Does charging battery to 90% Really extend battery cycle

[tomtom123]

I've been watching of of this dude's video and it's pretty fun to watch. https://www.youtube.com/user/bjornnyland/videos

I noticed he only charges his Tesla model S 18650 car battery to 90% because he says it helps extends overall battery cycle life in the long run. Is this really true?

Anyone here tried charging battery to only 90% max for Lifepo4 or li-ion nico battery and see if it extends the number of cycles you can get off a battery?

 

[parajared]

Sure does, and the little tiny amount of extra charge you cram in those batteries to get 4.20 volts is gone within the first minute or two of the ride anyway.

 

[Jason27]

Shallow discharges, followed by topping off charging does extend battery life. I have been using the same battery on my ebike for a few years now.

 

[FfredDRredD]

TT hope you don't mind hijack- I was wondering if charging slow helps also because one of the two 36v chargers didn't work when I got it so I use just the one that works and switch it between the two ports- Steve

 

[dnmun]

you can start your own thread on your charger and we can help you fix it. i assume you have two 36V packs in series so need both chargers at the same time.

 

[liveforphysics]

Yes. It really does.

So does never discharging below 20% or so.

Many batteries will last >10x more cycles if you charge to ~80% and never discharge below ~30%. Yes that means you only get half the capacity.

 

[Racer_X]

Yes. It really does.

So does never discharging below 20% or so.

Many batteries will last >10x more cycles if you charge to ~80% and never discharge below ~30%. Yes that means you only get half the capacity.

Subscribed to this thread waiting to hear from an experienced member on the subject and Walaaaaa!
Thanks for confirming liveforphysics

 

[zener]

Yes. It really does.

So does never discharging below 20% or so.

Many batteries will last >10x more cycles if you charge to ~80% and never discharge below ~30%. Yes that means you only get half the capacity.

This and keeping them always under 35*C and take a slow charge.

Sad that they only test the full charge - discharge cycles and not some 90%-15% and 85%-20% or similar would be good to know as buyer.

 

[dogman dan]

Doesn't the Tesla model S already have a fairly conservative charge discharge % built into it?

So if the 100% charge is already de rated to 90 or 95%, does this guy gain much by undercharging it 10% more than the designers planned on? Apparently so, but does it still work if he discharges deeper? If he has the range to go 80%-30%, then by all means do it.

I can definitely see stopping sooner having a big benefit, but why not charge to what the designers intended? Then stop with less dod. Which is worse, charging to 100% or discharging to 100%. Intuition tells me that if the top of charge is already de rated, then keeping the dod less might be the most important.

Waiting till the last minuite to start recharging makes a lot of sense too. So maybe charge to 80% at most before parking overnight could work, then finish the charge while you eat breakfast.

From what I have been reading, you might get the most benefit from parking in the shade, or even in a climate controlled garage if you live in the desert.

 

[Racer_X]

Waiting till the last minuite to start recharging makes a lot of sense too. So maybe charge to 80% at most before parking overnight could work, then finish the charge while you eat breakfast.

I have two LiPo bulk chargers. One charges to 90% 4.1v per cell and the other charges to storage level 60% 3.85v per cell.

I charge with my storage level LiPo bulk charger every night and let it sit until the morning.

In the morning I start the 90% bulk charger as soon as I wake up and by the time I am ready, my battery is ready for my commute to work or for any trip that will need 45% or more of my battery.

I also use the storage level 60% LiPo bulk charger alot on the weekends since my usual local commuting is 5km or less (stores, school, friends). I seldom go below 45v on my LiPos. Thanks to all your inputs it gives me peace of mind knowing that I am doing all that I can to prolong the life of my two LiPo packs.
So far 3 years of daily commute with my lipos and counting.... Batteries are still giving me good results.

 

[liveforphysics]

Charge rate isn't nearly as big of a factor as how high you charge, provided your rate is still low enough that you have adquate ionic mobility in the anode to prevent any metallic lithium formation between the SEI and anode material.

It's a very steep exponential curve for charge voltage vs rate of electrolyte decomposition. So, just charging to 4.1 vs 4.2 makes a massive difference in gas production and cell decay while a cell is just sitting charged.

If your cell uses all extremely pure extremely stabilized electrolyte and anode/cathode materials, you can make cells that don't puff noticably even sitting at 4.35v for years. Try to do it with a typical RC Lipo cell and you might be puffed in a day or two sitting. Most Lithium Cobalt cells we use in our ebikes benefit greatly in life expectancy running a 4.1-4.125v HVC and ~3.5-3.6v LVC. For NMC you want to be running the same HVC, but it's not damaging anything to discharge to 3.0-3.1v on LVC.

 

[dogman dan]

That's interesting info about the difference on discharge v for hobby lico and nmc.

I know I should charge to less v, but right now I am charging all my RC packs to 4.15. Just want that bit of range, and 4.1v was costing a lot of capacity. On the other end, I don't mind stopping at 3.6-3.65. Not that much range left below 3.6v.

I still have to wonder though, about the model S. What % charge is "fully charged"? I assume they are not setting chargers to charge to 4.2v per cell. If they only set to 4.1v now, why try to undercharge more than that is what I mean.

 

[DrkAngel]

This capacity map tells a lot.

Limiting charge-discharge to between 3.7V and 3.9V provides ~55% capacity ...
with an estimated 800% battery life! (possibly more?)

