This has always been a problem with running a 24v system and expecting
it to charge from a 12 v engine battery.

I suggested running a battery isolator connected to a third battery
(house battery), a 2000w mod. sine wave power inverter to step up from
12v DC to 120v AC,then using the 120v charger to fill the trollers
BTW, the charger would be 24v, supplying each battery (2-12v series)
@10a. each . I had it all drawn out, but the 'client' didn't want to
disturb his origional engine wiring to install the battery isolator.
No problem, after all it's his boat and not mine. Evidently it
wouldn't be do-it-yourself friendly enough for him, besides extra
weight and equipment etc, etc....

Then just recently he sen't me a link to this:

http://atkinsonelectronics.com/manuf...fs/MBCM-24.pdf

After reviewing the products schematic, I gave my opinion. FWIW

"I like it. I like everything about it. I see exactly what they're
doing and it makes a lot of sense. The trolling batteries are now
independent and the unit itself does the switch over instead of
having them hard wired in series with each other. I studied out the
first two tables, and it's simple to install. no modification to the
original wiring harness is necessary. Just a bolt-on operation. plus,
if necessary, you can jump start the engine battery from the trollers
if need be.

I dont' know how much extra is the 'auto-start' feature is,and I don't
know how necessary it would be but I thought that was cool too.
Batteries get low and you can have the engine start itself for
charging. Of course, the start up engine noise might scare off some
fish at the wrong moment, but....

Also, I'm not sure how much of a charge rate you'd actually get in the
trollers if you're only running a short distance. If you're only out a
couple miles out and run the trollers flat, I'm not sure if running
back that two miles would give a sufficient charge to them, because
now you're maintaining 3 batteries, instead of one. but then again.
it's trial and error on that part.

But I think these guys are on to something, and no more than it really
costs I don't think you could go wrong with it.

Just my simple opinion. and thanks for the link. it's interesting!"

Tim

So... I did some more looking around and have found that these have
some pretty good independent reviews. Not mere company propaganda.

So if you're trying to charge 24v out of 12v. this might be the way to
go.

Jsut thought I'd pass this along.