There's a chip called TP4056 that's quite good for charging li-ion/li-po cells. You can buy the chip really cheap, or like above - a finished board with usb power in for $1.50 (!) on ebay including shipping. I bought one, soldered on a couple of silicon wires with magnets attached to the end. Also added a plug-able tiny voltmeter (ebay, but this other one from fasttech also looks quite good). I'm not sure how the voltmeter affects the charging (as it feeds off the charging current), but I recon it should be quite fine.
Per default it uses 1 amp of charging current, which is quite good for large cells, but you can modify it by changing one of the onboard resistors - lower values and you can use it for smaller cells safely.
It's quite a decent little charger, it manages pretty close to true CC/CV (constant current / constant voltage). It does get a bit hot when charging at 1 amp, especially in the start when the voltage difference between input and output is large, but nothing too worrying.
Termination seems to happen according to spec - just around 4.20 volt.
All in all - quite happy with it. I recon the chip (or even the board) could easily be built into projects that need li-ion/po charging, or even into a battery pack. Can't beat the price! :)
16 comments
Very interesting. Do you think this charger board can be used to charge battery with solar pannel. There is usb solar pannel charger kit on ebay, but I am not sure it will really take care of batteries.
It could be nice to use solar energy with a TP-Link TL-WR703N as a result it only need 100mA. So maybe a battery of 2000mAh coupled with 400mA/5v solar cells should be ennought for 24 hours non stop run?
I am going to try the external antenna mod you describe in your blog, but instead I will use high directivity antena. (=12$ on ebay) I would creat long range wireless point to point link. Then next, it may be interesting to also try it using it with solar energy.
Regards
Crl
I've seen other people use it for solar charging, so that's certainly possible :)
Check out: http://budgetlightforum.com...
What I do not know however is how the charger will behave if the battery is used at the same time as it is charging. (However, it might be possible to rig a simple circuit with some logic and a diode or similar to avoid that if it's a problem.
Thanks for posting this.
Do you think I could use this setup to charge my Canon battery via USB?
Thanks, best regards
Mo
Sadly, no, not directly.
This chip only charges single cells (3.7v). Canon (and most other DSLR batteries) are 2 cells in series (7.4v). But any li-ion charger able to charge 2s batteries will do.
Thanks for your reply. I do use a 3.7V battery (NB-6L), so this setup actually should work?
In that case, yes, this should work fine :)
Awesome, thank you! :)
Hello, I have an identical charger but I want to change the current. Which is the resistor on the board that corresponds to Rprog?
Hello,
on my board it's the R4 resistor (connected to pin 2 on the ic)
Could it charge a Tablet 3.7v battery?
And Is the work load cut?
If the battery is li-(ion/po) then this will most likely do the trick yes.
Not sure if I understood the work load question.
Thanks and sorry my english is poor.
4,2v Full charge voltage is good for 3,7v or need it a 3,6 Full charge voltage?
li-ion/po have a nominal (operating) voltage of 3.7,
when full charge they have a voltage of 4.2.
So yes, this charger will work fine for a 3.7v li-ion/po battery
Check out: http://learn.adafruit.com/l...
Thank you. No further questions. Thank you very much.
Sorry for my english.
No problem! Happy to help! :)