HOW TO QUICKLY KILL A LFP BATTERY (PART#2)

[ghostwriter66]

HOW TO KILL A BATTERY (PART#2)

So my boss who has a PhD in Chemical Engineering went to China on business about a month ago and visited one of the largest LiFePO4 battery manufacturers in the world that we use. They gave him a very good tour and today we reciprocated their hospitality by hosting their Lead Design Engineer who is in the States for an upcoming Solar conference. It was a VERY interesting day with him with lots of hands on "Show and Tell". So I thought I would pass what I can on to those interested.

So what should we do with the marketing numbers when these manufacturers state 3000 – 5000 cycles before they drop below 80% or is dead?? He states that honestly with real-world (especially RV) use, anything stated to have over 2000 cycles is kind of getting into the "wishful thinking" section.

First – these batteries are tested in a wonderful 78 degree environment. Apparently the sweet spot for LiFePO4 (LFP) batteries is 78 degrees.

Second – to get the very highest duty cycles to report – they charge the battery to the target 100% SOC value at usually .5C and then STOP immediately once they hit that 100% SOC voltage and immediately discharge them down to the low voltage limit, and then STOP and then charge back up to 100% and repeat that cycle for about 2000 more times. Doing it that way – even after 2000 cycles – they still are able to get 80% of the aH of the original.

BUT in order to get the 5000 cycles they do the same but charge and discharge at .2C - putting so little strain on the battery that they can usually get incredibly high UNREALISTIC MARKETING numbers like 5000 cycles doing it that way.

HOW TO KILL A BATTERY

The fastest way to KILL a LFP battery is when ppl charge the battery to 90-100% SOC and HOLD it (FLOAT it) there. Also another DEATH BLOW is charge it (like Preppers) to 100% and then put on a shelf to be ready for the end of the world and let it sit. So the manufacturer tested this by charging batteries to 100% and letting it drop naturally to about 95% and then charging again to 100% and then repeating over and over. They also Charged to 100% and stored it untouched. After a year of doing this, the battery that they had Charged to 100% and stored was only able to deliver less than 1000 cycles of 100% to 0% SOC before it died. Same for the battery that did the 90-95% to 100% over and over. SO storing or keeping it fully charged for a year not only cut the cycles in half – but KILLED it after only 980 cycles.

According to this particular manufacturer – their sweet spot for charging to get the most cycles out of real world use is 80-85% to 20-25%. He actually said his personal settings on his batteries at home were 15% - 90% so take all of that with a grain of salt.

BEST WAY TO STORE LFP

The best SOC to store a LFP is 40% …is no less than 40% and no higher than 60% … Apparently 40% is another sweet spot for LFP…

 

[Supervstech]

So if you are storing cells, use them down to 60-40% BEFORE shelving them.

if USING the cells, 80-90% then down to 20-15%

I wonder why the cells are damaged from full storage? Maybe something in the electrolyte transfer... hmm

 

[ghostwriter66]

So if you are storing cells, use them down to 60-40% BEFORE shelving them.

if USING the cells, 80-90% then down to 20-15%

I wonder why the cells are damaged from full storage? Maybe something in the electrolyte transfer... hmm

He tried to explain it to us but i got lost within the first minute we he started talking about chemical interactions ... but something about all these little ions being shoved against one side of the battery ... so I'm copying this from his slides but not really understanding he said -- "Capacity loss in cells stored at high temperature and fully charged conditions resulted in faster degradation rates. Temperature had the most significant role in the degradation of the LFP cell and then the cell’s SOC. Comparing capacity losses between cells stored at the same temperature, but with different SOCs, found that the cells with higher stored SOC experienced increased rates of degradation in comparison to their fully discharged counterparts. In addition, storage at high SOC and high temperatures promoted such severe losses that the cells in question were unable to recapture capacity that they had lost reversibly."

I just nodded my head ...

