BoatBanter.com - View Single Post - The Similarities and the Difference Between a Batteries-Isolator and a Batteries-Combiner

JR North wrote:
The 50 amp Combiner from West Marine is the cat's pajamas for smaller 2
battery boats. Mine works perfectly. The .7 V loss through an isolator's
diodes is a major drop in charging voltage to the batteries.
wrote:

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

Thanks for the suggestion of the West Marine combiner. Seem like it
costs just a little bit over an isolator. This really makes sense for
me to get a combiner instead of an isolator. Then, I can avoid the
0.7-volt loss of charge.

Jay Chan