[00:02] there when it comes to the hottest battery chemistry in the electric car world lithium iron phosphate or lfp the f is silent while the electric car market is currently dominated by nickel manganese Cobalt or nmc batteries
[00:18] nickel manganese Cobalt or nmc batteries it's expected that lfp will surpass nmc by the year 2028 a not too distant future from a consumer standpoint one of understandably what are the best
[00:32] practices for ensuring my electric car's battery lasts as long as possible the depending on the chemistry of your battery now I already have a video explaining best practices for nmc chemistries which is absolutely worth
[00:47] checking out in this video we're going to be focusing on lfp batteries and boy oh boy is there are a ton of conflicting information out there with that said a brand new study does a great job of explaining how and why these batteries
[01:02] lose capacity over time which leads to logical best practices and you may be surprised by these considering what car manufacturers are saying you should be doing so let's start what they're saying you should do take for example Ford's
[01:17] electric crossover the Mustang Machi and first off a huge props to Ford here painless process to understand what battery chemistry the vehicle has quoting the owner's manual if the eighth
[01:30] Vin digit is a four or five you have a lithium iron phosphate lfp battery and if there is any other digit or letter you have the nickel Cobalt manganese NCM style battery every single electric car maker should be making it this easy to
[01:46] understand what chemistry your battery is now Ford's chemistry strategy isn't uncommon Tesla's is very similar where you'll find lfp batteries in standard or lower range vehicles and nmc batteries in extended or higher range vehicles but
[02:01] again the only way you'll really know without disassembling the battery is to be told by the car maker so once you know it's lfp what does Ford say you should do quote set the maximum charge level to 100% and charge to 100% at
[02:18] least once per month to maintain range accuracy now immediately you'll notice this is the exact opposite of what you should do for nmc batteries where for daily use you want to set that to a lower char charge limit say 70% okay
[02:32] what else does Ford say to do with the lfp battery quote during regular use you can increase the battery life by maintaining the state of charge at 100% when storing for an extended time that the battery state of charge be
[02:48] approximately 50% now grammatically that last sentence is a disaster but to be fair a Ford also I not often words correct also but what are they even saying first you can increase the battery life by keeping it at 100%
[03:05] second if you're storing it for a long time keep the battery at 50% these are obviously conflicting statements but there's a good reason for it and so in order to understand this we need to look at the voltage curves for both nmc and
[03:18] lfp batteries okay so here we're looking at stateof charge versus voltage so we have the state of charge of the battery ranging from 0% to 100% And we have the ranging from 0% to 100% And we have the voltage at the cell level ranging from
[03:32] voltage at the cell level ranging from 2.5 to about 4.5 volts here just for our diagram and we're looking at lfp in red and nmc chemistry in blue now you'll notice two distinct differences first of all nmc tends to operate at a
[03:47] of all and more importantly here for the discussion of this video lfp has a much flatter voltage curve versus nmc where it has a steeper slope so let's say you want to tell the driver of an electric car how much battery percentage is
[04:02] remaining well let's say your battery's chemistry is nmc and the cell level voltage is reading at 3.7 volts so you come across at 3.7 you come down and boom what do you know your battery is at 50% charge remaining well let's do the
[04:17] same for lfp now let's say you have a voltage readout of 3.3 volts well it voltage readout of 3.3 volts well it could be 75% or it could be 95% because it's a very flat section of that voltage curve for the L FP chemistry so you
[04:31] don't really know what is that battery percentage so you have to use a different methodology so what do they do well you essentially look at current battery and you start to calculate essentially how many electrons have gone
[04:44] where are we at with the charge percentage as you do this over time that readout starts to become less and less accurate and of course the driver needs to know an accurate estimation of how much battery percentage they have left
[04:58] so how do you correct that calculation once it starts to get off well as you can see if you charge up to 100% you start to have this voltage Spike and so you can immediately identify okay boom we're back at 100% And you can know for
[05:12] a fact all right we're at 100% I can reset the calculation for determining how much battery percentage we have left okay so now we understand why Ford says you should charge to 100% because otherwise it's difficult to know your
[05:24] battery's exact state of charge or remaining percentage so this leads to best practice number one charge to 100% at least once per month this isn't purely about battery longevity but more so that your vehicle accurately displays
[05:39] the charge percentage which is an obviously critical metric to know when driving around so then why do they say if you're storing the car for longer periods of time to leave the battery at 50% well generally speaking which is a
[05:53] dangerous thing to say with battery chemistries battery longevity is negatively associated with with both temperature and voltage that is to say when you're operating the battery at high temperatures and when it's
