Here is my entry to the "Stump the Forum" contest.

I'm trying to remotely assist a family member troubleshoot/repair an issue with a 18kw natural gas standby generator at his home. Apparently, it stopped starting for the no-load test on a weekly basis like its supposed to, and there isn't an authorized service provider able (or willing) to come out and look at it in a timely manner.

Bubba the neighborly shade tree bolt stripper says that "the battrey done blowed up" and it needs a new one, plus a diode.

I'm trying to get better info, and am looking at what I can find on the Internet, but I have a basic question that the online manuals don't seem to answer.
Would a unit this size (18kw, single phase) (model #20RESA) have an engine mounted alternator to charge the 12v battery, or would it instead rely on the supplied 120vac powered battery charger to keep the 12v battery topped off?
Logic tells me that since 120vac should always be present - either from the street or from the unit itself - then the charger is all it needs.

Not sure what diode Bubba is talking about either.

Thoughts?

I happen to have one on the farm and can tell you that there is no alternator. There's a "battery charger" in the engine diagram, which I assume is what you suggest - basically a trickle charger. No alternator.

Your friend's generator should have an LED panel on the inside, perhaps displaying a fault code?

The test run is usually programmed through the transfer switch anyway, so the problem may not be with the generator itself.

What does it do when it's scheduled? Assuming he knows when it's scheduled (and that the internal clock is set correctly), it might be useful to have someone at the transfer switch to watch the lights and at the generator (with the panel off) to watch the LED and see if any messages pop up.

We had ours decide to stop running the weekly cycle once. It would still kick on if I flipped the main, but it wasn't doing it's weekly test cycle. I just followed the procedure to reset/reschedule it at the panel and it seemed to do the trick.

I do all the maintenance on the generator, and in nearly 10 years now, it's only ever needed the basics (oil change, spark plugs, air filter).

FWIW, the battery isn't anything special. Just normal auto. Not even AGM. Does he have a load tester? (A decent enough cheap one is < $50 on amazon.) Even a multimeter he knows how to use - at least to figure out if the thing has juice?

I can't believe he can't find an electrician to come charge him way to much to look at it!

Good luck.

-Rob

I have a Kohler 8 KW.
Indestructible.
Sizing the battery- I put the largest battery I could with the most cold cranking power in the battery compartment.
Only a trickle charger as Rob stated--may only need to reset the schedule for weekly startup.

Check four fault codes and read manual and troubleshooting guide. 3rd hand remote troubleshooting is not the easiest thing in the world.

I had trouble for awhile with a 45KW diesel Koehler generator.

It often would not start for the schedule or when commercial power went out. It would attempt to but not turn over or start and then stop several times.

I thought it was the battery at first but then it would start every time from the manual start switch which ruled out the battery.

It turned out to be the control wiring coming from the automatic transfer switch.

The genset was mounted to the front of a semi trailer that contained a mobile MRI (65,000 lb trailer) and apparently the wiring was rubbing and exposed some of the copper conductor which would short out during cold weather.

Not saying it could not be the batteries...I did have to replace the batteries on a 2000KW generator at a hospital I worked at in San Antonio a few years.

My 20KW had an issue once, it would turnover but not start. Turned out to be a wire had vibrated loose from a connector.

Unfortunately I am not a mechanic so I can't tell you what wire or what it was connected to, but it was a small wire on the back side of the motor.

Usually no to engine mounted alternator.

Battery blowed up may be just a bad battery or an overcharged and damaged one (bad or unregulated charging circuit). The diode may be a reverse polarity diode to prevent connecting the battery backwards. Bubba may be on track if he can check the charging circuit for problems.

AS others have said hard to trouble shoot long distance.

Kohler generally uses either an alternator or a very small inverter/charger that is powered by the generator end to keep the battery charged when it's running.

Check the oil level. Most gensets have a low oil level kill switch, to keep it from using it all and trashing the engine. This fixed my cousin's Generac about 10 years ago, and I am still a hero! It may need a battery as well; hers had frozen and cracked due to not being charged for way too long.

Can it be manually started from the panel?

Of course, like stated above, check fluid levels first and on a regular basis.

The answers to your post are pretty much summed up by the replies. No alternator, trickle charger built in to the unit and weekly run cycle. A new battery or even a jump start ( not what I would do, but that is just me ) will tell you if the battery is the issue. Watergoat has a good point as well, mine when down for that reason one time but it was easily fixed.

Bubba knows all. Either the battery died or the battery exploded.

I service my uncles Kohler gen every year. About 2 years ago the same thing happened to his. Its a known issue with the battery charging system. The system is overvolting the battery and that combined with the constant charging of the battery can cause it to explode.

When not in use the battery is charged from the house's electrical. He should have a circuit breaker either on his house's electrical panel or on or near the transfer switch.

The diode pack bubba was talking about will reduce the voltage. It also has a relay on it to cycle the charging system on and off as needed.


Have them turn off the breaker supplying power to the generator.

Call kohler customer service and ask them to send him a Diode kit. The kit is free. They will probably need the serial # of the generator.

Turn off the charging system circuit breaker
Remove the old battery
Install the diode kit
Install new battery
Turn back on the charging system circuit breaker
Input the date/time and exerciser schedule. Instructions in the gens manual can be downloaded from kohlers web site.

