Roger Stockton via EV wrote:
A programmable load is fine for discharging batteries.

I believe the power devices are operated in linear mode, not PWMed, and have 
not observed any transients on the load current on any of the electronic loads 
I've used.

I agree. The programmable loads I've seen and used are all linear. Using PWM (without a massive filter to make it look like DC) would give you bad data, and invalidate the results.

By nature, the load is going to convert electricity into heat. If you're handling big power, a *lot* of heat. This creates an incentive for regenerative loads (using the power to run a motor, or push it back into the AC line, etc.) Some of the really big programmable loads do this. AC Propulsion has one rated at 100kw that does this.

A battery charger can be a particularly handy "load". I've "ping-ponged" the power between two batteries to test them both, discharging #1 to charge #2, and then when #1 is dead, flip it around and use #2 to charge #1 etc. This way, most of the energy is recycled, and you only need a small extra charger to make up the losses. I used Vicor modules for this, whose input and output are essentially DC.

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