24V charger

Joined
May 13, 2004
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That's cool, but my gut instinct tells me that if you need to charge your two 12v batteries from your 24v bank, that it would be best to charge them individually from a regular 12v charger. There's inherantly slight voltage differences between any two batteries, and they don't always charge up evenly when setup in series. That's why I've been told that guys who have been running 24v Cruisers have always rotated their batteries every couple of oil changes or so.
 
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Though that's a cool find, it will do more harm that good to your 24V cruiser's batteries.


A 24V charger will apply a current to your battery bank until they reach some set voltage (something between 28.0 & 29.5 V). (remember, a 12V battery charges at ~14.7-15.1V and when removed from the charger, it puts out ~13.8V)

Now, since you're getting your '24V' battery from two, 12V batteries in series (voltages add in series), the charger won't be able to tell if one of the batteries is in a lower or higher state of charge than the other. It only measures the sum of the two voltages. If you've got a weaker battery, the charger will over-charge the strong battery. Also, the 'weaker' battery will alway's get under-charged.

This is how I (and many others), killed my batteries in the past
(little things like a burned-out headlight, or even (god-forbid) a 12V stereo drawing from only one battery)



I always forget my electrochemistry, but over- and under-charging causes build-ups of Lead Oxide on the plates, and Hydrogen off-gassing (overcharging & hydrogen go together, correct?).


......Now, if you got some real monster, bad-a$$ 24V batteries from a golf-cart / military / aircraft, etc. for cheap, you could shoe-horn them under your hood and rewire them in parallel for a killer electrical system for your 24V winch.;)


cheers,
Steve
 
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Charger shuts off at 25.2V, and was designed with series batteries in mind. Although Battery warehouse could fix me up with a 24V battery, if and when the time comes.
 
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Hmmmm interesting.

I could only find information on their 12v stuff
http://www.battery-chargers.com/TB.htm


(the page with 24V stuff only lists the size of the charger case, and mass, etc).


Could you post up the webpage (or address) pls?

I'd be interested to know how it can tell the difference in state of charge between the two batteries...
....but if it can, it'd be an great (and no doubt cheaper) alternative to replacing a faulty toyota charging circuit or enabling the use of mix and match (capacity/age/etc) batteries.



Steve
 

brownbear

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Not to offend anyone,

But I think you are all over thinking this battery issue. If the batterys were installed new at the same time, this whole charging independantly or overcharging is not really critical.

when the battery's are hooked up either in series or parallel they act virtually as one battery, they will wear out at the same time, or close to(cells fail first).
charging independently is not a good idea in my op. So when you hook them up the higher battery has to spill over into the weaker one, why start off with a difference.
I also cannot see what rotating batterys would ever do? How is one battery being charged any different than the other. This is a major myth IMOP. Do you rotate batteries in your flash lights so they get drained at the sametime, no cause they act as one battery. The sum of the cells.

There is nothing wrong IMOP to hook up to a 24 battery charger, in fact that is all I would do. Charging independently is just asking to intiate an imbalance in the two batterys which I think is more harmfull.

Now all of this is my opinion only and is open to change is some one can convince me otherwise. I am not stubborn. LOL!
 
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My flashlight batteries don't receive any charge when they're hooked up in series in my flashlight.

I think the issue started way back when people tapped off of their low side battery to draw their 12V power. This caused the low side battery to draw down, resulting in sulphation. I have heard that the high side battery can become overcharged in a system where there is a bad low side battery, causing the high side battery to boil over.

This is how I have hooked up my system, drawing from the low side battery so that I can draw large transient 12V loads when I need it. I have my Solar Converter shunting current in load balance mode, and it keeps my batteries fairly equal to each other. I then flip my switch to turn it into strict convert mode when I need to leave my vehicle for days at a time, to avoid drawing down my batteries. My system has been very happy for almost two years this way, using two Interstate Workaholic batteries.

As I've stated in my post, mine is more a gut instinct type feeling. I have read on one website that concurs with your theory that batteries hooked up in a bank, whether in series or parallel, act as one battery, and that in series, a bad cell does not necessarily cause any problems with current flow. I'm going to be doing a bit more reading. :)
 

brownbear

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Stone said:
My flashlight batteries don't receive any charge when they're hooked up in series in my flashlight.

I think the issue started way back when people tapped off of their low side battery to draw their 12V power. This caused the low side battery to draw down, resulting in sulphation. I have heard that the high side battery can become overcharged in a system where there is a bad low side battery, causing the high side battery to boil over.

This is how I have hooked up my system, drawing from the low side battery so that I can draw large transient 12V loads when I need it. I have my Solar Converter shunting current in load balance mode, and it keeps my batteries fairly equal to each other. I then flip my switch to turn it into strict convert mode when I need to leave my vehicle for days at a time, to avoid drawing down my batteries. My system has been very happy for almost two years this way, using two Interstate Workaholic batteries.

