Team Kaizen - The Honey Badger

[Bodge Job]

Hey nice to see the new build going along well, was such a shame to see badger get flattened at Grantham! (I was the guy with the glitchy robot and Lipo that caught fire :P ). New build looks good, cant wait to see it in action! How ever with the electronics I think you're slightly misinterpreting how the maximum current ratings work.

The motor is what dictates the current, with the current depending on the voltage, and how fast the motor is spinning (stall being maximum current, and the fastest rpm being the lowest current).

The esc has no control over the current, it kinda acts as a very fast switch, so outputs what ever current the motor requires. The maximum current rating of the esc is the max current going through the esc before it gets damaged. Each company has a different way of deciding this rating so different escs cope differently. Some escs can cope with peak currents higher than their max rating (they just get very hot) and some will get damaged lower than their max current rating (particularly cheap escs, that can have exaggerated specs). This annoying nonuniform current rating system is where people's experience come into play. For example a ragebridge is rated at 40A but could cope with a higher current than a botbitz ecs rated at 85A, and both could cope with more current than a cheap ebay esc rated at 200A (irritating i know :L)

The battery also has no control over the current (unless you're working near its limits) , The maximum current rating of the battery varies meaning slightly depending on the battery type. With Lipos (and I believe LiFePo4) the max current is what the battery can safely discharge without damaging the battery. Lithium batteries will output a higher current than that, it will just damage them and can make them unsafe to recharge (hence the fuse rule for lipos).
Lead acid, and NiMd and NiCd batterys are slightly different as they won't output much more than their maximum rated current like lipos do. it can still damage them but not in the same way as lipos, as they don't become unsafe it just shortens their life.

This means you can have a battery with a max rating of 500 amps and a Esc rated to 200 Amps, but if you have a motor that stalls at 20 amps you won't damage the esc or battery. Its the max current of the motor that's important.
Its good to note that a motor will burn out if stalled for any length of time, and a burnt out motor will develop internal shorts so it may draw a much higher current than its stall current, so its good to have safety margins to help account for this or other faults. and many motors won't give a stall current, so again you'd have to use other peoples experience to find out what works.

This is a crude description, but I hope this makes things slightly clearer, it means it's fine to have a battery rated higher than your escs max current. If anything its better to do so. Just try to have the battery and esc rated to a much higher current than the motors are likely to use.