noob question about XTAR VP2 Charger and NCR18650GA protected batteries

zarko550

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ChrisGarrett

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Hi,

I have a noob question about at which voltage should I put my NCR18650GA protected batteries. I can see that on the batteries it says 3.7V, but on the VP2 charger there is no setting for 3.7 (http://www.mtnelectronics.com/image/cache/data/Batteries/PROGA-1-750x750.jpg), only 3.2V / 3.6V and 3.8V (http://www.mtnelectronics.com/image/cache/data/xtar/VP2/website32-12-750x750.jpg).

So I am confused about which voltage should I switch to when charging these batteries?

Thanks.

The 3.2v setting is for LiFePO4 cells, which come hot off the charger at ~3.6v and 3.8v setting is for the 4.35v cells like the LG D1/E1 18650s and the Samsung 2500mAh 16650s.

3.6v/3.7v is the nominal voltage for cells we commonly use here and some manufacturers use 3.6v and some use 3.7v in their testing protocols, but they both come hot off the charger at ~4.20v.

Chris
 

roadkill1109

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Wait, so you mean when it comes "hot" off the charger at 4.2 volts, we should immediately drop it down to 3.6 volts? Isn't 4.2volts the normal voltage of lithium ion cells once fully charged? I know for storage, you do have to drop the voltage for it not to degrade faster, but other than that, frequently used cells are okay to be left at 4.2 volts, right?
 

vadimax

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Wait, so you mean when it comes "hot" off the charger at 4.2 volts, we should immediately drop it down to 3.6 volts? Isn't 4.2volts the normal voltage of lithium ion cells once fully charged? I know for storage, you do have to drop the voltage for it not to degrade faster, but other than that, frequently used cells are okay to be left at 4.2 volts, right?

Correct. 3.6V is a storage voltage in case that cell will be idle for months or longer. Gives less degradation of the chemistry. Operation voltages are 2.8-4.2V.
 

ven

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Just a figure of speech roadkill, yes 4.2v fully charged, 3.6v is around 50% charge + or - a few % and a storage voltage.
 

Gauss163

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Correct. 3.6V is a storage voltage in case that cell will be idle for months or longer. Gives less degradation of the chemistry. Operation voltages are 2.8-4.2V.

The OP is referring to the 3.6/3.7V setting on the charger. This refers not to the storage voltage but, rather, the nominal voltage.

This nominal voltage need not be close to the typically recommended 40-50% SOC voltages for storage, e.g. for some common chemistries 3.6-3.7V is only about 4-15% capacity, which is too low for long-term storage.
 

ven

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Too add(presuming the cell in question is under 3.6v, which depending how close it is to that V would possibly negate this) you could use the 3.2v setting to charge the 18650 to 3.6v for storage.
 

Gauss163

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^^^ That doesn't work for all chemistries, e.g. Panasonic NCR's are about 40% SOC at 3.6V, but Sanyo URs are only 4% SOC at 3.6V. Follow the link in my prior post for more.
 
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ven

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3.6v is near enough for me imo and covers pretty much all my 18650 cells(inc pany A and B although in the minority). Sure you will agree, an NCR at 3.6v stored is better for it than 4.2v..............just to keep things simple and options are more readily available(3.2v setting) over $100 super all singing dancing chargers. Just an option to put out there for someone who may want to store an 18650 cell at 3.6v, the 3.2v setting will do it for them.

tbh most of my store cells at around 3.8v usually, even up to 4v although most of mine are ready to go(guess only around 20 cells in storage V right now).
 

zarko550

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Thank you all for answering my dillema and also for giving me extra info on what voltage should I store the batteries if I'm not using them for logner periods :)
 

Gauss163

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3.6v is near enough for me imo and covers pretty much all my 18650 cells [...]

3.60/3.65V is fine for storing NCRs, but it is terrible for cells like the Sanyo UR (e.g. many laptop pulls). You need to know the chemistry to be sure that LiFePO4 kludge will work.
 

ChrisGarrett

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3.60/3.65V is fine for storing NCRs, but it is terrible for cells like the Sanyo UR (e.g. many laptop pulls). You need to know the chemistry to be sure that LiFePO4 kludge will work.

Are we saying that we can charge all 4.20v ICR/IMR/INR/MCA/YMCA cells with the LiFePO4 3.2v setting to get them right at the 3.6x volt storage level, without trashing them?

I know we can charge 4.35v cells on standard 4.20v chargers with little effect, so I guess it makes sense, but I never thought of doing it at the lower end of the scale.

Chris
 

Gauss163

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^^^ A LiFePO4 charge is just a CC/CV charge to 3.60/3.65V, i.e. it's the same as a normal 4.20V Li-ion charge except it terminates at lower voltage (except possibly it may differ on precharge of overdischarged cells). So if that's a good storage voltage for your chemistry then it will work fine.
 
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ChrisGarrett

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^^^ A LiFePO4 charge is just a CC/CV charge to 3.60/3.65V, i.e. it's the same as a normal 4.20V Li-ion charge except it terminates at lower voltage (except possibly it may differ on precharge of overdischarged cells). So if that's a good storage voltage for your chemistry then it will work fine.

Ya learn something new. Good to know.

Thanks.

Chris
 

ChrisGarrett

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What was the long term storage voltage for say Imr 18650 and 16340?

We mostly shoot for 3.60v-3.70v. I just thawed out some Panasonic 3100mAh NRC-A 18650s from the fridge and they were in there for 3 full years. 3.70v-3.71v is what the showed once they warmed up for a few hours.

I drop all my cells down to that level, from 10440s-26650s, it doesn't matter. That's around the 40%-50% level for state of charge.

Chris
 

usdiver

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Does anybody know say if a imr aw 16340 get discharged too much and catastrophic to the battery, how low is too much? 2.7v?
 

ChrisGarrett

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Does anybody know say if a imr aw 16340 get discharged too much and catastrophic to the battery, how low is too much? 2.7v?

I had a couple of year old AW IMR 16340s and was running a Shiningbeam I Mini and FourSevens Quark Tactical one night and both got run down close to 2.0v.

I probably shaved a few cycles and more than a few mAh of capacity off of them, but they still work. I charged them right back up and we'll just see. Both are running right at 500mAh at a 500mA discharge on my Opus BT-3400, FWIW.

Chris
 
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