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Old 06-08-2011, 12:11 PM   #1
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Charging 6 Volt batteries in series

Hi all,

I am going to buy a pair of 6 volt batteries and am curious if there's anything special I need to do for charging.

Typically, during the winter I remove my batteries from the RV and leave them in my garage on a workbench where I can check them periodically and charge them with my battery charger.

My questions are this:
1. With the batteries in my garage (not wired together), can I charge a single 6 volt battery using my 12 volt battery charger or do the batteries *have* to be wired in series for charging?
2. With the batteries installed in my RV, how do I charge my two 6 volt batteries wired in series (NOT in parallel) using my 12 volt battery charger? (i.e. I connect the positive battery charger cable to the first positive terminal on the 6 volt battery--the same positive terminal that is connected to the RV. Then I connect the negative battery charger cable to the second 6 volt battery--the same negative terminal that is grounded to the RV, right?)
3. Any other gotcha you can think of (i.e. inline fuse for gas detector--can't remember the amp)?

Any help would be appreciated!
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Old 06-08-2011, 12:45 PM   #2
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Hello,

On 1) No, you cannot use a 12 volt charger on one 6 volt battery. You might consider a Battery Minder made for 6 volt batteries. They can handle up to 3 batteries at once. If a 6 volt Battery Minder, you would hook your 6 volts batteries in parallel if doing both of them.

On 2) I believe your connections are correct.
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Old 06-08-2011, 01:10 PM   #3
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Good questions. I had to research this one myself when I picked up my trailer with new 6-volts last week. Your chart is correct and how I connect my 6-volts.

I use a 12-volt charger with the 6-volts connected in series. I understand that the charger and the batteries must match volts.

I was going to ask a related question here anyway, but since you brought up the topic ...

Can anyone tell me if the charger can be hooked up to the batteries while the batteries are connected to the trailer or does the RV- and RV+ wires in the chart above need to be disconnected first?
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Old 06-08-2011, 01:22 PM   #4
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That question troubles me too. I know that others have posted that they charge the battery with it connected to the trailer with no issues. My "smart charge" at times puts 16.0 volts into the battery when it is doing some "equalizing". That worries me a little to have it connected to the trailer then. Normally I believe that 14.4 volts or so is the bulk charge. Will 12 volt electronics withstand 16 volts? Anyone know?
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Old 06-20-2011, 06:31 PM   #5
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Yeah, I would like to know if this type of connection to the charger is correct as well, before i try it out on my camper, with a new B&D charger next week......
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Old 06-20-2011, 10:33 PM   #6
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A week ago, I bought my 6 volt batteries from Interstate and asked the tech there if I can charge them while in the RV, he said that it would be no problem. I do have a battery disconnect that I enabled and I am charging the batteries now (while connected to the RV).

The batteries are awesome! Just got back from a four-day trip and the batteries didn't get below 12.7.
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Old 06-20-2011, 11:15 PM   #7
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yes u can charge two 6 v. bat in series. after all, on a standard 12 volt bat, u are charging 6 cells in series.
my gut feeling is that 16 volt charging voltage would not hurt 12 volt circuits. would think u would be more apt to have a problem with the plates of the battery, if that.

my comfort level would be a lower charging voltage than 16. u should be able to exceed by 10%. i use 13.8 as my base line so i personally would get concerned above 15.
i wouldn't try to use a 12 volt charger to charge a single 6 volt bat. u could do it but u would have to put something in series to give a constant 6 volt drop...like 10 silicon diodes in series.

very interesting question.
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Old 06-21-2011, 10:17 AM   #8
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Quote:
Originally Posted by MikeInColo View Post
A week ago, I bought my 6 volt batteries from Interstate and asked the tech there if I can charge them while in the RV, he said that it would be no problem. I do have a battery disconnect that I enabled and I am charging the batteries now (while connected to the RV).

The batteries are awesome! Just got back from a four-day trip and the batteries didn't get below 12.7.
Good to know. I also have a battery disconnect and thought that should work but you never know.

Quote:
Originally Posted by jimh View Post

my comfort level would be a lower charging voltage than 16. u should be able to exceed by 10%. i use 13.8 as my base line so i personally would get concerned above 15.
i wouldn't try to use a 12 volt charger to charge a single 6 volt bat. u could do it but u would have to put something in series to give a constant 6 volt drop...like 10 silicon diodes in series.

very interesting question.
I agree about the higher voltage. My Trojans need a 14.8 volt charge to charge effectively. I haven't tested the trailer's converter to see if it can put out that many volts but my Stanley charger does and it works fine.

This reminds me, in the past we had charged a single six volt battery with a 12-volt charger doing something similar to your diode trick, but ours was a homemade shunt that brought the volts down.
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