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Topic: Li-ion charger (Read 3171 times) previous topic - next topic

pata

Hello,
I'm thinking of using two 3.7V 3500mAh Li-ion phone batteries to power an arduino and rc car. I also would like to charge the batteries with a 5.5V 2.5W solar panel and saw a MAX1811(Li-ion charger IC) kit on ebay. I found it quite interesting but I would rather buy something for a 0.1'' solder board. Does anyone know a good alternative to this IC?

florinc

Quote
I would rather buy something for a 0.1'' solder board

This is the reason sparkfun makes breakout boards:
http://www.sparkfun.com/search/results?term=MCP73831&what=products

pata

Thank you florinc, I will consider that. But I would still like to ask if someone knows of such an IC for solder boards, I guess I should have said "an alternative IC to this IC" :)

pata

So I decided to buy two MAX1811 and they are working fine charging two phone batteries (3.7V) with a 2.5W solar panel. The thing is, I would use both batteries in series for powering my rc car and I can only use one solar panel, i.e. both batteries would share the same ground from the solar panel. I think that's not possible, is it?
Is there a way I could use both batteries in series and still be able to charge them with one solar panel? Or if I put them in parallel and use a step-up for the arduino and rc car, would the charger ICs still do their job?
I would really appreciate any help.

Edit: forgot to link the datasheet. http://datasheets.maxim-ic.com/en/ds/MAX1811.pdf

lemming

#4
May 25, 2012, 03:17 am Last Edit: May 25, 2012, 03:29 am by lemming Reason: 1
http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en543956

or the ready made breakout board:

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en544320

I use these with a 9 volt switch mode regulator (http://au.element14.com/xp-power/sr05s09/switching-regulator-9v-0-5a-o-p/dp/1861085) between the solar panel and this unit as the input voltage cannot go above 13 volts. A 12 volt solar panel can go to ~21 volts. You can use a linear regulator but you lose too much power and generate a fair bit of heat.

pata

#5
May 25, 2012, 04:55 pm Last Edit: May 26, 2012, 12:28 am by pata Reason: 1
Thank you for your suggestion lemming.

I'm sorry to bother so much but I just realized that these phone batteries have 3 (-) contacts and that they are isolated (no continuity). I always thought they were connected. Could I use one (-) contact for charging from one solar panel and one of the others to put the batteries in series, or is it to perfect to be true?

Edit: Never mind...the other contacts aren't Ground but temperature and something else :(

pekkaa


So I decided to buy two MAX1811 and they are working fine charging two phone batteries (3.7V) with a 2.5W solar panel. The thing is, I would use both batteries in series for powering my rc car and I can only use one solar panel, i.e. both batteries would share the same ground from the solar panel. I think that's not possible, is it?
Is there a way I could use both batteries in series and still be able to charge them with one solar panel? Or if I put them in parallel and use a step-up for the arduino and rc car, would the charger ICs still do their job?
I would really appreciate any help.

Edit: forgot to link the datasheet. http://datasheets.maxim-ic.com/en/ds/MAX1811.pdf


Do you need to charge the batteries while driving the car? If you don't, you could build a circuit what switches the batteries from series to parallel when you plug in the charger.

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