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2*12 Volt Batteries in series for 24V - What Trickle Charger?

Gustomaximus

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As per title I have 2 12V batteries for my Komatsu D31P dozer (see image link). I want to trickle charge for when the machine is not in use.

Would I get a 12V or 24V trickle charger? Or do I need to disconnect series and do independently?

https://photos.app.goo.gl/vgJDrqckjqAEqG6z8

Thanks in advance (again!) for helping a beginner :)

/Angus
 

fast_st

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24 volt trickle charger, check with Napa possibly. There is also a small solar brand marine unit for 24v.
022-258-DL-WH was one body mountable charger from battery tender, you can't use 2 trickle chargers
at once as they confuse each other. Unless you wanted to disconnect them and charge one at a time.

Are there really long intervals between use? 6 months or more? A battery disconnect might be just as good for that.
 

Birken Vogt

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2 12-volt trickle chargers has been Kohler generator's solution for decades. One hooked to each battery. It is also a better solution than a single 24 volt charger because the more cells you get in series the more chance one of them will be out of balance with the others. So long as each charger has no reference to ground they do not have any way to know that they are hooked to a 24 volt system, 12 volt system or a battery sitting on a shelf.
 

fast_st

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I tried a couple on a friend's surplus army truck some time back, either battery would be fine by itself but something about hooking up two caused one of them to go into error
 

361brock

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Ive been using 2 battery tenders on 24 volt systems for years. They work good, batteries last up to 10 years if used from new. If you can maintain specific gravity from new, sulfation will be slowed down.
 

361brock

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If no power where machines are stored, I use a pair of 12 volt solar panels, 1 on each battery.
 

LCA078

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I tried a couple on a friend's surplus army truck some time back, either battery would be fine by itself but something about hooking up two caused one of them to go into error
It depends on how the trickle chargers are internally wired to ground for the power outlet. If one leg of the charger is internally tied to ground with a 3-prong outlet, then you can't hook two of those chargers in series on two 12-volt batteries. Because of the common ground, you can't float the voltage to match each battery of a set of two wired in series. You'll need to break the 'series'. But if you have 'cheaper' chargers without a dedicated ground (ie- 2-prong), then you should be able to float them (ie-connect them in series). Still iffy depending on how the ground of the tractor goes through the steel tracks to the earth to the grounding rod of the power circuit which causes a common ground. Two 2-prong trickle chargers in series should work on a vehicle isolated from earth (ie-rubber tires). Same thing with solar panels mounted on a vehicle. Be careful on how the grounds are tied together, otherwise crazy things happen.
 
Last edited:

kshansen

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Maybe trickle chargers are different than the large booster chargers we had at the quarry but many time when a machine was low on battery power I often hooked two to the batteries of a machine with no problems.
 

Gustomaximus

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Are there really long intervals between use? 6 months or more? A battery disconnect might be just as good for that.

Intervals should be a few weeks (2-4) normally, or a 2 or 3 months max. I probably wouldn't go 6 months without using but good to know a disconnect is the best option if not planning to use.
 

Gustomaximus

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Australia
Thanks for the info. If I understand correctly I have 2 options:

1) 24V charger. Connect positive/negative one to each battery and charge that way across the series.

2) 12V charger x 2. Connect to each battery as usual. Seems people do this but recognise a chance something funky happens are there, and from LCA0278 2 prong would be better here to avoid common ground.

Question:
- Would a 3rd option be to get one 12v charger and swap batteries every so often? I walk past the machine almost daily.
- Im thinking to get either Ctek MXS7 12V and either going the 2x option or swap as generally 12V charges are more use to me and a 24v would only be for this.

Does that sound right or would people recommend other?
 

Delmer

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Since you're in Australia, get a solar panel and a charge controller with an adjustable set point.

Yes, swapping the charger will work fine. Get a smart charger for that one, because eventually you'll hook it up backwards.

Here, we can let batteries sit over the winter fine, they don't discharge in cold temps. Three months in hot weather would drain them though.
 

fast_st

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Intervals should be a few weeks (2-4) normally, or a 2 or 3 months max. I probably wouldn't go 6 months without using but good to know a disconnect is the best option if not planning to use.
My dozer is all non electronic, 1966, running once every few months hasn't ever caused trouble with starting, I did need to drag a charger and generator over to it when it was below zero out, the oils were just too thick.
 

LCA078

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A battery disconnect might be just as good for that.

A possible way to use your standard disconnect that comes with the tractor is to connect it in between the two batteries (one to the positive terminal and the other negative terminal of the other battery). This way you can 'disconnect' the batteries by breaking the series. Not a true disconnect because you'll still have a floating battery connected by one terminal but effectively it breaks the battery circuit from the tractor. This should also allow you have to use two trickle chargers without issue since the batteries are now separated. Just a thought
 
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