Alternative to an expensive 3 stage charger

Max,

Big Woolies and K Mart sell them at some of their stores. Failing that, call Brown and Watson, Scoresby, Vic (they're the distributors for Projecta stuff and offer excellent technical advice) to find out who they supply in QLD.

Cheers,

Jim.

Autopro in Toowoomba carry a full range of Projecta gear, so I'd guess that it'd be safe to assume that their Brisbane branches would too...
Also seen 'em at K-Mart, & Repco...
Agree with Jim, the BM140 is a useful piece of kit which does appear to do what it claims to do...
You may also wish to check out the (Projecta) ODP500 low-voltage cut-out which is connected in line between any 12v accessory & the power outlet, & prevents over-discharge of the battery.. These can be had for less than $20, & are rated @ 10A ... good value IMO...

Regards, Ed. C.

Adrian,

Sorry mate, but could you tell me what "UPS" stands for?

Cheers,

Roachie

Sorry Roachie, I was being lazy! Uninteruptable Power Supply. They go between the powerpoint and the computer so that if the power goes out it kicks in within a couple of miliseconds and the computer keeps going. "All" they are are a sealed battery (12v 7ah and up) and an inverter. When there is power they bypass the inverter and float-charge the battery but when power fails the battery connects to the inverter.

I toyed with the idea of using it as a very neat inverter setup in the camper but heat was an issue - they are designed to run for the life of the battery which for 7ah is about 4 minutes (enough for you to safely shutdown the computer)

Probably more than you ever wanted to know!

Adrian

Ray,

No, it is installed between the 240 volt battery charger and the battery.

Cheers,

Jim.

Moggs,
It actually converts a manual charger to a 2-stage charger, initially charging battery to 14.4v, then the auto-float control system maintains the battery at a constant 13.2v...
(also switchable for flooded & gel batteries)...
I doubt if it will replace a sophisticated multi-stage charger, but it's a useful item for anyone who already has a manual charger... I've had one for a while, initially thinking it was simply an auto cut-off (which it's not), & have only recently begun to realise just how useful this gadget is!...
I've found that it works a treat for maintaining those jump-start type battery packs in a fully charged state... (among other things)..

Regards, Ed. C.

You may find the problem wasn't the two different types of batteries, more than likely the float voltage was too high from your alternator, most cars these days are putting out 14.4V, most AGM type batteries like a float of about 13.8 and certainly no more than about 14.1V for any length of time. Check the manufacturers specs on the battery and see what they quote as a safe max float voltage.

Brett,
from reading your post, I understand that;
(A) the alternator puts out a definite voltage, eg it does not vary and it may be as you say, 14.4v and I don't dispute your information.

(B) AGM batteries like to be charged at 13.8v to 14.1v

(C) Wet batteries like at least 14.4v

With your information in mind, I find it hard to comprehend how a qualified person can sell someone a Dual battery system comprising of two different batteries that require two totally different charge rates from the same alternator, based on your information!

As I said you would need to check the manufacturers spec for the batteries, they are the only ones that know what voltage their batteries can be charged at. But basically any wet cell is ok around 14.4V any higher and they start gassing, won't kill them but you need to top them up and also have corrosion problems. Calcium impregnated batteries can withstand higher voltages before gassing I'm told. I have some 12V 100AH AGM cells out of a UPS system and I have checked the manufacturers data sheets and they specify a float voltage of 2.27V per cell which is 13.62, they say 2.4V per cell (14.4V) is ok for a faster charge BUT this voltage for extended periods will cause grid corrosion and reduce the service life of the battery. Now the 13.62V is a float voltage not the charging voltage, if the battery is not charged there is no problem charging it at 14.4V, this is what you'd probably call boost mode. As the battery is flat even though you are applying a source voltage of 14.4V the battery drags this down.
And re the alternater voltages it seems post 1996 vehicles have this higher alternator voltage, pre 1996 seem to be closer to 14V.
And re the selling of battery isolators, how many of these people have read and understood the specification sheet of your battery, probably not many. But as I said you really need to read up on the battery manufacturers specs and listen to what they say. I don't claim to be an expert on battery science, I just read the specs and follow their instructions

Just had a quick look at the Dynasty web site and they state a float voltage of 13.5v to 13.8V and a Equalization and Cycle Service Charging Voltage of 14.4V to 14.8V which is your rapid charge rate. Now you go and put this battery in a modern car with a alternator output of 14.4V it will charge very well but once charged your killing it.

