Question about unprotected batteries

[Jaffi]

Hey there

If I am using unprotected batteries (such as 10440), I have to take care to not over- or undercharge them. Overcharging should not be such a problem, assuming you are using a proper charger. But what about overdischarge? I think they should not go under 2.7v or something. So... if I am using them with a laser, should I check them with a multimeter from time to time, to not overdischarge them??

 

[HIMNL9]

Yes, if they go under 2,7 Volt each one and stay this level, also for just an hour, they start to die.

Better choice was use one of those drivers that stop to work under 2,7 / 2,8 volts, so they automatically act as a protection, but checking them time by time is also good ..... BTW, they don't suddenly die at 2,6Volt, ofcourse , but starts to reduce progressively the capacity of current holding .....

Anyway, not all knows that lithium cells have a life period that is independent from use and charge, too ..... mean, a lithium cell, usually, last 6 years, indicatively ..... and this indipendently from the use, so if you use your cell all the days, or if you left it fully charged in a tire as spare cell, keeping it as perfect conditions, after 6 years or few more, both are to throw away.

 

[LarryDFW]

Jaffi;

I have been using #18650 cells without PCB voltage protection for several years now.

As long as you are using top quality cells, you can go down to 2 VDC with no problems.
Just recharge them when they reach that level.

I have never even had a single cell vent.

LarryDFW

 

[HIMNL9]

Most of the times that the cells fails, is when are used for high current applications, or when you let them undercharged for some time.

I found several of them in laptops battery packs ..... mainly in old types, where the protector circuit was not too good, or when the battery maker don't care to use batteries that come all fron the same identical production lot.

When this happens, one of the cells start to under or over charge, and cause these applications requres high currents, soon it start to overheat and fail and the capacity of the cell go down ..... in most of the ones where i replaced the cells, there was always one of the cells that or was shorted, or was 0 volt and act like a resistor, or also it look fully charged with a multimeter, but when you apply a load, it go discharged in seconds.

Anyway, for test your batteries, the better system is multimeter + load ..... connect the multimeter and measure the voltage, then, keeping the multimeter connected, connect a load (a car lamp with 2 wires soldered on it is a perfect and cheap load ) ..... if the voltage go down some mV with the load, and then stabilize (cell charged, ofcourse), then it's ok, if instead the voltage drop significatively, or just continue to go down til it reach 2,7 or less in seconds, or also one minute, the cell is almost dead.


EDIT: THIS IS IMPORTANT ! ..... when you make your own battery packs, always try to get and use batteries from the same production lot, and if you have lasers that work with 2 or more batteries, always try to use the same batteries together and avoid to mix them - this improve battery life (this ofcourse don't mean that you are forced to use them in this way, is just a way for improve their life, and your lasing time )