I have a project in mind, to build an intelligent 3 stage charger from either ardruino or rasberri pi.

I plan to have a voltage and amperage monitor, and via the press of a toggle button have the charger change profiles for different batteries within my home.

  • 12v lead acid battery 7.2ah (alarm battery)
  • cellphone Lion battery 3.6v (cellphone)
  • rechargable AAA batteries 1.2v (appliance batteries)
  • even 12v Wet Cell 102ah battery (car battery)

The question is, what are the amperage ranges which I could work with to electronically switch rate of charge, current, voltage. etc. and what stops regular chargers from charging such a broad spectrum of batteries. Surely if I get a device to work in the volt and amp ranges required by each battery its just a matter of developing the code to switch modes?

I'm not really worried about form factor, just want a one size fits all charger?

  • \$\begingroup\$ What are you trying to do is a BMS (Battery management system) which monitoring the charge and discharge phases of your battery acording to SOC and SOH. \$\endgroup\$
    – R Djorane
    Dec 9, 2014 at 8:53

1 Answer 1


It's not too hard to design, as a computer controlled switchmode power supply. But it will be more expensive than just buying one of each kind of charger, and if you want to deliver 15V @10A (for charging the car battery) it will be quite bulky.

The key issue is that switchmode devices control output power by varying the pulse width. If you have 100% duty cycle corresponding to 150W (for the car battery) then the <1W for the AAA battery will be <1% duty cycle: a series of very narrow pulses widely spaced. That's bad for precision.

Then there's the safety issue. If you configure it for 12V @ 10A and plug it into the 1.2V AAA battery you'll have a nasty fire on your hands.

Charging just 3.6V (phone, 18650 cells) and Nicad/NiMH is a more reasonable prospect. Don't forget to build battery simulators for the three types before testing with actual batteries, so the inevitable bug in the design doesn't do damage.


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