altenator overcharging

[killick]

Sometime ago I raised the problem of my rebuild altenator charging at 15 to 15.6 volts. The general consences was that as long as it is charging only for short periods no harm will be done and that I should check the electrolite level in the batteries on a regular basis. This I have done and experienced no problems. The other day I ran the engine under load on the pontoon for about 30 minutes charging both batteries . Checking the batteries some 20 minutes later I found one cell in the starter battery boilling and both 15 amp fuses connecting the barreries to the solar panel regulator blown. The batteries are 50 amp Exides and appear to be normal lead acid. The dealer says it is lead calcium but I cannot find any indication of this on the batteries. Any asisstancs will be greatly appreciated. I am removing the altenator to have it bench tested.

 

[ianj99]

Which regulator are you using?

The built in ones usually regulate at about 14v. External smart regulators can go up to 15v depending on what type of battery they are set for, and the ambient temp so you do still have an overcharging problem.

 

[killick]

The solar panel has an external smart regulator which is functioning fine. The regulator on the alternator is part of the unit and is not functioning properly

 

[RAI]

Sounds like your alternator regulator needs fixing. It should output 14.4 V not over 15 V.

 

[pvb]

Why would a faulty alternator cause the fuses to blow on the solar panel charging feed?
.

 

[Bobobolinsky]

The solar panel has an external smart regulator which is functioning fine. The regulator on the alternator is part of the unit and is not functioning properly

Alternator regulator has failed, change it, it will kill your battery, maybe your LEDS. If you have a smart external regulator, you could route the alternator output through it

 

[killick]

It does not make sense but that is what happened

 

[Mistroma]

Alternator regulator has failed, change it, it will kill your battery, maybe your LEDS. If you have a smart external regulator, you could route the alternator output through it

It sounds as if the external "smart" regulator is primarily for the solar panel. If that's the case, I doubt it would be up to the job.

 

[killick]

The exrernal regulator is in fact dedicated to the solar panel and I would hesitate to wire the alternator through it

It sounds as if the external "smart" regulator is primarily for the solar panel. If that's the case, I doubt it would be up to the job.

 

[macd]

The dealer says it is lead calcium but I cannot find any indication of this on the batteries.

You probably wouldn't expect to, any more than a battery might describe itself as a lead-antimony battery. Both are used to add mechanical strength to the lead plates. The calcium alloy is claimed to reduce water-loss compared to antimony.

 

[nigelmercier]

Sounds like your alternator regulator needs fixing. It should output 14.4 V not over 15 V.

The output of a smart alternator regulator can easily be over 15V, it is what it measures at the battery that matters.

 

[killick]

The 15.6 volt was measured at the battery and one cell was boiling about 20 minutes after the engine was stopped

The output of a smart alternator regulator can easily be over 15V, it is what it measures at the battery that matters.

 

[pvb]

The 15.6 volt was measured at the battery and one cell was boiling about 20 minutes after the engine was stopped

Was the solar panel still connected? When you say "boiling", do you mean gassing or actually hot?
.

 

[nigelmercier]

The 15.6 volt was measured at the battery and one cell was boiling about 20 minutes after the engine was stopped

That's not OK, unless the regulator had gone into a high voltage conditioning or de-sulphation cycle.

 

[macd]

I doubt this is relevant to the OP's issue, but it may be of interest to others reading a thread on batteries boiling excessively. A couple of years ago I had this same problem on my last boat. I eventually tracked it down to a loose earth connection to the Sterling regulator. I presume that each time the contact broke, the regulator set itself to a new cycle, ramping up the voltage.
Installing a secondary earth lead helped me sleep better.

 

[killick]

Was the solar panel still connected? When you say "boiling", do you mean gassing or actually hot?
.

The solar panel was connected. By boiling I mean that the electrolite was actually being forced out under pressure like boiling water. The battery was not hot to touch.

 

[pvb]

The solar panel was connected. By boiling I mean that the electrolite was actually being forced out under pressure like boiling water. The battery was not hot to touch.

If the engine had been off for 20 minutes, and if the solar panel was connected, it would seem likely that it's a solar-related problem.