GEM e825 Error 51 Bad Batteries, or something else as well?

Just purchased a used 2001 e825 4 seater a few weeks back. I knew when I purchased it that the batteries were the wrong type as 5 of them were group 31 Energizers Commercial which they used to sell at Sams Club, but no longer. They are about 2 years old. Oddly, the 6th is an original GEM Gel battery. I know that mixing batteries is not a good thing but was gonna drive it until I need to purchase new ones. Been driving the car for the past 2 weeks with no problems. I let my buddy try and drive it, then all of the sudden an error code 27 showed up. Shortly after, error code 51 came on and the previous code never came back. At this point, the car will no longer work.

I then downloaded and tried the “Drive and Power System Troubleshooting Charts” from the Gem service manual, and stopped at Step 4, to check the Main Contactor and Battery Fuse Connection. Basically it says to measure the voltage at the FUSE connection. I did that and the reading was 40V. I then assumed it had to do with the batteries. I then checked all of the battery voltage and they are all in range (12.6V). Then I performed a load test on each battery. All of the energizer batteries came up “Weak” in around the 10-10.8V range. Surprisingly the GEM gel battery load test was the only good one and held over 12V. I still get the error 51 when I turn on the ignition.

I know that definitely need to replace the batteries, however, are there any other reasons that the cart is not running? I was assuming that even with weak batteries that the cart would still run, and the battery pack would deplete much quicker thus losing range? Also, at resting why am I seeing 40V with the main switch on at the battery fuse connection, when I get 72V off the main switch when it’s turned off?

Any suggestions would be great as I am having a blast driving and understanding how these GEMs go! Thank you!

Depends on where the fuse is.
Low voltage gives error 51.
Check voltage referenced to B-
Voltage at pin 1 on controller needs to be over 68v to start.

Thanks for the suggestion. I checked the B+ and B- leads going to the controller and the reading was about 76-77V. I turned the key to the on position, and it still measured the same volts and the controller did not have any errors. I pressed the accelerator as I checked the voltage, and it dropped all the way down past 30V, then when I released the accelerator it slowly climbed back to 76-77V. I pressed and released the accelerator a few times, which it repeated the same readings.

Prior to all of this, I individually charged each battery (lead acid), and performed a load test on each one, which pretty much all went down to 10.2-10.8V range (WEAK). I’ve already ordered GEL replacement batteries for this car, and should be able to install tomorrow.

So I am correctly assuming it’s definitely the batteries? Thank you in advance!

Batteries or connections.
Test across each battery and each connection to see which one drops.
By connection, I mean from battery post to the wire connected to it.
Start with batteries first.

I checked each battery across the posts to see if any of them dropped in Voltage as I depressed the accelerator, which none of the them did. Is there something else I can check?

Yes, you will have to work your way back from the controller to find where voltage is dropping.
Start with batteries. Either bank. Check across the whole bank. Not from posts but from cable terminals.

A simpler way might be with lights on. See if voltage drops a couple volts when lights are on.
If yes, you can check across each connection to find it.

I checked with lights on, and no drop in voltage. I am assuming now that it is the controller. Since this is a 2001 e825, I’ve been told that the GE T1 has had a bad reputation for failures is not worth rebuilding and good luck finding some out there who can rebuild it. I do have another 2002 e825 car (currently not running but eventually want to build it up) but don’t currently know which controller is in that one. I may switch the controllers if they are the same, but if it is a T2, then I don’t know if I can just swap them or need another wire harness to make it work.

You still need to find where the voltage is dropping.
Either batteries or connections.

i checked across the front bank across the terminals and didn’t see any drop, first the battery up front reading 12.6 v, then across the 2nd battery connection reading 26v, and no drop. I then did the same under the back seat for the four batteries, 12v, 26v, 40v, 52v and each time depressed the accelerator. No drop in voltage. Am I doing the correctly? Also when the cart stopped running originally, I hit a bump going into my driveway, so maybe loose connection somewhere else? Thanks for the responses as I really do appreciate the support!

It could still be between the packs or in the main contactor.

You need to duplicate the voltage drop at the controller. Below 30v. at controller under load.
Then check same using the meter common connected at battery B-. Red lead to B+ at controller.
Same drop or no drop.
If no drop, then neg. B- cable is the issue.
It should be easy to find but hard to explain.

I do not want to hijack your thread but I am having the same 51 code, I drove it last week for a while and put it away and then sat. i was going to drive it, turned the key and the 51 code came up. I checked the voltage and have 76.4 volts at the contactor, the main fuse is good and the 10 amp fuse is good. I did check the charger and it is charging 83.2 volts. Any clues, i hate to think the T2 controller is out.

I am still running the stock power set up, i have not had time to do the lith. conversion yet, everything is still sitting in the shipping boxes you sent me.

Here is where Sentry monitor sw would help you.
So hard to check volts at 23p plug.
51 is telling you the voltage is low on pin 1 when key turned on.
T2 compares voltages from internal 12v buss. Sentry shows that.
If p1 is ok, problem must be in controller.
Have you re-seated 23p connector?