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Charging two tractor batteries

U

Unruh

Member
The batteries on the tractor need to be recharged. There are two 12 volt batteries connected in series with one on each side of the tractor. If I put the charger on just one of them, will the one on the other side be charged as well?
 
Probably not. There are complex starting and charging systems on some JD tractors, so if we give yoy information it could let the smoke out of very expensive parts. So tell us what you have. In closing, if you disconnect the battery (one post will do) and charge them independently, no problems will happen. JimN
 
Excuse me! I could have known that we need to know what kind of tractor it is! It's a John Deere 4555. I know, the batteries are getting old and need replacing, but not today, but soon. I would think it's 12volt?
 
It's either two 6's in series or two 12's in parallel to obtain 12V for that model of tractor.
How many fill caps on each battery?
 
Six fill caps on the battery. I have to admit that I just looked at the one on (this) side, and took for granted that they were in series.
 
NO and YES! caution!

He said they were in series ie the - of 1 connected to the + of the other leaving a - on 1 battery and a + on the other to connect to your tractor. If you have 6v batteries you will end up with 12V. If you have 12v you will end up with 24v. with either you will need to connect you charger to the end - and + and charge the batteries as 1 with the total voltage. OR disconnect the batteries and charge each, 1 at a time with half the voltage ie the voltage of each individual battery.

Now if the are connected parallel the - and + of each battery is connected together. This result doubles the capacity but the voltage stays the same as the individual batteries and you can charge them together or separate.
 
Disconnect them and charge them independantly. They will get a better charge that way any way. If there are 6 fill caps it's a 12v, if it has only 3 fill caps it's a 6v. If they are maintenance free batteries put a volt meter on them to check the volts.
 
Thanks, guys, for the education. I'll know what to do - I learn so much from this forum! I read it quite consistantly. I'm grateful.
 
John B. is the only one that has posted the truth. If you try to charge them together, the strongest battery will control the charge and the weakest battery will be undercharged. That is why it's recommended to replace batteries in pairs.
 
Iffffffff theres actually two 12 volt batteries and they are in series as you claim,,,,,NO if you put a 12 volt charger across one of them ONLY IT WILL BE CHARGED NOT THE OTHER. To charge them both with a single 12 volt charger, you would have to charge them one at a time...

HOWEVER if it has two 12 volt batteries connected in paralell YES each will receive some charging current if you place a 12 volt charger across them...

NOTE if two are in paralell and one is bad, it could draw more current from the charger then the other.......

If you had a 24 volt charger and placed it across the series of the two 12 volt batteries YES each will receive charging current...

Hope this helps,,,,,,you need to be sure if they are series or paralell (as Id suspect) if you wanna charge them ALSO in dual battery systems its better if BOTH batteries are identical in type n size n design n age etc etc so one isnt caniballizing off the other lol

John T
 
From somebody that had a backhoe with 2 12v batteries in series and a slow short somewhere I could never find.

Buy a second battery charger. You can charge both batteries at the same time.

Since selling the backhoe, I've had more than one vehicle with a flat battery at the same time several times, having two battery chargers is very handy.

I keep one in the garage and the other in the barn.
 
Find the + post on either battery. Connect the charger's + clamp to it. Connect the charger's - clamp onto the chassis somewhere away from the battery.
The batteries maybe ok. The cable crimp into the battery clamp and the - cable to chassis connection often looks good but has high resistance.
Only way to really know what is going on is to measure voltage while cranking at each battery, post to post. Then measure the voltage from the starter's input post to the starter's cast body.
Thing is I've never had anybody in 6 years of asking that question come back with voltage answers. Everybody just throws parts at it hoping to hit the problem.
It’s very common to find a system with two 12’s in parallel. And find that either one battery is a dud and doing nothing. Or one battery connection is corroded. In either case one battery is trying to start the engine alone.
As previously stated. The batteries have to be a matched pair or the results are fair at best.
 
This is almost essential if the batteries are in PARALLEL - as in my GMC diesel truck - TWO - 12 volt batteries connected negative to ground, positive CONNECTED TOGETHER- 12volt system. Weak battery will eat other. Must replace in pairs. You need to check out your system and find out how it is wired. If it is wired in PARALLEL, you can charge them together, which is probably the best plan, as batteries will be charged to the same level. SERIES batteries will not charge both at the same time.
 
If in parallel they with both charge without problems unloess one battery has completely failed with a shorted cell.
 
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