wrote in message
oups.com...
I am trying to understand the functionalities of a batteries-isolator
and a batteries-combiner. Based on reading about this subject in books
and in this newsgroup, I have these understandings. I would like
people to check if my understandings are correct or not:

- They both prevent a weak battery from draining the strong battery
when those two batteries are in parallel (such as when we switch the
battery selector to BOTH).

- They both have to do with charging by an alternator.

- They both have nothing to do with from which battery that we get the
power from (the battery selector controls this). This means regardless
which device that I use I still need to remember to turn the battery
selector to the house battery when I have stopped the motor; otherwise,
I still may run down both the starting battery and the house battery.

- The isolator costs a 0.7 volt loss of charge that significantly
increases the charging time. That's unless we have something called a
remote regulator that we normally don't use in an outboard motor. The
combiner doesn't have this problem.

- The isolator generates a lot of heat (coming from the loss of 0.7
volt), and need good ventilation around the isolator. The combiner
doesn't have this problem.

- The isolator is a simple device that doesn't tend to fail. The
combiner may not disconnect fast enough under some circumstances (that
I don't quite understand).

- The isolator is cheaper than the combiner.

Is my understanding correct? Thanks in advance.

Jay Chan


Understanding not quite correct. With an Isolator, is pretty much as you
state, but you just leave the battery switch on 1 or 2. Whichever you want
for starting. Same with the combiner, but the combiner is a relay, that
will stay engaged until the battery voltage on one of the batteries drops
below about 13.5V To start from the battery being charged by the combiner,
you still have to switch the dual battery switch. I run a combiner on my
boat, and run the electronics off the #2 battery. I had to add an extra
disconnect switch for the electronics, as they are wired direct to the #2
battery. The starter gets power from whichever battery the dual batterytch
points to. Normally #1.