuses etc.

For example 2 AWG (33mm sq) cable running 30A will give you a drop of about 0.6 of a volt over 16 m ( 8 m there and back). That equates to a lot longer charging times or less than full batteries.

2)The batteries in the trailer will almost certainly different to the cranking battery and may require a higher charging voltage.

3)The Alternator will temperature compensate by lowering the voltage under the bonnet after a short engine warm up period knowing that the battery will be warm. In most climates, the van's battery will be 25 to 50 degrees colder than the compensated value, and will require a HIGHER CHARGE VOLTAGE THAN THE ALTERNATOR WILL DELIVER. No thickness of cable will fix that.

4)You can charge the batteries faster by increasing the voltage ( even in thick cable scenarios) when you don't travel long each day.

5)You can charge the AGM's at a faster rate than the wet cranking battery, necessary when the van's batteries are probably more discarged anyway.

6)You can charge the van's batteries from the aux battery in the vehicle when you are not moving. Despite Ian's statement which only applies to some cases


All valid reasons for this product IMHO, even if you two either don't understand it or sell it. Ayy ahh.

Your calculation on voltage drop appears incorrect.
2GGe cable of that distance at 30A 12V has a voltage drop of around 0.145V.

The rate of charge has to be equated to the DOD of the batteries and even using high resistance batteries that 30A unit would not compete if the batteries were at 50%.

You refer to AGM and with high recombination lower resistance batteries they will accept a higher SOC before reducing charge.

So letss assume with all thing equal we might end up with the same resultant charge in a given time from both systems so with that in mind you would have to think why buy one.
Ian

Hang on dont shoot me yet I put the wrong cable size into the calculator.

The voltage drop should read 0.241V.

The only way my calcs can get to 0.6V drop at 30A over that distance is with 6GGE cable and it actually comes in at 0.609V.

Ian

Iam / Mainey said

"If you have an alternator that can produce greater than 30A why strangle it and then use something supposedly to compensate for an initial poor wiring practice. "

Not sure where the 30 A alternator comes in, but here are some good reasons to buy the product.
( Who said anything about a 30A alternator)

1)Regardless of what cable you have, you get a voltage drop, across the cable, connectors, fuses etc.
(yes)

For example 2 AWG (33mm sq) cable running 30A will give you a drop of about 0.6 of a volt over 16 m ( 8 m there and back). That equates to a lot longer charging times or less than full batteries.
(Not in the acceptable industry standard that Im aware of)

2)The batteries in the trailer will almost certainly different to the cranking battery and may require a higher charging voltage.
(A cranking battery is normally a 14.8V so what are you going to use)

3)The Alternator will temperature compensate by lowering the voltage under the bonnet after a short engine warm up period knowing that the battery will be warm. In most climates, the van's battery will be 25 to 50 degrees colder than the compensated value, and will require a HIGHER CHARGE VOLTAGE THAN THE ALTERNATOR WILL DELIVER. No thickness of cable will fix that.
(Then under load there will be alot of dead batteries and potentialy cars.)

4)You can charge the batteries faster by increasing the voltage ( even in thick cable scenarios) when you don't travel long each day.
(100% correct)

5)You can charge the AGM's at a faster rate than the wet cranking battery, necessary when the van's batteries are probably more discarged anyway.
(Generalising with AGM that come in both low recombination and high recombinationwhere most used are hybred AGM low recombination you are absolutely wrong)

6)You can charge the van's batteries from the aux battery in the vehicle when you are not moving. Despite Ian's statement which only applies to some cases
(Can I state most cases where normal crankers are used)

All valid reasons for this product IMHO, even if you two either don't understand it or sell it. Ayy ahh.( Maybe by your thoughts I dont understand it but I dont want to sell it and you have not convinced me that anyone should buy it but I believe that your valid points only stengthen the reason to buy a unit that achieves the objectives and it is not that 30A unit.)

Come back again Boobook 2 your at least force teaching me how to use the site better and I thank you for that.

Ian

Ian on these points I think you are only considering a sub set of the applications.

5)You can charge the AGM's at a faster rate than the wet cranking battery, necessary when the van's batteries are probably more discarged anyway.
(Generalising with AGM that come in both low recombination and high recombinationwhere most used are hybred AGM low recombination you are absolutely wrong)

The scenario is when you have an Isolator between the cranking battery and the van. The cranking battery will be only slightly discharged ( from starting etc), but the isolated Van's battery may be well down from overnight use. Fridge lights etc. In this case my cranking battery only needs a slight top up and I need 50 - 80 AH in my camper.

Not absolutely wrong. Not wrong at all.

6)You can charge the van's batteries from the aux battery in the vehicle when you are not moving. Despite Ian's statement which only applies to some cases
(Can I state most cases where normal crankers are used)

Ditto Forget the cranking battery. I am talking about the aux battery in the vehicle which would be fully ( or nearly fully charged ) from driving during the day. I never mentioned cranking batteries, you seem to keep coming back to them.

