Charging batteries via USB

NETMF & Gadgeteer
21

I think that one is Li-Ion, but I would like to hear an answer on your question as well.

22

That one is Li-Po, Sparkfun just writes in a strange way, Polymer Lithium Ion…

The chip in the pack is for last resort to try and prevent a fire. You should never reach that point or your battery will not last long.

You should always use a charger that is designed for Li-Po. And you should make sure not to discharge below ±3V.

For a charger see [url]http://www.sparkfun.com/products/726[/url] or [url]http://www.sparkfun.com/products/674[/url]. I have used this chip a few times and like it, but it has a max 300mA charge rate.

Currently I use MC34673 from Freescale, that does 1A charge rate…

23

I have the first charger you listed. Seems to work so far.
That chip is interesting. How do you solder that QFN?

24

Hot air station. The hotplate thing might work too, but I have never tried it.

Note that, although that chip is 1.2A, it is REALLY tiny, 2mm x 3mm. It also does need some copper for heat sinking, else it will auto de-rate to a lower charge current to keep it’s temperature in check.

Also, Freescale provides free samples. :slight_smile:

25

Thanks. Would soldering the heatsink center pad onto a via-hole pad work for these kind of deals?

26

That would be best, but even just soldering the exposed pad to a 1cm x 2cm single sided ground plane will do.

27

Do you have more information on how to do cell balancing?

28

All that is needed is to keep the voltage on all the cells the same. This usually entails a way to individually discharge cells during the charging cycle.

See [url]http://www.evdl.org/docs/li_eq_2001.pdf[/url]. The Charge Shunting method is mostly used.

The easiest way is to either use a charger with balancer built in or to use a balancer that plugs into the battery’s balancing plug while charging via the battery’s main plug.

29

Thanks! For everybody else, if you have issue with the link above remove last dot.

http://www.evdl.org/docs/li_eq_2001.pdf

30

Hmm, that last dot is a bug… :slight_smile:

My message was “{url}http://www.evdl.org/docs/li_eq_2001.pdf{/url}.” with the dot outside the {/url}… :slight_smile:

31

Here is another interesting charger:

http://www.seeedstudio.com/depot/lipo-rider-p-710.html?zenid=503b295ac82f76dd562e2e2c2e5c3f44

32

Yep, that gives you a charger without cell balancing worries, the ability to charge from 5V(or solar) and it gives you 5V out. :slight_smile:

Only thing that worries me is the 100mA(350mA MAX) output.

That is more or less what I did, I just used this module for boosting: http://focus.ti.com/docs/prod/folders/print/ptn04050c.html

But it is more expensive than the whole charger that you linked to… :slight_smile: