I am new here, so, let me know if I am doing anything wrong.
Basically, I think I just successfully designed a non-dissipative active cell balancer using cheap jellybean parts. The cost for all material (excluding labour) is around £3 to balance a 2-cell pack at 1A.
I am actually quite surprised by how simple it is and I wonder why no one is selling it yet.
My design uses closed-loop buck converter topology. It looks almost like this: http://www.flyelectric.ukgateway.net/bal-circuit.htm
But, instead of opamps, it uses half-bridge driver.
The design is analogue based with no microcontroller or any special battery-chip involved. The close-loop is achieved by an LM358.
It is so simple that I am very excited to share it.
At the moment, it is all built on a perfboard and I am currently optimising the quiescent current (quite high actually).
The design is intended to be used while charging (maybe even running?).
The advantages are: low wasted heat, higher current (not tens of milliamps), and, small footprint (almost the same size as 9v battery).
I am planning to open source the design as I think the community will be able to improve it further and benefit from it.
But, before I open source it, I want to sell at least 10 of them (maybe on Tindie?) for around £8 each. The reasons are:
1) To recover my RnD costs (£15)
2) I want to buy a hot air soldering station (£25 on ebay) to assemble it
3) I want to teach myself pcb manufacturing (maybe £15?) and selling hardwares
I am willing to give free three prototype samples to anyone that answer these questions:
Do I need to worry about CE to sell it? I tried to research about it, but, it is difficult for me to understand lawyers' languages.
Breaking this down to simple English would be nice. as IANAL.
I know dealing with battery is dangerous, hence the question.
I will incorporate polyfuses and reverse-polarity protection in 2nd revision for extra safety.
What is the best place for me to sell this as cheap as possible? Is Tindie a good start? Or, is ES is good enough?
As this is my first time manufacturing my own PCB and sell it, any tips? I am planning to use SeeedStudio because of the low price (hopefully lower than £15).
Maybe a small review about the prototype.
I am in the UK at the moment, so, the free samples can be posted only to the person that are in the UK (to keep low shipping cost).
I am also interested to see someone else's design (that is <= £3) for me to compare against my design (I can't find any on google search, am I the first?).
Any guidance will be greatly appreciated.
I forgot to mention that, instead of wasting energy in resistors, the design will transfer the charge from strong cell to weak cell.