USB Ni-MH Battery Charger Part 1-The End and The Beginning

Monday, March 05, 2018

USB Ni-MH Battery Charger Part 1-The End and The Beginning

These series of updates will focus on building a Ni-MH battery charger powered from USB. The main motivation is this: my battery charger from Panasonic got destroyed.

It is a Panasonic BQ-CC16. I bought it in 2014-15 time with 4 of the Eneloop cells. My wireless mouse is using one of the cell and they last so long with one charge, so I only recharge them when about 2 of them are discharged. Anyway, my mouse was out of battery that day, so I replaced it with another cell, but all of them apparently were already discharged. So I brought out the charger, pop it the cells and switched on the power. I saw sparks and fire coming out form the charger and soon, my other devices connected to the same extension were out of power. I had just burnt my fuse in the extension. Luckily, the extension still works after I replaced the fuse, and it is cheap. But the charger is not….

See the scary burnt marks from the arcing inside the charger? I’ll think twice now for placing my handphone charger so near to me when I am sleeping…

It seems like the arcing happens at the trace near R02 and TP10. Very strange as they are not that close, and nobody has any complaints about this charger being that dangerous. So, maybe I misused the charger? I only charge like 3-4 times a year, so maybe some dusts have accumulated inside and caused the arcing? I would appreciate your comments if you guys have any idea how this happened…

The top side of the PCB. Seems well build to me. No flimsy dangling wires around. So why did it arc??? And the arc even blew my fuse…

Since I don’t know how the charger work, I can’t fix it. Maybe I’ll just connect some sort of DC supply to the secondary side.

Anyway, I initially wanted to buy a new charger, maybe multipurpose one, for Ni-MH and also Li-ion. But I thought that this would be a good project to build my own charger from scratch. I’ve been trying to build one, but the lack of motivation pushed me further and further, until this day…

I’ve looked up on several off the shelf ICs, the MAX712 and LTC4060. They seem easy to use and are quite promising. But their prices are to high for a possibly one off project like this. (Or would anyone wants to buy ? Hahaha) So I searched deeper and found BQ2002. It’s just a controller to switch a current source on and off based on the battery condition. So, I locked it down to this controller IC and started to research how to implement the current source. Stay tuned to Part 2, for my journey into the battery charger realm!