Jump-starting Li-ion batteries

[smegballs]

Obviously this isn't recommended due to risk of fire/explosion. Do it outside with gloves and eyepro etc etc (Not on the kitchen table like I did)....

I bust my phone screen last week so went to use my blackberry backup phone, the battery (new last november) had self-discharged to the point where the protection circuit had kicked in and the phone would not see the battery and hence could not charge it, measuring 0.8V across the terminals.

After writing to the seller asking after a replacement, and getting no reply, I wondered if attacking it with my power supple might get it going as by this point it was junk anyway.

So getting some flying leads on the power supply, I set it to 2V and touched it to the contacts of the battery for a second or so. I did this a few times, feeling the battery between each second-long connection to see if the battery was getting warm, it stayed cold throughout.

A few bursts of 2V didnt seem to affect the 0.8V battery voltage, so I upped it to 4.2V (max voltage of a singly li-ion cell), gave it a few goes with that, and saw a slight improvement up to about 1V. Decided to the up the voltage to 10V, and gave it three or so second-long bursts with that, then whacked it in the blackberry. The blackberry, now displayed the "battery-charging" symbol as opposed to the "no-battery" symbol.

Blackberry then booted up after a few mins and proceeded to charge the phone, I've being using the phone a day or so now and the battery life seems pretty much the same as it was before it went into sleep mode.

Try to keep your house non-burney and your fingers attached

[Charlie]

Did you current limit the supply? Also the protection circuit could protect from over voltage. I'd have given it longer at the upper recommended voltage but with a sensible current limit.
____________________
Past: Honda x8rs, Honda City fly, Honda Hornet 250, Honda VFR750, Yamaha xt600e.
Current: Honda CBR929RR & Yamaha XT660Z Tenere

[smegballs]

Sadly my supply only has adjustable voltage. I was thinking of making an in-line adjustable current limiting circuit to put before the load for situations such as this.

Also a one shot pulse generator, so I can zap things with a specified 1, 0.5, 0.1s etc pulse rather than just touching contacts together.

[Charlie]

Does your supply have 2 voltage outputs? MOSFET with the 2nd voltage controllable supply controlling the gate?
____________________
Past: Honda x8rs, Honda City fly, Honda Hornet 250, Honda VFR750, Yamaha xt600e.
Current: Honda CBR929RR & Yamaha XT660Z Tenere

[smegballs]

Nope. It's a big ancient lump with just a 2n3055 and a honking great heatsink.