-- Battery Shelf Life --

[Johnbear]

Here is the information from YESA's website for lifepo4.

Battery Maintenance And Storage



(1).Before first use, the battery should be fully charged, after 3-5 times fully charge and discharge, the battery can have max capacity.

(2).Timely charging can greatly extend the battery lifecycles, after discharging, the battery should be charged in time, and keep the battery in normal capacity, long time in low voltage will greatly reduce the lifecycles.

(3).The battery should be charged in ventilation and dry condition, avoid approaching fire, it's better to get the battery off the E-bike when charging.

(4).The Optimum working condition is 15-40. Beyond this temperature may affect the battery performance.

(5).Do not connect the positive pole and the negative pole directly, may short circuit and cause danger.

(6).Do not use organic impregnate to clean the battery, if on fire, do not use CO2 (carbon dioxide) fire extinguisher, But use CCl4 fire extinguisher.

(7).If the battery packs have some problem, please deliver to the manufacture or the authorized technician; please do not uninstall it by yourself.

(8).Do not put your E-bike in insulations in hot summer.

(9).When temperature is higher than 40, the battery lifecycles may reduce and the BMS may shut down the battery output for protection. Therefore, the battery should be avoiding insulation in summer.

(10).When temperature is below -10,the battery lifecycles will also reduce, and the battery can only keep about 70% capacity, therefore, your E-bike may cover less miles in winter, it's normal.

(11).The battery should be placed indoor in winter, so does charging.



Note For Charging:



(1).Must use the charger provided by the manufacture or manufacture authorized charger.

(2).Charger the battery with proper charger, the lamp turn red when charging, when the indication lamp turn green, this shows that the battery is full charged, 2-3 hours extra charging will be better.

(3).Do not connect the charger with the battery with AC power for long time when it's fully charged.

(4).Do not connect the charger with AC power without battery for a long time.

(5).Please charge the battery in dry, ventilated and no fire condition, do not uninstall the battery.

(6).Do not have any thing easily catch fire within 1.5 meters when charging.

(7).Do not charge near things easily catch fire or explode.

(8).It's better to get the battery out of the E-bike when charging, to release the heat.

(9).When charging, put the charger beyond children's touch, avoid danger.



Note For Discharging:



(1).Try to avoid high discharge current, too high current may reduce the lifecycles.

(2).Please accelerate slowly, avoid sharply accelerate when start the motor.

(3).Do not start from quiescence at brae, when toughly operation, better to pedal.

(4).When start in low temperature, it's better to pedal to start and keep the battery indoor.

(5).Go uphill, go on the bridge or run against the wind, better to pedal to support.

(6).Put the battery gently.

(7).When run in rain, avoid the water in the battery, BMS and motor, avoid short circuit.

(8).Take the battery off the E-bike or cut off the power when do not use it, avoid the load discharge from the battery, strictly prohibit to storage the battery in low voltage.



Note For Storage:



(1).The batteries shall be storied within environmental condition of 0~30 not less than 75% relative humidity. And don't dispose near the fire and expose in the sunlight.

(2).When in mass storage, it's better to keep 50% capacity, better to keep the battery no more than one year.

(3).In order to avoid over discharge, it's better to charge the battery in 3 months, charge it for 2 hours a time.

(4).For mass storage, take measures to avoid fire, keep each battery a distance or put some material to prevent it catching fire.

 

[Link]

"(5).Do not connect the positive pole and the negative pole directly, may short circuit and cause danger."

It might? There's a chance of it shorting out if you short out the poles? No, rly?

Those notes on not accelerating hard from a stop will be blatantly ignored, methinks 8).

 

[monster]

a picture is worth a thousand words. but safe's are worth zero, because he does not label the axis! :lol:

 

[Toorbough ULL-Zeveigh]

Lead Acid is easy... just keep the battery 100% full all the time and never drain it much and it lasts the longest.

That's about as useful as an air-conditioner that works great as long as there's snow outside & don't tax it too much or else it'll seize up.

 

[safe]

Here is the information from YESA's website for lifepo4.

(2).When in mass storage, it's better to keep 50% capacity, better to keep the battery no more than one year.

Well I guess we can say this is hard proof from YESA.

If you want to extend the long term shelf life and less frequent regular use of your LiFePO4 battery packs you NEED a two stage charging process:

Charge to 50% for Storage. (overnight or longer)

Charge to 100% just before Riding.

Are we in total agreement that this is what has to be called a:

"HARD FACT"

...without much debate left about it?

You can't easily prove the negative, so if you ignore the two stage process you still might get pretty long life because LiFePO4 is generally good stuff, but if you want to add an extra two or three years to the shelf life of your cells this will do it... this effects shelf life, but not cycle life.... an important point to remember.

A123 uses a lower baseline voltage for their chemistry so they are by design less effected by charge level, however, I'm sure even for them they could be given better shelf life at 50% than at 100% charge. One day all the cells might use A123's low voltage design and it will be largely ignored. Or not. Apparently the Chevy Volt people still think it's important for some reason and they are teamed up with A123.

 

[Ypedal]

Safe, this is not proof of anything, or evidence either.. this is purely your own assumption.. might be right.. could be wrong...

Until you personally buy a few dozen of these packs and test them for 10 years... this is all it is.. assumptions.

The chinese are notorious for copying sections from other companies sites without testing or even understanding what they type... :|

 

[safe]

Not convenient at all!

LiFePO4 is capable of being completely recharged in less than an hour. A half charge might be half an hour. Seems to me that if when you got up in the morning you turned on the coffee pot and switched on the top off charger that by the time you got done with breakfast the cells would be topped off. I suppose you could set the storage charge a little higher to like 80% charge and then just have to do 20% in the morning.

Sounds like your problem is a weak charger... you must be charging at less than 0.5C or worse. Many LiFePO4 cells can handle as high as 3C, though doing that might do as much damage as the storage issue tries to remedy. I personally would keep it down below 1C and closer to 0.5C.

 

[safe]

The chinese are notorious for copying sections from other companies sites without testing or even understanding what they type... :|

I'd like to see someone from A123 say:

"Oh yeah, the guys at Chevy Volt are keeping the charge of our A123 cells between 30% and 80% because of reasons that are not related to shelf life or long cycle life. It's because of XYZ..."

Until we get solid evidence to the contrary we should stick with the facts and the facts as we know them are that a full charge with LiFePO4 does more damage than a 50% charge.

Suggesting otherwise would be irresponsible...

 

[Ypedal]

[
Wouldn't to suggest otherwise be irresponsible?[/color]

Quite the oposite.

 

[Ypedal]

In regards to the Volt..

I could " Assume " that it might have something to do with Regen... might have to leave some capacity to soak up energy if you hit a big hill wen leaving home.. ? maybe ?

 

[safe]

Quite the opposite.

It just sounds like without evidence you are trying to prove something that makes you feel good. If you want to continue to charge your cells to full for the overnight hours then by all means go ahead and do it. The long term effects might be small enough that it will not matter that much. We're only talking about a decrease in decline rates from 10%-20% per year under normal full charge conditions to around 5%-10% decrease under half charge conditions. You will be adding only about a 10% improvement in shelf life... so a battery that might last 5 years using the full charge method might then last 6-7 years using the partial charge method.

Many might just decide the hassle is not worth that attention.

Also, most people cannot accurately run a two stage charging process so they really don't have access to the technology to do this.

I'll email Patrick and ask what the "pros" do with their cells in storage... maybe he can post and comment...

 

[Ypedal]

It's not about feeling good..

It's more that i'm worried a new member comes in here.. reads your threads and starts doing weird things to his/her packs... thinking you know everything under the sun about lithium chem/tech....

 

[safe]

It's more that i'm worried a new member comes in here.. reads your threads and starts doing weird things to his/her packs... thinking you know everything under the sun about lithium chem/tech....

Let me ask you this...

Can it HURT to store LiFePO4 at 50% overnight?

