Batteries losing 25% power sitting with key off

I had an earlier post thinking I had a problem with my charger, however it seems that my batteries are charging normally and then discharging rapidly. For example, if I disconnect the charger soon after a full charge, the batteries indicate 79V( I think) tested under the dash (within 30 minutes or so of the completion of charging). Showed something like 86V while charging. Within an hour it had already dropped to 75.7V and then down to 74.5V within a few hours. The dash still indicates 100% charge though. What are some number to use for comparison? Shouldn’t 100% charge be around 76V? If I just leave it plugged up for a day and come back to check on it, the dash will show 72%. I clearly have something wrong, just trying to figure out what. Is the charger pulling down the batteries after it charges? Are the batteries running down even without the charger because of some other cause? I did notice some current running through the frame when it was plugged in one time. The batteries are a few years old but have been fine, aside from short run times (Which I attribute to whatever problem I appear to be having). Any help will with troubleshooting the problem be greatly appreciated. Thx

You have one or more battries that are shot. Check them with a hydrometer the next day after charging.

Also try shutting off the main disconnect switch.

Thanks for the tip. I checked the batteries with the main switch off. Overnight they ran down to 76.3V from 79.somethingV immediately after the charge. They held 76.3V throughout the entire day with the switch off. However, previous to that, with the switch on, they ran down to 74.2V in about 4 hours. So I suppose I have a short or something pulling a draw on the system. Do you have any suggestions for things to check? I haven’t intentionally changed any wiring recently. It does have a radio installed that has been in for a couple years. Thx so much for your help.

The correct finish voltage should be 75.6. This is because each battery should be 12.6 with six 12 volt batteries or 8.4 with nine 8 volt batteries. The high reading observed immediately after charging is known as the surface charge. This will dissipate after an hour or so. My suggestion is to run the GEM hard until the batteries are weak and then carefully test each battery. If one or more is less than 12.7, it is likely bad. You are looking for differences in the voltage between the batteries. Just a few tenths of a volt indicates a bad battery. If all batteries read the same, then look elsewhere. It is unlikely that all of the batteries will wear out at exactly the same time.


Thanks Daniel. I have been messing with it off an on for a few days now. I just saw this response so I have not run the batteries down to test yet. I have six 12V batteries and they can hold between 76 and 76.4V with the switch off. I let it sit for 5 days with the switch off and they only ran down to 76V. I have pulled the two fuses from the main board (individually) to see if the batteries would not run down while switched on, but they still did. I have visually inspected all wires that I could see and they look good. With the cable removed, I tested from last battery positive terminal to the disconnected battery cable to see if there was a draw and it showed 72ish volts with the switch on so I assume that test didn’t mean much. Someone had recommened testing the batteries with a hydrometer but I don’t have one. I will get one this week and check. I appreciate you taking the time to help. I will report back with the volts once I run them down. Thanks again

A battery pack will lose about 1%+/- a day sitting with the main switch on.

Thanks, but they are truly draining 25% - 30% in 3-4 hours with the main switch on. With the switch off, they are fine… losing a very minimal amount like 1% or so.

You have a current draw. These can be tough to track down. Be sure the brake light switch is not sticking on. Be sure the wiper motor is “parked” properly. Takeout all of the fuses and see if the leak goes away. If not, your DC convertor may be leaking current. There was a recall on these a few years ago.


Thanks for all the help. I ran the cart down to about 75% charge. Pack charge was at 73.3%. I let it sit for a few hours and just checked the batteries individually with the cables still connected, main switch off. They didn’t seem to run down any more since parking it. So it seems they held the 73.3V for a few hours even with the switch on… making me believe now that there was no longer a draw on the pack. Two batteries were 12.7V, three were 12.5V and one was 12.4V. The batteries were purchased from Battery Source 08/2012. They said they may offer a partial pro-rated amount like a warranty. If not, I may look at Trojans unless you have a better suggestion. Or do you think the batteries are ok? I assume not based on the previous messages.

A disparity of .3 volts is considerable. Try running it down below 50% and then check the batteries. Be sure to use an accurate meter, such as one labeled “true RMS.” The $20 ones are just not as accurate. If one is lagging behind, it is time to replace it. But, if you are satisfied with the performance and range, it may last a while longer. There is much argument on whether or not to replace batteries individually or as a set. You will have to decide which works for you.


Thanks for the help everyone. Just an update. It looks like the batteries were kind of bad, or maybe the charger is not 100%. However, I trickle charged each battery overnight… a couple times. It took awhile to do, but the cart is charging up to 100% and the batteries do not run down. My theory is that they were only charging up to 72% and when I was watching the volts drop (by the gauge and DVM) it was because I was checking too soon after charge (immediately). IDK, I could be wrong, but they are fixed now. Thanks for all the help.

Good to hear you have it solved. Now go have some fun! :smiley: