It's possible those coils require higher voltage. For example a 48V forklift would use 48V coils and 12V is too low. Such equipments don't use 12V systems. You might try a quick touch with higher V.
major
major
1. A reversing contactor has two mechanical states, multiple relays need extra stuff for the same safety level, to prevent a dead short (i.e. the arduino has to sense the voltage on all of the contacts and ensure they open/close in the right sequence and aren't stuck).If it is dead I will just use multiple single contactors controlled by my arduino.
Not sure I am keen to rewind the contactors. I think I am more confident getting the arduino to do the protection.1. A reversing contactor has two mechanical states, multiple relays need extra stuff for the same safety level, to prevent a dead short (i.e. the arduino has to sense the voltage on all of the contacts and ensure they open/close in the right sequence and aren't stuck).
2. Ever consider a contactor rewind? for 72v to 12v you would conceptually take the wire off, make 6 even strands out of it, put the wire back on in parallel. I don't know how well it comes apart.
Yes, I had the same thought. I'll see what is available locally.something like this might be an option too
http://www.ebay.com/itm/Boost-DC-DC...940208?hash=item35ead2a5b0:g:-hgAAOSwBLlU9qKi
or come at it the other way and buck the pack voltage with a low power circuit. You would control a small 12v relay that controlls the big relay/buck.