Li-ion batteries, sudden-death syndrome

[sandall]

Anyone with experience of sudden-death syndrome with drill batteries? My Makita, which had a reasonably-charged battery (18V G-series) last time I used it a few weeks ago, was totally dead this morning & the charger just gives a double-flashing red light. First thoughts are a broken connection between cells or a dead cell, but I'm a bit nervous about doing an  autopsy on it.

[sunray]

Could be either, My experience of similar is a cell overheats during discharge current.

I suspected this to be the situation so mocked up a battery with a very undersized cell and monitored the voltages during heavy discharge. The small cell quickly discharged and went reverse polarity, swelled and heated. As it cooled it went opencircuit. Tried it several times with similar results. The one cell which didn't go open circuit let the smoke out at next charge.

[dmxlights]

I have found li-ion battery packs that get cold can do what sandall has described. I have by cordless drill in the car this last few weeks one of my batteries was full charged and was showing half full on the inacator on it and the other was half full from the last time I used it was showing low. I took both in and let them warm up to room temp and then charged the low one and the other showed fully charged again.

I would let it warm up to room temp and then try and charge it again to see if it will.

[sandall]

Thanks both. No sign of overheating Ray, just dead on switch-on. I've tried keeping it in a warm place all day Tony, but still dead.

[sunray]

21 hours ago, sandall said:

Thanks both. No sign of overheating Ray, just dead on switch-on. I've tried keeping it in a warm place all day Tony, but still dead.

What I've been able to recreate is discharging a battery normally but in doing so one cell overheats as it's being charged reverse polarity, at that point the 'tool' is working normally (with a reduction of voltage)...

As the cell cools(I'm guessing) something contracts and fails, come back to use it sometime later it's open circuit.

 

The effect is it works normally one day (albeit with a bit of heat which may not have been apparent) and doesn't work the next day.

[Jivemaster]

IF it's built of 18650 cells then there should be five, and each may have a resettable internal fuse under the button. To find out you's have to dismantle the battery carefully. Even with the price of batteries how much must you value your time at? Any "repair" still only yields an old battery that has failed once.

[Martin]

I'm not familiar with the "G-series", but with the Makita 18V LXT batteries, if the built in battery management circuit detects a fault with the pack and you try to charge it about 3 times on the charger, then it bricks the built in circuit board.  Even if you manage to replace the cells, then the battery management board will still not let you charge, so you need to replace this too.  So it's usually not worth repairing these batteries.  Even if you do, then you are likely going to want to replace all the cells.  You also need a spot welder to make the battery connections.

[sandall]

8 hours ago, Martin said:

....... if the built in battery management circuit detects a fault with the pack and you try to charge it about 3 times on the charger, then it bricks the built in circuit board. 

That produced a moment of panic, as I've been trying charging with the battery as various temperatures, but it looks like the charger for these has a smaller brain, as it appears to be charging the spare battery ok🙂.

13 hours ago, Jivemaster said:

 Even with the price of batteries how much must you value your time at? Any "repair" still only yields an old battery that has failed once.

Fair point🙁.

[sandall]

There seem to be lots of Chinese "compatibles" about, but in the end I chickened out & bought a new full-price one from CPC (still made in China of course).