The diode kit is easy to install. Install video:

https://www.youtube.com/watch?v=Oa30yTEFxkY

Update-

So the battery was really done. Top was loose, split. Chunks of the sides were completely separated, and there was electrolyte in the battery well.
I didn't even bother to have him check the voltage across the terminals - no point.
Don't know if it froze and popped, or shorted and exploded. Either way, a new battery was required.

So he pulled out the remains, cleaned up the spilled electrolyte, and headed to the auto parts store. Bought a new battery, installed it and reset the date/time/exerciser settings, then tried it out. Started up fine, and ran OK.
Then it started as scheduled via the exerciser.

So now the only question is the charger. Seems to be reading a steady 14.1vdc at the battery. Right after it started, the indicated voltage dropped to 12.2v, then slowly climbed back up.

Seems a bit high to me. But I'm 600 miles away, so additional troubleshooting is tough. But this matches exactly the issue outlined above by Motomag, so we are certainly on the right track.

Right now, I'm having him cycle the voltage once a week, and if it stays stable, maybe it'll keep from blowing up again until I can visit and lay hands on this thing. That's currently looking like February. Going to call Kohler Monday morning and inquire about the warranty deal.

Any other thoughts?

Typical charge voltage for an automotive battery is 14-14.4 volts.

Agreed, but not a constant 14v with no load. Also, I have no easy way of determining how many amps its pushing at that 14.1vdc. Thats my larger concern.

My current plan is to keep the 120vac breaker feeding the generator turned off, except for a 30 minute period each week. At the same time, he will run the gen for its weekly exercise.
I shouldn't need that 120v for the ATS to do its thing if they lose power, right?

quote:

Originally posted by motor59:
So now the only question is the charger. Seems to be reading a steady 14.1vdc at the battery. Right after it started, the indicated voltage dropped to 12.2v, then slowly climbed back up.

Seems a bit high to me.

It sounds normal to me. You actually charge batteries above their nominal rate. If you put a meter on your car battery while it is running, it likely charges to at least 14 volts.

Interesting question that led me down a path.

I have a 2017 model Kohler 14kw RESA. Looking at the electrical schematic on page 55 it shows that the battery charger input/output is part of the RDC2 controller. So I took some panels off of mine and physically traced the 120v input wires from the terminal block to the RDC2 controller and from there they go to ground and hot on the starter and feed to the battery.

My unit reads a consistent 13.2-13.4v DC on the control panel. I manually started the unit and using a multimeter watched the battery. After starting it went to 14.4v for about 30 minutes and dropped back down to 13.6 for another 20, then 13.3 since then. My battery is less than 9 months old sealed gel Duracell battery. I do not have an inline amp meter otherwise I could tell you the amp draw. I also can't find a schematic for the controller itself, but I assume for mine it is 12v 6a because see below.....

Following the path, it seems that the previous generation of home standby Kohler's had the charge controller as a separate unit in the generator or in the transfer switch if you bought it as a kit. In these units the charge controller is a 12v 6a for the 14/20kw and a 10a or 15a for larger units. Those controller bulk at 14.2-14.4v and float the battery at around 13.2v

I did not see anything about the "diode kit" but assume that is something related to the units that use AC power trough a DC rectifier? I honestly don't know.

Hopefully this is info you can sift and doesn't confuse the situation more.

Update-

Kohler is sending me the diode kit at no charge. Should arrive in 7-10 days. Interestingly, they were pretty cagey about the purpose for this kit; the rep wouldn't come right out and say that it corrects a problem - only that it drops the charging voltage by a volt or so. Whatever... I wish I could see the actual service bulletin that addresses this situation.

I did get a text message that the unit cranked but did not start this weekend for the periodic no load test.

So now I need to find a time when we're both free for some more remote diagnosis work. I really hope that we don't need to go back to Bubba... it turns out that he's the nearest Kohler authorized service provider. Since he was apparently more than willing to sell us (for $110.00) the diode kit that is being sent at no charge by the manufacturer, my trust level is low.

Sigh...

quote:

Originally posted by motor59:
Update-

Kohler is sending me the diode kit at no charge. Should arrive in 7-10 days. Interestingly, they were pretty cagey about the purpose for this kit; the rep wouldn't come right out and say that it corrects a problem - only that it drops the charging voltage by a volt or so. Whatever... I wish I could see the actual service bulletin that addresses this situation.

I did get a text message that the unit cranked but did not start this weekend for the periodic no load test.

So now I need to find a time when we're both free for some more remote diagnosis work. I really hope that we don't need to go back to Bubba... it turns out that he's the nearest Kohler authorized service provider. Since he was apparently more than willing to sell us (for $110.00) the diode kit that is being sent at no charge by the manufacturer, my trust level is low.

Sigh...

Chances are that Kohler isn't giving Bubba the kits for free, or Bubba simply didn't call and ask them. A lot of times manufacturers have an inherent issue and hope the end user just pays for them.

A question about the weekly no load test run. Is that recommended somewhere?

Our (Outback) solar system fires the Kohler residential 8KW generator for 15 minutes on the first Sunday of the month to exercise it, but that is just once a month. I'd think that the weekly start wear and tear would be excessive and overkill, but what do I know?