As I've stated in my post, mine is more a gut instinct type feeling. I have read on one website that concurs with your theory that batteries hooked up in a bank, whether in series or parallel, act as one battery, and that in series, a bad cell does not necessarily cause any problems with current flow. I'm going to be doing a bit more reading. :)

Thanks Stone, One thing to mention, my anology is not taking into account your draining of 12 from a low side battery. Also to note, As I have heard of certain cruisers using 12 for headlights......etc, I am not taking that into account.
Any time an imbalance is present, you rotating the battery theory does sound ok. Althought it sounds like a flawed system from the get go.

I still concur that anytime the batterys are hooked together they act as one tho.

your flashlight(lets therorize) is rechargeable. the individuall batterys are 1.5 volts, together you have 3 volts, your load is a bulb of 3 volts. You use the flash light and later recharge, later to do this over and over. This is my point, unless you are stealing from one battery more than the other(in your truck for 12v) then in my theory you have batterys that are doing the same thing, acting as a 3v(or 24v) battery. positioning either battery in the flashlight will not give any other results. being on the top or the bottom.

Now duracell or energizer could manufacture a battery that is not as good as the other, so could motormaster, or delco. But that is beyond your control.

As I said before, if your a 24v system only drawing 24volts, I see no reason why you could not just charge with 24v. If the batterys are of the same age, the over charging and undercharging should not occur. One thing that could hinder the equal charge when doing both batteries with 24v is dirty connections, which act as resistors and lower the voltage being applied to the battery.

Or source out 24v batterys for your truck. They run around 5-6 hundred. 1700 if you want one as big as I buy for the aircraft I maintain. And its lead acid too.
 
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wow, this thread has more legs than I thought. I don't think that the charger can differentiate between batteries, It is simply the charger going into float mode at 25.2V. 25.2/2=12.6V, if one battery is down a whole volt, the other will only be overcharged by 1.6V, 12.6+1.6=14.2V, pretty negligible. If one battery is down consistently by two volts, you have a dead cell, and the battery is fuct anyways. I have gone out of my way to avoid discharging one battery, all 24V bulbs (Lordco has 'em, just ask, H1 through H4), and an industrial power 15 amp 24 to 12V converter. Although I wish I had known about the solar setup at the time, sounds much more efficient.

Now, here's a question: If I run a 12V trickle charger (2A) backwardsthrough the converter, will it charge the batteries at 24V?

I know that if the power goes out, and you power your house with a generator, and you don't turn off your main breaker, the 110v coming out the generator will go out your service mast into the transformer, get stepped up to 72KV, and fry the poor dude working on the line (remember this to avoid hearing things like: "manslaughter", and "negligent homicide";) ).
 
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None electrical fella yaking here:

In a perfect world the two batteries in series may well "virtually be one battery" however in the real world this rarely seems to be case. Whether this is from slight differences in internal resistance's, connections, length of cable...etc, I don't know. I do know that many times you can check each battery on the poles, and there will be anywhere from a .05 to .50V difference in a standard set-up. Trucks run for years with minor differences. Over time it will shorten battery life.

This is with no low side tap.

Old salts would recommend swapping the batteries at each oil change to try and minimize this difference, and extend battery life as long as possible...in the shaky 4 banger diesel environment.

The 12V headlights on 24V cruisers are not creating or adding to this imbalance afaik, as one headlight is fed from the 24V side, and the other headlight fed from the 12V side...creating an equal draw.

I see no problem charging the batteries individually with a 12V battery charger. Over time, if you are discharging (running it down a lot) and charging I agree that a larger imbalance may occur, however when would this happed on a 24V system if you are managing your batteries?

I also don't see the need for the additional expense of wanting a 24V charger. What is your purpose here Chang-kuao-lo? Are you running down both batteries and wanting to put them on a charger overnight? Are you tapping onto one battery, running it down, and want to hook up a 24V charger so it will bring the low "cells" up overnight?

Certainly if you buy a 24V battery you would need the 24V charger.

There is an advantage of having two 12V batteries. I have jumped a number of 12V trucks from one battery in my string. 12V batteries also seem to be getting cheaper. I was in Costco the other day and could not believe the price of the red tops and Kirkland brand 24 series batteries.

Chang-kuao-lo. 1.6V is not insignificant. You will sulphate one battery and cook the other over time with that level difference, as the uncharged one gets more and more punky...sending more and more charge to the other.

hth's

gb
 

brownbear

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Greg_B said:
, and there will be anywhere from a .05 to .50V difference in a standard set-up. Trucks run for years with minor differences. Over time it will shorten battery life.