 

[SolarRat]

He tried to explain it to us but i got lost within the first minute we he started talking about chemical interactions ... but something about all these little ions being shoved against one side of the battery ... so I'm copying this from his slides but not really understanding he said -- "Capacity loss in cells stored at high temperature and fully charged conditions resulted in faster degradation rates. Temperature had the most significant role in the degradation of the LFP cell and then the cell’s SOC. Comparing capacity losses between cells stored at the same temperature, but with different SOCs, found that the cells with higher stored SOC experienced increased rates of degradation in comparison to their fully discharged counterparts. In addition, storage at high SOC and high temperatures promoted such severe losses that the cells in question were unable to recapture capacity that they had lost reversibly."

I just nodded my head ...

I believe that info is all here: https://uwspace.uwaterloo.ca/bitstream/handle/10012/12177/Catton_John.pdf?sequence=3

 

[danphillips]

Thank you for sharing this information, I have done a lot of research and reading between the lines have deducted the same recommendations.

This is more important to RV and boaters as we commonly connect to shore power and leave our batteries on charge/float for weeks at a time.

i plan on installing a battery disconnect so that the batteries can be kept at a 50% charge state while not in active use.

 

[ghostwriter66]

I believe that info is all here: https://uwspace.uwaterloo.ca/bitstream/handle/10012/12177/Catton_John.pdf?sequence=3

Thanks -- but i got lost at "INTRODUCTION" ... I'm more of a stick figure drawing type of explanation girl ...

 

[ghostwriter66]

Thank you for sharing this information, I have done a lot of research and reading between the lines have deducted the same recommendations.

This is more important to RV and boaters as we commonly connect to shore power and leave our batteries on charge/float for weeks at a time.

i plan on installing a battery disconnect so that the batteries can be kept at a 50% charge state while not in active use.

One person on another forum that was an RV'r said that he carried one regular 12V AGM to go wiht his 600aH bank of LFP ... when he was boondocking he used the LFP .. and when he was on shore power he flipped a switch taking the LFP offline and putting the one AGM on ... makes total sense .. that way the AGM which loves to be charged constantly at 100% takes the brint of all the shore power stuff ... and the LFP are sitting at 50% becuase he turned off the SCC before morning came around to run the batteries down ...

 

[Deleted member 4428]

It sounds like you and your boss are realists who ignore all the marketing hype found on line....good for you Thank you. What does your company do? If you feel this is not a appropriate question for this forum, feel free to PM me.

 

[FilterGuy]

HOW TO KILL A BATTERY (PART#2)

So my boss who has a PhD in Chemical Engineering went to China on business about a month ago and visited one of the largest LiFePO4 battery manufacturers in the world that we use. They gave him a very good tour and today we reciprocated their hospitality by hosting their Lead Design Engineer who is in the States for an upcoming Solar conference. It was a VERY interesting day with him with lots of hands on "Show and Tell". So I thought I would pass what I can on to those interested.

So what should we do with the marketing numbers when these manufacturers state 3000 – 5000 cycles before they drop below 80% or is dead?? He states that honestly with real-world (especially RV) use, anything stated to have over 2000 cycles is kind of getting into the "wishful thinking" section.

First – these batteries are tested in a wonderful 78 degree environment. Apparently the sweet spot for LiFePO4 (LFP) batteries is 78 degrees.

Second – to get the very highest duty cycles to report – they charge the battery to the target 100% SOC value at usually .5C and then STOP immediately once they hit that 100% SOC voltage and immediately discharge them down to the low voltage limit, and then STOP and then charge back up to 100% and repeat that cycle for about 2000 more times. Doing it that way – even after 2000 cycles – they still are able to get 80% of the aH of the original.

BUT in order to get the 5000 cycles they do the same but charge and discharge at .2C - putting so little strain on the battery that they can usually get incredibly high UNREALISTIC MARKETING numbers like 5000 cycles doing it that way.

Interesting that you bring this up. Just in the past day or two there was a question about charge cycles in another thread and I posited that the only real value in the advertised charge cycle was to compare one battery to another....if they used the same conditions for doing the count. It would be difficult to use it for predicting what might happen for other charge patterns/environments.

