Strange battery behavior

[solar00]

For my blue-ray laser I'm using the blue trustfire batteries from DX (14500 800mah 3.7V Li-ion)
But then after charging it it didn't work anymore.
It measured 4.18v with DMM then I tried a second battery which worked fine.

After a few minutes I tried the first battery again and it worked so how is that possible?

I have a third battery which didn't work as well but when it's fully charged it only measured 0.05V so I guess that one is bad.

Normally I recharge the batteries once a week after less than one hour use(without discharging them) but that shoudn't be a problem with Li-ion I guess

 

[diachi]

:-? Are they Protected ??

 

[solar00]

Yes these are protected batteries.

 

[billg519]

I have had this strange behaviour twice, both times with 18650 lithiums. One of them suddenly refused to accept charging after a few recharges, the other would not let me charge it the first time upon receipt from DX. For the one that suddenly stopped being able to be charged, I took my 5v regulated bench supply and gave the battery about 1/4 second pulse of 5 volts. Repeated this 3 times, put battery in charger, it has been fine ever since. The bad from DX battery, it had a bad protective circuit, so I removed protective circuit, and only charge in a charger that cuts off automatically at 4.15 volts.

You must have a powerful bluray to be using 14400's. (6x burner diode?) I have blurays that use rechargeable CR2's and blurays that use 10440's. Smaller battery, smaller laser. Still get good battery life.

Hope this helps ...
Anyone else got any cures for funny battery behaviour?

 

[solar00]

It's using a single 14500 and puts out 132mw , (it's a blu-ray made by IgorT)

How do you remove the protective circuit from a battery?
And can this be the cause for a fully charged battery not functioning even if it is charged?

 

[billg519]

Igor T makes excellent top quality stuff. This man knows what he's doing. I thought that you must have some special laser. You certainly do!

The protective circuit is the negative contact of the battery. Have you tried measuring voltage by measuring with the negative meter probe pushed through the blue plastic insulation on the side of the battery? That way, you are skipping the protective circuit when taking the voltage measurement. This can help tell you if it's the circuit or the battery. If you read 0.05 volts with negative probe on normal end of battery and read 3.8 volts (for example) by poking negative probe through the blue plastic, then protective circuit is probably dead. If shot of 5 volts trick won't help then you could consider amputating the protective circuit. With razor knife, cut blue plastic off battery. disconnect from positive pole the flat insulated lead that runs down the battery to supply + to the protective circuit. Be careful not to short battery when doing this!!! Then, remove protective circuit from negative end of battery.
Put black tape or thin heatshrink onto battery case to replace blue plastic. You now have an unprotected cell that must be charged in a charger known to cut off at a safe voltage.

If battery is fairly new, report fault to DX, they might send you another battery.

Hope this helps ...

 

[solar00]

I'll try to revive the battery this weekend,

The laser itself is indeed very nice, Igor did an excellent job, I'm using it almost every day.

 

[diachi]

Yeah, It's most likely that the protection circuit has broken, I've read about that happening with a few types of DX Li-Ions.

Just bypassing the circuit should fix it .

-Adam