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Questions About Panasonic NCR18650B Batteries

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Oct 30, 2013
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I just purchased 2 of the NCR8650B batteries that came with a cheap chinese charger. The output of the charger is 4.2V/650mAh.
It contains one led light that is supposed to (i think) turn from Red to Green once the battery has been charged. Below are some measurements.

Battery #1
Before Charge 3.57V
After approx 2 hrs 3.83V
After Approx 4 1/2 hrs 4.08V
After 6 hrs 4.21V

Battery #2
Before Charge 3.57V
After approx 3 hrs 3.90V
After Approx 5 hrs 4.13V
After 6 hrs 4.23V

Once the batteries reached 4.2x Volts I pulled them off the charger.
The led light on the charger never turned from RED to GREEN.
After I pulled them out and re-inserted them the led light stayed GREEN.

Should the led light changed to GREEN once the V hit 4.2x VOLTS or does it keep charging to say 4.3 volts and then turn the light from RED to GREEN? Is this how other chargers work? I pulled the batteries out when they read 4.21/4.23 volts because I was afraid I would over charge them. What voltage do most charges cut off their power?
One other question about these batteries.
Why do they recommend that you do not store them fully charged?
Anyway, I have 2 batteries charged and am just waiting for my laser to arrive.

Thanks!
 
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May 14, 2013
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Once the batteries reached 4.2x Volts I pulled them off the charger.
The led light on the charger never turned from RED to GREEN.
After I pulled them out and re-inserted them the led light stayed GREEN.

Should the led light changed to GREEN once the V hit 4.2x VOLTS or does it keep charging to say 4.3 volts and then turn the light from RED to GREEN? Is this how other chargers work? I pulled the batteries out when they read 4.21/4.23 volts because I was afraid I would over charge them. What voltage do most charges cut off their power?
One other question about these batteries.
Why do they recommend that you do not store them fully charged?
Anyway, I have 2 batteries charged and am just waiting for my laser to arrive.

Thanks!

Yes the light should change to green at 4.2V but maybe its not exactly 4.2V with all chargers especially the cheap ones, you probably pulled them out just before it would have turned green.

As to why you shouldn't store them fully charged I don't know the answer.

Alan
 
Joined
Dec 29, 2009
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storing them fully charged puts unneeded stress on the separator layer, and can affect the overall life of the cell. I don't know if it results in increased internal resistance/lower capacity, or if it just increases the risk of damage.

Cheap chargers sometimes charge to 4.25V to account for the cell's voltage settling due to a lack of a CV phase, I'd guess. Not the healthiest way to achieve 4.2V, but is often still within maximum specifications for some batteries.

To make these cells stay healthy, you might consider investing in a better charger. Otherwise, just keep doing what you do: monitor your voltages and remove if voltages get too high. Even with a fancy charger, I still wouldn't leave them charging unattended, but then you would be able to rely more confidently in the charge termination of the nicer charger.
 
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To make these cells stay healthy, you might consider investing in a better charger. Otherwise, just keep doing what you do: monitor your voltages and remove if voltages get too high. Even with a fancy charger, I still wouldn't leave them charging unattended, but then you would be able to rely more confidently in the charge termination of the nicer charger.


At what voltage would you say is too high when charging?
Would 4.3, 4.4. 4.5V be to high?
 
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Yes. 4.25V is generally the maximum. However, this is only because some datasheets specifically state this. NCR18650B datasheet, I just looked at, does not mention anything higher than 4.2V. By charging to 4.25V, you may shorten the overall life of the cell, or you may do something worse, but Panasonic does not state specifically that there is wiggle room. [http://industrial.panasonic.com/www-data/pdf2/ACI4000/ACI4000CE54.pdf]

For example, this old Sanyo DS for the UR18650F shows max charge voltage to be "4.2V +/- 0.03V", so they are saying that 4.23V is the maximum for that cell for it to still perform as described. You should still strive to keep it at 4.2V or lower for your maximum charge voltage. [http://www.batteryonestop.com/baotongusa/products/datasheets/li-ion/SANYO-UR18650F-26A.pdf]

Perhaps someone more in tune with recent Li Ion chargers could recommend you a decent charger that is not prohibitively expensive.

You could also peruse HKJ's review website: Batteries and chargers
 
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Joined
Sep 14, 2010
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At what voltage would you say is too high when charging?
Would 4.3, 4.4. 4.5V be to high?

General rule of thumb is 4.25v for the upper end ...

Of course these things are variable , depending on the quality of the battery ..
A really good quality battery might handle 4.25v easy ...
I have a Sanyo that always goes to 4.23v , no matter the charger used , why ?
Maybe because its a little bit better , has lower internal resistance , so charges a little higher .. Is this the end of the world ?

Thats up to you , some people dont like charging over 4.18v , some demand 4.2v , I just go with the flow as long as nothing is wrong ...

Over 4.25v , you better start checking , as its getting into the No No region , though if you study battery failures , such small over charges dont = explosions .. It takes something more dramatic than that ...
As for shortening battery life , really ... SO you shorten battery life 3 or 6 months , heck high current discharging is probably the most damaging if compared to slight overcharging ..
And with so many high performance lights out there .... Could be a lot of batteries being stressed to the max ..
 
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ScottW

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