Charging Questions

[John, CD28]

After 30+ years, and several prior owners, the original electrical panel in my Cape Dory 28 was ripe for replacement. So, I bought a mini battery selector switch and a prefabricated electrical distribution panel from Blue Seas Systems, set them in teak veneer plywood to cover the old hole, and wired it up. All works well.

As often is the case, this solution generated more questions:

1) If I run the motor with the battery selector on both (1+2), am I really charging both batteries? Or is my older (weaker?) AGM batter just sucking power out of the newer AGM battery?

2) Can the 70amp alternator (w/built in voltage regulator) on my little Beta 14 pump out enough amps to actually charge two group 31 AGM batteries at the same time without burning up?

I'm not much of an electrical wizard, so any and all ideas are greatly appreciated.

John
CD28 #241
Tantalus

[Paulus]

Both batteries will see the charging voltage of around 15V - the battery that is weakest will allow the most flow, splitting what is available, i.e. the 70A max.

A bad battery would "take" the 15V without allowing too much flow to it; a good battery will accept more current.

Picture a gravity tank with a supply to two lower receiver tanks with an upside down T - opening a valve to one vs opening both willnot increase the available flow. a bad battery would present a restriction in flow.