[06:08] operating at a higher state of charge because a higher state of charge correlates with a higher voltage by storing the battery at 50% you're storing it at a lower voltage so this means you'll have less degradation over
[06:21] time okay so we've got best practice number two when storing your car for extended periods of time store it at a lower state of charge as an example Ford recommends 50% now at this point you'll realize why it's difficult for Ford to
[06:36] recommend best practices in the owner's manual on one hand you need to charge up to 100% in order for the battery to be properly calibrated on the other hand charging to 100% frequently results in more battery degradation it's basically
[06:50] a lose lose scenario because you can't satisfy both conditions so what is the best practice well there's an ideal answer and then there's a realistic answer to explain this we'll look at a study that I referenced at the beginning
[07:05] of this video conducted in Jeff Don's lab who has been described as Tesla's secret weapon it's not a secret Don's lab has received grants from Tesla for research and he is a co-creator of the patent for nmc in the year 2000 which
[07:21] again is currently the most popular battery chemistry on the market for electric cars simply put the dude knows batteries so what does the latest study out of his lab say the first sentence of the conclusion quote cycling near the
[07:36] the conclusion quote cycling near the top of charge 75 to 100% state of charge top of charge 75 to 100% state of charge is detrimental to lfp graphite cells end quote it goes on to State quote time spent cycling at high states of charge
[07:49] spent cycling at high states of charge is critical to minimize yikes okay so there's a lot of context that's very important here in an ideal world where the only thing you care about is battery longevity the third best practice is
[08:03] simple operate at lower state-of charge ranges when possible this comes directly from the study in which they State we would recommend that lfp cells for long lifetime applications operate at low states of charge on average with
[08:18] states of charge on average with charging up to 100% only on occasion now it's important to state that this recommendation is based on the results of this study so what did they do and how did they reach this conclusion the
[08:31] goal was to see how the operating window of the battery impacted longevity so they looked at five different state of charge ranges 0 to 25% 0 to 60% 0 to 80%
[08:44] charge ranges 0 to 25% 0 to 60% 0 to 80% 0 to 100% and 75 to 100% for each of these ranges the batteries underwent 2500 hours of cycling okay so all of the different ranges tested had the same amount of total energy going through
[08:59] them so if you did 0 to 25% okay well if you do that four times that's the same as going 0 to 100% one time so regardless of which battery range you're regardless of which battery range you're looking at 0 to 60 0 to 100 75 to 100
[09:14] any of them they all have the same amount of total capacity going through the batteries it'd be the equivalent of driving your car on Four short trips and charging after each trip or one really long trip and only charging once both
[09:29] scenarios take the same amount of time and energy but they use different range percentages of your car's battery now in addition to these five different state of charge ranges they also tested three other variables temperature the
[09:41] electrolyte used and the graphite used for the negative electrode of all of these variables the most significant variable in this study was the state of charge window that the cells operated in the simplistic overview is that the
[09:55] lower the operating window of state-of charge range the better so operating an lfp battery from 0 to 25% had the least degradation followed by operating 0 to 60% which was better than 0 to 100% which was better than 75 to 100% okay so
[10:12] why well there's two parts to this first the battery state of charge and second the active cycling or charging and discharging okay chemistry is complicated so if you want the most detailed explanation I'm going to write
[10:27] out below basically a long longer version of what's happening within the chemistry of this battery and what's causing it to reduce in capacity over time this short story is the biggest failure mode for lithium iron phosphate
[10:41] batteries is a reduction of lithium inventory in other words that lithium your battery between the positive and the negative you're reducing that lithium inventory so if you reduce the total amount of lithium you can shift
[10:56] other well that means you have less total capacity less capacity your battery is not as useful as it once was so part of why this occurs if you're at a higher state of charge you're at a higher voltage so these negative
[11:12] reactions that are occurring within your electrolyte are accelerated that are consuming that lithium inventory now this is true regardless of the battery this is true regardless of the battery type so if it is lfp or if it is nmc but
[11:26] it has a graphite electrode for the negative side well then it's going to have this occur okay but what about the cycling part of the equation going from cycling part of the equation going from 75% to 100% okay so specific to lithium
[11:40] doesn't really matter if you're at the higher end or the lower end this is still going to occur but when you're cycling that battery you're going to end up taking iron from the positive electrode dissolving it and depositing
[11:54] it onto the negative electrode and this consumes lithium inventory which which again degrades the battery so to summarize by keeping the battery fully charged you're keeping the battery in a state that creates harmful compounds as
[12:09] you cycle the battery these increased harmful compounds result in dissolving iron from the positive and depositing it onto the negative okay this all sounds really scary right the thing is the testing for this experiment was done at