Old salts would recommend swapping the batteries at each oil change to try and minimize this difference, and extend battery life as long as possible...in the shaky 4 banger diesel environment.

gb
I think it should added that it might not only be connections but general battery health that could contribute to the difference. Starting at manufacture a difference could start.

To me clean connections go a lot farther than rotating, as well if its a type of battery that requires maintenance such as topping up fluids, to keep on it. Personnally I like gel batterys. Who wants to top up batterys?

If you want a 24 charger try Princess Auto and maybe Napa, the heavy duty roll around ones all have 24 on the dial. I have one a work. Can't be that expensive. Much easier than always disconnecting to charge, that said it is rare I ever need to charge up my batterys..........And if all had was a 12v one, I would disconnect.

Going backward thru the converter should work, but the heat created might wear it out quicker. And attention must be used to make darn sure it is with in the limits on the converter.

Do your batterys go dead on a consistent basis?
 
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no, just use it once in a while. Saves the pain of disconnecting, and resetting the clock, stereo, cd changer, etc. Already got it in, about $120. Had a cell go on one of the Delcos, and the bastids wouldn't honor the warranty down here, "go back to the point of purchase...", yeah, right, that's only 3,000 miles away. I always found that a trickle charger was handy on the old Dodge D50 Diesel(really a Mitsubishi, great little truck 50MPG!) I had, in wintertime since the glow-plugs were a pretty big draw. Not such a big problem on the BJ being 24V and all, twice the volts=half the amps.
 
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whats the difference in the different color tops on the optima batteries?

I'm gonna put new cables and batteries on my truck next year so i'm just curious.
 
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24 volt chargers from princess auto was only 200$ on sale.. use it all the time on the cruisers or unimog. lots of industrial stuff also uses 24v.. great for boosting when you have no time to charge up batteries for hours. If I am in no rush I will set up two little 12v chargers.
 
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The reason for the imbalance between the two batteries is the 'drain' on the low battery. Most people tap off this battery for the radio which is 12 volts. I know that the proper way for powering the 12 volt accessories would be to install a 24-12 volt converter. But the fact remains that the low battery in most 24 volt Land Cruisers get drained at a different rate from the high side battery. And because of this the batteries need to be swapped every so often.
I don't think that using aircraft lead acid batteries would be practical either, especially if you live in a cold climate. As you know these batteries don't like the cold. An electric battery blanket could solve that problem though.
Another problem would be mounting them under the hood. You probably use Concorde batteries in your planes. The shape of them are odd. You can fit a RG-390 possibly but something big like a RG-44 probably won't fit. Another problem would be the connector to the battery. Elcon connectors are nice though as they're quick release....




Thanks Stone, One thing to mention, my anology is not taking into account your draining of 12 from a low side battery. Also to note, As I have heard of certain cruisers using 12 for headlights......etc, I am not taking that into account.
Any time an imbalance is present, you rotating the battery theory does sound ok. Althought it sounds like a flawed system from the get go.

I still concur that anytime the batterys are hooked together they act as one tho.

your flashlight(lets therorize) is rechargeable. the individuall batterys are 1.5 volts, together you have 3 volts, your load is a bulb of 3 volts. You use the flash light and later recharge, later to do this over and over. This is my point, unless you are stealing from one battery more than the other(in your truck for 12v) then in my theory you have batterys that are doing the same thing, acting as a 3v(or 24v) battery. positioning either battery in the flashlight will not give any other results. being on the top or the bottom.

Now duracell or energizer could manufacture a battery that is not as good as the other, so could motormaster, or delco. But that is beyond your control.

As I said before, if your a 24v system only drawing 24volts, I see no reason why you could not just charge with 24v. If the batterys are of the same age, the over charging and undercharging should not occur. One thing that could hinder the equal charge when doing both batteries with 24v is dirty connections, which act as resistors and lower the voltage being applied to the battery.

Or source out 24v batterys for your truck. They run around 5-6 hundred. 1700 if you want one as big as I buy for the aircraft I maintain. And its lead acid too.
 

coleman2347

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If you don't mind, some questions?

Ok, I had my 24 volt system BJ40 about two months before I decided to rebuild it and upgrade the engine to a 24 volt 15b. As it is in a bunch of parts now I am unable to run over to the place it is and check it, hence the questions.
Doesn't my BJ40 (1978) have a 24 volt alternator?
I thought the bulbs and everything else was 24 volt, not true?
When I rebuilt the gauge cluster I noticed there was a resistor on the back of the gauge cluster that 12 volt does not have.
As I understand it the starter is 24 volts. I have never had a 24 volt truck before and even though I worked on A/C (28 volts) for many years it obviously is not the same..any education you could give me would be greatly appreciated...Lee
 

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