How I charged an old removable mobile phone battery

[okeydokey]

I recently re-discovered an old 1995 or thereabout Nokia phone, the battery as dead as a dodo, it wouldn't charge - BUT gave it 4 hours with a car battery charger on the 6 hour setting and it bounced back to life has been good ever since.
Might be something about a higher charging amperage ?
If anyone knows why it worked please enlighten thanks

 

[Bingy man]

Many years ago I used to fit prepayment meters ( the electronic card type) often when going to a faulty meter we would have a dead battery and these were 6 or 8 1.5 volt batteries wired together. If a new battery didn’t work we would connect 2 batteries to wake the faulty one. Not exactly sure by but it was like a jump start or a defibrillator to restart the heart .. there are electronic engineer members that will probably be able to explain it .

 

[Dabop]

I recently re-discovered an old 1995 or thereabout Nokia phone, the battery as dead as a dodo, it wouldn't charge - BUT gave it 4 hours with a car battery charger on the 6 hour setting and it bounced back to life has been good ever since.
Might be something about a higher charging amperage ?
If anyone knows why it worked please enlighten thanks

Not a recommended practice mind you lol...

The issue is most lithium chargers (probably all, at least I've never come across one that didn't) won't even try and charge a cell that is too low in voltage (because they are prone to thermal runaway when in this state) so it is a safety thing...

Admittedly I've done it myself lol- but if you do- make sure it is in an area where if it DOES catch fire, it won't cause any damage- (I put in on the concrete floor of the shed well away from anything else) and keep a beady eye on it- if it starts to heat up, turn it off and let it cool down (several 'small bites' will work better than one 'brute force' attempt...)- I use a 'lab power supply' rather a car battery charger, these are better as you can limit the current into the cell to a specific maximum

Even so, they will often 'come back to life', but expect a capacity loss with them though

 

[johnwalls26]

Having retired from the photographic trade I have a long experience of lithium cells. The problem is the matching "smart" charger is designed not to charge if the battery has drained below a certain voltage. The answer is to look for another charging method to bypass that charger. Use the "jump start" technique, + to +, neg to neg with another fully charged battery of the same or slightly higher voltage and connect outdoors for about 15 minutes. The dead battery should then work on the mains charger. Lithium cells should be good for over 500 charging cycles used with care.

 

[Adam W.]

Having retired from the photographic trade I have a long experience of lithium cells. The problem is the matching "smart" charger is designed not to charge if the battery has drained below a certain voltage. The answer is to look for another charging method to bypass that charger. Use the "jump start" technique, + to +, neg to neg with another fully charged battery of the same or slightly higher voltage and connect outdoors for about 15 minutes. The dead battery should then work on the mains charger. Lithium cells should be good for over 500 charging cycles used with care.

Please tell more about this, thanks.

 

[johnwalls26]

I think the last I recharged was a small 1.5 amp18v DeWalt, Just identify the + and - terminals and tape insulated wires between another fully charged 18 or 21v battery to form a circuit. I usually would do this outside on a table for 15 minutes keeping an eye on it. Then return the battery to the mains charger and it should resume charging to a reasonable capacity. I also suffer from !,2 NiMh solar rechargeable failures on outdoor lighting which benefit from an annual mains charge, it is basic battery maintainance.

 

[TomGW]

Please tell more about this, thanks.

It's the same with car batteries. If your flat battery is utterly dead the charger doesn't detect that it is connected to a battery at all so nothing happens. Connect the dead battery, in parallel, with a charged battery and the charging process begins. This way the totally flat battery is piggy backed on the charging circuit and starts to charge.

 

[John Brown]

It's the same with car batteries. If your flat battery is utterly dead the charger doesn't detect that it is connected to a battery at all so nothing happens. Connect the dead battery, in parallel, with a charged battery and the charging process begins. This way the totally flat battery is piggy backed on the charging circuit and starts to charge.

You can get a bit of a spark when paralleling the batteries, though...

 

[Stevekane]

Many thanks for this info, my son has a Hitachie drill that he says will not charge, I think its because he has allowed it to sit flat,,so will give it a try.
As to Car batteries, Ive found in recent years that connecting up jump leads and trying to start often results in the engine barley turning over and my teqnique now is to conect the jump leads and allow the car to just sit with the doner car running for a couple of minutes, then try and the car spins over as it should, I guess its partly charged the battery and made it more receptive to jump starting?

 

[John Brown]

Many thanks for this info, my son has a Hitachie drill that he says will not charge, I think its because he has allowed it to sit flat,,so will give it a try.
As to Car batteries, Ive found in recent years that connecting up jump leads and trying to start often results in the engine barley turning over and my teqnique now is to conect the jump leads and allow the car to just sit with the doner car running for a couple of minutes, then try and the car spins over as it should, I guess its partly charged the battery and made it more receptive to jump starting?

It can depend on the thickness of the cables. I've seen so-called jump leads that look like they'd struggle at 20 amps, let alone 200. I have an old set that were made with cable from a forklift charger, very thick but also flexible.

 

[Stevekane]

Fully agree with that John, there are some really horrible ones around. Mine are branded up as Michelin and came in a nice bag, there was a guy at the bootsale had a big box of them and was selling them off at a couple of £ a set, he said they were given away with of one of the french car brands! Anyway I bought 3 for myself and the kids and they are lovely leads, soft rubber and fine braided copper wire and by far the best leads Ive ever had, of course the kids lost theirs but mine are still in there bag in the spare wheel, I should have bought the whole box and with a nice write up sold them on ebay!
Steve.

 

[GuitardoctorW7]

It's the same with car batteries. If your flat battery is utterly dead the charger doesn't detect that it is connected to a battery at all so nothing happens. Connect the dead battery, in parallel, with a charged battery and the charging process begins. This way the totally flat battery is piggy backed on the charging circuit and starts to charge.

Yeah my battery charger won't sense a totally dead battery. Another way to get it to kick into life is to get a 9V PP3 (MN1604) and wire it across the terminals with the charger clips in place and it springs into life, obviously remove the PP3

 

[Dabop]

Many of the newer 'smart' car chargers suffer the same problem- they need a certain voltage to sense before they will 'fire up'(I've got 5 different car chargers here, four of which are smart- and I have had to use the old 1980's vintage 'dumb' Arlec 4A one to get 'dead flat' batteries to start up and get enough charge to get the 20A smart chargers to start charging...
(and yes- beware of many modern jump starter leads- my old ones the copper is the same thickness as the entire cable of many of these new ones- and many of those that thickness is almost entirely insulation!!!)

I bought a set of 500A 'heavy duty leads' for the tilt-tray- and ended up cutting them up to use on my 60A charge controllers for the solar panels- even on those, they get warm at 60A!!!!
500A my buttocks...
To give you an idea, the cables are about 15mm in diameter, but the copper core is only 5mm in diameter..

They literally struggled to jump start the Hilux, let alone a 8 tonne Mercedes diesel truck....

 

[John Brown]

We have a lightweight Bosch cordless hedge trimmer, and the Lithium battery was totally dead, and the charger wouldn't even recognise it. Have seen the cost of replacement batteries, I decided today to attempt a fix. The plastic casing came apart with relative ease, revealing three 18650 cells and some electronics.
The voltage of the pack was at 1.6 volts.
I connected it up to my bench power supply with the voltage limited to 12V,(the terminal voltage of three 18650 cells in series is more than 12V, but my bench PSU hasn't been calibrated for decades, and I was only looking to tickle it back to life)and a current limit of 0.5A, so about C/4 for a 2.0Ah battery, and left it for about an hour.
Now the charger recognises it, and charged it OK, in fact my wife trimmed a hedge or two.
So it is possible, but I'm lucky that I have a good bench power supply with current limiting. Although I think I know a fair bit about this stuff, I'd be wary of using a car battery charger, or directly connecting some other power source. Unless you're watching the whole time..