a neat trick I have been developing and still am but has showed good promise is to but a large capacity fet or IGBT that dumps though a small resistance directly across the supply lines. Trigger the Fet with a voltage comparator that switches it on above the 27 volts but switches off agian at 27 volts. This works as a simple but so far very good voltage clamper.
Some snubber caps are probibly going to be needed too. both at the motor and the battery end. High current switching could cause random noise in the circuit.
I am developing a solid state control system for running the electromagnets at a friends salvage yard. I have one of his 250 volt 50 amp electromagnets to actualy test with.
when the power shuts off I have to dump 250 volts at 50 amps for up to 4 seconds to someplace or it kicks the volt spike up to the point it will jump over 1 inch gaps and arc out! (how many joules is that?)
Or blows the 1200 volt IGBT's to pieces. which usualy happens first!
I cant just feed it back to the generator.
Like I said this application seems to be doing well. However it will be next summer before the snow melts and I can actualy run it in the yard to do real world application testing.
I could be wrong but would it not maybe cheaper to use higher voltage rated components on the high current side? or a better quality battery?
I have a lot of friends that always ask me questions about how to get away with using bad or marginal parts that are not up to the task for doing what they need. I typicaly tell them throw it out and use the right part for the application.
I had a friend that wanted to set up a portable jump start unit using old riding lawn mower batteries because he could get them for very cheep. He had an older diesel truck with weak batteries. Thats what the jumper unit was to be used for.
I told him to just spend the $250 and get new truck batteries. Why lug around 20 crappy lawn mower batteries and cables to do the same job as one good battery in the first place.
Just my thoughts.