Parallel 12v battery wiring

[takingatrip1]

I added an additional battery and have some confusion as to how to apply the solar charging leads and how to apply the load leads for the camper.

Parallel connection positive to positive / negative to negative I got that part !


But which way to connect the rest ? I am currently connected like option 1 below but not thinking thats the best way. Option 3 or 4 maybe ?

 

[MarkBC]

I like #4. it 'encourages" the most uniform distribution of charge and load. I have a similar setup, and that's how I have mine. But #3 is almost as good.

(And, if your parallel-connecting wires are heavy enough gauge and tightly, cleanly, connected to the posts (i.e., minimum resistance to current), even 1 & 2 aren't bad.)

 

[wuck]

See if I can do this on a tiny phone screen!

Don't use #1 or #2, as battery #2 will never get the same charge as battery #1. Battery #2 has the extra resistance of both interconnect cables in the charging path so extra loss trying to pump charge into it.

Circuit #4 is nearly as good as #3, except the sensed voltage - the voltage the charger reads to determine charge voltage/current is a bit off as the load (camper) now has those two interconnects in the path. With circuit #3, the charger senses the true battery voltage regardless of load, just like it is a single battery.

 

[Wandering Sagebrush]

In my opinion, three is your best bet.

 

[takingatrip1]

Thanks Mark, Ive got the wire length and hardware to do # 3 right now and was advised 4 was the best way so I'll get the parts for that next.

 

[craig333]

How much better? I'm currently doing #1 because it was much easier to wire that way. I'm not arguing 3 is better but by how much?

Worth going to the trouble to rewire my batteries?

 

[takingatrip1]

See if I can do this on a tiny phone screen!

Don't use #1 or #2, as battery #2 will never get the same charge as battery #1. Battery #2 has the extra resistance of both interconnect cables in the charging path so extra loss trying to pump charge into it.

Circuit #4 is nearly as good as #3, except the sensed voltage - the voltage the charger reads to determine charge voltage/current is a bit off as the load (camper) now has those two interconnects in the path. With circuit #3, the charger senses the true battery voltage regardless of load, just like it is a single battery.

Thanks for explaining this...even I understand

 

[wuck]

Craig, I haven't done the math on the difference. With the big cables you added the difference is negated to some extent. If we were building electric vehicles with the high currents involved then circuit 3 is a must have. In our campers at the lower charge and discharge currents maybe not so much. If you're disinterested in re-re-wiring and just want to go camping (yea!) Maybe swapping the battery positions annually would help even the wear.

 

[craig333]

I have a plan for rewiring it down the road. Not in any hurry to get it done. I'm too keen on swapping 75# batteries around.