lithium protection

timmeh87 · Post by **timmeh87** » Thu Mar 09, 2006 12:38 pm

do you guys remember back when i said id make a circuit to display your remaining battery capacity with LEDs? well... im still not done. more accurately, i havent even touched that project since before christmas. basically i managed to fry all 5 of the chips i had... then i had to order more. i have 5 more now, but i just havent got around to it. mainly because i dont personally need a circuit that does that

BUT

i DO need a lithium protection circuit for my portable, and i DO need to make it myself, because then i get my batteries for free (a deal i struck with one of the higher-ups on the solarcar team).

so this is what i have created thus far:

features:
- Dual mosfet charge/discharge control
- Protects against overvoltage, overcurrent, undervoltage, and overtempterature
- Low power consumption (~20 micro amps)
- Dallas 1-wire interface, can talk to most microcontrollers

i found mosfets specifically designed for battery protection, and i designed it so that its all surface-mount, one layer, no holes. i figure it will be very cheap to produce. i dont have a number yet, but probably like 5 bucks apiece.

is there anyone particularly interested in getting me to make one or two for you? i know you can probably buy them online for cheaper.

id be happy to give out the plans for free though.

NES_fanatic · Post by **NES_fanatic** » Thu Mar 09, 2006 2:23 pm

I'd buy one maybe. but first I should see what the heck me portab;e is turning into. It's going in a million directions at once.

Post by **marshallh** » Thu Mar 09, 2006 2:59 pm

Nice job so far. Are you using Eagle for the PCB?

How does the Dallas one-wire interface compare with I2C? I assume it is a serial protocol.

Hm... this should be fairly easy to rig up to a PIC16F627, you'd be able to have up to 8 leds for the voltage display if you used that chip.

tim, do you have a PIC or ATmega programmer? I have a PIC programmer, and I could write the assembly code for interfacing with the dallas chip.

timmeh87 · Post by **timmeh87** » Thu Mar 09, 2006 4:53 pm

i personally have never used any proprietary serial interfaces on microcontrollers before. rs-232 all the way

. i would also assume that 1-wire is similar to i2C.

i dont own my own programmer, but i have unlimited access to a microchip ICD2, it does most everything. possibly even DSpics. someone on the team said that we already have code to interface with 1-wire lyign around somewhere (the protection system on the last car used dallas chips. 27 of them)

unfortunately, the only thing this protection chip has in its registers are boring things like overvoltage flags and the like. no remaining capacity or anything. its only a protection chip.

i do have a chip that does all sorts of fancy things like that, but it has like 18 pins, and i wanted to keep this project simple and cheap.

Nonsense Man · Post by **Nonsense Man** » Thu Mar 09, 2006 6:23 pm

how far did you get onthe LED project cause thats what i want to do when i make a gcp

timmeh87 · Post by **timmeh87** » Thu Mar 09, 2006 6:29 pm

i made a board and had it all wired up, but it just never worked. it needs to be troubleshot. thats about it. its hard though, since, unlike a computer, it has no visible outputs unless it is working properly. makes it harder to fix...