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It's still sorta related - if the lithium battery is removable, and it's got some stickers on it, then there *must* be some protection circuitry inside. (Obviously this also relies on it being a real Toshiba part, and not a knock-off - in which case all bets are off.)
I don't think I'm going to be able to get the battery apart. It's sealed really good. I'll throw 15 ohms or so on it and see how it goes.
h james, you said tha tletting the voltage down to 2.5 volts might damage it a little bit. I'm surprised that the protection chip wouldn't kick in before that.
DIY, I'll keep you updated on the maxim chip. What are you building by the way?
Doing a full discharge of a lithium battery isn't exactly healthy for them, Usually most devices have multiple levels of protection - typically tripping the on-battery protection is one of those "in case all else fails" things.
The last time I pulled apart a Lithium Ion cell, the plastic "case" was <1 mm thick and glued directly to the battery. Destructively (and carefully) cutting/melting the case was the only way to get at the internals.
Anyway, just keep an eye on it, and when recharging it back up, be sure to go through the low-current "precharge" first.
James
hee hee, missed that DIY! Cool. I was thinking of building something similar to that. That's a supercool project.
Yup, I'll watch myself when I charge the thing. Hmm, at the 1$ per battery, I just might have to see what happens when it gets overcharged!! I'll keep my distance though
UPDATE: I got the max1881 and it seems to be working beautifully, it's charging the battery as I speak. Extremely simple implementation. I have one beef though. It says that it can charge at a rate of 500mA. The entire cirucit is only pulling 80mA from my variable voltage supply though, 50mA if I take away the indicator LED.
I'm guessing this is just because the battery cannot charge at a quick rate?
The "500mA" is only during the constant current part of the charge. After the battery hits ~80% capacity, the charger will go into constant voltage mode and the charge current will taper off. The charger chip should be setup to timeout, or cease charging when the current going into the battery drops below C/10.
Either that or the battery is toast - it would be a good idea to monitor the battery through a full discharge cycle and calculate its real capacity.
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