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Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 14406
Experience:  Certified on Onan and Generac generators
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I have a Generac Gaurdian 17KW Standby generator. The battery

Customer Question

I have a Generac Gaurdian 17KW Standby generator. The battery will not hold a charge for more than 3 or 4 weeks. I have replaced the battery now 3 times and even had someone come out and ensure the trickle charger is working properly. I don't know if something is draining the battery or what is going on. When working properly the generator does come on once a week for about 10 minutes. Otherwise, it sits there in standby mode. Please help.
Submitted: 5 years ago.
Category: Small Engine
Expert:  Hank F. replied 5 years ago.

Thank you for choosing Just Answer for the solution to your problem.
My name is XXXXX XXXXX I am going to assist you with this.


What is the model number of your genset?


How did you test the trickle charger?


Customer: replied 5 years ago.



Thanks for your interest. I think its model number 005885-0 or 005886-0. Here is a link to the Generac Site showing my unit.


Its 2 years old so I don't know if anything has changed since I bought mine.


Regarding the trickle charger, I actually had the company that installed the generator come out and they tested the charger several ways. The final method was by removing the battery leads and testing between the positive cable to the negative battery post. The reading was 2.4/2.5 amps. They seamed very confident that the charger was working; however, every 3 or 4 weeks the battery goes dead. As I mentioned earlier, I have even replaced the battery several times to ensure it was not just a fluke.


Thanks again for your assistance in this matter. Its very frustrating and huricane season is almost here.





Expert:  Hank F. replied 5 years ago.

How strange.


The charger was tested correctly - by the amp output.

And it is working overtime.

The max output should only be about 2.5A, and it should only put this out if the battery is very low.

If the battery is fully charged, it should only put out about 0.2 amps.


The first thing I have to mention is that if this set is only 2 years old, it should still be under warranty.

If so, you really need to let a Generac representative take care of it.

Working on the set yourself could very well void your warranty.


The problem is that the charger is built into the control board, so it can not really be isolated from the system - at least not easily.


If I were working on this set, what I would do would be to go to the set and take the cover off the control panel.

I would disconnect the wire number 56 from the starter relay (to keep the engine from trying to start while I do all of this).

Then I would CAREFULLY disconnect the small wires marked N1 and N2 from the terminal block. CAREFULLY, as these wires carry 240 volts. I would cap them off tightly to keep them from shorting out.

Disconnecting the N1 and N2 from their power source will disable the charger on the board.

Then I would remove the positive battery cable from the battery.

I would take my multimeter and set it to DC Amps, and connect the red lead to the positive post of the battery, and the black lead to the battery cable.

this would tell me if there was a draw on the battery while the set is sitting idle, with the switch in AUTO.

There should be no noticeable draw.

If there was, then it gets really hard, trying to find it.


Hank F., Technician
Category: Small Engine
Satisfied Customers: 14406
Experience: Certified on Onan and Generac generators
Hank F. and other Small Engine Specialists are ready to help you
Customer: replied 5 years ago.



One point of clarification, the trickle charger is actually located in my transfer switch. Are you saying there is another part of the charger located in the control board?


I certainly won't try to fix this myself. Can you recommend anyone in the North Houston area by chance.



Expert:  Hank F. replied 5 years ago.

Not another part of the charger - another charger period, by the sound of it.

This controller has a charger built right into it.


Which transfer switch do you have?


I do not know anyone in that area, except a cousin I haven't seen in about 10 years.

But I can get you a list of all the authorized dealers in that area, if you would like.


Customer: replied 5 years ago.
I have the transfer switch from the 20KW unit. There is a trickle charger in that transfer switch. I know of a few authorized dealers in the area, I just don't know if they are any good, but I will try one of them. Thanks for your information. I will pass it on to the tech when I get one out to look at the unit.
Expert:  Hank F. replied 5 years ago.

There are 95 authorized dealers within 50 miles of Houston.


If you want to take a peek at them, go to


Good luck with it all.


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