Are 12V batteries hooked up in series or parallel?

[Bobfirst]

I feel stupid asking but only one way to learn !

[Overland]

Parallel for 12 volt.  But to make sure that it's confusing, if you get the AGMs, then they're 6-volt and will be paired, two each in series then the two sets are paralleled.

 

There's a diagram in the back of the manual that shows exactly how they should be connected.

 

[attachment file=Screen Shot 2018-11-26 at 6.11.38 PM.png]

[Bobfirst]

Does one battery tender monitor both 12V batteries since they are in parallel?

[Overland]

That’s correct, though battery monitors and chargers don’t really care how the batteries are connected. Some are more advanced, but in general they just look at the voltage of the system as a whole to determine the state of charge.

[RnA]

A 6 volt battery has 3 cells in series @ ~2 volts.  A 12 volt battery has 6 cells in series.  Same as hooking 2 6 volt batteries in series.  The voltage adds as cells are added in series.  The amp-hour capacity stays the same.  Two 6 volt 100 amp-hour batteries in series will be 12 volts 100 amp-hours.  Two 6 volt 100 amp- hour batteries in parallel will be 6 volts 200 amp-hours.  I say ~ 2 volts per cell because at full charge and rested a 6 volt battery is really closer to 6.3 volts and a 12 volt battery is closer to 12.6 volts or ~ 2.1 volt per cell.

 

A good resource is Harold Barre’s book <u>Managing 12 Volts - How to Upgrade, Operate and Troubleshoot 12 Volt Electrical Systems.</u>

 

-Randy

[topgun2]

Hopefully I'm not stepping on anyone's copyright toes but I found this over on the Fiberglass RV Forum:

 

http://www.marxrv.com/12volt/12volt.htm

 

http://www.marxrv.com/12volt/12volta.htm

 

Bill

[ScubaRx]

"Are 12V batteries hooked up in series or parallel?"

 

12 Volt batteries are always hooked up parallel if your intention is to keep the system at 12V.