I don't know which is true or false about LiFePo4

[parajared]

I am a non-BMS user and I have taken an interest in keeping my LiFePo4 pack alive and well.
As we all know, stuff posted on the internet is always undoubtedly true and we should never really suspect its accuracy; however after perusing the boughs of the internet I have come across several claims about LiFePo4 that are in complete discord with each other and I’m just not sure which claim is right.

For instance it’s been widely said that LifePo4 can be damaged if brought above 4 volts but…
1.
A) “Trickle charging a fully charged cell for hours on end even if it's voltage never exceeds 4 volts will damage it.”
B) ”So long as the cells don’t overheat and there isn’t enough amperage to overcome the internal resistance of the cells to reach 4 volts the cell is totally fine.”

Or…
2.
A) The only way to identify when a LiFe cell is out of balance is during discharge. You need at least 1c discharge to see the differences.
B) You can identify out of balance cells by checking either the resting voltage or charging voltage of each cell.

Or…
3.
A) Discharging to 100% is just the same as discharging to 50%. People just discharge to 80% to keep out of balance cells from dropping below 2 volts. You would get 1000 cycles out of a 100% DOD pack and 2000 cycles out of a 50% DOD setup, so really just the same amount of energy.
B) Discharging a pack below 80% prematurely wears out the battery regardless of whether the cells dropped below 2 volts or not.

 

[liveforphysics]

I am a non-BMS user and I have taken an interest in keeping my LiFePo4 pack alive and well.
As we all know, stuff posted on the internet is always undoubtedly true and we should never really suspect its accuracy; however after perusing the boughs of the internet I have come across several claims about LiFePo4 that are in complete discord with each other and I’m just not sure which claim is right.

For instance it’s been widely said that LifePo4 can be damaged if brought above 4 volts but…
1.
A) “Trickle charging a fully charged cell for hours on end even if it's voltage never exceeds 4 volts will damage it.”
B) ”So long as the cells don’t overheat and there isn’t enough amperage to overcome the internal resistance of the cells to reach 4 volts the cell is totally fine.”


If the cells use premium purity solvents and electrolyte, they would be fine to live at 4v. However, the stuff we get for ebike LiFePO4 cells is typically the cheapest dirtiest stuff anyone will consider adding to a battery, and it does off-gas and decompose when held at elevated voltages and to prolong the life of the cells while just sitting, keeping the voltage ~3.6v max is a good idea. If you by chance have some premium quality cells (unlikely), then 4vdc would be fine.

Or…
2.
A) The only way to identify when a LiFe cell is out of balance is during discharge. You need at least 1c discharge to see the differences.
B) You can identify out of balance cells by checking either the resting voltage or charging voltage of each cell.

In the buffering voltage plateau area ~3.2-3.3v, resting voltage is NOT a reliabile indicator of SOC. I've seen situations with a mildly colder cell at 30% SOC have a higher resting voltage than a warm cell at 80% SOC. To easily know SOC reliably with LiFePO4, you gotta either have it at say <3vdc resting or above 3.4vdc resting IMHO, others may have a better technique, but I've found nothing I really trusted besides coulomb counting for LiFePO4.

Or…
3.
A) Discharging to 100% is just the same as discharging to 50%. People just discharge to 80% to keep out of balance cells from dropping below 2 volts. You would get 1000 cycles out of a 100% DOD pack and 2000 cycles out of a 50% DOD setup, so really just the same amount of energy.
B) Discharging a pack below 80% prematurely wears out the battery regardless of whether the cells dropped below 2 volts or not.

Shallow cycles involve the least physical volume changes in the cathode materials, which means the least fracturing, and using the pack in the middle of the cells capacities only will often extend the cycle life by and order of magnitude or more. That said, I think most low quality cells die fast just from cheap solvent decay and things rather than actual usage, so for practical reasons it might not matter to you. I say might not matter, because if you even get ~3 years of use, I doubt you will be interested or caring much if they still work, LiFePO4 tech is like a computer from a decade ago.

 

[cal3thousand]

This is good thread. Good questions. And a GREAT answer from Luke.

 

[USAEBIKECO]

I agree with Luke. Lifepo4 is old technology.

If you want to get longevity out of your pack shallow discharges are preferable to fully depleted battery.

 

[hillyterrain]

If Lifepo4 is old tech, what would you use? Still use the trusted old tech or start already with NCM? (I'm worried about the limited life-cycle) or similar? Any favorites?

 

[dogman dan]

To prevent Lester from getting flack for sayinjg it himself, I'll say it. NCM, from Chicago Electric Bikes. :wink:

Seriously though, Lifepo4 is not so old you can't use it. It just takes up a bit more space to get a given voltage mainly. Weights are a tad more but not that much in bike size packs.