Hi Sandman,

I have a DBE150S isolator as well and it isn't a diode type at all. If you open it up there are relays which do the switching and circuitry for delays, spike protection and current limiting. When the engine is on it parallels the batteries - when off it isolates them. I even measured the voltage in verses out and it is within 0.02 of a volt. If it had diodes then there would be at leset a 0.6 volt drop. A quick search revealed that there are electronic isolators, diode pack isolators and relay isolators around. The diode type are not really used anymore as it introduces a 0.6 volt voltage drop between batteries which means an insufficient charge to one of them. The common fix for this is that the regulator needs to be increased by 0.6 volt to counteract the effect of the diode but then another diode has to be put inline with the starter battery to make the circuit balanced. This isolation works well on solar regulators where the output can be varied but is not practical for an alternator.

With regards to my problem, I think brett has the right answer in that AGM batteries do not like to be sitting at 14.4 volts forlong periods of time as they are designed to charge at a slightly lower voltage that lead acid batteries.

Please don't think I am saying anyones setup is wrong or won't work but mine obviously didn't and at the cost of AGM batteries nowadays, it may pay to be mindful.

Regards
David

I'm having a few problems coming to grips with this guys. If the batteries are simply paralled by this isolator then how can it treat each battery individually as quoted above from the Piranha website.

Quote: "The alternator is able to recharge each battery according to its own individual needs." Now that's got me stumped.

That's the million dollar question, I've always suspected that there was not much electronic about the Piranha isolators and David confirms this. They still use relays for the switching like any other isolator, the only electronic bits are for current overload protection and the cut in/out voltages, just the same as most isolators on the market.
Re Piranha's quote it may be misleading but not incorrect, any two battery's in parallel will charge according to their own needs as their own internal resistance governs the charge current, but once fully charged it's a different story, your now talking float voltages which vary depending on type of battery. The only way to do this properly is to virtually build a switchmode inteliigent programmable battery charger and power it off 12V. Far too complicated and expensive for what we're doing.

I think your on the money. However when you put 2 batteries of different states of charge together in a circuit they will equalise very quickly to assume almost identical voltage and capacities.

David,

Yep, you are correct in that the DBE150S is not a "diode" type isolator.
It is an "electronic" isolator providing additional features.

However mate, I don't believe you are correct in your statement:-
"When the engine is on it parallels the batteries - when off it isolates them."

My understanding is that both batteries remain electrically isolated from each other, at all times.

Hi Sandman,

A quick test will reveal they aren't. Disconnect the main and aux leads, connect 12 volts to the ignition on of the isolator, wait for approx 45 seconds for it to activate the isolator (in built delay to prevent large transition of current from one battery to the other when they are at different states of charge) and then measure the resistance from main lead to aux lead. You will find it is basically a short circuit. This prooves that it is purely a switch isolator (or relay).

You can also test whilst connected. With engine running, check voltage at main battery and voltage at aux battery, if within 0.1 volt (voltage drop of the isolator cable and relay) then they are paralled (best to do when battery voltage has stabilised as when you first start the engine the battery voltage increases slowly so reading a voltage of one battery and then the other will reveal that the volatge has increased a bit due to state of charge rising). Rev the engine and the voltage at the main battery will be exactly the same as the aux. That means there is absolutely no isolation when the isolator is activated.

There are isolators which do a different job and they have the alternator connected directly to the isolator and then the isolator switches in either battery to be charged depending on its voltage. This is a true isolator and I think the Rotronics falls under this catagory (anyone?).

