Batteries being overcharged.

[SimonA]

I have an Adverc battery management unit fitted which is flashing a green light (It's done this since I brought the boat last year). I thought this meant the battery was charging but have discovered it means it's overcharging.

Today I put a voltmeter across one of the batteries to see how many volts it's getting while charging. It seems to jump about all over the place from 13.5 to 14.7 and flickering up to 17 volts for a split second every so often.

I disconnected the Adverc unit and it made no difference at all to the voltage.


My set up is 2 batteries being charged from one engine alternator with the Adverc unit.

Should the voltage from the alternator jump about all over the place or remain fairly constant?

 

[claudio]

The voltage should be constant. I would check all connections from the alternator to the batteries. Measure the voltage drop from the +ve terminal of the battery to the +ve terminal of the alternator. Do the same with the -ve terminal of the battery and the -ve terminal of the alternator. There should be hardly any voltage drop, 0.5V max but depends on charging current. If the voltage is 'jumping' around then you've got a faulty connection. If its not then its probably a faulty alternator, have it checked out by an auto electrician. Good luck.

 

[claudio]

Actually, after re-reading your post, I would suspect a rectifier diode has gone down in your alternator and it is passing AC to the battery.

 

[SimonA]

Would I be able to tell if it's the rectifier by changing the voltmeter to AC? I presume there should be no AC current present.

 

[claudio]

Yes, yous should be able to detect AC if you switch the meter to the AC reading and connect it across the battery.

 

[andy_wilson]

No idea about an Advec, but a couple of thoughts, or 3

One method of high-rate charging is to provide an alternating voltage above and below the gassing point, something like 13.5 / 14.5 V.

Secondly there may be a setting for standard wet cells, gel electrolyte and AGM batteries, which have diiferent charging characteristics and therefore charge settings.

Thirdly, it could be just faulty, but I would check all the connections first, bad sensors could provoke bad charge levels.

 

[William_H]

It sounds like something is making then breaking contact. The first thing I would check after obvious lose wires is the condition of the brushes and slip rings of the alternator. Intermittent contact will give intermittent charging.
olewill

 

[Danny]

Does your alternator/Adverc setup use remote sensing of the battery voltage? This would be an extra wire coming back to the Adverc, probably from one of the battery terminals or from the common side of the battery changeover switch. It's worth checking the connections if you have this arrangement. The voltage sensed on this wire is used to control the alternator output.

 

[pampas]

If it made no difference when disconnected then its your regualtor thats gone.