GEM with new batteries,Delta Q error low battery voltage code

Hello all and Happy Holidays! We are working on a 2009 GEM with 6 gel batteries installed about 6 months ago. The batteries are perfect, all over 12V with the pack over 72V but the Delta Q charger keeps flashing the pause,flash, flash, pause code continually which means it thinks the battery voltage is too low, but it’s not. We directly hooked up the charger bypassing the GEM junction box stuff and it seems to be working. It seems something inside the junction box is causing the Delta Q not to see the correct battery voltage kicking the error code issue. Anybody know what may be the issue? Thank you.

Master switch turned on?

Yes if the Master Switch below the dash is turned off the Delta Q will flash error.

And if you don’t have the temp sense (I think that’s what it is) hooked to the battery ground (it’s the little square black box with a ring terminal ) that will also error out your charger.

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Yes, the switch is definitely on. Thank you.


The charger is connected direct to batteries excepting the main switch.
Black wire to B- on controller which comes direct from B-.
Red wire to load side of switch/breaker. Other side of switch goes to B+.
Check voltage at the red and black wires from charger while attempting a charge cycle.

Yes, definitely on. Thanks

I do not see a temp sensor on this vehicle. Did all the GEM cars have them? This is a 2009 model year

They all have them. The cars have 2 wires in the back they are Orange/.With black stripe one has a Male spade and the other has a female spade they need to connect together OR hook up the bat temp Sence.

In this picture, is this little black piece on the wires what you are referring to as the temp sensor? If this is are you saying that it may be bad which is causing the low battery voltage code? By bypassing the this (skipping over the temp sensor giving direct ground to these wires) I assume this will prove the theory? What do you think? Thank you very much for you help!

We know this charge will begin charging the batteries correctly in the beginning of a charge cycle but after a short period of time it kicks the low voltage code

Sensor reads 10k to 12k if it’s good.
One wire is B-, the other should read a small voltage from the charger.

I’m pretty sure your trick will work. I think either it’s hooked up right and the delta Q will fire up or the charger will recognize it doesn’t have ground and NOT fire up. That black box is a switch.

When the ground is normal temp it’s closed and gives the charger a Ground and when it warm or hot the Switch opens up and takes the ground away from the charger.

Checked the temp sensor and got 21k ohms the first time, 19.65k ohms the next time. Does this mean the sensor is no good?

Possibly, I will have to research the change in resistance with temperature.
68f mine was about 11k.
I can heat mine up a bit. Meanwhile if you have a 10k resistor, swap it in for a test.
Also check the voltage from red to black while charging. See if voltage actually goes low or if the charger reports low voltage in error.

Bringing temperature to freezing with ice reads 15k.
Is it freezing where you are?

It’s around 40 degrees outside but we have been experimenting with plugging in the charger and the sensor ohm’d at 18k almost immediately after it kicked the low voltage code 2 and still mounted on the negative terminal of the battery

Seems that way. Bring sensor inside. At room temp it should be about 10-12k.

Well, we found out something that is most likely the cause. While the Gel batteries are only 6 months old and all six batteries measured over 12V (surface charge) each we put the batteries on a 72V Lester discharge tester and one of the 6 batteries dropped all the way to 5V immediately while the others hovered at around 11.5V on the discharger. Looks like we have one defective battery. We’ll replace this one battery and see what happens but think we may have found the problem.

Late notice but this was not the problem. Replaced the single weak battery and had the same problem. Replaced the pack and had the same problem. It was an “over charge” error code, not under charge. Eventually replaced the charger and it resolved the issue but have the same situation again on another identical GEM car. Hoping there is another solution out there so we don’t have to buy another new charger again.

Using a DQ charger with good batteries, connections, and correct profile, there is next to zero chance that a new charger is needed.
I’ll stop short of saying never, but something else is wrong. IMO
You can always test charger by removing it and connecting it to a known good battery bank with correct profile.
If conditions are much different than I experience in se Mn., such as super hot operation, I’ll stand corrected.
I’m sure enough that I will exchange working chargers for new. +$200
No guarantee it will fix problem.