I can't agree more with what Luke says. Two pingbatteries I have owned lasted just about the same calendar time 3.5 years. One had 700-800 cycles, the other 220. They just timed out as the solvent died I bet. That makes 2000 cycles hard to do in time unless you cycle them a LOT.

I have no NCM experience, but my lico has timed out at about 2 years with way less than 500 cycles. Still using some of it at nearly 3 years, but it's saggy, tired, and half the capacity.

What do your think Lester? Do you know yet how long the solvent lasts in the batteries you have been selling? Anything better than 3 years when kept at full charge ready to ride would be plenty good. It's been nearly three years now that you had those hasn't it?

The thing about discharging the cells at a certain rate sounds more like a resistance test. Likely though, a high resistance cell would be the one that gets out of balance.

Re the trickle charging, I did that to my first ping, and it still lasted as long as the next one. It didn't damage it to use an sla charger for a full year. Guess the cells were "good enough". The old style bms may have helped with that, since they would have kept bringing the cells down.

No bms, ideally you'd be using a charger that turns completely off when done. Like a hyperion or two 8s RC chargers if you have 16s.

 

[etriker]

I have a pack of the Lifepo4 old tech made from cells from 2006 still going strong.

What in the world were they thinking making battery cells that would last that long ? ? ?

Most all of the newer tech stuff is designed to last about 3 or 4 years ?

 

[arkmundi]

If Lifepo4 is old tech, what would you use? Still use the trusted old tech or start already with NCM? (I'm worried about the limited life-cycle) or similar? Any favorites?

http://libattery.ustc.edu.cn/english/introduction 3.htm

The newest addition to the lithium-ion family is the A123 System in which nano-phosphate materials are added in the cathode. Although the manufacturer has not officially announced what metal is being used, it is widely believed to be iron. They claim to have the highest energy density of a commercially available lithium-ion battery.

I'm just questioning that LeFePO4 is "old tech." Yes, excepting the patented A123 nanophospate process. A123, now owned by the Wanxiang Group is a favorite here at endless-sphere. Sourcing the cells for a battery can be problematic, however. See http://em3ev.com/ for what some of us feel is the best priced reliable supply right now (coming from Hong Kong - factor in shipping).

 

[parajared]

Meh,
Batteries suck in general; there's only so much chemically accessible energy that can be stored in a certain mass. We're still eking out some incremental improvements, but those are never more than a couple of percentage points of additional capacity a year. Real improvements, like layered graphene sheets, are years or decades away, and truly game-changing technologies like fuel cells and nuclear fusion are so far off on the horizon that they're honestly closer to science fiction than anything else at this point. The only advances we're likely to see in the near future won't be improved batteries, but more efficient systems; LiFePo4 is fine.

 

[jonescg]

Can anyone else see the silliness of buying a battery with X capacity, but only using 0.5X and hauling all that extra weight around? It's the age old conundrum of plug-in hybrids versus pure electrics. Why carry a large mass around if you aren't going to use it most of the time? The convenience of having another 50% left in the tank is pretty good - in the same way that having a spare bedroom in the house is great for the once or twice a year you have someone over. But is it worth paying the extra rent?

If the environment and mad consumer culture were not as important, we'd buy a cheaper battery and hammer it to 95% DOD a hundred times before it dies, then buy another.

Just mulling ideas, that's all

 

[dogman dan]

Cheaper battery and hammer it is kind of what many do with hobby king lico packs.

But this go round, I'm going to try undercharging about 5-10% and continue to try to leave 10% at the bottom most rides. See if that really helps, IF I continue to store it charged. The bike has to be ready to ride each morn.

It's a big sacrifice though, to not use a full 20%. Makes my 48v 10 ah into a mere 8 ah. About like carrying two pounds of inert lead on the bike.

As for the C rate, I think 25% of the stated c rate of an hk pack is hammering it.

 

[liveforphysics]

Can anyone else see the silliness of buying a battery with X capacity, but only using 0.5X and hauling all that extra weight around? It's the age old conundrum of plug-in hybrids versus pure electrics. Why carry a large mass around if you aren't going to use it most of the time? The convenience of having another 50% left in the tank is pretty good - in the same way that having a spare bedroom in the house is great for the once or twice a year you have someone over. But is it worth paying the extra rent?

If the environment and mad consumer culture were not as important, we'd buy a cheaper battery and hammer it to 95% DOD a hundred times before it dies, then buy another.

Just mulling ideas, that's all

I agree hauling even a single gram of extra vehicle weight around a racetrack feels like a step in the wrong direction. However, I will balance that by saying making a life of vehicle battery that never needs to be so much as looked at for many 10s of thousands of miles also has something that feels pretty damn nice about it as well.

