DIY pass through charge (power path) circuit

Thread Starter

Joe Stavitsky

Joined Apr 5, 2020
After a few hours of Google, I finally found a useful reference for a "ups style" charger circuit for li ion batteries.

However, the IC specified has 2 problems for my application

-output to system load maxes out at 1A; I need 3.

-marketed solely for single cell batteries. Not clear on exactly what is meant by this. What would happen if I connected 4 cells in parallel to battery out?

Application note for IC;

Many thanks in advance



Joined Feb 24, 2006
In your research you should have encountered: Battery University, which is an authoritative reference on these and other matters. Li-Ion batteries have specific requirements for charging and monitoring the process. IIRC batteries in parallel interfere with the monitoring of the state of charge for each individual battery. Doing this is potentially dangerous and unsafe. Proceed with caution.


Joined Feb 24, 2006
Yes, I know BU well but it didn't occur to me to check them. I blame lingering health issues :/.
They are way better with the explanations for why you need to do certain things and avoid doing other things. I don't do much work with batteries, but I know enough to double check when it is required.