Generator Battery not charging

[Bartlett Bob]

I have a 1997 DB 400 with Westerbeake Genset. The battery keeps discharging while at dock. Boat is plugged in to shore power which shows operational on both legs. Battery Maintainer is on and maintaining the main batteries, no problem.

Mounted on a 2 x 4 post behind the Genset battery is a small black box with a red rectangular push button that is between the Genset battery and maybe the main batteries or charger/maintainer. Can someone tell me the function of this switch/breaker/?

 

[Stee6043]

Any chance you could share a photo of the "black box"? Your generator battery should be connected to your charger/converter in the same way as your main batteries, generally.

 

[Bartlett Bob]

I am going over there is a few minutes and will take a picture of the device. l will post this afternoon

 

[bbwhitejr]

I have a dock neighbor who kept losing gen battery. I have never really figured out if they are/are not connected to the battery charger. His was not. His is a 8kw Kohler that had a ceramic fuse blown. He replaced it and all good for the past 18 months or so.

Bennett

 

[dtfeld]

Most Sea Rays of this size with the CAT engines with have dual Group 31 for the main engines and a separate battery for the generator. All should be connected to the battery charger, and that connection would not be interrupted by the battery solenoids, so essentially a direct connection. Sea Ray did not install fuses between the charger and battery that I have seen.

It very well could be a bad charger, a bad leg in the charger, or a bad battery. All pretty easy to check and eliminate as a first step.

Without a picture of what you have, it’s hard to tell what that might be but likely aftermarket.

 

[ttmott]

Those red buttons are the charger/converter circuit breakers. Is there a "50" (50 amps) on the button?
Open it up and take some voltage measurements on both sides of the breakers.
Looks like this?

 

[ttmott]

If that battery was changed and they did not remove the AC power then touched that Pos battery cable to a ground it will trip that circuit breaker.

 

[dtfeld]

This is the DC layout from the Sea Ray Owners Manual for the 400 DB. Not specific to the 1997, but likely pretty close. It shows a 50A breaker on the generator that is between the converter and battery. That breaker is popped, would prevent the charger/converter from maintaining the battery.

However, the generator battery is directly connected to the genertor, so as long as the alternator is charging and you have a good battery, you should be able to start and run the generator.

 

[dtfeld]

Your original post refers to “operational on both legs”. You should have 3 charging circuits, at least if you have the original converter/charger.

 

[Bartlett Bob]

Wow, thanks so much for all of the input from everyone, very informative. As it turns out, there is a thermal fuse on the cable from the charger to the generator battery. see picture below. I couldn't get my glasses and old eyes down there to see it but taking the picture answered all of the questions. Great Idea Stee6043. The circuit breaker is tripped so that is why my battery is not charging. Not sure what caused it to trip but will reset today and then keep an eye or camera on it!

dtfeld, when I said both legs operational, I meant shore power (both 120 volt legs of incoming AC) sorry if I confused you. I guess maybe my battery was low and when I hit start the genset tried to start using too much power from the battery maintainer causing a thermal fault???? just my logic. Anyone wish to chime in on that?

 

[km1125]

You might want to get that generator battery tested. There really shouldn't be any load on it other than starting the generator. It should last FOR MONTHS without getting a charge, and the generator itself should be recharging that battery every time the generator runs, so if you are even running the genset once a month for an hour or so the genset battery should NEVER get low enough to not start the generator.

That said, I know a lot of folks tie their battery charger into the generator battery. If you do that, then there should be a circuit breaker close to the battery so that any short in that line would be protected from the genset battery causing an overcurrent condition.

Not sure what you mean when you write "I guess maybe my battery was low and when I hit start the genset tried to start using too much power from the battery maintainer causing a thermal fault????". If the battery was in poor condition and could not supply current to the starter, even though it's being charged by the charger, and you hit the "start" button, you could cause an overload condition to the charger and cause it to fault out. I had a Guest charger that would do that and resetting power to the charger would clear the fault. NOT a problem with the charger, it would be a problem with the battery not being able to supply enough current.

 

[Bartlett Bob]

Thanks KM1125, I just got back from the marina, I had the battery on a handheld automotive charger over night and I disconnected it as it said the battery is fully charged. I checked the voltage of the battery with no charger or load and it read 12.8 volts. I reset the yellow lever on the thermal circuit breaker and the voltage jumper to 13.8 volts so the onboard boat charger is charging thru the breaker.

I then tried to start the genset and while the solenoid will click and the shut off solenoid will turn on the fuel, but the generator will not turn over. I suspect not enough amps due to a dead cell or two. Apparently someone borrowed my jumper cables that I keep on the boat so I will buy another set and then jump from one of the CAT engine batteries to the genset and see if that spins the generator. If so bad bat. process of elimination and still learning about the boat after 4 years.

