Wiring two batteries in to one

[Bone Collector]

Hey guys, I was wondering how to wire two batteries together but keep it a 12 volt system? Also once this is done do I have to wire my on-board charger to both of the batteries or just one?

 

[redbug]

here yo go...
https://www.zbattery.com/seriesparallel-pf.html


you will want to charge them separately

 

[russ010]

red to red, and black to black for 12v system (parallel)

I have 4 batts on my boat, and I charge them together (2 batts at same time)... as long as your batteries are of the same size, brand and age (really important) you can charge them together. however, it's really best if you do them separately