Battery charger not keeping up when AC and Gen are on?

Okay, I will clarify for you – the generator part of the gen set does not have an alternator, the engine part of the gen set does. And, I don't know if, when you don't have a separate starting battery for the generator if it (the alternator on the engine) puts a charge back into your battery bank. I have never turned my convertor off when the generator was running to see if the batteries started losing voltage. However, if as you suggest,the alternator is bad, then the convertor would also have be bad if the batteries were losing their charge in the case as stated and the batteries are in good shape and able to take and hold a charge.
 
You may need a bigger battery charger - my 2004 has a 10 amp side and a 20 amp side. I use battery 2 as my house battery and have the 20 amp lead hooked up to it. I do not have problems running lights/fridge/blower with this set-up.

You can try running both converter leads to one battery so that you can push 20 amps into it and see if that solves your problem. If it does, then you will know what component to upgrade. Be sure to set your battery switch to the battery hooked up to the converter - do not set it to both. This is also a good time to verify that the converter is wired correctly to the batteries - mine came from the factory with both sides of the charger hooked up to battery 2, which is not how I wanted it configured.
 
The following is an incorrect 'if xxx then xxx' statement::

JerryS said:
if as you suggest,the alternator is bad, then the convertor would also have be bad if the batteries were losing their charge in the case as stated and the batteries are in good shape and able to take and hold a charge.
Click to expand...

If the alternator is bad, then the converter is probably GOOD because the batteries are making it most of the night.

I am assuming that the alternator is bad and not recharging the batteries. SO... the generator ENGINE is drawing more amps than the battery charger can supply, causing a drain on the batteries. I would bet this is occuring when the compressor on the AC kicks in and the genny works harder. Eventually the batteries are too low to be useful.

Just because a charger is 'rated 10 amps' does not mean thats what its kicking out. Temp plays a factor and with temps 100+ the amperage takes a huge hit.

In Iraq with 120 temps, our 60,000w gen sets were actually only kicking out a top of 47,000w due to the temp.

(re-worded below, as I was kind of compareing apples and oranges)

OP said the batteries are about 4 months old, so I would discount them for now. What happens if only one battery is selected?
Do you still get through the night or will everything shut off sooner?
 
Last edited:
Thanks for all the great info. After researching last night I have confirmed the Kohler 5ECD does have a 15 amp alternator that should be charging the batteries (Or at least producing about an even give / take) while operating. Next time I'm on the boat I'll take a multimeter and check the voltage of both batteries first with the gen off and then again with it on, but with nothing else active (Blower, converter, lights, etc). The voltage should increase while its on, otherwise I'll check the #6 fuse and see if it's blown, which would stop the charging current from reaching my batteries and lead to a slow battery drain while the gen is operating.
 
I buy into Gary's theory. I suspect the load placed on the batteries with lights, stereo, blower exceeded your chargers capacity. The repeated running down of the batteries has made them weaker and now they can't hold a charge. If they are only 4 months old, return them under warranty and change some of your cabin lights to LED's.
 
having been there on mead and had that same problem. same temps ect. the first thing you need to check, is to see that your converter is putting out. then if the current is getting to batteries.

ours had the circuit breakers disconnected and fuses installed. they had burned out when the batteries ran low on water and over charged.

the batteries would only charge when motors ran and would eventually run down.
 
I did check my generator today to confirm that it does not use the gen set to put a 12vdc charge into the boat batteries. Since I do not have a separate starting battery for the generator, the 12vdc charging system (alternator and voltage regulator is not used). If I did have a separate starting battery, it has a 10 amp circuit for that purpose, hardly enough for a battery bank. I don't believe that those circuits are intended to be used for anything other than keeping a charge in a generator starting battery.
At this point, everybody is just guessing. The OP has not stated:
1. What the output voltage reading for the generator is with the AC unit on.
2. Whether the converter is turned on.
3. If he has checked for blown fuses.
4. What the output voltage is at the convertor.
5. Whether he has had the batteries tested or even looked at them to see if there are any dry cells.
 
Last edited:
chandalen said:
.......
So you have an AC that prob needs 15 amps if not 30 amps. A gen engine that prob needs 8 amps to run, an alternator that should be kicking out 10 amps but lets ignore that for now. Your at 23 amps at least peak, if not more. AT BEST if the battery charger is a true dual bank, and actually does kick out 20 amps at the same time your running -3 amps below what you need.
Click to expand...

I am wondering how you can tell me that I am wrong about something when you are mixing AC and DC requirements. Running the Air Conditioning has nothing to do with the battery charger. The air conditioning raw water pump, fan, and condensor are getting 120VAC from the generator side of the genset, not 12VDC.

The above quote was from post #23 before the writer edited it. It is almost funny, the guy is telling me that I am wrong about a statement that I made, but, it is obvious that he does not even know the difference between AC and DC.
 
Last edited:
Because the battery charger is running off the same 120v system the AC is.

I did edit my post as my explination was compareing apples and oranges. Kept it simple.
 
Last edited:
chandalen said:
Because the battery charger is running off the same 120v system the AC is.

I did edit my post as my explination was compareing apples and oranges. Kept it simple.
Click to expand...

You had to edit your post because you were wrong and the statement "Because the battery charger is running off the same 120v system the AC is" makes no sense. The convertor runs off of the 120VAC from the generator and the battery charger receives it's output from the generator engine. And, in this case, he has a 15 amp battery charger circuit, but, since he does not have a generator starter battery, my bet is that the circuit is not being used.
 
Last edited:
Went back to the boat and discovered the Kohler #6 fuse (15A ceramic) was blown. According to the generator's manual, this is the fuse that controls outgoing 12volt charging voltage from it's internal 8 amp alternator. My onboard battery charger / inverter is only raising the voltage of each battery by .3 volts while the generator is operating it.


I'll replace the fuse and see if the genny is supplying power to the batteries on my next opportunity
 
Bucit said:
I may be missing something but why would your AC run down your batteries? It will only run on 120ac and that is supplied form the genny. It has nothing to do with DC voltage coming form your batteries.
Click to expand...


I was thinking the same thing. Why have the blower going?
 
You must log in or register to reply here.

Forum statistics

Threads
113,187
Messages
1,428,221
Members
61,099
Latest member
Lorenzo512
Back
Top