Separate Charging Systems ?

[SV Demeter]

My Perkins 4-154 currently has 2 alternators on it. One is smaller and appears to be an OEM Motorola probably 55amp but is not wired up. The other is a 100amp Balmar with a nice bracket and good sized belt. This is doing the charging now but we are going to be redoing most of the wiring as there is an isolation diode being used to charge the start battery.

I am considering setting up the original smaller alternator to charge the start battery and as a back up for the balmar. Will get the old guy cleaned up and tested int he process.

My other consideration was to just set it up as a back up alternator and use either a an ACR or the Digital Duo to charge the start battery.

Thoughts on either of these charging solutions?

[btrayfors]

Either way would work OK.

Since you already have the smaller alternator for the start battery, why not just leave it that way.

If your battery banks are wired to a 1-2-ALL-OFF switch, you could always use either alternator to charge either/both battery banks.

You're right to lose the isolation diode. Eliminate one source of problems. And, if the smaller alternator turns out to be a dud, just use an EchoCharge or DuoCharge to maintain the start battery.

Bill

[idpnd]

You're right to lose the isolation diode. Eliminate one source of problems.

I was thinking about using an isolation diode for my separate starter battery project - what's the issues with that please?

[btrayfors]

Voltage drop which, if not accounted for, leaves battery undercharged. Potential failure of diodes.

Much better to use an EchoCharge or DuoCharge type device to maintain the start battery.

Bill

[DeepFrz]

Voltage drop which, if not accounted for, leaves battery undercharged. Potential failure of diodes.

The voltage drop of course is eliminated if the sensing wire comes from the battery side of the diode, preferably directly from the battery bank.

Yes, diodes do fail, but so do EchoCharge or DuoCharge units. By replacing the diodes you are not eliminating a point of failure, you are just replacing one with another. I have never seen any study that shows that one type of battery separation is more reliable than another.

[btrayfors]

Deep,

I hear you, but differ somewhat.

1. In many typical alternator installations there is no sense wire.

and

2. While I agree it's possible, I have never seen an EchoCharge fail. I have seen isolators fail...just threw one in the trash last week.

Guess you just pays your money and takes your chances :-)

Bill

[SV Demeter]

Im not interested in the isolation diode approach. The thing gets warm which tells me its wasting energy. Im wondering whether I should use the small alternator as a spare or as both a spare and as the charging source for the engine battery. If I do then I dont need to buy an ACR or Series Combiner (echo charge Digital Duo). By adding the series combiner do I add any redundancy? I suppose I would need a second multistage regulator to charge the start battery as I probably would not want to rely on the old school solid state regulator. Not even sure what sort of regulator is connected to the smaller alt. might be internal even.

[btrayfors]

I believe you really ought to spend an hour or so discussing options with a qualified marine electrician. You'll feel a lot better about your decisions.

(I'm not volunteering, but could recommend a good electrician if you want).

Bill