Electronic Expert Required - Battery Charging

R

Ray1000

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I have a flat Re-chargeable 26650 Li-ion Battery 3.7v 5000nAh 18.5Wh and no charger.

It had 2.78 volts and was lighting a torch yesterday ... it now reads 0.00V on a digital meter.

I wondered if I have something in the house to make one just to check if it will charge.

If so I can send for a USB charger.

I'm thinking if something from my collection is the right spec I could modify it to connect to the battery.

Also ... whats the difference between a charger and an adaptor - the type powering all our routers?

Thank you
Ray

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Lithium-ion batteries need quite specialised chargers, but if the voltage is showing zero, likely it is now completely unrecoverable, however....

You could attempt to put some charge into it, from a 6v battery, with a small, low wattage lamp in series with it, whilst monitoring the voltage across the cell. Stop the charge, when it shows 4.2v across the cell.
 
Thank you Harry ... I just need to check I have understood correctly

And, is it OK to put the tester across the battery while its transferring power?

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Having no idea how long it would take I held it on for 1 minute and the voltage went from zero to 2.84V so I tried it for a further 30 seconds ... it was still 2.84V ... I repeated the 30 secs it remained at 2.84V

Tried it in the 1000 lumens torch and it lights up OK

Turned the torch on and off a few times and it's reading 2.83V

I was using a 12V Burglar Alarm Battery charged to 6.2V and couldn't instantly find a bulb that would illuminate on that battery so I did it without.

Does the 2.84V ceiling signify anything about the battery.

It's odd that before yesterday the battery had been stood in the torch for months if not years and had 2.78V which very quickly ran out.

Ray
 
Every time I’ve asked a question on here I’ve ended up with a solution … it will be a miracle if I manage it on this occasion.

I’m trying to bring a Suprabeam Q7xr back to life.

When the battery only had 2.78 volts the torch worked as it should high, medium, low output and flashing.

Now there’s 3.78v in the battery the torch doesn’t work at all.

What it does do is momentarily flash every other time time the button is pressed beyond the click point.

You can have it momentarily flash with every press if you stop short of the switch clicking.

I’ve ruled out a problem with the switch, if you remove the end containing the switch and switch the torch on by shorting the - end of the battery to the case it still just flashes.

The torch has a pcb somewhere in it
 
Also when the battery had only 2.78 volts and worked normally it would only do so for a few minutes, the light would go out and the battery voltage would be zero.
 
I was going to mark this thread title as SOLVED but the option doesn't seem to be available.

I'm happy with the battery charging now - thank you for the help - but need to have a new title related to the torch problem.
 
Thanks MP but as Harry says he kindly explained that earlier ... and while I'm here ...

Q1. what is the purpose of the bulb being in the circuit ?
and
Q2. is the only way to reduce the voltage back to 2.7ish by connecting a bulb and waiting for it to go down?

It's just that the torch worked at 2.7v albeit dimly ... and I wanted to see if it worked again.

I think there may be an electronic component within the torch causing the problem

Ray
 
Ray1000 said:
Q1. what is the purpose of the bulb being in the circuit ?
and
Click to expand...

To reduce the 6v voltage/ limit the charging current.

Ray1000 said:
Q2. is the only way to reduce the voltage back to 2.7ish by connecting a bulb and waiting for it to go down?
Click to expand...

Yep. To reduce the voltage of the cell, it will need to be discharged. The bulb, serves that pupose.
 
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