Just a quick question:

what is the common or average size, (diameter of the actual metal cable) used in the scenario where the aux battery is in a Caravan or Camper Trailer being ~8 Mtrs (16 Mtrs return) away from the Alternator.

Maîneÿ . . .

Mainey
It depends on the terminal amps and I have developed a chart where I go from 5Ft to 30Ft in incriments of 5Ft.
From 10GGE to 2GGE and from 20A to 50A in increments of 5A.
I have colour coded it to show Green as being Efficient charge Blue is some charge and Pink Forget it.

25ft covers 8M and it is for supply and return.
At 8M 20A is pink on 10GGE 1.027V Drop and is 6MM auto or 4.5MM2
20A is blue on 8GGE 0.646V Drop
20A is Blue on 6GGE and is 5.3mm diam average but depends on maker
20a is Green on 4GGE and is 6.5MM diam ditto with 0.255V Drop
20A is Green on 2GGE and is 10MM diam ditto

6GGE is the largest cable for 50A Anderson Plugs & drop for above 0.406V

2GGE is the largest cable fo 120A Anderson Plugs & Drop for above 0.161V
Ian

Bloody old dill
It should read It depends on what amps you have to get at the terminal voltage.
The higher the amps the greater the volt drop.
Ian

BooBook2
The statement that you can charge an AGM battery faster than a Flooded wet cell battery is an old wives tale which Charles Sterling has proven with some testing and that testing is not something done for his own benefit it can be performed by anyone under the same conditions with the equipment.

As Ive stated before there are AGM batteries and there are AGM batteries and the bulk of them used by RV travellers are low recombination make believe AGM batteries where the resistance limits the battery input capacity.

The fastest charging AGM is the high recombination battery such as Optima Oddysey,Lifline and Decca Sea Mate.

The high recombination batteries are voltage sensitive and are recomended to charge at 14.2V and should never exceed 14.4V or the battery can be damaged.

You agreed that the higher the voltage the faster the charge and flooded wet cell can accept 14.8V and with temperature compensation you can rapid charge a flooded wet cell .

Now you bought the cranker into the equasion also where you referenced the cranker is isolated from an auxiliary so I suppose you could say we are both swimming in a can of worms.

I can charge on the run up to 300A at 12V with Sterling gear efficiently and with an AVR12V Regulator and a ProSplit R 12V120A 3 Outlet charge three batteries and manage them independently and safely with speed and efficiency so why would any one want to play with toys.
Ian

Boobook2
I might add that a seller previously stated on this forum about the C rate you can charge a battery at and that person was backed up by an engineer and when I asked for a better and further qualification of the statement none was forthcoming.

I suppose it could be considered in two lights .

Did I ask an idiotic question that was wrong and shouldnt be answered .

Did it mean that it couldnt be answered as the statement was wrong.

Ian

I think your first line should include the value of 13.8 V and not 23.8 V

There is a good article on these types of converters see here The power units in Jayco vans are of this type and are as pictured in the circuit diagram at the bottom of the article.

Ian - most people consider your "alternator to battery" chargers to be too big for battery banks under 300 - 400 A/H. A better unit for the 100 -120 A/H batteries in vans would be the RanOx battery booster or perhaps even the Redarc battery booster.

PeterD

Peter
You are correct silly me I rush thinking Im taking too long and it wont let me upload 13.8V in the correct figure.

Now on another matter the word "most" assumes a majority.

The essence of DC charging is to get the most charge in your batteries in the shortest time to minimise run time so you need to maximise what is available from your alternator and with a Sterling you can do that with temperature compensation.

When the Ranox can produce the capacity to do just that then it will be an acceptable alternative to a Sterling Battery to Battery unit but then we are talkin about 2 different products Im taking about an alternator to battery charger not a battery to battery charger and as yet I have not seen another one other then the Sterling unit and he lead the field in this technology.
Watch other units rise in price with increased capacity.

Ian

Peter
The article by Collyn is an excellent example of power supply chargers and I can state that they are not suited for Australia as we want to free camp we want some form of self sufficiency and we deal with importers of 5th wheelers and we know pelople do not want to have to pull into van park and the like at all times because they have no alternative to allow them not to.

We have one Australian unit built by Dryden that we have totally set up and it sat in the main street of Katherine in stinking hot conditions running air con off batteries and then recharging on the run with Sterling equipment.

I do not put myself up as an expert I would say you know more than me but I know when Ive got a good product and how it can be used to advantage.
Ian

Ian said

"Hang on dont shoot me yet I put the wrong cable size into the calculator.

The voltage drop should read 0.241V. "

Actually me to. I screwed it up also.