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Old 07-11-2014, 05:58   #16
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Location: W Carib
Boat: Wildcat 35, Hobie 33
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Re: Battery charger shows 18volts WHY?

Quote:
Originally Posted by shantycrew View Post
I'm puzzled.

1. How can I have 18 v and 26 amps going to a fully charged engine battery.

2. How can two alternators be controlled by one Next Step regulator.

....
First off of course, stop the 18V charge before you bake your batteries, if you have not already.

Specifically, which NS do you have?

Re NS controlling two alternators. The older NS's field output circuit was designed for sufficient amps to handle this, the new ones are not. If you connect two alternators to a newer NS, it will work for a little while, but will ultimately damage the NS, which is likely what has happened. The correct way to install a newer NS with two alternators is with their "alternator driver" for the second alternator.

When my old NS developed problems (after about a decade of good service), I replaced it with two newer NSs, one for each alternator, this has the advantage of full redundancy too.

There is a thread on Ample Power's support forum about twin alternator installations. And, in my experience, their support has been excellent.
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Old 07-11-2014, 06:12   #17
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Re: Battery charger shows 18volts WHY?

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Originally Posted by cwyckham View Post
I think you've found the problem, but your solution is wrong. The engine battery uses virtually no Amp-hours to start your motor. There is no way that you need a 100 Amp alternator on there. It's a total waste of all that charging power.

A better solution would be to wire both alternators to your house bank and then use a cheap "echo charge" from your house bank to your engine start to keep it juiced up.

I would still consider two regulators, though. Most high output regulators should have temperature sensing on them (and on the batteries for that matter) and you couldn't really do that with a single regulator.

Maine Sail may have an opinion on running two alternators from one regulator (even into the same bank). Hopefully he'll chime back in.
+1. Way over amped just to charge a start battery. A lot more benefit to dumping all those excess amps into the house bank.

A solution to consider, which is not hard to implement, is to route the charge from both alternators into the house bank and then automatically parallel the start batteries to charge them. The NS even has an output specifically for this purpose. Using this feature, when battery voltage sense (wired to house bank) is 13V or greater, the NS will energize the parallel pin. This pin is wired to a solenoid which parallels in the start bank. A standard properly rated continuous duty solenoid can be used.
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