Botbitz 85a esc..... in a heavy?

[overkill]

There are plenty of FETs in large packages like the one you found - if you have some spare gold bars to pay for them . I did some detailed research and concluded that unless you need to switch thousands of amps, FETs in a smaller package like the TO-247 has the best combination of current capability, heat transfer and size. I picked the IRFP4004 FET and mounted four of them to a small heatsink with copper strips to connect the source and drain pins. Its fairly compact and will comfortably switch 120A continuously in a real-world situation - more if I increased the heatsink or used a fan.

If you want to DIY a single direction FET switch,have a look at the OSMC circuit: http://www.robotpower.com/downloads/...2sch-clean.pdf. you just need to duplicate one of the low-side FET legs and then find a suitable driver. The HIP driver chip isn't necessary as you are only driving one string of FETs and you don't need the voltage pump as all the FETs are on the low side of the circuit.

[Max]

I guess this is essentially a package of mosfets: http://docs-europe.electrocomponents...6b800bbecc.pdf

Could be used with a switching frequency of up to 3kHZ but I fear that could be a bit too low. Not sure how well it would perform though and imagine when used in this sort of application as with mosfets the 100a rating would drop down a lot.

[overkill]

I have lost count of how many of those I have blown up! I used two 100A SSRs to switch a short Mag motor (no PWM) and they regularly died if the motor came close to stalling. Internally, they have two FETs in TO-220 cases. The other problem with these SSRs is impact resistance; mine had a thin a brittle plastic shell that quickly shattered. I had to cut the top of the shell off and inject potting epoxy to make them rugged enough for combat use.

On the other hand, they are super easy to control and the screw-on terminals make wiring easy too.

[marto]

I tried something similar to this had a tendency to blow up although I think it could have been due to doing pwm in two micros. It might work but I couldn't be sure. Big heatsink block helps a lot and you might just get away with running a single 85A on a reasonably geared motor.

Steve