Battery question - hooking two batteries (marine and car/truck) together
 

On Aug 13, 7:54 am, Short Wave Sportfishing
wrote:

You need to determine what the charging rate is for your alternator.
As Rob said, it should be somewhere around 6 to 8 amps. I don't think
you mentioned the size of the engine - that would help a little.

Wow - great response. Thanks to all - I'm soaking up all the info I
can. To answer this question, I'm running a 115 hp Johnson outboard.

Matt

Battery question - hooking two batteries (marine and car/truck) together
 

On Mon, 13 Aug 2007 12:58:11 -0400, Gene Kearns
wrote:

On Mon, 13 Aug 2007 11:31:46 -0400, Wayne.B
wrote:

http://tinyurl.com/2gsqak

I like the description of this one better:
http://tinyurl.com/2hw397

That's an isolator, not a combiner, big difference. The combiner is
an automatic switch and there are no voltage losses, basically a smart
relay.

An isolator uses diodes to keep one battery from discharging the
other, and the diodes have a forward voltage drop, typically 0.6
volts. That makes it impossible to bring the batteries up to full
charge unless the alternator has an external sense wire, and most do
not. It's possible that this may not make any difference with an
outboard but I'm not sure. The diodes will create power losses in any
case, that's why they are mounted on big heat sinks.

I've used both and greatly prefer the combiner. I've got two of the
150 amp units on my trawler so that both engines or either one can
charge the inverter bank when under way. They work very well and have
a lot of protective logic built into the switch.