Is there any possible scenario that you can imagine where 50% charge storage would make matters worse?

What would be worse is to not recharge an empty pack... and let me WARN EVERYONE that doing so would cause more damage than simply charging to full. You need to get to 50%... not 20%... so without a charger that gives some kind of feedback about the degree of charge you might be at risk of causing harm.

Proper cautionary messages have now been officially made.

 

[Ypedal]

I've spent 3000 $ + of my own hard earned money to try and figure that out first hand.. but i don't yet know. :wink:

I do agree that charging 50 % instead of 100 % could result in a slip of the brain cells that leads to forgetting to fully charge before heading out for a ride... then drain below 2v per cell and damage the pack permanently.... THAT is a real concern.

 

[safe]

I do agree that charging 50 % instead of 100 % could result in a slip of the brain cells that leads to forgetting to fully charge before heading out for a ride... then drain below 2v per cell and damage the pack permanently.... THAT is a real concern.

Agreed.

The problem is that chargers are made to be simple and cheap. The Zivan chargers have programmable charging patterns so you could make decisions about a storage charge if you knew that the cells would be sitting around for a while. Most chargers simply charge to "full" and give no other option. I'll be curious about Patricks response when it comes because he's got all the tools and would be the best to know.

My SLA's are very simple... you just keep them 100% full all the time and any amount less than full translates to direct losses. The deeper you go the worse the loss. Lithium seems to follow a shape where the high and low is bad, but the middle charge is good. So it's a little more complicated.

 

[EMF]

Here is the information from YESA's website for lifepo4.

(2).When in mass storage, it's better to keep 50% capacity, better to keep the battery no more than one year.

Well I guess we can say this is hard proof from YESA.

If you want to extend the long term shelf life and less frequent regular use of your LiFePO4 battery packs you NEED a two stage charging process:

Charge to 50% for Storage. (overnight or longer)

Charge to 100% just before Riding.

Are we in total agreement that this is what has to be called a:

"HARD FACT"

...without much debate left about it?

You can't easily prove the negative, so if you ignore the two stage process you still might get pretty long life because LiFePO4 is generally good stuff, but if you want to add an extra two or three years to the shelf life of your cells this will do it... this effects shelf life, but not cycle life.... an important point to remember.

A123 uses a lower baseline voltage for their chemistry so they are by design less effected by charge level, however, I'm sure even for them they could be given better shelf life at 50% than at 100% charge. One day all the cells might use A123's low voltage design and it will be largely ignored. Or not. Apparently the Chevy Volt people still think it's important for some reason and they are teamed up with A123.

Wrong again! Item 2 clearly is a recommendation for mass storage of batteries for one year. Batteries that are not used for 12 months!

The way I read Item # 2 was, that this is not the profile of a customer. It's the profile of a supplier or distributor. Or someone that hardly ever uses the battery. Even having said that- they make no mention how long it takes to fall into the category they are describing-other than 12 months.

Don't try to shoehorn your opinion into that statement from YESA it doesn't fit. Or at least we can't be sure.

Therefore- it is not a fact..

Why don't you get a few cells and like Doc and other people around here do some testing and provide us with some real data? We ought to have some hard data in about 2 or 3 years from now.

Another thing you could do is email somebody at YESA and other manufactures and ask them. Maybe this woiuld help us to know the truth.

 

[safe]

Change Is Destructive

When you think about anything in life if there is a change from one condition to another that change will be disruptive and inflict damage on some part of the system. The "status quo" usually is less stressful than a changing condition. In mechanical systems this is normally expressed in terms of heat.

With batteries of all chemistries whenever there is a change in voltage within the cell there is some damage that takes place.

So it's pretty easy to see that high discharge rates will always contribute negatively to the life of a cell. Cells also prefer certain states over others and so time spent in less desireable states whether in transition or not contribute to cell damage. For Lithium based cells time spent at voltage below a certain level (usually about 2.5v) contributes to damage. Li Ion cells clearly are damaged at high sustained cell voltages (4.2v) even without cycling, but the information is not available about LiFePO4. We do have some "clues" coming out of the Chevy Volt / A123 alliance that keeping the cells within a 30% to 80% range is beneficial to cell life, but we don't know why exactly and can only speculate at the moment.

