2019 Gem car E4 probelm

Hi I am new here. I habe a 2019 Gem car E4 that was dead totally dead nothing would come one. I found the 12V battery to only be at 3 volts while the 48 volt batterries were at 49 volts.

I charged the 12 volt battery and now car is working good except it says it has no bars on the 48 volt system still. I dont have a wiring diagram and i have a few questions.

What charges that 12 volt batery? I see in the parts diagram there is a 48v to 12 v converter.

Yes, the converter through a relay charges the aux battery.
SOC will come back after a full charge cycle.

1 Like

Thanks. I have the vehicle charging. Do you know when the 12 volt battery get charged? While driving or durimg the charge cycle?

No I don’t. I would expect it would charge when ever the switch was on, plus when charging.
Relay controlled by the gem ecm. It’s marked on the fuse box cover. I wonder if your relay is missing.

1 Like

Im wondering if someone left the ligths on the drain that 12v battery down to 3 volts. If it wasnt charging i dont think you would be able to drive it down to 3 volts.

Well when i head back to work on Friday im gonna look into it some more.

All the relays were there. Im gonna see what the 12 volt battery voltage is when im driving

Any time that key is on the 12v system is supplied by main battery.
If your dc converter is bad, you would be running everything from the aux battery.
Once you turn the car on, disconnect aux battery. Should make no difference until next time you start.

That little 12v accessory battery may need replacing if it went down that low.
It may never hold a charge again.

just put a volt meter on the 12V battery then turn the key on and see if the voltage changes, turn the key off and plug the main battery charger into 120VAC and see if the voltage on the 12V battery changes. Your answer is in these two simple tests.

So I am finally back on this vehicle. I have the new battery. I am not getting any power into the 48 to 12 convertor so obviously none out. The 12v battery voltage does not change with the key on or charger plugged in either.

Im going to order a service manual so I can look at a wiring diagram.

Make sure that the dc relay was installed at the factory or when upgraded. Right rear looking at the fuse box from under the hood.

1 Like

This model has the relay. I have the wiring diagram now. The relay is not being grounded I can see is the problem. IT looks like it is up to the BMC to ground this relay. everything else on the relay is good. constant 12v, battery voltage, and 14 volts from the dc dc convertor.

Im not sure if the BMC is bad or there is a reason why it is not grounding the relay?

So just to clarify the dc to dc converter is working correctly. I am getting voltage in and voltage out to the relay. The 14 volts out is getting to the relay just not to the battery because the relay is not getting a ground from the BMC

I also read that the BMC has to be flashed so even if I order a new one it wont work untill it has been flashed?

Well I figured out the battery temp sensor wasnt hooked up so I believe that was the reason the 12 volt batterybwasnt getting charge after I replaced the dc to dc converter