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Old 05-11-2014, 07:08   #1
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Battery charger shows 18volts WHY?

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.

Due to negligence I have managed to kill my engine battery due to a complete lack of electrolyte, and have now installed a new one.

Anyway, I decided it was time to trace all the wiring of my charging system which consists of one Balmar 100 amp alternator that feeds the engine battery and a 160 amp alternator that looks after the house bank.

Both field wires and ground go to my Next Step regulator and are tied together on the one tab for each.

As far as I know this system has been performing OK since I bought the boat a year ago and so I paid it no mind but now I have this overcharge thing going on and I can't get my head round how this one controller can regulate two separate charging circuits.

And why have I got 18 volts coming out of the Balmar, and could this have been the reason I boiled away all the electrolyte on the old battery and never noticed this fault.
The house bank fed from the other 160 amp alternator is working as it should, never above 13.6v.
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Old 05-11-2014, 07:24   #2
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Re: Battery charger shows 18volts WHY?

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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.

Due to negligence I have managed to kill my engine battery due to a complete lack of electrolyte, and have now installed a new one.

Anyway, I decided it was time to trace all the wiring of my charging system which consists of one Balmar 100 amp alternator that feeds the engine battery and a 160 amp alternator that looks after the house bank.

Both field wires and ground go to my Next Step regulator and are tied together on the one tab for each.

As far as I know this system has been performing OK since I bought the boat a year ago and so I paid it no mind but now I have this overcharge thing going on and I can't get my head round how this one controller can regulate two separate charging circuits.

And why have I got 18 volts coming out of the Balmar, and could this have been the reason I boiled away all the electrolyte on the old battery and never noticed this fault.
The house bank fed from the other 160 amp alternator is working as it should, never above 13.6v.
Figure out where voltage sensing goes and you'll likely find your answer...
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Old 05-11-2014, 09:54   #3
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Re: Battery charger shows 18volts WHY?

Hi Maine sail, The battery sense wire on the Next Step goes to the house bank, or do you mean the wire on the cockpit volt meter. I also had the same reading on my multi meter when I checked it at the engine battery terminals when the engine was running.
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Old 05-11-2014, 09:59   #4
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Re: Battery charger shows 18volts WHY?

With the house bank at a lower voltage the dual service regulator is telling both alternators to put out full power (or at least high power). The alternator that feeds your house bank is charging the house bank just fine. But the alternator that is charging your start battery is putting out way too much current, which raises the voltage, because the regulator is sensing the house bank voltage.
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Old 05-11-2014, 10:19   #5
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Re: Battery charger shows 18volts WHY?

I think you have just proved why having two separate alternators and batteries tied to one regulator is a really bad idea. Get a separate simple regulator for the Balmar and make sure it senses the start battery voltage.
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Old 05-11-2014, 10:27   #6
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Re: Battery charger shows 18volts WHY?

As the other Don says. The only way this system could have worked within reasonable range of normal is if you have a 1-2-Both switch and parallel the batteries while charging. In that case the Both position will maintain both batteries at the same voltage and send the charging current where it is needed. Not saying that is the system I would design/use, but that could be the original intent of whoever put in the system the way it is.

If you are going to do separate charging then you need separate regulators. While we call them "voltage regulators" they aren't really. The regulator/controller senses voltage and then changes the alternator current output to maintain the desired voltage. But there is no voltage regulation in the sense that the controller somehow limits the voltage that can go to the battery, the voltage of the system is really driven by the battery and the current you are putting into it.

In your system the regulator/controller is seeing the house voltage and telling the alternators to put out a fair amount of current. The starting battery then goes to the voltage required to accept that current, which in this case is 18V and plenty to cook the battery (and possibly damage any connected electronics).
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Old 05-11-2014, 12:06   #7
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Re: Battery charger shows 18volts WHY?

OK, thanks guys I now see things more clearly. When I bought the boat it did have the 1+2 switches wired in such a way that they could be parallel. After reading some stuff in Nigel Calders book about house banks and engine batteries being separated I decided to rewire the switches, and actually replaced them as they were passed their sell by date.

One reason for me changing the arrangement was that when we first bought the boat there seemed to be something that was always draining the engine battery, which we couldn't trace immediately so separating the engine battery seemed a quick fix solution, which seemed to work.