One day we will know.

So everyone can "roll the dice" right now and take your chances with holding high voltage levels with LiFePO4 during storage situations. It might not hurt, or hurt not very much. We just don't know.

 

[EMF]

I know one thing - LifePO4 is the best option for an ebike battery pack that we have at the moment. Even if you don't handle them exactly perfectly, (aside from overdischarge which is why you need LVC) these batteries are the best bang for the buck.

NOW with real world help from the battery suppliers and extremely talented members of this forum...we have a few sweet solutions for the care and feeding of LifePO4. Ones that can really, maximise your cycle life and enhance the return on your LifePO4 investment.

Not to mention, they are designed for ebikes!

 

[OneEye]

So everyone can "roll the dice" right now and take your chances with holding high voltage levels with LiFePO4 during storage situations. It might not hurt, or hurt not very much. We just don't know.

Agreed, it is a roll of the dice; however it's no more a gamble than buying a pack with 40% more capacity in order to stay within 30% to 80% state of charge rather than utilizing the 30-100% zone. There is an investment cost involved in oversizing battery packs (and weight, and size concerns). You can quantify the investment cost if you like, and compare it with whatever assumptions you want to make about an equivalent rate-of-return, inflation, falling or rising battery prices over time, and any number of other variables. Add in a sensitivity analysis to your estimates, and then factor in the possibility of nano-wire batteries or some other "break-through" tech making all this talk useless by the time shelf life in the LiFePO4 pack becomes an issue. For many riders, the vehicle weight and pack size considerations may have more significance than the non-cycle related rate of battery degradation.

All in all it's gamble either way you go.

 

[safe]

...it's no more a gamble than buying a pack with 40% more capacity in order to stay within 30% to 80% state of charge rather than utilizing the 30-100% zone.

You've misunderstood the concept.

When the bike is in storage (overnight) you leave it somewhere between 50% to 80% in order to increase it's shelf life. Then minutes before your ride you "top off" the cells to 100%. Then you ride. Then you reset the charger back down to 50% to 80% for the next night. Repeat again and again.

This way the cell is only exposed to the higher voltage for the short time of your ride and not overnight.

The idea is to reduce the exposure time of high or low voltage to the cell. I don't see any possible negatives to this because you still get to use the full capacity when needed. The only possible negative is that you have to think a little about what you are doing and have a charging system that is adjustable.

 

[EMF]

...it's no more a gamble than buying a pack with 40% more capacity in order to stay within 30% to 80% state of charge rather than utilizing the 30-100% zone.

You've misunderstood the concept.

When the bike is in storage (overnight) you leave it somewhere between 50% to 80% in order to increase it's shelf life. Then minutes before your ride you "top off" the cells to 100%. Then you ride. Then you reset the charger back down to 50% to 80% for the next night. Repeat again and again.

This way the cell is only exposed to the higher voltage for the short time of your ride and not overnight.

The idea is to reduce the exposure time of high or low voltage to the cell. I don't see any possible negatives to this because you still get to use the full capacity when needed. The only possible negative is that you have to think a little about what you are doing and have a charging system that is adjustable.

How in the hell do you add 20-50% charge to a battery pack "minutes before your ride" ?

 

[EMF]

...it's no more a gamble than buying a pack with 40% more capacity in order to stay within 30% to 80% state of charge rather than utilizing the 30-100% zone.

You've misunderstood the concept.

When the bike is in storage (overnight) you leave it somewhere between 50% to 80% in order to increase it's shelf life. Then minutes before your ride you "top off" the cells to 100%. Then you ride. Then you reset the charger back down to 50% to 80% for the next night. Repeat again and again.

This way the cell is only exposed to the higher voltage for the short time of your ride and not overnight.

