Easy battery storage

[Mr.Cl0ud]

I have always some spare 18650 in drawer and I bought nitecore ums4 battery charger with adjustable cut-off voltage.

So what do you think about setting charger to 3.7v cut-off (intended to charge LiFePO4) with four discharged batteries in and charger prepare them for storage.
I can repeat this after few months to keep them in good condition without labouring too much.
Is this program somehow bad for Li-ion batteries (I'm charging at 500ma and charging current can be set between 300-2000ma) or it is good idea?

I'm not native english speaker so I hope my post is understandable.

 

[zoiDman]

Hi Mr.Cl0ud. Welcome to the ECF.

It is recommended that 18650 batteries be stored at about 1/2 their working Voltage. So storing them at 3.7 Volts should be Fine.

Charging them at 500ma is said to be one of the ways to Maximize the Lifespan of your Batteries. Although the difference between 500ma and 1A charging may be small.

 

[BillW50]

So what do you think about setting charger to 3.7v cut-off (intended to charge LiFePO4) with four discharged batteries in and charger prepare them for storage.

Like zoiDman mentioned, that is perfect storage voltage. They probably won't drop much in voltage for 5 years or more.

Charging them at 500ma is said to be one of the ways to Maximize the Lifespan of your Batteries. Although the difference between 500ma and 1A charging may be small.

That was the old belief. But since electric (EV) cars (big bucks into research) there has been tons of studies and now the belief is every second charging degrades the battery regardless of the current. So charging at 500ma is more harmful than charging at 2000ma. Since the latter is spending less time charging.

Although the old rule of charging at 1C still seems to work. Meaning whatever the capacity, charging at that rate is perfectly fine. Have a cell with a capacity of 2500mah, then 1C would be charging at 2500ma.

 

[Rossum]

So what do you think about setting charger to 3.7v cut-off (intended to charge LiFePO4)

That is exactly what I do -- I use the LiFePO4 setting to bring them to "storage voltage".

No I must was pedantic and state that cut-off voltage for LiFePO4 cells is 3.6V, not 3.7V.

 

[zoiDman]

That was the old belief. But since electric (EV) cars (big bucks into research) there has been tons of studies ...

Just be Cautious when Evaluating things involving Big Bucks from Study Data.

JMO: But Charging a 2500mAh 18650 Cell at 2.5A just Aint Right.

 

[UncLeJunkLe]

I charge everything at 1A.

 

[BillW50]

Just be Cautious when Evaluating things involving Big Bucks from Study Data.

Well that is true. But this is data from numerous different studies all showing the same thing. And remember that EV manufactures warranty their battery packs. Tesla I believe is 8 years. They would go broke if their batteries couldn't handle fast charging everyday for 8 years.

JMO: But Charging a 2500mAh 18650 Cell at 2.5A just Aint Right.

Sure it is. I do so all of the time. Some lithiums can be charged two, three, and more amount of the capacity. But 1C has always been the de facto standard for safely charging batteries. The datasheet for the Samsung 25R for example, claims they can be fast charged up to 4A.

 

[zoiDman]

Well that is true. But this is data from numerous different studies all showing the same thing. And remember that EV manufactures warranty their battery packs. Tesla I believe is 8 years. They would go broke if their batteries couldn't handle fast charging everyday for 8 years.

One thing to Remember is there is Huge Expansion of Capital being invested in future for Profit EV Charging Stations.

And if I'm going to Leverage a Bunch of Charging Stations I sure would like to be able to Charge the Maximum amount of Customers in any unit of Time. ie: The Fastest Charging Rates Possible.

So there is a Huge Incentive to show that somehow now Very Fast Charging is OK.

Sure it is. I do so all of the time. Some lithiums can be charged two, three, and more amount of the capacity. But 1C has always been the de facto standard for safely charging batteries. The datasheet for the Samsung 25R for example, claims they can be fast charged up to 4A.

Not Say'n you Can't.

But I got the Impression that the OP was looking to Long Term Storage / Max Lifespan vs Fastest Charge Possible.

Because Isn't it Always a Trade-Off?

 

[BillW50]

One thing to Remember is there is Huge Expansion of Capital being invested in future for Profit EV Charging Stations.

And if I'm going to Leverage a Bunch of Charging Stations I sure would like to be able to Charge the Maximum amount of Customers in any unit of Time. ie: The Fastest Charging Rates Possible.

So there is a Huge Incentive to show that somehow now Very Fast Charging is OK.



Not Say'n you Can't.

But I got the Impression that the OP was looking to Long Term Storage / Max Lifespan vs Fastest Charge Possible.

Because Isn't it Always a Trade-Off?