 

[ttmott]

Thanks KM1125, I just got back from the marina, I had the battery on a handheld automotive charger over night and I disconnected it as it said the battery is fully charged. I checked the voltage of the battery with no charger or load and it read 12.8 volts. I reset the yellow lever on the thermal circuit breaker and the voltage jumper to 13.8 volts so the onboard boat charger is charging thru the breaker.

I then tried to start the genset and while the solenoid will click and the shut off solenoid will turn on the fuel, but the generator will not turn over. I suspect not enough amps due to a dead cell or two. Apparently someone borrowed my jumper cables that I keep on the boat so I will buy another set and then jump from one of the CAT engine batteries to the genset and see if that spins the generator. If so bad bat. process of elimination and still learning about the boat after 4 years.

Did you read the bat voltage after that?
I suspect the battery is kaput.
Put one of the others on the generator and see if it cranks.

 

[ttmott]

The charged voltage doesn't tell much other than it is holding a surface charge. The only way to determine the health is to measure the specific gravity of the electrolite. Which you can't do on many modern ones.

 

[Nater Potater]

The charged voltage doesn't tell much other than it is holding a surface charge. The only way to determine the health is to measure the specific gravity of the electrolite. Which you can't do on many modern ones.

That, or perform a load test. Arguably the only reliable way of testing a (fully charged) battery: https://www.harborfreight.com/100a-...e=go&utm_medium=social&utm_campaign=shortener

 

[The Bill Collector]

Thanks KM1125, I just got back from the marina, I had the battery on a handheld automotive charger over night and I disconnected it as it said the battery is fully charged. I checked the voltage of the battery with no charger or load and it read 12.8 volts. I reset the yellow lever on the thermal circuit breaker and the voltage jumper to 13.8 volts so the onboard boat charger is charging thru the breaker.

I then tried to start the genset and while the solenoid will click and the shut off solenoid will turn on the fuel, but the generator will not turn over. I suspect not enough amps due to a dead cell or two. Apparently someone borrowed my jumper cables that I keep on the boat so I will buy another set and then jump from one of the CAT engine batteries to the genset and see if that spins the generator. If so bad bat. process of elimination and still learning about the boat after 4 years.

You shouldn't need to jump, just use the battery emergency switch which connects all your batteries together.

 

[km1125]

If you had "a dead cell or two", then you would have NEVER measured more than 12v once the charger was removed. Each cell contributes about 2.1V to the overall status, so "a dead cell or two" would -at best- result in you measuring 8.4 to 10.5 VDC on the battery. Since you did measure more than 12, it's likely the battery is highly sulfated, which would result in VERY HIGH internal resistance. THAT is what makes the battery unable to deliver amps when it looks "fully charged".

All of that is also assuming you're ruled out one of the most basic things, that being the actual connections between the battery and the generator. Both on the positive and negative sides of the circuit.

 

[km1125]

That, or perform a load test. Arguably the only reliable way of testing a (fully charged) battery: https://www.harborfreight.com/100a-...e=go&utm_medium=social&utm_campaign=shortener

They also sell this unit:
https://www.harborfreight.com/digital-automotive-battery-analyzer-66892.html

Which can test a variety of batteries and tell you more about what's going on inside the battery. The clips that on on it though are VERY CHEAP, so if you get one either be very careful with those or plan on replacing them with a better set.

 

[techmitch]

That, or perform a load test. Arguably the only reliable way of testing a (fully charged) battery: https://www.harborfreight.com/100a-...e=go&utm_medium=social&utm_campaign=shortener

They also sell this unit:
https://www.harborfreight.com/digital-automotive-battery-analyzer-66892.html

Which can test a variety of batteries and tell you more about what's going on inside the battery. The clips that on on it though are VERY CHEAP, so if you get one either be very careful with those or plan on replacing them with a better set.

The first link posted is only a 100 amp unit. A proper "starting" battery test involves bringing the battery to full charge, letting it sit for at least an hour or two and then load testing with a tester that will pull 200 amps for 10 seconds. The battery should not drop below 10 volts and bounce back fairly quickly depending on cranking amp rating.

As to the second link. You really need to spend a lot more than that to get a good electronic digital battery tester.
Note: lead acid, agm, gell, and others all have different charge and testing equipment, specs. and requirements.

 

[km1125]

....As to the second link. You really need to spend a lot more than that to get a good electronic digital battery tester.
Note: lead acid, agm, gell, and others all have different charge and testing equipment, specs. and requirements.

You certainly CAN spend more, but you don't really NEED to. I've used that very tester on hundreds of batteries and so far it's been very predictable telling a good battery from a bad one. We use a much more expensive one in the commercial business. That more expensive one hasn't been any more accurate in the good/bad battery diagnosis, but it it MUCH more durable. We would have destroyed dozens of the HF units if we opted for those, but paying a premium is certainly worth it in that case.

Oh, and that first tester? Not my link, but the "100A" is what the unit draws for the test. The meter is "calibrated" for up to a 1000A CCA test, so it should work reasonably well to determine the relative capabilities of a battery.