The idea is to reduce the exposure time of high or low voltage to the cell. I don't see any possible negatives to this because you still get to use the full capacity when needed. The only possible negative is that you have to think a little about what you are doing and have a charging system that is adjustable.

How in the hell do you add 20-50% charge to a battery pack "minutes before your ride" ?

Also, the concept you <<Safe>> cannot grasp is that all this extra activity turning dials up and down on a theoretical charger, probably ain't gonna do squat as the battery may have only set 10 hours! This whole thread is based on a series of assumptions and is going to confuse the hell out of people comingf in here for help and useful information.

 

[OneEye]

Granted, Safe, I wasn't addressing the two-stage charging scheme as described.

If you can adopt this sort of a scheme without too much additional investment (fetcher recently launched a thread exploring a PIC based charging and battery management solution to piggyback on Gary/Bob and Beagle's ideas) and can maintain the discipline and foresight to hit (or schedule) the top-off charge an hour or 1/2 hour before your ride, by all means go ahead.

What the rest of us seem to be saying is the early indications suggest the chemistry is not nearly as shelf-unstable as other lithium chemistries. If this proves true (as you say "a roll of the dice") then the extra effort and discipline to implement a two-stage charging scheme are largely rendered unnecessary-- the per-cycle degradation will significantly outpace any time-related degradation you are mitigating.

From what I've read, the shelf-life instabilities of LiMnO and LiCoO chemistries is primarily related to lithium's hunger to oxidize. It is so hungry to oxidize that it will actually strip the Oxygen from the MnO and CoO to attach directly. Once the lithium has oxidized directly, it is no longer available for the battery's normal chemical cycle. In the LiFePO4 cathode, the Phosphorous-Oxygen covalent bonds are much stronger than the Manganese-Oxygen and Cobalt-Oxygen bonds in the other chemistries. This should mean much less time-related degradation of capacity. The cycle-life improvements are potentially related to the volumetric stability between the crystal structure of the charged and depleted anode. Without improvements in shelf stability, safety, and cycle life over LiCo and LiMn, the chemistry wouldn't have made it to market due to lower energy density (both weight and mass) per cell.

 

[OneEye]

This whole thread is based on a series of assumptions and is going to confuse the hell out of people comingf in here for help and useful information.

Thanks EMF for reminding me I need to relax and "let go" when I don't get universal acceptance of a point I'm trying to make. This sort of thing is what gets me into trouble at home :? . I need to remember that in forum discussions 100% agreement is not required. Often it is enough to raise a point and the parties can agree that the information does not absolutely support one perspective or the other, then leave it to enlightened individuals who peruse the thread to come to their own conclusions based on their peculiar set of circumstances.

 

[safe]

From what I've read, the shelf-life instabilities of LiMnO and LiCoO chemistries is primarily related to lithium's hunger to oxidize. It is so hungry to oxidize that it will actually strip the Oxygen from the MnO and CoO to attach directly. Once the lithium has oxidized directly, it is no longer available for the battery's normal chemical cycle. In the LiFePO4 cathode, the Phosphorous-Oxygen covalent bonds are much stronger than the Manganese-Oxygen and Cobalt-Oxygen bonds in the other chemistries. This should mean much less time-related degradation of capacity. The cycle-life improvements are potentially related to the volumetric stability between the crystal structure of the charged and depleted anode. Without improvements in shelf stability, safety, and cycle life over LiCo and LiMn, the chemistry wouldn't have made it to market due to lower energy density (both weight and mass) per cell.

If that's true that's just great.

Believe me I would love to find out that all the old problems have been solved with the new chemistries, but it's just frustrating that no information seems to be leaking out about it. Why might this be? The only reason I can think is that it takes a long time to do shelf life testing and no one seems curious enough to try it. Or possibly they are doing the testing but unwilling to divulge the secrets for competitive reasons.

We get information leaking out of the Chevy Volt team that suggests they are committed to a 30% to 80% range of use for their A123 cells and it makes me wonder what they are up to.

What's needed is more solid information and I'll be the first to express my frustrations about the lack of it.