View Single Post
Old 10-19-2010, 09:53 AM   #3852 (permalink)
Master EcoModder
Join Date: Apr 2009
Location: Charlton MA, USA
Posts: 463

EVVette - '71 Chevy Corvette Coupe
Thanks: 31
Thanked 172 Times in 92 Posts
Originally Posted by princeton View Post
They are actually 200V zener diodes that act as flybacks when drain voltage goes less than source (ground) but also act as voltage limiters to protect my 300V mosfets.

No there are no input capacitors. I will probably place some input capacitors across the battery terminals. I didn't see a need for them taking up space in my controller. The only real purpose I can see they serve is to protect the battery from rapid discharge current and prolong its life. They are not absolutely necessary in all systems, in my opinion.
First, What current are the zener diodes rated for? That have to be able to take the same amount of current as the MOSFETS can put out.

Also, with no capacitors near the fets, the controller will only last but a few seconds. Maybe not even that. The capacitors are in place to absorbe the voltage spikes from switching to protect the MOSFETS, not to help the batteries. They need to be placed as close to the switch as you can get it, with the smallest inductive loop.

__________________ - 1971 Corvette Coupe Conversion to all Electric! - Machining, CNC, Robotics and Electronics.

You can download RTD Explorer for the Cougar controllers at
  Reply With Quote