Important to notice is that each .1V does not contain equal mAh!
3.8V to 3.9V stores 400% the energy as 3.9V to 4.0V.
3.6V to 3.7V stores ~17% the energy as 3.7V to 3.8V!
3.5V to 3.6V stores <10% the energy as 3.7V to 3.8V!

Logically:
Discharging from 3.7V to 3.6V might degrade cyclic life to the same degree as discharging from 3.8V to 3.7V ...
Equals 600% damage per mAh! ... ?

See - Battery Deterioration

 

[Racer_X]

Limiting charge-discharge to between 3.7V and 3.9V provides ~55% capacity ...
with an estimated 800% battery life! (possibly more?)

Great info! I have noticed that when I charge to 3.86V = 46.4 on my 12s LiPo I have quite of bit of range with my battery packs.
My 10ah can go about 6km and my 15ah can go about 10km before it hits 3.7V OR 44.4v on my 12s LiPo.

If I was to experiment and use one brand new pack of LiPo batteries at these levels from the very beginning it can theoretically last at least 10 years before significant capacity loss start to show. That is a long time with the same pack!

 

[DrkAngel]

See threads about mapping battery capacity ... for determining optimal charges and discharges.

Capacity Profile
Capacity Map
Capacity Mapping
Lithiums - mAh/100th V - Discharge Tests
Determining Optimal Charge Voltage

 

[Punx0r]

If I was to experiment and use one brand new pack of LiPo batteries at these levels from the very beginning it can theoretically last at least 10 years before significant capacity loss start to show. That is a long time with the same pack!

Unfortunately batteries also have a calander life as well as a cycle life!

 

[Ykick]

Yes it does. And avoiding deep discharges and uncomfortably high operating temperatures. Plus, leaving an extra bit of capacity often saves the day when things fail to go as planned.

 

[DrkAngel]

Limiting charge-discharge to between 3.7V and 3.9V provides ~55% capacity ...
with an estimated 800% battery life! (possibly more?)

Great info! I have noticed that when I charge to 3.86V = 46.4 on my 12s LiPo I have quite of bit of range with my battery packs.
My 10ah can go about 6km and my 15ah can go about 10km before it hits 3.7V OR 44.4v on my 12s LiPo.

If I was to experiment and use one brand new pack of LiPo batteries at these levels from the very beginning it can theoretically last at least 10 years before significant capacity loss start to show. That is a long time with the same pack!

I've seen no investigation as to whether:
lower voltages prolong life vs limiting use to energy rich regions of voltage prolong life?

Staying within these energy rich regions seems more logical!

This is the capacity map I made from 2600mAh Sanyo cells I've been recycling.

It concurs fairly nicely with the above LiPo graph.
3.7V to 3.9V looks optimal, but I have been charging to 4.05V so as to take advantage of that last capacity bulge.
4.05V figures to a ~300% cycle life over 4.2V at a minimal capacity loss.

Tougher for me to figure are the Recycled LiPo I acquired.
They have an inexplicable capacity bulge at ~4.12V.
I had to run the test twice!

Limiting charge to 4.05 is most effective at prolonging life cycles ... but this neglects the storehouse of energy between 4.10V and 4.15V.

My solution will be to typically charge to <4.05V for normal use and occasionally charge to >4.15V for longer trips etc.
My standard pack holds 7s12p = 25.9V 25.92Ah but I typically use <5Ah for around town errands.

 

[dogman dan]

Still gonna wear out fast if you park it in the sun where I live.

My personal experience with pings for example. One had 700-1000 cycles on it and lasted 3.5 years. Another had 200 cycles and puffed and died at 3 years. Neither one died of cycles, they died of my garage.

In my climate, 3 years is what you get, more or less.

HK packs last 2 years. In my climate, it's a calendar thing unless you go out and murder it faster.

 

[cwah]

yeah no point to try to preserve them so much from life cycle as calendar life is going to kill them in few years time anyway :lol:

 

[wineboyrider]

Still gonna wear out fast if you park it in the sun where I live.

My personal experience with pings for example. One had 700-1000 cycles on it and lasted 3.5 years. Another had 200 cycles and puffed and died at 3 years. Neither one died of cycles, they died of my garage.

In my climate, 3 years is what you get, more or less.

HK packs last 2 years. In my climate, it's a calendar thing unless you go out and murder it faster.

That's why I am thinking about refrigerating my packs when not used ..

 

[liveforphysics]

There is a thermal kinetics decay equation for batteries based on a bunch of factors.

The rule of thumb you get from it is for every ~10degC up your calendar decay rate doubles. For every 10degC cooler it's cut in half. Just don't go much below freezing unless you know for certain your cells can handle storage there.

 

[Ykick]

My RC Lipo calendar life has been pretty decent. 3-1/2 years, about 1000 shallow cycles finally down to about 60-70% original capacity.

However, I tend to treat RC Lipo like a good guitar so if it's too hot or cold for me it's probably too hot or cold for my guitar or battery pack.

 

[mrzed]

So basically you need to store batteries like a potato. Cellar temp with your fine wines and winter squash, onions and apples.

 

[999zip999]

don't over discharge the batteryand ll will be fine. Do fully charged and balance. To extend battery life. Midrange is the best not the top not the bottom.