Would anyone have specs on this cell?
- Thread starter ebike11
- Start date
e-beach
10 MW
e-beach
10 MW
From what Justin Le has found, it is not the bottom end of the charge that kills the cells early, it is the top end. However it is all about full cycles. If you only go 80% of DOD, you aren't going very far unless you have a huge battery pack. But, your cells will last while you aren't going very far.
Yes maybe even more stupid to charge with AHT all the way to 4.2Vpc and let the pack sit there, but it isn't an either/or thing, avoid the shoulders on both ends if you want longevity.
The Avg DoD vs lifecycle charts are so clear, objective proof and all vendor tests agree, there really is no room for differing opinions on the general principle.
Yes, ideally the capacity usage should be centered around the midpoint voltage, not at the top or bottom.
The Avg DoD vs lifecycle charts are so clear, objective proof and all vendor tests agree, there really is no room for differing opinions on the general principle.
Yes, ideally the capacity usage should be centered around the midpoint voltage, not at the top or bottom.
john61ct said:
Yes i thought that to get more life from the pack then I thought from posts on here that mentioned to stop charging at 4.1v is recommended. But in another thread i posted...some people say just charge all the way to 4.2v...so conflicting views
Yes, several reasons for that.
Some want every scrap of possible range, and just don't care that much about longevity, happy to just replace their pack more frequently.
Some just don't believe the range sacrificed is that tiny.
Some just don't believe the cycle losses are that great.
And some just want to follow what vendors tell us, interpret the min/max specs as reco's for normal usage.
Some want every scrap of possible range, and just don't care that much about longevity, happy to just replace their pack more frequently.
Some just don't believe the range sacrificed is that tiny.
Some just don't believe the cycle losses are that great.
And some just want to follow what vendors tell us, interpret the min/max specs as reco's for normal usage.
hemo
100 W
From my experience the top 0.1v carries little capacity ( In a typical 10s5p or 13s 5p pack) and certainly no where near 10% of cell capacity or range.
I find within 1 -1.5 miles that any voltage if charged to 4.2v is used up very quickly and cells are down to 4.1v or there abouts. For the sake of such a low range loss it pays not to shorten cell life for the sake of that 0.1v of little use.
If battery has a BMS fitted charge to 4.1v and occasionally (every dozen or so full charges) charge to 4.2v just to ensure balancing isn't varying to much. Balancing is quite easy to understand if a battery/pack is suffering, mileage will be somewhat compromised and an unbalance lower group will induce lvc/cutting out sooner.
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I find within 1 -1.5 miles that any voltage if charged to 4.2v is used up very quickly and cells are down to 4.1v or there abouts. For the sake of such a low range loss it pays not to shorten cell life for the sake of that 0.1v of little use.
If battery has a BMS fitted charge to 4.1v and occasionally (every dozen or so full charges) charge to 4.2v just to ensure balancing isn't varying to much. Balancing is quite easy to understand if a battery/pack is suffering, mileage will be somewhat compromised and an unbalance lower group will induce lvc/cutting out sooner.
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DogDipstick
100 kW
hemo said:
( I think you mistyped 0.10v vs 1v) ( most cells use all vapacity from 4.2 to 3.2... 1 volt. )
It really depends on the cell and chemistry.... The SOC map. My ebike cells have a load of ah above 4v, and alot below 3.6v in Ah capacity. The 4.05v-4.15v charge puts in like 4 Ah of 15. Below 3.6 you have about 7Ah. Thats 10Ah of the whole, with only 5Ah in between 4.05v and 3.6v... Majority of the capacity is above and below those.
I am forced to charge to 4.07v/cell, for the controller HVC. However, having the extra Wh ( cells) in the string is more important to me than the lost capacity by not charging past 4.07v....
As a whole, @ 20s, charging to fullfullfull, 4.15v/cell, I had 1270 usable Wh.
Now, @ 21s, charging to almost but not quitefull, to 4.07v, I have a total of 1300Wh usable, small increase, but the lifespan will have increased much more. I do not mind riding with 13-14Ah usable, not using the top 1.5Ah for 15.5Ah total.
None of those voltage numbers being tossed around mean anything at all
unless you specify, at rest, while charging or while discharging.
No one is advising stopping charging at 4.0V or even 4.07V.
A 4.07V stopping point is giving up more capacity than is justified by longevity.
And measuring **charger output** between say 4.15V and 4.2V, means nothing about the mAh that are actually stored in the cell.
Similarly no one is advocating stopping usage when **resting** voltage is above 3.4V much less anything nuts like 3.6V
And under load the LVC needs to be **much** lower.
How low is up to each use case, the users' needs and preferences
unless you specify, at rest, while charging or while discharging.
No one is advising stopping charging at 4.0V or even 4.07V.
A 4.07V stopping point is giving up more capacity than is justified by longevity.
And measuring **charger output** between say 4.15V and 4.2V, means nothing about the mAh that are actually stored in the cell.
Similarly no one is advocating stopping usage when **resting** voltage is above 3.4V much less anything nuts like 3.6V
And under load the LVC needs to be **much** lower.
How low is up to each use case, the users' needs and preferences
DogDipstick
100 kW
john61ct said:
(Im saying different cells have different SOC maps, do you agree? For real, take a HK lipo down below 3.8v alot and you got a dead puffed lipo.. after a few high power pulls....
but our EV cells like give mega-mAh out under 3.8v/cell... like > 60% based on what I have found.... of the MAH...)
You left out the most important bit
None of those voltage numbers being tossed around mean anything at all
**unless you specify, at rest, while charging or while discharging.**
And yes that is exactly the point, the **current rate** is what makes all the difference.
Far more than minor chemistry differences, unless you get into LTO or LFP.
None of those voltage numbers being tossed around mean anything at all
**unless you specify, at rest, while charging or while discharging.**
And yes that is exactly the point, the **current rate** is what makes all the difference.
Far more than minor chemistry differences, unless you get into LTO or LFP.
DogDipstick
100 kW
john61ct said:
True, I was at the assumption of OCV at rest.
hemo
100 W
Yes it was a typo on my part, I have modified the post to reflect the error.
DogDipstick
100 kW
john61ct said:
Well, John, Ty you were right. I just did a full baseline on bike ride for distance.
I just took a ride, and the increase in speed between 21s and 20s is negligible. The power is negligible. The range decrease is not.
Even though a significant increase in voltage, with 1 more cell, the 21s string is restricted to 85.6v... so as not to trip controller HVC. The 20s charged voltage was 4.15v/cell, and I would get 14-15 ah rides. ( 1270wh?)
Now my charged voltage is 4.05v / cell, and I only pulled 13Ah out with my bike and the 21s.. (1300wh) because of the increase in LVC and the restriction of HVC. No gains for the power or speed and the range was almost worse, with the 4.05v cutoff point. Hit the LVC and had to pedal the last mile, and got the ( practically the same) same range +/- a mile. With one whole 15Ah cell extra in the string, but the Wh were no there.
Dammit Experience wins again. Durrnit.
DogDipstick
100 kW
I looked again and it was nowhere near 1300wh.. more like 1100wh total till I hit LVC.