This new situation only came to light when I discovered a fault on the "old" next step regulator. Turned out that the field wire was always live, shorted between the battery+ in wire. This meant that the alternators were being fed current even when the ignition was switched off and were warm to the touch, hence a dead system when we got back on board after a week away.

With a new Next Step fitted this problem went away but quickly showed up this over voltage thing from the Balmar, which I could switch off, luckily.

So I think you've cracked it, I'll rewire the 1+2 switches to how they were until I can buy another regulator for the balmar as I quite like the idea of two separate charging systems.

Thanks a bunch folks
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Old 05-11-2014, 12:13   #8
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Re: Battery charger shows 18volts WHY?

Each alternator should have its own regulator. I have been paralleling two alternators into the same 12 volt system for over twenty years and have never had a problem. There is no such thing as "feedback" from one alternator to the other. All an alternator knows is the system voltage and will create more current until it reaches the regulated voltage.
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Old 05-11-2014, 12:33   #9
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Re: Battery charger shows 18volts WHY?

Hey Don, you said just get a simple regulator for the Balmar, do you have any suggestions as the Next Step NS2 seems very pricey at $299 or is that about right for what I need.
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Old 05-11-2014, 12:34   #10
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Re: Battery charger shows 18volts WHY?

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...
This new situation only came to light when I discovered a fault on the "old" next step regulator. Turned out that the field wire was always live, shorted between the battery+ in wire. This meant that the alternators were being fed current even when the ignition was switched off and were warm to the touch, hence a dead system when we got back on board after a week away...
Field current frequently doesn't show up in monitoring system because of where it gets taken off. Most Balmar (and most standard) 12V alternators have a 2.4 Ohm winding, which means the max. field current is 6A. If you had two alternators connected and a live field current that would be a 12A continuous draw. These faults can be tough to find, because, as you noted a short to the B+ at the regulator can cause field current to flow and yet it probably doesn't show up on your consumption monitor.
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Old 06-11-2014, 10:37   #11
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Re: Battery charger shows 18volts WHY?

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.
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Old 06-11-2014, 11:08   #12
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Re: Battery charger shows 18volts WHY?

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Hey Don, you said just get a simple regulator for the Balmar, do you have any suggestions as the Next Step NS2 seems very pricey at $299 or is that about right for what I need.
You should be able to get a regulator which puts out a fixed 14.2v for under $50. You have to be careful, as the Balmar is designed for a field circuit which goes from the 12v+, through the regulator, through the brushes, and to ground, while many alternators have a field which goes from the 12v+ to the brushes, to the regulator and then to ground.

I'd give Smith Co a call at 970-353-3121 and have a talk with them--they are a big ebay seller of alternators and regulators.
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Old 06-11-2014, 11:34   #13
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Re: Battery charger shows 18volts WHY?

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You should be able to get a regulator which puts out a fixed 14.2v for under $50. You have to be careful, as the Balmar is designed for a field circuit which goes from the 12v+, through the regulator, through the brushes, and to ground, while many alternators have a field which goes from the 12v+ to the brushes, to the regulator and then to ground.

I'd give Smith Co a call at 970-353-3121 and have a talk with them--they are a big ebay seller of alternators and regulators.
Also check the manual for your particular Balmar. Some have a built in regulator that you can "activate" by shorting from one terminal to another. Mine has this which I consider to be an excellent "get home" feature if I have a regulator failure.
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Old 06-11-2014, 23:48   #14
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Re: Battery charger shows 18volts WHY?

get a 2nd regulator. or change the engine one to internal reg. keep the batterys separate

even if you move both alts to house bank I wouldn't split the field. that is way too much current for the regulator to power both. I'm surprised you're not blowing reg. fuses. probably doesn't have one! or was oversized.
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Old 07-11-2014, 04:56   #15
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Re: Battery charger shows 18volts WHY?

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that is way too much current for the regulator to power both. I'm surprised you're not blowing reg. fuses. probably doesn't have one! or was oversized.
Most of the Ample regs and the Balmar MC-614 can easily drive two alternators, they were designed to be able to do this. With two alts feeding the same bank, so they are properly sensed, one regulator, such as the above, can drive two alts. This would not be my first choice but it can be done..... The MC-614 can drive 20A to field, for typical bulk durations, and could run at 15A continuously.
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