Question Battery Charge Management Output Current Question

Aug 2, 2019
I am using this "one port play and charge with CMB" board as instructed by this BitBuilt Guide. It works fine in my N64 portable prototype 1 (not stress tested though).

As I move into a prototype 2, my concern is that the BCM module referenced above is rated at 3A max. Since the N64 is rated at 2.7A(3.3V) / 0.8A(12V), and also running audio/video on board this will be consistently driving the BCM well over it's max output current. Based on specs, it appears I shouldn't be using that BCM if I want it to withstand the test of time.

Has anyone found a higher current BCM like this to use, or have you used this consistently under high current loads without issues? Other thoughts/solutions to this issue?

Thank you for the advice.



2 and a Half Dollarydoos
Staff member
Feb 5, 2017
Banana Bender Land, Australia
Working out current draw across different voltages isn't as simple as just adding up all the As. When working out current draw across multiple voltages, you have to convert Voltage relative Amps to Watts via the formula: Volts x Amps = Watts. The BCM can supply 8.4V x 3A = 25.2w. So taking the numbers you've listed here (assuming they're accurate), 3.3v x 2.7A = 8.91w and 12v x 0.8A = 9.6w, add them together and you get 18.51w total draw with a remainder of 6.69w for your peripherals. It's also worth keeping in mind that the N64 doesn't require 12v input to run, you can remove the 5v LDO and supply 5v directly to the 5v line. This would most likely slightly decrease the overall current draw due to lowering inefficiencies.

That board should be enough to run a N64 portable, but I'm not super familiar with the N64 so I'll differ recommendation to someone more experienced with the system.