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Bypassing inverter in Inverter Gen (220vDC)?

dehv

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Oct 26, 2020
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I got a deal on a 3000W honda clone inverter gen with blown inverter.

Testing off the HV DC plug going into the inverter board gives 220vDC at idle (ECO on) and 240cDC with ECO mode off.

I was thinking of just running off that (the diode bridge output) into a high voltage input charge controller, but the input tolerances seem to max out around just below 200V OC tolerance for the affordable (PowMR/Makeskyblue) units. I really don't want to buy a midnite solar/outback just for this. The best i can find is a 40a with 250v OC input tolerance, but that's pushing $300.

Purpose is bulk up 48v battery bank as efficiently as possible in winter off grid use. I was thinking whatever it puts out a idle should be enough to meet loads and give a slight charge on no sun/wind days. (200-500w)

Theory 1 (Delta Wye):

Tap into the 3 phase delta going into the rectifier, either using just 2 delta leads (inefficient) or running to a delta wye transformer, with each wye output leg rectified then on it's own MPPT/buck controller ($100 for 60A PowMR x 3) would be the same price as single 40A 250v unit, more redundancy, but what a waste of space, and transformer losses and cost? (about $200 for a 2KVA TX

Theory 2 (PWM SSR):

Assuming the loaded voltage output would be below 190v DC at idle, perhaps a PWM driven solid state relay could slowly load up a PowMR until the loaded voltage drops below 190? Maybe with extra inductor and HV cap to smooth it out...

Or just buy a $300 inverter board and use the built in charger of my inverter (sunny island 4248US)

#overthinking
 
Did you have the DC filtering capacitors in place when you measured the DC voltage or was it just the bridge rectifier?
You would get different results depending on that.

Most switch-mode power supplies run just fine even on DC as long as the input voltage matches. 90-230v universal input 48v server power supplies go sometimes for peanuts. Or 48v telecom battery chargers.
 
Caps are all on the potted inverter board.

I have a collection of server supplies, interesting I'll have to give that a try, maybe run 4 with outputs in series to bulk up the battery pack. Thanks.
Did you have the DC filtering capacitors in place when you measured the DC voltage or was it just the bridge rectifier?
You would get different results depending on that.

Most switch-mode power supplies run just fine even on DC as long as the input voltage matches. 90-230v universal input 48v server power supplies go sometimes for peanuts. Or 48v telecom battery chargers.
 
Which Honda clone? I've been under the impression that all of the inverter generators use a 3-phase alternator, which wouldn't be compatible with a standard bridge rectifier. Or is it a 3-phase bridge, which I assume would have 3 inputs and 2 outputs? The Honda EU gens run the alternator straight into the inverter module with no rectifier in-between. FWIW, here are scope shots of 2 of the 3 phases of the eu2000i alternator output. The first is with no AC load, the second with full AC load. The peak voltage varies a bunch.

Double_noload_1.JPGDouble_fulload.jpg
 
Which Honda clone? I've been under the impression that all of the inverter generators use a 3-phase alternator, which wouldn't be compatible with a standard bridge rectifier. Or is it a 3-phase bridge, which I assume would have 3 inputs and 2 outputs? The Honda EU gens run the alternator straight into the inverter module with no rectifier in-between. FWIW, here are scope shots of 2 of the 3 phases of the eu2000i alternator output. The first is with no AC load, the second with full AC load. The peak voltage varies a bunch.

View attachment 70908View attachment 70909
3-phase bridge rectifiers are reasonably common item and can be bought for something like 1usd for a small one like 15A 1000v
 
I think MattiFin has a great idea with regular switchers. They usuall have simple rectifier front-ends and would know you were feeding them DC.
 
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