High current charging using a voltage multiplier or switched direction DC?

RogueRose

Joined Oct 10, 2014
375
If a charging system, let's say a 170A alternator, is charging a car battery, but you also need a 60v or 72V auxiliary battery supply - which would give you 5-6 12v batteries (smaller - maybe lithium of some type) in series. Would it be possible to build a voltage multiplier (you'd need large caps I know, how large, IDK...) that would charge that battery bank being fed from the alternator?

On the topic of caps, if I wanted to do 12-14.4v "steps" then I'd look at a 16v or more likely 25v cap for each multiplier stage. How do I determine what capacity is needed per amp of output, like would 4700UF provide 1A of constant current or would it

I found this page that says 70,000uf @14.4v gives 1C or 1amp?
https://ncalculators.com/electronics/capacitor-charge-calculator.htm
Well if that is the case, then it looks like supercaps might be the only option (not financially though) to make a higher current voltage multiplier charger

Could using a standard transformer possibly work and alternate the direction of the DC current to jump the V up to 60 or 72V?
If I could get 3-7A charge rate from any method, that would be ideal but I'm lost on any method to do this..

On a side note, if someone is using a PWM to run a 24v motor on a 72v supply, what controls the amount of current a PWM device can handle and how high a current can these things handle? 1-5, 10, 20, 50, 100+ amps?

mvas

Joined Jun 19, 2017
539
To go from 12 Volts DC to 72 Volts DC, use a Switching Boost Converter.

The MOSFET, Wire, Fuse, PCB Traces, etc will dictate the max amount of amps a PWM can handle.