This also points out the need to understand what a particular spec means.

HOW TO KILL A BATTERY

The fastest way to KILL a LFP battery is when ppl charge the battery to 90-100% SOC and HOLD it (FLOAT it) there. Also another DEATH BLOW is charge it (like Preppers) to 100% and then put on a shelf to be ready for the end of the world and let it sit. So the manufacturer tested this by charging batteries to 100% and letting it drop naturally to about 95% and then charging again to 100% and then repeating over and over. They also Charged to 100% and stored it untouched. After a year of doing this, the battery that they had Charged to 100% and stored was only able to deliver less than 1000 cycles of 100% to 0% SOC before it died. Same for the battery that did the 90-95% to 100% over and over. SO storing or keeping it fully charged for a year not only cut the cycles in half – but KILLED it after only 980 cycles.

According to this particular manufacturer – their sweet spot for charging to get the most cycles out of real world use is 80-85% to 20-25%. He actually said his personal settings on his batteries at home were 15% - 90% so take all of that with a grain of salt.

If we are running the battery at 15-90% SOC, it makes the earlier debate about top balancing kinda mute. If you are starting with reasonably matched cells, it seems unlikely that doing a top balance would make any significant difference at this charge pattern.

Also, in an interview with BattleBorn (Not with Will), they made the comment that the prysmatic cells were much more sensitive to SOC than the cylindrical cells and that is where the LiFePo reputation comes from. Did your guy get into that at all? At first I thought the BB guys were throwing out BS, and there is no difference. But I have since started to wonder about it. Could the packaging make a difference.?

BTW: If Battleborn is wrong about their specs, they are going to get in trouble with their 10 year warranty.

BEST WAY TO STORE LFP

The best SOC to store a LFP is 40% …is no less than 40% and no higher than 60% … Apparently 40% is another sweet spot for LFP…

I am very interested in the battery storage discussion. (I have an application where batteries will be unused for significant periods). In the cell specs I have read, If they talk about storage at all they usually say something very much in line with what you are saying. However, in the drop-in battery specs, they sometimes (often) say to charge the battery every X months.

There is clearly not a knife edge difference between storage at one SOC and another. There is going to be some kind of curve where the farther from the sweet spot you operate, the worse it is. Did you get any kind of info on the shape of the curve? (Is there a knee in the curve wher it starts getting a lot worse?) As an example, if you were using the 20-85% SOC charge pattern and walked away for a year, would you avoid most of the problem?.

 

[cass3825]

One person on another forum that was an RV'r said that he carried one regular 12V AGM to go wiht his 600aH bank of LFP ... when he was boondocking he used the LFP .. and when he was on shore power he flipped a switch taking the LFP offline and putting the one AGM on ... makes total sense .. that way the AGM which loves to be charged constantly at 100% takes the brint of all the shore power stuff ... and the LFP are sitting at 50% becuase he turned off the SCC before morning came around to run the batteries down ...

This is brilliant. My AIO needs to sense battery voltage before it will pass shore power through to the load terminals. Substituting a small FLA pack in place of the LFP pack when connected to shore power for more than a day is a great solution! Thanks for posting this!

 

[ghostwriter66]

It sounds like you and your boss are realists who ignore all the marketing hype found on line....good for you Thank you. What does your company do? If you feel this is not a appropriate question for this forum, feel free to PM me.

I work in a section that mostly specializes in Petroleum exploration ... Being from LA I have to hide that from most of my friends though ..LOL .. but now work with the South Texas- Mexico division and honestly enjoy the space ... allot of hands on stuff which i enjoy ...and unlike Will's videos - when we mess up and blow something or catch it on fire we don't have 50,000 subscribers commenting ..

 

[ghostwriter66]

Interesting that you bring this up. Just in the past day or two there was a question about charge cycles in another thread and I posited that the only real value in the advertised charge cycle was to compare one battery to another....if they used the same conditions for doing the count. It would be difficult to use it for predicting what might happen for other charge patterns/environments.

