What is the max safe temperature for a nimh battery???

Here's some guidelines -

http://www.rc-monster.com/forum/showthread.php?t=2200

Besides the obvious - you have the body vented I hope, run a fan of some kind. I run a novak setup on esc and a pr of integy fans on the motor heatsinks.

I run 7 cell paks in my "stock" Emaxx, and only the motors get hot - 7 cell Maxamps 4400s. I'm still running brushed motors in it and they get 160-170F. I have to let it cool down between pacs. Batts are warm - a little cooler that when they come off charger. I asked when I got my 4400s if they needed breakin - Jason said no. Yours may be diff, you might want to run them easy for a few cycles. I've always heard temps like 160F is damaging the cells - that damage appears as shorter batt life.