Hi, I just made a couple of 4x18650 16.8V battery packs for multi-purpose use using spare 18650 battery holders I had. I will be using it for my bike light and to run a laptop with a regulator when I’m away from home and grid power is not available.
The question is how do I protect the individual cells from overdischarge? I know the simple answer is to use protected cells but in my experience the pcb in those cells cut off at 2.3V. I don’t think its advisable to run them down that low. I would be more comfortable with a 2.8V cut off per cell. Is there any PCB that cut off between 2.7V and 3V?
The link was to Battery Space
And a page with several options for 4s packs. Try it now. EDIT above link is to custom PCM’ which cost way more. They also have less expensive models. The “battery guage” is just a jack where you can plug in their guage which is not included. The balancing function is a really good idea if you plan on charging them as a pack rather than as individual cells.
Also, Battery Junction has them cheaper and in singles. Hope these help
Just saw a link to battery space on the BLF browser page under “AdChoices”-“LiFePO4 Battery/Pack” They must be a current sponsor. They had more than just the>$30 options.