Watch some of Professor Jeff Dahn's videos. He's one of the top lithium researchers.
Professor Jeff Dahn - YouTube

 

[zoiDman]

Watch some of Professor Jeff Dahn's videos. He's one of the top lithium researchers.
Professor Jeff Dahn - YouTube

Gotcha.

I'll put him on My To Watch List.

 

[Mr.Cl0ud]

That is exactly what I do -- I use the LiFePO4 setting to bring them to "storage voltage".

No I must was pedantic and state that cut-off voltage for LiFePO4 cells is 3.6V, not 3.7V.

I measused voltage of my vtc6 batteries charged with ums4 on LiFePO4 setting with multimeter and they are about 3.7v as it is on display of charger (in setting and in charging status). I don't have any LiFePO cells to test. Is it possible that charger is overcharging LiFePO or it is only for types with higher cut-off voltage?

 

[BillW50]

Is it possible that charger is overcharging LiFePO or it is only for types with higher cut-off voltage?

Yes it is. But they are not as volatile as other lithiums. You are more likely to just damage them than have them explode.

 

[Mr.Cl0ud]

Like zoiDman mentioned, that is perfect storage voltage. They probably won't drop much in voltage for 5 years or more.



That was the old belief. But since electric (EV) cars (big bucks into research) there has been tons of studies and now the belief is every second charging degrades the battery regardless of the current. So charging at 500ma is more harmful than charging at 2000ma. Since the latter is spending less time charging.

Although the old rule of charging at 1C still seems to work. Meaning whatever the capacity, charging at that rate is perfectly fine. Have a cell with a capacity of 2500mah, then 1C would be charging at 2500ma.

Good to know that.
I thought that lower current will generate less heat to slow down battery aging.
And second reason is that I am charging at night so batteries spend less time fully charged in chager till I wake up.
So better is to fast charge them with 2000ma (it's bellow 1C of my batteries) in evening and wait to put them out before I go sleep.

 

[zoiDman]

...
I thought that lower current will generate less heat to slow down battery aging.
...

Charging at Lower Current does generate Less Heat. And Heat is a Significant Factor in Battery Aging.

And that is why Many High Current - Fast Charge application like Electric Vehicles have some form of a Battery Cooling System to Limit Temps while charging.

---

I would Highly Recommend Not Charging Batteries while you are Asleep. If there is a Problem, you would want to be Awake when it happens.

 

[UncLeJunkLe]

source: Battery Charge Current Ratings Table | E-Cigarette Forum

 

[BillW50]

Charging at Lower Current does generate Less Heat. And Heat is a Significant Factor in Battery Aging.

And that is why Many High Current - Fast Charge application like Electric Vehicles have some form of a Battery Cooling System to Limit Temps while charging

Charging say a Samsung 25R @ 3A results in an 15°F temperature increase (I measured it) for less than an hour. So how much does a 15°F increase shorten longevity? Not nearly as much as 5 hours charging @ 500ma according to Professor Jeff Dahn. He has the data and graphs to prove it.

I would Highly Recommend Not Charging Batteries while you are Asleep. If there is a Problem, you would want to be Awake when it happens.

Always wise to never leave lithiums charging unintended. But some people will anyway and at least get a charger that covers all of the protections. And even charging while being intended, best to check the temperature of the batteries once in awhile. As almost no charger checks for the temperature. But a few do.

 

[zoiDman]

... So how much does a 15°F increase shorten longevity? Not nearly as much as 5 hours charging @ 500ma according to Professor Jeff Dahn. He has the data and graphs to prove it.

...

Would Love to see that Data and those Graphs.

Because the Concept that Charging a 18650 Single Cell at High Current is better than Charging at Lower Current kinda fly's in the face of Conventional Wisdom.

 

[zoiDman]

Charging say a Samsung 25R @ 3A results in an 15°F temperature increase (I measured it) for less than an hour. So how much does a 15°F increase shorten longevity? Not nearly as much as 5 hours charging @ 500ma according to Professor Jeff Dahn. He has the data and graphs to prove it.

...

BTW - What type of Max Battery Temps are you seeing when you Charge at 3 Amps?

 

[UncLeJunkLe]

Are you done stocking up post? # 23492144

 

[BillW50]

Would Love to see that Data and those Graphs.

Because the Concept that Charging a 18650 Single Cell at High Current is better than Charging at Lower Current kinda fly's in the face of Conventional Wisdom.

Professor Jeff Dahn - YouTube

Recharging Lithium-Ion Batteries Rapidly Not So Harmful After All

BTW - What type of Max Battery Temps are you seeing when you Charge at 3 Amps?

Well if the room temperature is 72°F, then battery temperature rises to 87°F.