Then what I don’t get is why (and ignoring common power tools like drills) we see vacuum cleaners which cost €800 (Bosch etc) whose batteries also degrade rapidly. Those batteries are not so tiny. I have one such at home, a few years old, which runs only for 5 minutes i.e. almost useless but not completely useless.
To me, this just does not hang together. There is something weird going on, because it is completely obvious that a vacuum cleaner whose batteries last 10-20 years would be fantastic selling point.
As Graham says, the reality is likely to be somewhere in between. If I was developing an EV, I would definitely conceal the battery degradation for obvious customer perception reasons: if you display the capacity readily visibly and accurately, the customer will see that he has done one long drive and the range of the vehicle has dropped by (say) 0.5%. It won’t take a PhD to work out that this is not going to look exactly great. It is like if say you make an oven, and the users sets +250C, the temperature display must show +250C, not +249 or +251 which would just worry people. I have designed products where the customer specified exactly how the “faking” is to appear.
There’s no faking going on 
Batteries do degrade, but even within 5 years it’s so little it’s hardly noticeable, if you use/charge it correctly.
There are 5 rule of thumb to get the most out of the battery (EV battery. Other batteries are different)
I’m installing 2 chargers now. One in the garage and one outside. They are max 7.4 kW, but can be adjusted down. I will leave them at 2-3 kW or perhaps less. Super tiny boxes, and super simple. They are called amina 1, and it’s the most selling charger in Norway right now. They also have an amina S which is max 22 kW and fully online, but not something I feel is necessary for my usage.
Peter wrote:
a vacuum cleaner whose batteries last 10-20 years would be fantastic selling point
Unfortunately not. As everyone can easily observe, a lot of white goods sold these days are utter crap compared to what they were 20-30 years ago. They are also a lot cheaper than they used to be. Since a lot of the competition is on price, manufacturers produce as cheaply as they can – if they don’t explicitly engineer for “planned obsolescence”.
The market segment willing to pay for quality is small.
And nobody would believe them anyway unless they provide a warranty.
kwlf wrote:
I used to use A123 LiFePo batteries for my model helicopters
I have model helicopters and the batteries are simply abused by them. We want them to charge quickly, to be light, and to provide prodigious currents and last as long as possible – doing all the things that shorten the life of a lithium battery (very high charge rates, charging to 100% capacity, and extremely high discharge rates right down to minimum allowable charge state).
Cars by contrast don’t care so much about weight and tend to charge slowly most of the time (home charging is a small fraction of their ‘C’ rating) and typically only get charged to 80%. Cars are also running at a small fraction of their maximum allowable ratings most of the time, unlike an RC heli which is close to 100% all the time. Highway cruising is typically less than 30% power.
RC heli batteries last a LOT longer if you treat them like car batteries (only charge to 80%, use a lot more battery than needed, and massively derate the whole system by keeping the head speed low). For instance, my batteries seem to last forever when I went from a 6S 3D style setup to a 12S scale flying style setup on my T-Rex 600.
That’s all true, but I was using them in model helicopters… None of the crazy 3d stuff, but still high discharge rates. I even completely discharged a few of the cells leading to forced landings. Any LiPo would have been toast, but they keep on going. Their specific energy was less than that of LiPos (I think 20-30%) so they were never going to hit the competition circuit, but for me their robustness more than made up for this.
I wonder whether they fell by the wayside partly because of the move from hybrids to fully electric vehicles. Something like the original Prius essentially had a very small battery pack (not A123 as far as I’m aware) with the range of just a few miles. The idea was that you were charging and discharging it constantly as you braked and accelerated. The rate of charge / discharge per cell was much higher than it would be for a larger battery pack i.e. if you have a battery pack with 5 miles range capable of absorbing all the energy from descending a hill, your charge rate will be 40x higher than a battery pack capable of powering you for 200 miles (OK, the car with more batteries will be heavier so the difference won’t be quite as pronounced, but it will still be substantial). As batteries became bigger, the advantages of A123 became less important.
Here’s another data point, from KIA.
They normally offer a 7 year warranty, which is obviously very popular.
With EVs, they don’t consider it a warranty job unless the battery capacity has dropped to 70% of new capacity. IOW, there seem to be cases of capacity loss of 30% within 7 years.
Another thing, mentioned previously, is that you can’t get GFV (guaranteed final value) finance on EVs after two 3-year terms. IOW, the lenders don’t want to be on the hook for the vehicle after 6 years. You can get finance but not GFV.
So something funny is going on…
I put it to one guy in the business that the mfgs might be “oversizing” the batteries by say 10% so they can conceal (or greatly reduce upon presentation) the monthly or annual capacity loss for say first 5 years, after which it will likely be with the next owner anyway… he thought this is most likely.
Peter wrote:
I put it to one guy in the business that the mfgs might be “oversizing” the batteries by say 10% so they can conceal
Well, range is the number one selling point among the general public. Oversizing the capacity and reduce range does not sound remotely factual. As I said earlier, what they indeed do is to say that charging to 100% is decremental to battery life. When charging, the default is 90% (for instance, could be 80 or 95 or something similar) and you have to change this if you want 100%.
Also 70% is a very large change, and is not really likely to happen during the first 10 years.
The suggestion was that a 30% capacity loss has been seen; they exclude anything less from warranty claims.
Also he said that if they get this sort of loss, they don’t replace the whole battery. They replace just individual cells. Now that’s a different thing – anybody can get duff cells.
Our first generation EVs (2014) had a nominal range of 150 km but lost just under 30% in 4 years. Interestingly, the buyer of these cars is still using them and maybe lost another 10% in 6 years. He’s planning to put new batteries in, larger capacity, range 200 km at 5k€ each. Not a bad deal I think.
My assumption is that those batteries really did not like to be charged to 100% and drawn down to say 10% which was done regularly. Hot climate here in summer probably did not help either. Our current EVs have a larger battery and we are easily able to keep the charge between 40% and 80%. One car is now 6 years old, 80k kms and has maybe lost 2% of capacity, the other 2.5 years old, 50k kms and lost nothing. The instructions of the latter car: “keep the charging level between 20 and 80% for battery longevity. Occcasional charging to 100% is not a problem”.
We charge at around 3kW AC, supposedly that is better than high power DC.