[12:23] testing for this experiment was done at a constant 40° C or at a constant 55° C Sig significantly hotter than the average temperature of where most people live you do the testing at higher temperatures because you can accelerate
[12:36] the degradation and learn faster if you want to see if a battery can last for 20 years in normal conditions well if your test uses normal conditions it will take 20 years to complete but with harsher testing you can get a better idea in a
[12:52] much shorter period of time if a battery will last that long and Plenty Of Studies have shown that even in challenging conditions a well-designed lfp battery can easily last the lifetime of the vehicle whether that's 200,000 Mi
[13:06] or longer regardless as far as your individual lfp electric car the third best practice remains operate at lower state of charge ranges when possible but what an absolute pain to charge your electric car to say 50% most of the time
[13:22] and then occasionally to 100% I think there's actually a very convenient solution here which leads to best practice ractice number four only plug in your car when you need to this is 100% counter to what you should do with
[13:36] an nmc battery because small charge cycles are really important to an nmc battery it's also 100% counter to what Tesla says in their owner's manuals in Tesla says in their owner's manuals in all caps bold leave your vehicle plugged
[13:49] in there's a good reason Tesla says this which we'll get into but let's go back to the lfp cycling study now again this was at elevated temperatures and thus faster degradation but the battery cycled from 0 to 100% had less
[14:04] degradation than the battery continuously cycled from 75 to 100% okay and so you feel more confident about this consider what Tesla says inside their lfp battery EVS on the charging screen they State quote we recommend
[14:19] keeping your charge limit at 100% And charging fully once per week this is a very carefully worded sentence you'll notice it basically tell tells the owner to avoid the exact scenario this paper says is worst for your battery small
[14:34] charge cycles at the top end of your battery charging fully once per week means letting it drain down but also eventually charging to 100% so the computer knows what the battery's actual state of charge is so this raises a
[14:48] really interesting point if you don't have a place to charge your EV at home you might be better off buying an lfp battery EV for two reasons first they need to somewhat regularly be charged to 100% And if you want to minimize your
[15:03] trips to the charger well it's nice to go there charge it up to 100% and bring it back second because it's more beneficial to drain the battery further down rather than just operated on that top end that means again less visits to
[15:18] the charger so this is beneficial for those who don't have a charger at home if you can charge at home which chemistry you pick is less important if you go nmc you can benefit from frequent small charges and keeping the battery's
[15:31] maximum charge limit at a lower level and if you're going on a longer trip well then you can charge it up to 100% when you need it now I'd love to close the video there but it's important to realize that the purpose of this video
[15:44] was to discuss the best practices for battery longevity alone that is it it is not to say what are the best practices overall which I think the automakers do a better job of Tesla says just leave it plugged in that's just plain good advice
[15:58] because if you come out to your garage and you go to your car and it hasn't been plugged in and your range is too low rightfully you're going to be upset if a storm hits your area and all local electricity is out and you've set your
[16:12] battery percentage to 25% for battery longevity well yeah you're not going to out of there and you don't have any charge also you should never let your battery get down to 0% period it can cause permanent damage to the battery
[16:27] now smart manufact facturers will build in a little bit of a buffer to help prevent this from happening but still if you have just one cell out of all the cells in your battery pack that gets a little too low it can cause big problems
[16:40] so draining the battery pack really really low is a very real risk you should avoid despite the best operating window in this study being from 0 to 25% finally generalizations about best practices when you have a huge variety
[16:55] of existing chemistries are difficult to make I read a bunch of papers in compiling this video but they may not match the conditions you live in or the chemistry of your car for example in the main study I've discussed in this video
[17:10] they readily admitted that one study shows that cycling lfp graphite cells over a lower average state of charge leads to more capacity fade than a higher average state of charge which is the opposite of our findings though in
[17:25] this other study they were cycling the battery cells with much higher charging and discharging rates though still that other study found that storage at high state of charge causes more capacity fade than at low state of charge so
[17:39] chemistry is hard Innovation takes time things are always changing nobody knows anything except sometimes we do if you enjoyed this video there's two videos I really think are worth checking out first what are the best practices for
[17:53] battery longevity for an nmc battery a very popular chemistry for today's EVs electric vehicles better you really need to understand how lithium ion batteries work so I have a dedicated video just explaining that which is great for
[18:07] insight on lithium ion batteries if you have any questions or comments feel free have any questions or comments feel free to leave them below thanks for watching