Bz4X battery charging

I asked the Toyota tech help about this question which seems to come up all the time for other makes of EV. The consensus for most EV users seems to be that you charge to 100% maybe once a month to 'balance the Battery cells' and normally just charge to 80% or 90% overnight to help preserve Battery life. It's hard to find any substantial scientific evidence one way or another about this. There is nothing specific in the bZ4X Toyota manual.

However, somewhat to my surprise Toyota did give a very clear response:

"Our Technical Team have advised that you can recharge fully as much as you wish on AC charging. Battery balancing is carried out during AC charging, when the battery nears a full charge. The only restriction is the amount of DC charges within a certain time period."

That seems clear enough...!

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On 2/21/2023 at 3:11 PM, dab1054 said:

that you can recharge fully as much as you wish on AC charging

That's essentally wjhat we figured.

And also, maybe with the bZ4X have the 71Kw nominal / 64Kw usable Battery, is 100% SOC really 100% ??

If it's 100% of 64Kw , then the Battery may not ever be getting fully 100% charged ?

The consensus seesm to be that Toyota did this to protect the Battery and extend it's usable life, if correct that seems a good thing

May not be relevent but when I bought the PHEV I did a lot of reading through the US forums and the consensus was that although the SOC might say 100% the reality was that the internal software only allowed up to a 90% real charge. this would allow for the extra capacity to be used to maintain the Battery condition over the years of use and also to be 'released' as and when the Battery capacity falls off with charging up to 100%.

Honestly this about not charging your Battery to 100% because it will shorten the life of it is a myth only. Charged fully every time you can or quick top iOS here and there and you won’t have any problems. Not good perhaps to be fully charged at 100% and left without use for extended time. Usually cars and technology comes out of the box at around 80% soc. Another thing to avoid is draining completely and leave it drained for days weeks or months. 

Doing a quick calculation on available Battery information- bZ4X total Battery is 71.4kWH and usable is 64kWh so that means that the Battery should never charge beyond 89.6% of total capacity (at least as it is currently configured) even if this is displayed as 100%. I guess Toyota engineers do have a lot of serious experience with EV/hybrid batteries right from the early days of the Prius. This was a big factor when I decided to go for the bZ4X.

The only downside to charging to 100% seems to be that you lose regenerative breaking for a while.

On 2/27/2023 at 11:44 AM, dab1054 said:

Doing a quick calculation on available battery information- bZ4X total battery is 71.4kWH and usable is 64kWh so that means that the battery should never charge beyond 89.6% of total capacity (at least as it is currently configured) even if this is displayed as 100%. I guess Toyota engineers do have a lot of serious experience with EV/hybrid batteries right from the early days of the Prius. This was a big factor when I decided to go for the bZ4X.

The only downside to charging to 100% seems to be that you lose regenerative breaking for a while.

Maybe they reserved first %0-5 and and last %95-100 to maintain Battery health and protect it from memory affect. 

All Battery live longer it charged to 80% then if you need the extra range charge it up accordingly to lets say max 100% if you need it full range that day plus you electric rate is cheaper at home than on your recharge locations.

Fast chargers/superfast will stop at 80% capacity.

The Battery reserve will be at both ends so that zero is never a flat Battery as well as the fully charged reserve. Not just the extra miles that can be driven with the system showing zero miles range but the protection buffer designed into the system. Fully discharging the Battery would be disastrous and it's always protected but I'd not want to speculate how much used for protection. Maybe some of the potential 'release' of battery will come from reducing the Toyota engineers original resevers?

On 3/1/2023 at 7:02 AM, ernieb said:

Fully discharging the battery would be disastrous a

Why would it be disastrous ?

For exmaple have has iPhones and laptop batteries comletely flat, but they charged up fine.

Actually thinking about this, what is you left the bZ4X unused for a few months when for exmaple overseas, the Battery might go flat ?  Suppose you could leave it connected to the charger with some sort of limit on max SOC

It's not the sort of thing that you want to do on a regular basis, the chemistry works best for performance and long reliability if it's used/maintained in the 20% - 80% range. As I said above the manufactures protect against complete discharge in the car, phones and laptops. In the case of the bZ4X I guess it's some of this guard band that they will release to the user.

There seems to be a general recommendation with all the car manufactures to not leave the car with 100% charge for long periods, not regularly use fast charges and an assumption that they will not let the EV car run to stopping just in the same way as we don't in a petrol/diesel car.

Fully depleted Battery in any device including bev on regular basis cause Battery health issues on chemical levels and (weaknesses  in Battery capacity and performance) , reduced range. Information widened available online. Since over at least 10 years now most if not all devices and cars has built in protection for overcharge or discharge and owners should not need to worry about charging or discharging. Only not recommended to leave the battery fully discharged for extended period of time as this can indeed cause future problems. For example you live your car at long stay at the airport for 3 months with close to 5% soc and on your return you may find impossible to use the car. 80% been most common long term storage capacity used on many devices including electric cars, scooters, bikes etc. Our ev is now two years old and has almost been fully charged every time by a street 7kwh charger at least twice a week and battery remains at 100% health. Total mileage 12000 

The general consensus with lithium cells is the 20-80% rule for the best life to use ratio.

