Series Battery Problems

[usmc81301]

I seem to be having a problem with my batteries. The back battery seems to loose voltage to the point the vehicle won't start about every 5 weeks. I know there are others post that talk about having two alternators, but since I only have the one 24v generator I am still confused. I thought the batteries should be equal in power since they are in a series. Any suggestions?

 

[WillWagner]

The battery that looses voltage is probably junk, 6 TLs are good for that!. Remove the dogbone, charge them seperatly and load test them individually. Do you have a 12 VDC accessory that you have added that could be pulling the battery down?

 

[usmc81301]

I did have a 12V adapter on one before but I took it off. I had both batteries checked and charged at the place I bought them. But, whatever battery is in the back looses the charge. I have swapped the batteries before and then they trade places. The good battery from before, I put in the rear and then it slowly died the same as the one before. Whatever battery is in the front is always charged just fine.

 

[ida34]

I would clean up the terminals and check check all the connections. I am leaning towards bad terminals but your problem does not make too much sense from an electrical standpoint. The only thing I can think of is bad connection between the terminal and the rear battery.

 

[Westech]

that happens to all my Hmmwv's too.. if we don't start them every couple weeks we have to jump them. There is something some place that draws some how. There that should explain everything

 

[m16ty]

Well if the back battery has a bad connection so does the front one. The batteries are in series so the connections have to be good for either battery to work. The only way I could see this happening is that you have a 12V draw off of the back battery wired separately from the main cables. If both batteries are good there is no way (that I can see) you could draw off of one and not the other unless there are separate wires drawing off of the back battery only.

 

[Spin]

Ok, lemme get this straight.. Back battery bad, front good. Series circuit. If the back battery is going down in charge, then my educated guess is that the plates in the front battery are going bad, thusly discharging the rear battery. This is to say that there are no taps off either battery for 12vDC. Reason that I am saying this is because I argued with another soldier back in the day in regards to the same issue. He replaced the "DEAD" battery, with a new one, and it went bad. Checked all the connections, cables etc, replaced as needed/wanted. I told him to change the "GOOD" Battery and load check it, bad battery... So look at the non-culprit in this situation, you might be suprised.

Spin

 

[ida34]

The series circuit connection is on the terminals. The terminals can have a bad connection to the battery and the integrity of the series connection is still not compromised. Do I think it is likely? No, but I see no other way for this to happen without a 12 volt draw or a bad battery. I would think a bad connection between the battery and the terminal would trigger a battery imbalance that would fry both batteries.

 

[TedG]

On one of my hmmwv's, the battery(s) were dead. It started the day before without issues. When I went to charge them independantly, I noticed a little spark when I reconnected the negative terminal on the rear battery. I isolated the spark to the 100amp dual voltage generator but it was not the cause of the drained battery. One battery had a bad cell which took down the other cells and other battery.

While on the subject of grounds being clean, do you have the grounding kit installed?