Generator doesn't charge batteries

[MGRodems]

I have a 4-100 AH AGM house bank that is charged by the engine, 640 watts of solar, and shore power via the converter (charger). The 6kw genset runs well but is rarely used. On a 66 day trip this summer around the Great Lakes, I fired up the genset and noticed that it was not charging my batteries. It ran everything else as if I was on shore power. If I switch from shore power to genset, I lose the charging of the batteries. The converter breaker doesn't trip so all connections are the same - just the source is different. What could be causing this?

Any ideas?

[cr180]

Interesting problem. Theoretically, the converter charger should function as long as the AC input voltage is above minimum input voltage prescribed by the vendor. Have you checked generator output voltage? I ask because mine was low and had to adjust generator speed (rpms) up to correct.

[tenchiki]

One would think that 6KW would be enough to run any charger, however some chargers won't run if they don't think they can get enough current. Also, do the frequencies match?

[MGRodems]

Both the genset and the converter are original equipment (1988), but appear to function properly otherwise. I will check the voltage output on the genset next.

[Squanderbucks]

Even without the onboard battery charger you should get some charging from the alternator on the generator if it has one - mine does.
If the genset is running and all other AC voltage items on the boat are running except the battery charger then I would expect it to be a break in the wiring or open circuit breaker. Also, on my installation there is a high amp inline DC breaker on the bulkhead near the batteries that gets tripped sometimes if the battery is way down and tries to charge (i think that is why). Anyway resetting it allows normal charging.

(1.) Check AC breaker to the Charger (does it turn on) and if not (2.) does it have power to it, (3.) check any DC breaker in the charging line to the battery, and (4.) see if there is an alternator on your genset.

If there is a break in either the AC line to the Charger or the DC line to the battery it could likely be possibly a wire crimp that has come loose or failed.

[Stu Jackson]

Originally Posted by Squanderbucks

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If the genset is running and all other AC voltage items on the boat are running except the battery charger then I would expect it to be a break in the wiring or open circuit breaker........................
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Yup, can't think of anything else.
Maybe it never did run the "battery charger" part of the system.
Or something that previously worked stopped doing so.

Who knows?
ONLY the skipper, at this point. Need to do some wire tracing, for starters. Or some DVM work. Asking us can't help, not the same as being there, is it?

[Cadence]

If it worked in the past and isn't now with the gen. running everything else, it's probably time for wire tracing. Remember to trace both not just the "hot". check the switch or relay whichever is applicable for burnt contacts.

[Capt. Ray]

The generator's alternator should only be connected to it's cranking battery not house banks.

Originally Posted by Squanderbucks

Even without the onboard battery charger
you should get some charging from the alternator on the generator if it has one - mine does.
If the genset is running and all other AC voltage items on the boat are running except the battery charger then I would expect it to be a break in the wiring or open circuit breaker. Also, on my installation there is a high amp inline DC breaker on the bulkhead near the batteries that gets tripped sometimes if the battery is way down and tries to charge (i think that is why). Anyway resetting it allows normal charging.

(1.) Check AC breaker to the Charger (does it turn on) and if not (2.) does it have power to it, (3.) check any DC breaker in the charging line to the battery, and (4.) see if there is an alternator on your genset.

If there is a break in either the AC line to the Charger or the DC line to the battery it could likely be possibly a wire crimp that has come loose or failed.

[waterman46]

Originally Posted by Capt. Ray

The generator's alternator should only be connected to it's cranking battery not house banks.

Yes, your generator probably has a separate winding and rectifiers to produce about 14V at low current for maintaining the start battery. It’s a completely separate system from the main AC output.
Since know your charger works when you have the switch in SHORE position and connected to shore power, and all your other AC gear works when you run the generator, it seems the fault must not be in the switch or the wiring anywhere. Seems that the converter is connected to generator but is not getting the right AC voltage or frequency from the generator.
At least check the AC voltage of the generator with charger switched off and on and especially when battery charge state is low ( high current demand). You should have a permanently installed AC voltmeter but use a DVM also.
Many AC devices are tolerant of variations in frequency and voltage. Heaters, incandescent bulbs, stoves, toasters. What do you run that does work OK on the generator power? Did this problem only happen on your trip when the batteries were already discharged or does it happen even when batteries are fairly well charged already?

[AlanR]

Originally Posted by tenchiki

One would think that 6KW would be enough to run any charger, however some chargers won't run if they don't think they can get enough current. Also, do the frequencies match?

Battery chargers don't think, they sense a low input voltage if they draw more current than the generator can supply.

What frequency do you expect from a DC generator?

The OP does not mention a charger, maybe he expects the 12 volt output from the generator to charge his batteries, but he needs a higher voltage from the battery charger.

[smac999]

Originally Posted by Squanderbucks

Even without the onboard battery charger you should get some charging from the alternator on the generator if it has one - mine does. .

It would only be charging the gen battery. Or the battery that starts the gen. Which is likly Not the house.

[hatchetjoe]

A few months ago I posted about the same problem on my Albin 28. The house and engine batteries charge fine on shore power but they do not charge if I am on generator power. However, I found that if I run my air conditioner (AC) while on generator power the charger will then charge the batteries normally. Sometimes I can stop the AC after about 10 minutes on the generator and the charger will continue charging other times it stops as soon as the AC turns off. I assume that the modified sine-wave from my small generator (NextGen 3.5 kw) is not compatible with the original onboard charger (ProTech 1230i) but is changed or modified by the AC running. My portable 15 amp Victron Blue Smart Charger works fine if I plug it into an outlet while the generator is running. I hope you can find an answer to your problem and post it.

[MGRodems]

Thanks for all of the great responses. I don't think it is the switch or wiring since I can switch the sources from shorepower to genset and back and get the charger to function properly when in the shore power position. I will check the voltage and play with the loads to see if I find anything out. I am currently not aboard or in the water since I just returned from a 66 day Great Lakes summer trip and had to haul out upon returning (no slip available), so it may take a while to figure it out.

Again, thanks for all of the responses.

[Captain Bill]

Some battery chargers will not work if the power is "dirty" or the current is too far out of phase with the voltage. Depending on the type of voltage control on your genset this could be caused by a capacitor going bad. Resistance loads are usually not sensitive to this but electronics are. Most modern battery chargers are computer controlled and do not like power that doesn't meet their input specs and will not turn on. You didn't specify the brand of genset or the method of voltage regulation it uses, so it's hard to tell if this applies to your setup or not.

[Be Free]

Originally Posted by Captain Bill

Some battery chargers will not work if the power is "dirty" or the current is too far out of phase with the voltage. Depending on the type of voltage control on your genset this could be caused by a capacitor going bad. Resistance loads are usually not sensitive to this but electronics are. Most modern battery chargers are computer controlled and do not like power that doesn't meet their input specs and will not turn on. You didn't specify the brand of genset or the method of voltage regulation it uses, so it's hard to tell if this applies to your setup or not.

I've seen generators with "dirty" power get "cleaner" when there is a little more load on them. Put a little more load on the generator and see if the battery charge starts working.