Regards
David

David,

I believe your testing procedure is faulty.

Some time ago I completely discharged a deep cycle wet cell battery.
There was NO impact to the primary (starting) battery at all.
That's the whole idea of having an isolator in the first place. (whatever the type, or brand)
If what you are saying was correct and the two batteries were connected in parallel, BOTH batteries would discharge, as they would be electrically (physically) connected together.

I will restate my comment that both batteries are electrically isolated from each other. You could run a winch, etc. off the primary battery until it is absolutely flat as a lizard drinking and guess what? The secondary battery will have as near a full charge as before the primary was drained, to the extent that one can physically jump start the vehicle using the secondary battery by PARALLELING it with the primary, or, if the primary was completely buggered, by replacing it with the secondary one altogether.

Cheers.

.
.
........... N O ..........

Anyone with a more reassuring .....NO....

i.e. explanation

John,
on both the Pirahna and the Rotronics technical specifications information sheets it is stated they can both be used with "different styles and types" of batteries...Eg, Deep Cycle and also Starter batteries, battery chargers and solar panels also.

However one of the cheaper solenoid manufacturers sent me an E-mail to my direct question to them, about the use of Deep Cycle batteries and Cranking batteries with their system, and they don't recomend the method at all, it even states they are going to change their web site info as well.

cheers

Using lead acid deep cycle and lead acid cranking should pose no problems as they operate almost identically (physically and chemically)but lead acid anything and AGM (or Gel, Calcium, etc) could have potential for problems as the battery chemistries and charging requirements are totally different.

If you look at any smart charger there is usually a switch (in the case of the BM140) which selects the different charging program needed for lead acid or AGM/Gel. If these devices have them that that would indicate there our vehicles charging system is quite limited when dealing with the various types of batteries that could be used.

I would liken it to charging a NiMH AA battery and NiCAD AA in the same charger (this is a very broad analogy).

The BM140 in the orignal message would be perfect in an in car charging system to islolate the charging of AGM batteries as it is the BM140 that is doing the charging and not the alternator (although it does provide the source).

Regards
David

David C's suggestion sounds like a good one - put a BM140 before the AGM to ensure that it doesn't get a higher voltage as a float. This would be a particular problem in the Disco as it has a calcium battery with a higher alternator voltage setting. Any comments? A good investment of $48 to save a $250 battery?

Adrian

Adrian,
If you're interested in picking up one of these, K-Mart currently ('till wed. 2nd Mar.) have 25% off Exide batteries, battery chargers, power packs & jump starters, & that includes the BM140...
Good value IMO...

(Usual disclaimer... No affiliation yada yada...)

Regards, Ed. C.

G'day Wok,
My observation>>>
Projecta SC8000/P.B. (manual) charger rated @ 4.75A cont., Exide Endurance N70Z cranking battery, BM140 controller between charger & battery... readings taken from 2 separate digital multimeters, 1 connected to batt. clips (output), & the other where charger connects to controller (input)....

While charging, the input & output voltages remained within 0.01v of each other 'till battery was "full"...
During my little "test", the BM140 switched to "float" @ 14.48v... When the batt. voltage settles back to around 13.2v, the controller "cuts in", & gives it a quick kick up to 13.38v & cuts out again, & this cycle is repeated indefinitely.... In "float" mode, input voltage (from charger) hovers around 13.68v....

Different charger/ battery/ condition of battery, may or may not produce different readings, but it (BM140) does appear to be very effective in doing what it claims to do...

I have absolutely no idea about the inner workings of such things, but I hope that helps to answer your query....

Regards, Ed. C.

Thank you Ed,
.
Thats one part of the info I need! Now I need the info when the charger output is 13.8V [like common chargers eg Arlec]
.
I have a suspicion it doesn't boost the Bulk Stage to 14+ V when the charger output is below 14.8V.....just need to know before I invest in one.

cheers