If we are running the battery at 15-90% SOC, it makes the earlier debate about top balancing kinda mute. If you are starting with reasonably matched cells, it seems unlikely that doing a top balance would make any significant difference at this charge pattern.

BTW: If Battleborn is wrong about their specs, they are going to get in trouble with their 10 year warranty.

I am very interested in the battery storage discussion. (I have an application where batteries will be unused for significant periods). In the cell specs I have read, If they talk about storage at all they usually say something very much in line with what you are saying. However, in the drop-in battery specs, they sometimes (often) say to charge the battery every X months.

There is clearly not a knife edge difference between storage at one SOC and another. There is going to be some kind of curve where the farther from the sweet spot you operate, the worse it is. Did you get any kind of info on the shape of the curve? (Is there a knee in the curve wher it starts getting a lot worse?) As an example, if you were using the 20-85% SOC charge pattern and walked away for a year, would you avoid most of the problem?.

So as to battery cycles - "THEY" were saying that if they dropped the charge to .2C and the discharge to .2C and ran the same test (hit max, stop, hit bottom, stop, hit top, repeat) then they could get numbers like 8000-10000 cycles ,, BUT honestly "THEY" feel that most "real"users knows that 2000-3000 is realistic so why trick someone into FAKE SPECS and then losing a customer for life??

Agree about the 15-90% and TOP balancing ... I was just passing on what "THEY" said was the perfect way and of course I am pretty lazy as an EE and will simply throw all the batteries seperately on charger - set it for 3.6v and stop it until the amps go to 0 .. then hook them all up and finish TOP charging ... THEN obviously never check them again really since i am never hitting 100% - or even barely 90% ...

Right now Battlehorn can be pretty lenient on their warranty since obviously their cost to get both Batteries and the BMS from China is going to be pretty much WHOLESALE CHEAP prices and all they are really doing is dropping a battery and a BMS in a Box and slapping a "Engineered and Manufactured in the USA" sticker on it ... so probably it someone ever did the math the battery they are selling for $900 may only cost them $250 to make ... I mean right now - shipping the batteries cost more then batteries for most of us ... I just bought 4 DELIGREEN 200aH 3.2 for $78 each (the shipping literally cost me more) .... and lets face it Battleborn will start to lower their prices significantly as Chinese manufacturers set up US Warehouses in the states and give them a run for their money ... AND form what i understand i think with Battleborn you have to pay for shipping the battery back to/from them so thats NOT cheap either

 

[ghostwriter66]

This is brilliant. My AIO needs to sense battery voltage before it will pass shore power through to the load terminals. Substituting a small FLA pack in place of the LFP pack when connected to shore power for more than a day is a great solution! Thanks for posting this!

Thanks - finally someone I didn't piss off with my answers ... LOL

 

[electric]

Thanks - finally someone I didn't piss off with my answers ... LOL

@ghostwriter66 , please don't take it personally. When someone makes bold and generalized statements, they get attacked, it's just a nature of social media. I really like your posts on the forum, most info you post has truth at the bottom of it, but details aren't always understood, so they bring scrutiny.

 

[electric]

Also, in an interview with BattleBorn (Not with Will), they made the comment that the prysmatic cells were much more sensitive to SOC than the cylindrical cells and that is where the LiFePo reputation comes from. Did your guy get into that at all? At first I thought the BB guys were throwing out BS, and there is no difference. But I have since started to wonder about it. Could the packaging make a difference.?

BTW: If Battleborn is wrong about their specs, they are going to get in trouble with their 10 year warranty.

Yes, I remember laughing at that statement. Total BS. Trying to make their batteries look superior... they are not. Good battery, no doubt, but no better than any other LFP battery.
They will never be in trouble with warranty because warranty statement is written to give them complete control to deny any claim if they want to. They are not denying claims yet ( as far as we know in public forums ) because it would hurt their bottom line at this stage of growth and high prices. But eventually the price war will kick in and profit margins will shrink, and then you will see warranty denials. Just give it 2-3 years.
There are so many business dynamics unknown to public, which will come out eventually.