Why Charge to 80% and the use of smart BMS in Zen 52V,20Ah UL-2271 battery

[Ravi Kempaiah]

One of the features that we have implemented in our Photon Pro and Ultra bikes with 52V, 20Ah batteries is the smart BMS with the adjustable limit for an increased lifetime.
These modes can be changed with the simple click of a button on the control display. I don't know of any other E-bike that comes with such a feature. Our hope is that people make use of this feature and prolong the life of the battery.

You may want to watch this video to understand why 80% charge benefits the overall lifetime of batteries. It's not just us, Tesla and Apple also recommends 80% charge for batteries [see image below]

 

[il Munduato]

My Samsung tablet.
They've had this feature for years.

I've been following this advice from Battery University and set my version of the DIY Smart Charger to optimal charge voltage (51V for a 48V battery) by default

In terms of longevity, the optimal charge voltage is 3.92V/cell. Battery experts believe that this threshold eliminates all voltage-related stresses; going lower may not gain further benefits but induce other symptoms(See BU-808b: What causes Li-ion to die?)



@spokewrench... just another fad

 

[mbremner]

Hi Ravi,

I believe that I have seen some discussion of occasionally charging to 100% in order to "balance" the cells. What is your recommendation regarding this practice? If you recommend it, how often do you think it should be performed?

 

[Ravi Kempaiah]

Hi Ravi,

I believe that I have seen some discussion of occasionally charging to 100% in order to "balance" the cells. What is your recommendation regarding this practice? If you recommend it, how often do you think it should be performed?

Our BMS balances the cells even at 50% state of charge.
The primary reason for charging to 100% is to recalibrate the BMS for accuracy. It is good to charge to 100% once a month and then draw it down. So, the BMS knows what is true 100% regarding voltage.

 

[il Munduato]

Our BMS balances the cells even at 50% state of charge.
The primary reason for charging to 100% is to recalibrate the BMS for accuracy. It is good to charge to 100% once a month and then draw it down. So, the BMS knows what is true 100% regarding voltage.

But for clarity.. The full 100% charge doesn't change the battery's capacity, its to keep the percentage fuel gauge accurate on the display... Correct?
I've always read the calibration instructions reversly. You drain the battery down near cut off and then fully charge to mark the low and high points. But again this is for display accuracy and doesn't change the battery's capacity in any way... And only if your system has the built in ability to calibrate.
Then one could argue that a full discharge and charge are 2 of the major factors in battery degradation after temperature... Is it really prudent to do so unnecessarily?
I find fuel guages can be more trouble than they are worth. Knowing your battery voltage and how it acts near full and near empty more helpful... But this might be too much trouble for the average Joe so I digress.

Is this still the case or are things changing/improving?

 

[Mike_V]

I do not believe you are correct in your assumption Mr. Ravi Kempaiah. Show us your data upon which you based your conclusion. Where is the data used by Dr. Jeff. Dahn?
Because here is fresh ongoing cyclical test data 100% each and every time ( after time ), see for yourself, IF you can read a graph and IF you understand electrical theory.
1) 12/24/21 https://endless-sphere.com/sphere/t...-high-power-density-cylindrical-cells.114473/
2 12/26/21 https://endless-sphere.com/sphere/t...high-energy-density-cylindrical-cells.114486/

 

[peterh_nz]

My Samsung tablet.
They've had this feature for years.

Yes, ditto my Samsung mobile.

 

[Mike_V]

One of the features that we have implemented in our Photon Pro and Ultra bikes with 52V, 20Ah batteries is the smart BMS with the adjustable limit for an increased lifetime.
These modes can be changed with the simple click of a button on the control display. I don't know of any other E-bike that comes with such a feature. Our hope is that people make use of this feature and prolong the life of the battery.

You may want to watch this video to understand why 80% charge benefits the overall lifetime of batteries. It's not just us, Tesla and Apple also recommends 80% charge for batteries [see image below]

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Mister Ravi Kempaiah:
1) Will you reference the long term cyclic test data for your products that show they 'last longer' if your customer uses this feature?
2) Will you refernce the test data used as the basis for the colorful pages of Jeff Dahn's summary or Tesla's or Apple's reference data
( for different cells? ) that you based your product claim upon?
Mike

 

[Ravi Kempaiah]

Mister Ravi Kempaiah:
1) Will you reference the long term cyclic test data for your products that show they 'last longer' if your customer uses this feature?
2) Will you refernce the test data used as the basis for the colorful pages of Jeff Dahn's summary or Tesla's or Apple's reference data
( for different cells? ) that you based your product claim upon?
Mike

We do our own extensive testing. We have tested major E-bike batteries, including Bosch.
The testing includes cycling at 35 degrees C and 45 degrees C, and based on this testing data, we are confident of offering 3-year warranty on batteries.
You can see our batteries being tested in the second picture. We have 88 channel testing different cells and we have almost every major 21700 cells manufacturer and we do very extensive testing.

 

[il Munduato]

We do our own extensive testing. We have tested major E-bike batteries, including Bosch.
The testing includes cycling at 35 degrees C and 45 degrees C, and based on this testing data, we are confident of offering 3-year warranty on batteries.
You can see our batteries being tested in the second picture. We have 88 channel testing different cells and we have almost every major 21700 cells manufacturer and we do very extensive testing.

View attachment 186698

View attachment 186699

Do you add the hot sauce during or after.... and how do you know when they're done?

 

[Blunoser]

Lol, I put that S**t on everything.. But seriously, the real question is, what kind of wine to go with?

 

[Mike_V]

We do our own extensive testing. We have tested major E-bike batteries, including Bosch.
The testing includes cycling at 35 degrees C and 45 degrees C, and based on this testing data, we are confident of offering 3-year warranty on batteries.
You can see our batteries being tested in the second picture. We have 88 channel testing different cells and we have almost every major 21700 cells manufacturer and we do very extensive testing.

View attachment 186698

View attachment 186699

"Quoted"
1) 12/24/21 https://endless-sphere.com/sphere/t...-high-power-density-cylindrical-cells.114473/
2 12/26/21 https://endless-sphere.com/sphere/t...high-energy-density-cylindrical-cells.114486/


Product claim as above:
"One of the features that we have implemented in our Photon Pro and Ultra bikes with 52V, 20Ah batteries is the smart BMS with the adjustable limit for an increased lifetime.
These modes can be changed with the simple click of a button on the control display. I don't know of any other E-bike that comes with such a feature. Our hope is that people make use of this feature and prolong the life of the battery."

I have not seen any data, from any source, that shows the measured life improvement during repeated cyclic testing at 80%.
The data that I referenced above is for true cyclic testing at 100% to measure cell design development.