Solar Charging

Taking the GEM to the next level - TOTAL POWER INDEPENDENCE

I have a 2002 GEM e4 and would like to charge it with PV Solar.
I have an 80vDC, 272 amp solar source.
I assume that the solar source should connect directly to the Control and not go through an inverter. Before I destroy or blow something up, is there any advise out there?

The supply to the batteries must be regulated to avoid overcharging. The problem with using a inverter is that most of them have relatively low DC input voltages. Tripp-Lite has units with higher DC input voltages of 36 and 48 volts and an output of 120 VAC. Another option is from Clayton Power who sells 36 volt inverters with 230 VAC output that would be compatible with the Delta-q charger found in newer GEMs. These will work if you can use Ohm’s Law to reconfigure the power source to a lower voltage. I have not yet seen a direct 72 VDC to 120 VAC converter.


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Thanks, Daniel. You are always a plethora of information.

I was hoping I could go directly to the controller. I realize there is a significant power loss going through an inverter; I’m told as much as 40%. Any thoughts on going directly to the controller?

Regards. Bob

Modern inverters have a nominal efficiency of about 95%. At light load, they won’t even get warm to the touch. The same goes for modern chargers and DC/DC converters. Notice how the Delta-q and Quick Charge units do not even need cooling fans. Electrical conversion has come a long way. I’m confused when you say “connect to the controller.” Do you mean the motor controller? Any charger should be connected across the battery pack so that the master switch, main fuse, and main contactor can function properly.

The power figures quoted for your solar array, 272A @ 80VDC, works out to 21,760 watts! That must be a huge array. By comparison, a 100 amp AC mains service work out to 24,000 watts. You could charge a dozen GEMs. Somewhere there is a 72 VDC/72VDC battery charger. I do know that many locomotives use a 72 VDC starting and accessory load system. A (variable) 72 volt winding from the main armature is fed to a power regulator that charges the 72 volt battery and supplies lighting, cab heat, and even special 72 volt radios. Such a regulator should do the job considering the starting batteries in a small locomotive are about the same Amp hour capacity as the deep cycle pack in the GEM. Of course, this old-time power regulator would only work with flooded batteries.
My suggestion would be to use an inverter of at least 2 kW capacity as a 15 Amp 120 volt plug works out to 1.8 kW. The DC connection to the array can be made by either tapping at the appropriate voltage or by paralleling the cells to reduce the output voltage. In time of low light ( and hence low output voltage), the inverter will shut down so that there is no damage to the charger or risk of the batteries discharging back into the array. Using an inverter will allow any type of charger and therefore any type of battery.
Keep in mind that I am not an expert on photovoltaic power.


A solar charger are that give solar energy to supply electricity to devices or charge batteries. Solar charger charge led acid batteries up to 45va to 400va. A solar panel can produce charging voltages depending upon sunlight intensity, so a voltage regulator must be included in the charging circuit so as to not over drive (over voltage) a device such as a twelve volt car battery.


i have a 2015 gem e4 would you or would you know anyone that could hook me up with a solar panel installation on my car … i would haul to anywhere just about to get one installed on it



i have a 2015 gem e4 would you or would you know anyone that could hook me up with a solar panel installation on my car … i would haul to anywhere just about to get one installed on it


Fyi , a solar panel will probably add 3-4 miles a day if left in the sun to charge all day . That is why few do it .