LIFePO4 charger

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LIFePO4 charger

Postby dolabra » Wed Feb 06, 2013 9:31 pm

People have been showing their lipo chargers lately, so I thought I would show mine. Actually mine is designed to charge LiFeP04 batteries, LiPO's safer cousins, and was built from the parts on hand using a pic12510 to implement a rudimentary pulse charger. it implements a constant current/constant voltage charge profile by measuring the battery voltage and charge current and pulsing a pass FET to limit voltage/current. It was built on a home-etched board with a built in USB connector and a paper "silk screen"

LiFePo4 charge to 3.6 volts rather than 4.2 as for most LiPo's, so I added a switch to choose the voltage, but truth to be told I don't use it for LiPo's because I don't trust it. I only use it to charge LiFePO4 batteries from a garden light and I use the battery in various battery powered projects.
Attachments
2013-02-06_21-02-23_869.jpg
back of the charger, with added thickness and connector for liPO that I don't use.
2013-02-06_21-01-44_284.jpg
ugly home etched, red wired, solder slopped board
2013-02-06_21-00-55_347.jpg
paper silk screen protected with packing tape
2013-02-06_21-00-24_868.jpg
Charger with Battery installed
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Re: LIFePO4 charger

Postby Sjaak » Thu Feb 07, 2013 1:21 am

Nice build!!

Are you having the same probs as matseng with the batteryclips? Ie cut isolation on the batteries?
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Re: LIFePO4 charger

Postby rwinscot » Thu Feb 07, 2013 2:49 am

Excellent.

[ rubs hands together ]

In your travels have you run into any fuel gauge options for LiFePO4? It would be great to have set of leds (maybe 4) that indicate charging progress.
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Re: LIFePO4 charger

Postby dolabra » Thu Feb 07, 2013 8:26 am

@Sjaak, I have had no problem with those clips.

@rwinscot, I haven't seen any fuel gauges, nor do I see many chargers designed for LiePO4 batteries. The ones I have seen are in hacker unfriendly packages, which is why I went this route. There is an LED on the board, the paper covers it, but it shines through ok. It has 4 states - Constant on = constant current mode. Slow flash = Constant Voltage mode. Off = Charge complete. Rapid flash = Error, no battery detected, voltage below 2.5v (I think I don't remember), or voltage at VCC. With only 8 pin device I couldn't squeeze more LED. I do wish I had put a power LED in there.
Attachments
charger.png
Layout of the board
charger.png (6.07 KiB) Viewed 1958 times
charger-sch.png
Schematic. Nothing too fancy
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Re: LIFePO4 charger

Postby rwinscot » Thu Feb 07, 2013 2:12 pm

...and it's a first-class job - simple and gets the job done. IMO, it's easy to get carried away with surface mount components, multi-layer designs, and fancy-dancy feature-packed ICs.

Solid work. That is all. ;-)
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Re: LIFePO4 charger

Postby dolabra » Thu Feb 07, 2013 2:56 pm

It is a 2 layer design, only the second layer is done with red wires :)

thanks.

By the way I think surface mount is a boon for home etchers ---- I can't stand drilling holes.
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