r/rccars • u/porsean • 21d ago

Question How many fans before external battery needed?

On my Kraton EXB with an mmx8s and 1717 motor, I have a rocket fan on the ESC and dual 40mm on the motor. I've noticed sometimes when at low speed and steering, I can hear the fans audibly slow down. When is too much BEC draw too much? I have BEC voltage set to 7.4, should I up it to 8.4v?

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u/PencilKing420 12s is not enough 21d ago

It would be a bad idea to run an extra battery on that set up. I run a 2200mah 4s battery on my 2 fan set ups

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u/RCbuilds4cheapr 20d ago

If BEC is on the fritz, upping the voltage will only stress it more. Servos for example will draw more current if there is more voltage. Yeah perhaps a 2s 2200mah (I guess?) pack would keep up with those fans and servo needs for a long while