New warning insert in MMM box: "DO THE MATH!"

[pasan]

Originally Posted by SpEEdyBL

It's not current that's the problem but the voltage spikes that kill the esc. Even though a 48 amp battery can supply the needed current, it's voltage spikes will be a lot more violent, compared to those from an 80 amp rated battery. C rating mostly decided on being able to hold a voltage, which makes higher amp capable packs better. You'd be amazed at how high voltage spikes can get during braking, easily twice the pack nominal voltage with bad packs. Since the the MMM and MM both have 30 volt fets this was not an issue with the MM as 3s was the rated limit.

A little confused... I understand most of the intricacies behind brushless technology, but why would bad packs cause higher voltage spikes?

[Pdelcast]

Originally Posted by pasan

A little confused... I understand most of the intricacies behind brushless technology, but why would bad packs cause higher voltage spikes?

Because during braking the ESC has to dump power back into the battery. Packs with poor C ratings have high internal resistance, so to get the power back into the battery the voltage has to rise. The lower the internal resistance of the battery (higher C rating) the lower the voltage drop during accelleration, and the lower the voltage rise during braking.

[littlegiant]

Originally Posted by Pdelcast

Because during braking the ESC has to dump power back into the battery. Packs with poor C ratings have high internal resistance, so to get the power back into the battery the voltage has to rise. The lower the internal resistance of the battery (higher C rating) the lower the voltage drop during accelleration, and the lower the voltage rise during braking.

Will bigger capacitors help prevent damage then?

[shaunjohnson]

caps are for huge amps for split seconds. acceleration can go on for more than a few seconds.
hence a good battery is needed.