Electronics > Power/Renewable Energy/EV's

"Simple" way to prevent over-voltage cutoff on battery powered inverter

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Ziggo:
I want to use a "60V Max" battery from Greenworks to power a 1500W inverter. The battery uses 15 Li-Ion cells in series so it's voltage under load will be under 60V. However, the no-load, fully charged, voltage will be above 60V. I would like to use an inverter that has a high-voltage cufoff of 60V.

Is there some, relatively simple, way to keep the voltage under 60V to the inverter? The inverter is a Mean Well and I would prefer to stick with a quality brand rather than getting a ~72V max Chinese inverter (which are also not that easy to find). Efficiency doesn't really matter, especially if it's only in effect above 60V.

I've found a buck converter that can handle 720W, but not any that can go to 1500W. The only thing I've come up with is a simple power resistor that is switched in and out with a comparator circuit so it's only in-line when the power switch to the inverter is on and the battery voltage is above 60v.

f4eru:

--- Quote ---I've found a buck converter that can handle 720W,
--- End quote ---

Could you put two of those in paralell ?
Also, perhaps make sure those buck can handle a >99% duty cycle, to pass through once the battery has dropped a litttle...

David Hess:
60 volts at 1500 watts is 25 amps.  How much higher will the voltage be?

If it is small enough, then some switched power diodes in series can drop the voltage a couple volts.  I might be clever and use power MOSFET body diodes, so turning on the MOSFETs bypasses the diodes once the voltage is low enough.

If the voltage is a little higher, then it might be worth using a low dropout linear regulator.  This solution is essentially the same as the MOSFET body diode solution, but fewer devices are required.

Ziggo:

--- Quote from: f4eru on October 31, 2022, 08:14:21 pm ---
--- Quote ---I've found a buck converter that can handle 720W,
--- End quote ---

Could you put two of those in paralell ?

--- End quote ---

I'm worried about using them in parallel since I don't think they will share the load well.

Ziggo:

--- Quote from: David Hess on November 01, 2022, 03:40:32 am ---60 volts at 1500 watts is 25 amps.  How much higher will the voltage be?

If it is small enough, then some switched power diodes in series can drop the voltage a couple volts.  I might be clever and use power MOSFET body diodes, so turning on the MOSFETs bypasses the diodes once the voltage is low enough.

--- End quote ---

Yes, the diodes should be better than a resistor since they will drop a constant voltage. I think the max will be around 63V. Then, I just need to decide whether (and how) to drop them out when the battery voltage goes below 60V.

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