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Homebrewed Electricity => Other => Topic started by: Vance357 on October 25, 2017, 08:14:23 PM

Title: Getting low voltage DC from an inverter generator?
Post by: Vance357 on October 25, 2017, 08:14:23 PM
I have a little "Powerhouse" 500w inverter generator that seems to have died. It runs great and only has 13 hours on it so the engine has plenty of life, but I think the inverter part is dead. (No AC output) This thing doesn't have a lot of power but I found it to be very handy only weighing about 20lbs and just sipping gas. Obviously, a new inverter (assuming I could even find one) would probably cost more than a whole new generator.

I'm wondering if I could modify what's left to charge 12v batteries directly? I understand that the inverter normally gets high voltage variable DC as it's power source. The gen head appears to be a permanent magnet spinning inside a stator much like a motorcycle or outboard motor.

Is there some sort of charge controller or other device I could buy that would convert the high voltage DC down to charge a 12v battery directly? Back when it put out 120v AC I could easily run a 25 amp 12v charger, but I would think I could get even more amps directly if possible.
Title: Re: Getting low voltage DC from an inverter generator?
Post by: Mary B on October 25, 2017, 10:39:38 PM
Strip the inverter section off and measure the DC output to see what you are working with. Then I can make a suggestion. Until I know the voltage it is hard to guess if it can direct battery connect, need a step down converter of some sort... heck it could possibly feed a cheap MPPT charge controller but need to know that voltage!
Title: Re: Getting low voltage DC from an inverter generator?
Post by: Vance357 on October 26, 2017, 04:16:21 AM
I'll try to get a voltage reading, but it will be a bit difficult with the casing torn apart. They really have a ton of wires and stuff crammed into the plastic housing, it's quite a mess. I would assume it is higher than 120v, though I could be wrong. Looks like the stator has 3 different sets of wires coming off of it, not really sure why.

Mostly just wondering if there is a modern charge controller that can deal with such high voltage DC, I'm not really familiar with the different types available these days.
Title: Re: Getting low voltage DC from an inverter generator?
Post by: OperaHouse on October 26, 2017, 04:52:55 AM
Generator is likely three phase and the controller potted.  That three phase rectified will likely produces over 160V.  That can be put into a three phase rectifier (six diodes or two bridges).  Any 12V $20 switch mode power supply can run off that DC.

Two problems:  That inverter engine will have a solenoid to control speed, that is why it sips gas. It doesn't have to run at a constant speed to make line frequency.  That will need some control or it jest runs at idle or over speed.  Most 12V supplies are adjustable up to 13V.  More than that is needed to charge the battery.  An adjustable supply with current limiting could be purchased for $40 with current limiting.  Probably won't last with that kind of abuse.  So, you are back to spending more than you wanted.

Most modern electronics have switch mode power supplies. Just a rectifier making that raw DC would be cheap and power small stuff up to maybe 100W with engine fixed to just above idle speed.