Battery voltage is missleading

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lukewells

Senior Member
Aug 13, 2008
70
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www.arcadeuk.com
I know some people on here test their battery voltage to find out if a battery is good or bad, but this is not a reliable method:-

I had a dodgy battery (originally it would not charge.. but I cured that by discharging it with a resistor) ... so fully charge the battery.... but the vapour was really weak, I swapped atomisers and still weak. I put my known good battery on the atomisers and both produced loads of vapour.

So I got my multimeter on the duff battery and blew through the LED to turn it on and it read 4.2volts.

I then put my known good battery on and it read 3.7volts

I can only assume that my duff battery is producing good voltage, but not suppling enough current.


I just received my new replacement battery today, and it is reading 4.2volts and producing loads of smoke...


Just thought I would share

Thanks

Luke
 

NerdyCinderella

Super Member
ECF Veteran
May 14, 2008
511
1
Gotham City
I just posted this on another thread. Maybe it would be better here for coordination:

I have 3 NJoys and 1 generic (I think) pen styles.

When my NJoy batteries died they died suddenly. My generic batteries just died but died slowly. Sought of ran out of steam.

Has anyone else experienced this difference with their dying batteries?

Any insight or thoughts on why that would happen?
Thanks
 

trog100

Moved On
ECF Veteran
May 23, 2008
3,240
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UK
I know some people on here test their battery voltage to find out if a battery is good or bad, but this is not a reliable method:-

I had a dodgy battery (originally it would not charge.. but I cured that by discharging it with a resistor) ... so fully charge the battery.... but the vapour was really weak, I swapped atomisers and still weak. I put my known good battery on the atomisers and both produced loads of vapour.

So I got my multimeter on the duff battery and blew through the LED to turn it on and it read 4.2volts.

I then put my known good battery on and it read 3.7volts

I can only assume that my duff battery is producing good voltage, but not suppling enough current.


I just received my new replacement battery today, and it is reading 4.2volts and producing loads of smoke...


Just thought I would share

Thanks

Luke

a battery voltage drops when its placed under load.. its the voltage under load that matters.. a dud battery can read 4.2 volts under no load and drop to nothing under load..

your 3.7 one under no load would still be 3.7 or very close under load.. your dud one would drop to nothing as soon as a puff was taken....

so yes voltage under no load can be misleading..

trog
 

lukewells

Senior Member
Aug 13, 2008
70
1
www.arcadeuk.com
Hope it didn't go too low! If Trog was here he would know what to say! Maybe it discharged on that resistor a little too much?

The battery was not charging ... it was showing fully charged after a few seconds in the charger. But was not powering the atomiser. This can happen with Lithium Ion batterys that have been left in a charged or discharged state for a long time as the anode oxidizes. This can be sometimes cured to some extent by deep discharge/re-charge cycles.

After I discharged with a resistor, the battery charger then allowed me to fully charge the battery for 2-3 hours and it worked again.... but was very weak (I already knew it was a duff battery, but was trying to rescue it)

Every Lithium Ion battery should have a protection circuit that stops the battery being used once the voltage drops to a certain point, so it should not be possible to fully discharge the battery with a resistor... it should only discharge up until the point when the safety kicks in. If the e-cigs batteries don't have the safety circuitry in them then they are not worth anything at all.
 

trog100

Moved On
ECF Veteran
May 23, 2008
3,240
13
UK
the e cig batteries do have the safety circuit built in.. they stop the charge are 4.2 and the discharge at 2.7..

i load test my suspect ones.. sometimes the safety circuit itself fails and cuts the battery off at a far higher voltage than it should.. this has the effect of the battery seeming to be flat when it isnt..

in short the average e cig battery is being discharged at higher "C" rate than a lithium battery should be.. to work reliably and last a reasonable time they need to be bigger..

the need to make them look like real cigarettes make the use of a realistically sized (from life and functionality point of view) battery impossible..

trog
 
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