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Old 08-28-2017, 07:16 PM   #1
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batteries in series..

I want to add another battery to my fifth wheel. Do both batteries need to be identical?

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Old 08-28-2017, 07:28 PM   #2
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In theory they SHOULD be identical, but I've seen many mismatched battery models that are running in tandem. I run two "29" series deep cycle marine batteries in my fifth wheel because I have a pure sine wave inverter for supplying good clean 120v power while boondocking for a short time.

However, you always want to connect batteries in parallel unless you are attempting to increase voltage. Parallel is positive to positive and negative to negative. You can connect any number of 12 volt batteries in parallel and still stay at 12 volts.

You can connect two 6 volt batteries in series (one battery positive to the other battery negative) and then you will have 12 volts from the solitary positive on one battery to the solitary negative on the other battery. Forest River electrical engineers do not recommend this arrangement for the existing converter that is installed in their units.


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Old 08-28-2017, 07:31 PM   #3
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If you have a battery and you are adding another one to add capacity, you want to add in parallel not series. As for what kind, you want the added battery to be the same battery technology ( probably flooded Lead Acid), same capacity and close in age. You are probably OK with 6 months to a year in age if you have not abused the existing battery.

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