Charging rates and battery capacities - big difference?

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1dash1
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Charging rates and battery capacities - big difference?

I was checking the capacities of my four Basen 26650 cells and noticed a significant difference in capacity results, depending on whether the cells were charged at a 500mA rate or a 1A rate. Both tests were discharged at the same rate of 500mA.

Charger: Liitokala Lii-500
Normal charge test results (1000mA charge rate/500mA discharge rate):

  • Basen Black 26650 (#1) = 4318
  • Basen Black 26650 (#2) = 4397
  • Basen Black 26650 (#3) = 4384
  • Basen Black 26650 (#4) = 4475
    Average = 4394

Charger: Liitokala Lii-500
Normal charge test results (500mA charge rate/500mA discharge rate):

  • Basen Black 26650 (#1) = 4750
  • Basen Black 26650 (#2) = 4778
  • Basen Black 26650 (#3) = 4750
  • Basen Black 26650 (#4) = 4665
    Average = 4736

Difference: 7.8%

 

While I was aware that discharge rates would significantly affect the apparent capacity of cells, I wasn’t aware that the charge rates would have such a large impact.

Is this correct (more charge is loaded into the cells at a lower charge rate) or am I interpreting the test results incorrectly?

And if this is correct, where is the energy being stored? (The battery charging cycle is terminated when the cell reaches somewhere between 4.20V and 4.25V. If I tried to charge the batteries at 500mA immediately after they have finished recharging at 1A, I’d expect nothing to happen – there’s no place for the energy to go.)

Has anyone else encountered this same isse or know more of the subject? Is this normal behavior?

If this is normal behavior, then I would almost always choose the 500mA charge rate in order to maximize the cell capacities. 8% difference would be worth the longer charge times, IMO.

Rule 1-1 as it applies to life, take it as it comes.

Edited by: 1dash1 on 04/24/2016 - 19:47
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Note: All four of the tested Basen 26650’s were the newer, light-weight (88g-89g) version.

Rule 1-1 as it applies to life, take it as it comes.

Bort
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The voltage may be rising slower on the low charge rate hence extra juice before termination?
Just a theory

I’ll have to try this on a battery when i get a chance

Batteries like NiMH won’t overcharge, they just bleed extra energy as heat, but li ion will accept more juice, at the cost of battery life, and higher failure/explosion risk.

Since both are terminating at the same voltage (presumably) the extra juice should not affect risk, but will of course affect cycle life because full charges reduce li ion lifetime regardless of this phenomenon.

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Could there be a correlation between this thread, and this one ??

http://budgetlightforum.com/node/45700

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This is part of how normal cc/cv works. The end termination current is dependent on your charge rate.

At 500mA charge rate, a 10% termination current would cutoff charging at 50mA, allowing a bit more to be pushed into the cell.

But not all chargers use a termination current that is a set percentage of the overall charge rate. So this may or may not be a factor with the Liitokala Lii-500. This is why seeing a actual chart of the charge profile is so useful.

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I have more 26650’s ordered and will charge at the 500mA rate. Curious too. I have had good luck with them in use.

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I have the Liitokala Lii-500 and have noticed that the lower (500, 300) charge rates to pack more juice in, but not this much difference. typically it is around 10-20mAh

sweet spot may be to charge fast up to 4.2 then switch to low charge rate for the final >200mAh of charging.

(“It’s good that most people can’t remember their previous lives. Otherwise
things would be a lot more complicated than they already are.”
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HereAgainAgain wrote:
Could there be a correlation between this thread, and this one ??

http://budgetlightforum.com/node/45700

Previously cross-referenced. http://budgetlightforum.com/comment/933007#comment-933007

 
 

Halo… wrote:
This is part of how normal cc/cv works. The end termination current is dependent on your charge rate.

At 500mA charge rate, a 10% termination current would cutoff charging at 50mA, allowing a bit more to be pushed into the cell.

But not all chargers use a termination current that is a set percentage of the overall charge rate. So this may or may not be a factor with the Liitokala Lii-500. This is why seeing a actual chart of the charge profile is so useful.

“A bit more to be pushed into the cell” is expected, but 340mAh more???

