GBM wrote:
"Jeff" wrote

My personal preference is for an EchoCharge, which is only a few
dollars more. In fact, I was willing to buy one even though I already
had a combiner similar to the ACR. My issue is that I frequently
discharge my house bank and then spend an hour or more charging at
fairly high voltage. A combiner would be overcharging the starting
batteries during these times. The EchoCharge allows the starting
batteries to trickle charge, while the house bank getting 90 Amps.


Jeff,
If the combiner is set to close the contact at say 13.5v, my concern is that
with House at low level, this might not happen before I want to turn the
engine off, so the starting battery gets no charge at all! This would
presumably be true for Echo-Charge too.

I don't follow. Unless you have a real dead battery, which can screw
up all the readings, the alternator will put out 14+ Volts right from
the beginning. The contacts will close and both will be charged. The
starting battery should never be less than 90% so it should get close
to fully charged while you're warming up the engine.

There are cases (hopefully rare) when you'll have to do some charging
just to get the house bank up to a reasonable state, but you don't
want to combine a dead house bank with the starting bank anyways.

A trickier issue might be charging from a weak source, such as a solar
panel.



Regarding the Echo-Charge vs ACR. In the case of the combiner, once the
contact closes, the alternator "sees" both batteries. Wouldn't the current
flow distribute itself where needed?

The current will "distribute itself" but there will be one voltage,
and that may be too high. In my case I use AGM starting batteries
which can be killed by overcharging.

But you do raise a question: if the regulator is instructing the
alternator based on its perception of the battery state, how does it
tell the difference between the house bank and the starter bank? You
must make sure that everything is sensing at the correct point. For
instance, I had to disconnect the alternator from the starter and
starting battery since the primary recipient of the juice was to be
the house bank.

These issues convinced me that the EchoCharge was the way to go: the
output of the alternator went to the house bank, so the regulator's
sense was driven by that. The EchoCharge acts as a second regulator,
doing the proper thing for the starting bank. The only bad scenario
is a dead starting bank and a full house bank - this requires some
special jumpering, either a switch (as I had in my previous boat) or a
jumper wire (which I have provision for in my current boat).

I have read that the current to the
starting battery should be limited by the wire gauge used.

Dangerous thinking there - small wires limit current with a voltage
drop. The reduced voltage may prevent the battery from overcharging
but the wires will be heating up! Also, it means that what the
regulator thinks is a trickle charge will be no charge at all at the
end of the voltage drop.

I think I read
that oversizing the connections can cause problems such as too high a
current flow through the combiner. In the case of the Echo-Charge, how does
it "control" the current flow? Is it just a resistor?

I don't know the internals, but I'm sure its not a resistive load -
that would generate heat, which it doesn't do. There are lots of ways
to do it with modern components. If you buy a 15 Amp battery charger
how does it control the flow when the socket you plug into can deliver
200 amps? It certainly isn't by wire size!

Perhaps someone with a deeper understanding of electronics will
correct me, but I've never heard that "oversized" wires cause a
problem by passing too much current. On the contrary, the voltage
drop can really mess up any attempt to regulate the charge voltage.