Is Charging of Li Ion battery with series resistor Safe ? Is there any safety concern ?

jpanhalt

Joined Jan 18, 2008
11,088
Similar control design. What happens when the voltage at the non-inverting input is lower than the voltage inverting input?. The output is connected to the gate od a P-mosfet. Will that mosfet be continuously on or off? What happens is you remove charge current control from that charger?

I am not about to try it. If well designed, as I suspect it is, the charger will enter an overload state. Which comes first, thermal overload or current overload?

It seems we have moved -- not progressed -- from trying to resolve a legitimate question to answering questions about all the different ways to do it wrong. I am not interested in continuing on that path.

I hope you find something that works for you. Good luck.
 

bassbindevil

Joined Jan 23, 2014
373
I strongly suggest getting a "BMS" or "PCM" (protection circuit module) module that provides protection from over-current, over-charging, over-discharging (disconnects at low battery voltage), and provides balancing. Those are just a few bucks from ebay or your favourite Chinese electronics supermarket (or free if salvaged from scrapped lithium batteries). Some boards don't include balancing, read the description carefully, and look at the board pictures to confirm they have balance resistors. I wouldn't call these a real BMS, since they don't have any real smarts to send data to a computer and most don't have a temperature sensor, but they are enormously better than nothing. (And better than some cordless tool batteries sold in real stores.)

These modules are not a substitute for a proper lithium charger circuit that correctly limits current and voltage. I bought a board on ebay based on the SY6912 chip; it can be configured for 1 to 3 cells, and up to 2 amps (I removed shunt resistors to limit it to 1 amp, since it got unpleasantly warm at 2 amps). There are MAX745 boards which cost more but can handle up to 4S packs; I haven't tried one. A cheap or temporary option might be a camera battery charger from a thrift store.
 
Top