Battery School, generator start with two "almost" identical batteries

[henni]

Given these two batteries, one in a 7000w generator, the other in a jumpstart

What is significant in that they could not both function as a Generator start battery ?

Shotgun AGM 12V 10Ah 255CCA
Neptune AGM 12V 22Ah 235CCA

The Shotgun was originally in a Honda generator, the Neptune in a JNC660 jumpstart

True, they are different sizes but connection cables exist.

Trying just to learn if there is something about initial amps when engine cranks that would prevent one (Neptune) from handling what the other (Shotgun) does.

The Honda starts just fine from pull start, even without any battery.

 

[jhellwig]

Never mind I see what you are saying. They will both work to start a generator. An engine that size doesn't pull that hard that it will matter.

 

[bullwinkle]

I’ve used my JNC-660 to start the Predator 13 HP engine on my log splitter lots of times. The engine even charges it back up while it’s running (IIRC coils under the flywheel).

 

[fantastic]

Are you just wanting to connect them in parallel to use them both at the same time to start the generator. If so that should work fine so long they are the same nominal voltage ("12v"). The other issue is their age between the two. It's not advisable to use a much older one with a newer battery. If I've misunderstood you...It's getting late...LOL

 

[eljefino]

You'll be fine, they're within a rounding error in CCA spec and the bigger battery will have an easier time and longer life.

 

[henni]

OK, thank you for all replies.

So apparently, while these were built for different purpose, nothing else to be aware of, for example, internal BMS that would prevent Neptune to act as starter battery ?

 

[Jetronic]

a jumpstart IS an external start battery, why would that BMS stop that?

Parallel connection is fine, both will give what they can according to their internal resistance, the one with lower resistance will provide more curent.