There are 2 main reasons for this:

1) Lithium cells have limited charge cycles (e.g. from 0%-100%-0% is one cycle), but a partial charge cycle doesn't count for a full cycle so you can effectively get more cycles out of it from partial charges.

2) Li-ion cells are happiest at ~50% SoC (As opposed to Lions in a cell, which are hungry and have big teeth  ). The further you get from that, the faster it degrades when it's just sat there, with being stored at 0% or 100% having the highest degradation.

I should clarify that I'm not saying you'll suddenly loose 50% capacity by doing these things, just that it'll make the Battery capacity go down faster than it would otherwise over the course of its life.

For instance, my laptop batteries would typically last 2-3 years, but since I set a 20-80% charge profile on this one (Thinkpads FTW) this one has lasted me 5 years so far and I've lost maybe 2 hours of run-time out of the 9 it originally started with I think? Not too shabby!  

Another thing is charging speed - Anyone who's played with RC cars will know that if you quick-charge all the time, the Battery degrades faster than if you do a normal charge; This is another reason why EVs are best if you can charge at home - Home charging puts very little stress on the Battery, whereas doing nothing but 300kW rapid charges every time will reduce the battery life noticeably faster. The newer EVs and charge points have mitigated this somewhat by only putting out maximum charge during the middle of the battery, where it has the least detrimental effect, and is why the last 20% can take as long to charge as the initial 80%, as they deliberately slow down the charge to nearly a trickle to avoid damaging the pack as much.

This does lead to people complaining why they're never getting the headline charge speed all the way through, only for part of the charge, but this is most of the reason why!

Looking at Zap Maps, ABRP etc. there seems to be many different speeds of chargers, from really low 7Kw right up to 200Kw !!

In practice, what is the likely / achievable speed of charging the bZ4X , especially if doing more than two rapid charges per day ?

Assuming avarage temperatures for this time of the year of course, say 6 degrees C to 10 degrees C

I tend to get by on 50Kw chargers as they’re fairly common. 

The other thing to consider is that if you’re using a 150 or 200Kw charger and only charging at 50 or 60 you’re potentially blocking a faster charging car from getting away quicker.

EV charging is a combination of maths, etiquettes and patience. 

9 minutes ago, Malop said:

I tend to get by on 50Kw

Thanks for that.  So if using a 50Kw charger, how long roughly to does it take go from say 20% to 80 / 90 % SOC ?

EVDB publishes a charge rate curve showing the rate for both a 150 kW charger and a 50 kW charger.

With a 150 kW the charge rate starts at close to 150 kW at 20% and tails off to around 30 kW in a fairly linear fashion by 80%. So an average charge rate of around 90 kW.

With a 50 kW charger the rate starts at around 50 kW at 20% and maintains that until over 70% before tailing off to around 30 kW at 80%. This corresponds to an average charge rate around 45 kW (approximately).

20% - 80% corresponds to a charge of 60% of the 64 kW useable Battery - so a demand of around 40 kW (approximately) - which would take around half an hour at a 150 kW charger  and closer to an hour at a 50 kW charger.

All figures entirely theoretical based on the best information I have available - i.e. no practical experience ... 😉

And such charge times will be subject to availability and other load on the chargers, but the bottom line is that a 150 kW charger (or above) will supply charge at only twice the rate of a 50 kW charger (not three times or more).

14 hours ago, lightboxcar said:

In practice, what is the likely / achievable speed of charging the bZ4X , especially if doing more than two rapid charges per day ?

Assuming avarage temperatures for this time of the year of course, say 6 degrees C to 10 degrees C

You have to look at the EV charger screen to see the kW rate- so mostly I have missed the whole period of charging while sitting down with a coffee/snack so probably have missed the peak kW. In very cold weather (-3C)  I have seen as little as 28kW but in warmer weather (8C) I have seen 50-70kW but nowhere near 150kW claimed. In practice I found that it is best to allow about 45 minutes to go from 20 to 80% at current temperatures- might get a bit better when it is warmer or when Toyota do the software upgrade.

On 3/28/2023 at 9:32 AM, philip42h said:

EVDB publishes a charge rate curve showing the rate for both a 150 kW charger and a 50 kW charger ...

... and if I'd bothered to use my poor befuddled brain for reading rather than arithmetic I could also have noted that the EVDB gives answers to the questions asked ...

The table below shows all details for rapid charging the Toyota bZ4X AWD.

• Max. Power: maximum power provided by charge point
• Avg. Power: average power provided by charge point over a session from 10% to 80%
• Time: time needed to charge from 10% to 80%
• Rate: average charging speed over a session from 10% to 80%

Doh! 🙄

This is the fastest I have got on a 350kw charger at 15c on a BZ4X FWD

10 hours ago, Tom_Dww said:

This is the fastest I have got on a 350kw charger at 15c on a BZ4X FWD

 

Banbury off M40 near Tesla charge stalls but not Tesla

and on the Tesla charge point in Banbury

Very interesting range and Battery charging speed calculators, with sliding scales, on Toyota website. 

Not sure how long they've been on there, but very informative, helpful and also i believe will settle a lot of people's fears from what to expect from BZ4X 

Just need to scroll down BZ4X page to get to them

3 hours ago, egg said:

Just need to scroll down BZ4X page to get to them

Can you post a link?