 

[dogman dan]

If I can make my new HK 14s pack last 3 years instead of 2, It puts about $120 in my pocket. Not a lot of money, but with no job now, it becomes a lot. Realllly a lot when the pack increases in size.

So I'll lug the 2 pounds of extra weight. Actually, 6 pounds, I just bought another 5 ah, to further lighten the load on the typical discharge to Sams Club and back.

On that trip, I'll be carrying a full 3 pounds of never used capacity, and another 3 of seldom used battery weight. I'll have the range to go all the way to main street downtown and back with the extra 5 ah. On that trip to main street, I'll likely charge higher and use it all. 25 miles round trip.

 

[maramusa]

How about the true or false that LifePo4 batteries are more environmentally friendly than other battery technologies, due to fact that LifePo4 is naturally occurring mineral and can break down in nature without toxicity.
I am in the middle of my first build, and though my Headways will be heavier, I guess being an electric bike its nice to know that the batteries don't 'counter' all the nice green feelings.

Does this mean I can throw my headways in landfill or in the ground and a nice tree will sprout forth. I'm not sure. I guess other components in the battery and casing may be toxic. I wonder how much worse Lipo or Lico etc are really.
....speaking of which, how do people dispose of old LifePo4 batteries..maybe another thread required for that.

It's interesting that Tesla hasn't been challenged much in the media for using Lithium Colbalt batteries (or is it Lithium Manganese) in the Model S that may effect the cars environmental credentials.

 

[dogman dan]

I would say true that lifepo4, or lico, would be more "eco" than any lead, NiCad, or nimh, because of the lack of heavy metals.

I don't I know if the metals in limn, or similar chemistries is toxic on disposal. Much depends on the landfill you will be tossing it into. I don't hesitate to toss lightbulbs into my trash, since we now have a modern, bottom sealed landfill. Not really supposed to, but it's not going to go into the groundwater at the new dump. The old dump, closed about 20 years ago, everything that went into it is now leaking into the ground.

Best disposal is to discharge them to 0v, then take them to a battery recycling drop off place. For all chemistries.

 

[maramusa]

I would say true that lifepo4, or lico, would be more "eco" than any lead, NiCad, or nimh, because of the lack of heavy metals.

I don't I know if the metals in limn, or similar chemistries is toxic on disposal. Much depends on the landfill you will be tossing it into. I don't hesitate to toss lightbulbs into my trash, since we now have a modern, bottom sealed landfill. Not really supposed to, but it's not going to go into the groundwater at the new dump. The old dump, closed about 20 years ago, everything that went into it is now leaking into the ground.

Best disposal is to discharge them to 0v, then take them to a battery recycling drop off place. For all chemistries.

I wouldn't lump lico with LifePo4, ...my main point was comparing the different Lithium battery chemistries and wondering if it is a factor for anyone
As far as I understand

lico is the worst as Cobalt is toxic in environment,
LiMn not as bad but not good as has heavy metals,
but LifePo4 is neither toxic nor contains heavy metals

from wikipedia http://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery

"The use of phosphates avoids cobalt's cost and environmental concerns, particularly concerns about cobalt entering the environment through improper disposal.

I now go to bathe in some lifepo4

 

[voicecoils]

...Why carry a large mass around if you aren't going to use it most of the time? ...

After an ebike ride, if my battery's not flat, I'm annoyed I carried the extra weight for no benefit. If the battery runs out before my ride's over, I''ll be mad that the battery was too small.

I even get pissed off thinking that as the battery discharges I still have to carry the whole weight the whole time! :lol:

 

[liveforphysics]

As far as I understand

lico is the worst as Cobalt is toxic in environment,
LiMn not as bad but not good as has heavy metals,
but LifePo4 is neither toxic nor contains heavy metals

Realistically, they are all about the same. Yes, some cathode coatings have various things you would enjoy less in your drinking water than others, but the proper way to dispose of any variety is to give it to a recycler, and it (typically)remains a sealed package until that happens regardless of the type.

 

[dogman dan]

Cobalt blue is the most common ceramic colorant in the world, and fairly safe to the user. Red is another story. Red used to be lots of lead. The great orange in fiesta ware was uranium. None of that used anymore. Red is weak now.

Perhaps you think of radioactive cobalt? That's nasty stuff for sure, but kids love it's blue sparkly qualities when some shows up in a third world junkyard from the medical device.

 

[arkmundi]

Cobalt blue is the most common ceramic colorant in the world, and fairly safe to the user. Red is another story. Red used to be lots of lead. The great orange in fiesta ware was uranium. None of that used anymore. Red is weak now.

Alright, this has nothing to do with ebikes or batteries for them. At mfa.org yesterday on my way to see One Track Heart, walked through the New Blue and White exhibit. Really extraordinary.

So I can really dig cobalt blue right now. Can someone make me a t-shirt like that?