how do you find the maximum current that can be drawn from a lithium battery?

Can you make a ups from car battery/car battery charger and a inverter?

I will not actually do it, I was wondering if it was possible

@yasar I believe that's more or less how it's usually done, but I am not an expert.

@ThePhoton I guess you are right: wikihow.com/Build-Your-Own-Uninterruptible-Power-Supply

@yasar You can make a UPS with a car bettery. But a starter battery [car battery] will last only few cycles in a UPS. A starter battery is designed for high output current, but not for deep discharge. Deep-cycle batteries are normally used in UPS. (Some details in this old answer.)

@yasar lead-acid+inverter+charger is basically a UPS, yes, but you want a battery designed for deep-cycle (deep-discharge) service, such as a marine deep-cycle battery or a golf-cart battery, not an engine starting battery as they aren't designed to be discharged deeply

I want to find the server which runs the HNQ algorithm and do to it what Dave did to HAL 9000.

@NickAlexeev did it pick something utterly unsuitable to be a HNQ again? :/