Does charging only to 80% really make a difference?

[FLKiaEV]

That is, as far as battery longevity goes, does only charging to 80% make a big difference? I know that charging to 100% is not actually charging to 100% because of the upper buffer, but am I wasting usable range by not just charging to 100%? Anybody know what Kia says about this? I didn't see anything in the manual about the benefits of 80% charging. If it makes no real difference longevity-wise I'd like to go ahead and just charge to full.

[IanL]

With the major component of customer resistance to EVs being range, it is no surprise that KIA would choose not to publicise the benefit of restricted charging, if it is real. Whether it IS real is hard to pin down, but this article asserts it is. Scroll down to "Avoiding Full Charging". I choose to play safe.

[FLKiaEV]

Thanks. In that case though, does "full charging" mean to charge a battery to its actual full capacity or to what the management system is reporting as full (which might only be 90-something percent not counting the upper buffer)? I'll check out the article.

[IanL]

If the BMS masks the reserve, it presumably does not allow it to be accessed for charge or discharge, until the capacity has deteriorated sufficiently to require it to be unmasked to restore the usable capacity.

[FLKiaEV]

That makes sense. Coincidentally, I received in the mail today an item I ordered a few weeks ago: An OBD-II dongle that works with the "Soul Spy" app I installed on my phone (via bluetooth) which should give a lot of highly detailed information about the state of the battery. It's a Konnwei KW902, which is the brand and type that the author of Soul Spy (and Leaf Spy for Nissan Leaf owners) recommends. It was about $20 on Amazon. I'll let you know how it goes if you're interested.

[ksoul2084]

Basically, the ideal charging pattern strictly for the longest possible battery lifespan is 40-60%. Battery degradation increases non-linearly as you use the battery outside of that range, with the low and high extremes being the most harmful, and a much more gradual/small effect as you extend to 30-70, 20-80, etc.

This may sound negative, but the same type of argument can be made that a fossil fuelled engine's lifespan is likewise reduced based on the RPMs the engine sees outside of the its "sweet spot".

The worst case scenario is to charge your car to 100% and leave it there for a length of time. Only charge to 100% if you know you'll be driving the car within hours of the charge completing, as a best practice.

It is unfortunate that KIA didn't allow us to select 80, 90, 100% as the charge limit so we had more flexibility.

[FLKiaEV]

Yep, that's what I've heard too (about staying between 40% - 60%). I rarely charge it to 100% and if I do it's because I'm going on a slightly longer journey and I drive the vehicle within a short time after charging has finished.

On that note, I saw a YouTube video last week where a guy was using Leaf Spy on the used Leaf (2012 I think) he bought that used to be a taxi. Leaf Spy (and Soul Spy too I'm pretty sure) shows how many times your vehicle has been DC quick charged and this one showed that this former taxi had been quick charged about 7000 times! Battery capacity was in the low 70s, which is not great, but considering that kind of abuse, I have to say I was pretty impressed! Especially for the notorious Nissan Leaf battery.

Anyway, I will probably hook mine up on my next days off and see the SoH for my battery pack. I bought mine used but it had very low miles on it (only about 17000 miles on a 4 year old car. Not bad!), so I expect the battery SHOULD be in pretty good shape.