2001 F-250 7.3l diesel that I keep a battery tender on during winter but my failed and replaced alternator last week has me questioning some things. Is one battery on the starter and the other the accessories or do they all feed together? Do I need to be charging each battery independently or can I just hook up to one to charge?

 

On trucks with diesel engines, the two batteries are wired together in parallel. In effect, they are one big 12 volt battery, but with TWICE the cranking amps that a single battery could provide. Which the diesel engine needs. You could just hook up to one battery to charge them both, but if you could hook to the positive on one and the negative on the other, that might be marginally better.

 

overthinking here.. but true

due to the different lengths of the battery cables... one battery works a LITTLE harder then the other..

but to your question .. as stated to the above post... Yes Parallel..

 

 

Overthinking . . . perhaps. There is a British web site by a company that deals primarily with marine battery banks. I was surprised to see the way they claimed the math worked out. That said, with only TWO batteries, probably not worth worrying about.

SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

 

Thanks all. Very helpful.