Trying to use a customised USB C breakout board as an interface for balance charging LiPO batteries

Power Battery Products
, , ,
1

Hi,

I’m working on developing a device that requires a small ~12V internal battery. I have ended up using a 3s LiPo battery which delivers 11.1V and is enough, I’ve tested it through several battery cycles. My product is built into a watertight aluminium box which has 4 screws. To charge the device currently I have unscrew them, unplug the power connector from the device and connect it to the balance charger, and also plug up the 4 cable balancing connector. I would like to make this all work using a USB C interface.

I’ve tested it directly using a USB C cable with the ends chopped off and can make it work by running those through a 6 pin XLR connector. I would really prefer to use a USB C connector as it’s much smaller, and I haven’t been able to fit all the components in the closed box with the XLR route regardless. I’m hoping there is a way to route both the positive/negative 12 volt power, as well as the 4 ‘signals’ from the balance connector through a USB C connection, 6 separate cables in use. Does this seem possible?

I could either chop one end off a USB C cable and wire it to the 6 cables inside the box, and then have the remaining male end of the cable waterproofed but accessible from the exterior without undoing the 4 screws. I have a waterproofing solution for this already. Then on the balance charger end I could chop the ends off the 6 cables required and wire them to a female USB C breakout board. If this would work, which pins would I use, and what apart from the 6? I have a feeling like this wouldn’t work because nothing would be telling the CC pins, USB C chip or however it works, what to do. Is that right?

So I guess instead I could have 2 female ports, one on the box itself, as an interface to the 6 internal cables, and the other on the balance charger end, with the 6 cables routed to the same pins on another female USB C breakout board. And then just connect the 2 with a regular USB C cable?

I realise that even if any of these options work there is room for error with people plugging a normal USB C cable in to the device and things going wrong, I’m not worried about that at this stage, but would be willing to hear any tips about that, like perhaps it would be a non issue as the USB C chip on the charger wouldn’t allow current to flow in that case anyway?

Any help appreciated.

Regards,

Alex

2

Hi Alex,
Welcome to the Digikey tech forum. Here’s a good article to read on using USB-C as a charging option. This should give you some insight to your questions.

3

Hi Steve,

Thanks very much, I’ve read that now. This feels like a stab in the dark but I’m thinking if I use a TI chip to tell the connector to pass through the 4 balance signals on certain pins, maybe the data pins, it might work. I’m sad to see the 12V option disappeared with USB PD 3.

I still feel like I’m a ways from the finish line but will keep trying to ingest info for now.