 
 

Ronin42 wrote:
I have the Liitokala Lii-500 and have noticed that the lower (500, 300) charge rates to pack more juice in, but not this much difference. typically it is around 10-20mAh

sweet spot may be to charge fast up to 4.2 then switch to low charge rate for the final >200mAh of charging.

Now that is what I would have expected, something more along the lines of 1% or 2% difference.

Rule 1-1 as it applies to life, take it as it comes.

HereAgainAgain
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1dash1 wrote:
HereAgainAgain wrote:
Could there be a correlation between this thread, and this one ??

http://budgetlightforum.com/node/45700

Previously cross-referenced. http://budgetlightforum.com/comment/933007#comment-933007

Sweet – cheers Smile

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1dash1 wrote:
Halo… wrote:
This is part of how normal cc/cv works. The end termination current is dependent on your charge rate.

At 500mA charge rate, a 10% termination current would cutoff charging at 50mA, allowing a bit more to be pushed into the cell.

But not all chargers use a termination current that is a set percentage of the overall charge rate. So this may or may not be a factor with the Liitokala Lii-500. This is why seeing a actual chart of the charge profile is so useful.

“A bit more to be pushed into the cell” is expected, but 340mAh more???

It certainly seems to be a larger difference than one would expect. But remember these cells aren’t manufactured by one of the real major players in li-ions (Pana/sanyo,LG,samsung,sony). Perhaps these cells suffer at a 1A charge rate. It’s not like there is an official datasheet for them. And even at 500mA, the cells don’t all track that well. #4 is deficient by almost 100mAh. Big name quality cells tend to track together closely.
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Halo… wrote:
Perhaps these cells suffer at a 1A charge rate. It’s not like there is an official datasheet for them. And even at 500mA, the cells don’t all track that well. #4 is deficient by almost 100mAh. Big name quality cells tend to track together closely.
#4 is weird. Question

100mAh less than the others when charged at 1A.
100mAh more than the others when charged at 500mAh.

Rule 1-1 as it applies to life, take it as it comes.

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When you discharge at 1A voltage drop is bigger then at 0,5A so if you remove battery from charger after discharging at 1A you will get higher voltage, maybe around 0.2-0.3V That can explain 300 mAh?

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NikolaS wrote:
When you discharge at 1A voltage drop is bigger then at 0,5A so if you remove battery from charger after discharging at 1A you will get higher voltage, maybe around 0.2-0.3V That can explain 300 mAh?

thats an interesting thought
however the OP has discharged both at 500mA using the charger which i believe only has a 500mA discharge option.

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Quote:
however the OP has discharged both at 500mA

Oh my bad, I would try another circle with 1A, and then compare results. Maybe they are getting better and better with usage… Big Smile

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NikolaS wrote:
Quote:
however the OP has discharged both at 500mA

Oh my bad, I would try another circle with 1A, and then compare results. Maybe they are getting better and better with usage… Big Smile


It could be if they are new batteries with very few cycles
I’ll have to try this with my liitokala 300 sometime, when i have the time to burn

The Journal of Alternative Facts TM

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cbrake10
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If I’m not mistaken, the LiitoKala discharges at a rate of 250ma when the 500ma charge setting is selected.

-Clark

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cbrake10 wrote:
If I’m not mistaken, the LiitoKala discharges at a rate of 250ma when the 500ma charge setting is selected.

I checked and you are correct! [link]

I’m chagrined to have missed that Blushing , but thank you for helping solve the mystery Smile .

Not sure if it completely solves the discrepancy, but it might account for half of it.

Rule 1-1 as it applies to life, take it as it comes.

JPLight
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As I ow a Lii-500 as well I was just going to say this. cbrake10 was faster. Wink
I am pretty sure this is the main reason for your “mystery”.

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I charged my Basens at 1000ma, let them rest overnight, then selected the normal test function & 1000ma discharge rate which I believe is actually a discharge of 500ma with the Li-500.
The strangest thing with my Basen“s is that immediately off the charger they only show a charge of 4.16v then settle at 4.15v after resting.
My other new cells charged with the Lii-500 show 4.19v immediately off the charger & 4.18v resting voltage ?

Ian