Li-ion rechargable battery circuit (w/out removing battery from prop circuit)

Fred Hawkins

I want to make a prop board·that runs on a li-ion battery and be able to recharge it like a cellphone or what have you. In other words plug in the wall wart and recharge. Being able to keep the prop going would be nice but not particularly important.

I'd also like to skip reinventing this particular wheel. So far the best info I have on the idea are a handful of ti pdf, which sell ti chips.

So what I am asking for are:

1) a decent schematic, propeller centric if possible
2) other information sources from grunt level and up...

My seat of the pants implementation so far consists of
bq24305 protection circuit
bq24080 charger ic
tps63001 3.3v regulator

but I·welcome better thinking....

·

Ale

The charger ic can be powered (and the battery thus charged) via an USB port. Keep in mind that it comes in a 10SON package where the pins are separated 0,5 mm. Those packages are _tiny_

I made for my battery powered propeller board some other decisions: 2 NiMH batteries and a boost regulator (TPS61070). The display will be powered by other set of 3 or 4 NiMHs and a separated regulator (is a 5V LCD). I think that LiPo batteries discharge way too fast (well my laptop does!). But they are small... and specially thin .

I think you can draw the circuits yourself, the datahseets by Ti are quite good. I did not have problems so far and have used 3 different regulators so far besides some other class d amps and so on. I always started with the recommended application circuit and made the modifications that I thought useful. Mistakes where generally at some other point.

Fred Hawkins

Small is good. My target space is·inside a cylinder that·is about ·5/8" (ID).

evanh

How long is the cylinder? AA cells will fit that diameter I think. Ale is correct, the new NiMH cells have way better charge holding characteristics than the current generation LiIon cells. If you want it to be stored between uses without a recharge then NiMH is far superior.

As for recharging LiIon's, a set voltage limit is all that is needed, just like a lead-acid. Nothing complicated is needed unless you are trying to fast charge them.


Evan

Duffer

Fred,

SparkFun sells a small LiPo charger that uses a MAX1555 chip. Their page: http://www.sparkfun.com/commerce/product_info.php?products_id=726·also has the schematic for the board and they sell both the MAX1555 chip and the connectors that you would need to build your own. I would not recommend trying to charge LiPo batteries with anything except a charger designed expressly for LiPo batteries. They can overheat and cause REAL problems if not handled properly. BTW - The circuit is designed for in-circuit charging from USB or +5V.

Good luck,

Duffer


Post Edited (Duffer) : 6/23/2008 1:05:01 AM GMT

Fred Hawkins

evanh,
length is on the order of a couple feet. I probably will have to try both -- though weight considerations have me looking at li-ion's first. The TI chips are expressly designed for li-ion batteries.

Duffer,
Looks nice but expensive -- compare with a $1.29 board from these guys: http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2721
(Might be too cheap; I worry.) Nice selection of batteries too. I may even skip the inside the box rechargable to try out their $20 rcr123a charger and 4 battery combo.
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=3476

Fred