Battery charging and flashing LED

[nuttycyclist]

Some years ago I was given a quite nice torch that also had a handlebar mount for cycling use. (I think it's this http://www.canwelum.com/zoom-led-flashlights/t6-01.html)

It's sat on the shelf at home and is my "go to" torch for finding toys under the sofa or going out for an evening walk, and has been on the bike at times.  My only gripe is having to rotate through all settings with the click button - it's annoying turning a torch on only for it to flash SOS out in morse.

Last time I thought it was getting dim it took forever to charge (battery and charger included in the package) and the charger LED never went from red to green so I just gave up after a day or so and bunged it back in the torch.  This time the LED is green but flashing red.  This has confused me.

Online research of the battery suggests that they are very good, hold their charge for ages if not used (I agree) and charge quickly (I've never found this to be the case).  This isn't a normal Li-ion 18650 3.7v battery, but apparently has onboard electronics to protect it.  Full charge is apparently 4.2v and at 2.75v it shuts down to protect itself.

I got the multimeter out.  It was about 2.9v  .  The empty charger was showing 4.26v.   Monitoring the battery whilst being charged it rose to 3.43v over the course of yesterday.  I obviously unplugged it overnight.  Today it has risen to 3.72v (the rise from 3.70 to 3.71 to 3.72 has been about 4 hours).  The LED on the charger is still flashing red/green.  Battery is still cold to the touch.


So the questions for the jury are whether this charger or battery is stuffed, is this the normal (anybody else got one?) or where can I get a new one?  The website above doesn't seem to sell to the public, and I cannot find any others.  There are many 18650 batteries and chargers out there, but this doesn't seem the normal as it is 65mm long to cater for the onboard electronics.     Also, should I stop charging it now, or wait until it hits the 4.2v mark?

[Diver300]

Can you measure the charging current?

Is the voltage measured when charging or when not? Is it possible to measure both? If the voltage is above about 3.5 V, there shouldn't be more than about 0.1 V difference between no load and slow charging.

[nuttycyclist]

It has been many years since I've got that technical    

Multimeter has "max amps" and so I need to choose sensibly.  I can't remember how to interpret the output though

Max	Reading
2	.001 <-> .003
200m	00.1 <-> 00.3
20m	0.01 <-> 0.03
2m	.001 <-> .003
200u	00.1 <-> 00.3

I presume from those figures that the charging current is extremely low!

I'm now up to 3.74V, and charger LED is still blinking.  Battery still cold.

[Diver300]

Those readings indicate that there's too little current to be measured. If the readings are correct, they would indicate a dead charger.

[nuttycyclist]

That was my fear.  However I can't seem to find a new charger online.

The good news though is that the battery is now up to 3.75v.  I'll see what it is at the end of today...

[rafletcher]

That was my fear.  However I can't seem to find a new charger online.

The good news though is that the battery is now up to 3.75v.  I'll see what it is at the end of today...

https://www.amazon.co.uk/EBL-Universal-Battery-Rechargeable-Batteries/dp/B08NVH73XL/ref=sr_1_6?dchild=1&keywords=18650+charger&qid=1621234699&sr=8-6  ?

[nuttycyclist]

That was my fear.  However I can't seem to find a new charger online.

The good news though is that the battery is now up to 3.75v.  I'll see what it is at the end of today...

https://www.amazon.co.uk/EBL-Universal-Battery-Rechargeable-Batteries/dp/B08NVH73XL/ref=sr_1_6?dchild=1&keywords=18650+charger&qid=1621234699&sr=8-6  ?

Thanks.    I'd seen many such as that.  However these canwelum batteries appear to be longer than normal 18650 batteries due to onboard electrics?  I may be getting confused but they are 68mm long whereas a normal 18650 battery is I think shorter according to online research. 

In addition the canwelum site says that these batteries, due to the onboard circuitry, aren't suitable for e-cigarrettes (which other sites seem to imply the main use of these batteries are) so I'm therefore worried about using a generic charger in case it's not compatible with the onboard circuits.   Who knows, maybe it's the battery protection circuits that are causing the low charge current?

[Diver300]

Who knows, maybe it's the battery protection circuits that are causing the low charge current?

The protection circuit built into the battery means that it's virtually impossible to measure the actual battery voltage.

If you are measuring the voltage of the battery+protection circuit during charging, and that voltage is 3.7 V or so, and the current is tiny, the current isn't being restricted by the protection circuit.

If it were the protection circuit limiting the current, the voltage would be close to the open-circuit voltage of the charger.

Protection circuits are common in 18650 batteries. The warning about e-cigarrettes is that they may take too much current for the protection circuit.

I think that a separate charger would be fine. https://www.ebay.co.uk/itm/331439097248 would probably work.

[TimO]

Diver300 beat me to it!

Almost every Lithium battery has protection circuitry. Very very occasionally you may find one intended for a specialised use that doesn't include it, but that's never the case with general ones. It sounds like they're trying to make a big-thing of something which is actually perfectly normal, and sensible.

Generally this provides overcharge and short circuit protection, because both of those can cause a Lithium cell to literally burst into flames. Some also provide undercharge protection, because that can fairly easily destroy the battery in a less spectacular fashion, but that seems to be slightly more randomly provided (or documented).

[grams]

The protection circuit built into the battery means that it's virtually impossible to measure the actual battery voltage.

The normal state of the protection circuit is both mosfets fully on, which is approximately equivalent to a dead short, so the cell voltage will be present at the terminals.

[Diver300]

The protection circuit built into the battery means that it's virtually impossible to measure the actual battery voltage.

The normal state of the protection circuit is both mosfets fully on, which is approximately equivalent to a dead short, so the cell voltage will be present at the terminals.

I agree, but if the battery protection circuit is limiting the current, that means that one or other of the MOSFETS is turned off.

[nuttycyclist]

....
I think that a separate charger would be fine. https://www.ebay.co.uk/itm/331439097248 would probably work.

Well I finally got around to sitting down and mass ordering everything on my ever-increasing list (I hate shopping, especially internet shopping).

It arrived yesterday.  Battery doesn't fit in it. 

At £3.99, I can't be bothered to return it as it'll cost me a fair % in postage back.

I'm wondering whether to take the dremel to the case and modify it so that the battery might fit.

[Diver300]

....
I think that a separate charger would be fine. https://www.ebay.co.uk/itm/331439097248 would probably work.

Well I finally got around to sitting down and mass ordering everything on my ever-increasing list (I hate shopping, especially internet shopping).

It arrived yesterday.  Battery doesn't fit in it. 

At £3.99, I can't be bothered to return it as it'll cost me a fair % in postage back.

I'm wondering whether to take the dremel to the case and modify it so that the battery might fit.

Is the charger too short or too narrow for the battery, or is it something else?

[nuttycyclist]

Charger about 1mm too short.  Battery will fit in, but the sliding tab is too thick and takes up the space.

If I cut the end out of the plastic to make a hole for the sliding tab to recess into, then it might just about squeeze in....