My latest project involves charging a 12V, 3S LiIon battery over a POE connection, so limited power. I want to charge the battery over a day, at around 5W, then use that power at night for radio stuff. For the POE splitter, I think I want to use 12V output, so I basically need a buck-boost charger, or one that can go into linear mode at higher input power levels, relative to battery level.
I initially started looknig into the IP2368 USB-C bidirectional battery charger modules, but I couldn't get it to work on a straight DC input without shorting across the input FET with tweezers. The datasheet mentions a version, IP2368_PA that would work, however it doesn't look available, and the company has yet to get back to me.
I found the IP2326 modules, available on Ali and Amazon, and decided to try them with a 3S pack. The datasheet recomends 5V +- 10% input, but absolute max is 20V. Unfortunately, I found absolute maximum to be around 16V, at which point they either catch fire or stop working.
For characterization, I had a half-charged Lipo pack, 3s3p of 18650s at ~11.5V and I started at 1V, going up to 16V input where the chip died. I got the following results, with the module set to 3S, and RISet set to 270K \omega, which should make 0.3A current, which it generally held to.
It seems that the board gets pretty hot at 1W of heat dissipation, maybe could push it it a bit with heatsinking. As far as efficiency goes, 8-9V seems pretty great, but 5V isn't bad. I think for my application, I'll use USB and go with 5V.