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Discussion Starter · #1 ·
I was curious how everyone was planning to charge their Solterra. I couldn’t find any official advice from Subaru, and Toyota seems to be saying go ahead and charge the bz4x to 100%. Do you trust Toyota’s very conservative battery management and assume there is a decent buffer they are hiding at the top, or are you playing it safe for long term battery life and charging to an 80% limit most of the time unless you’re planning a longer drive? I am leaning towards setting to 80% most of the time since my day to day driving is not a lot of miles.
 

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2021 Ascent Limited; 2023 Bolt EUV Premier w/S&S, SC
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This is a good way to start a flame war! ;) Lots of different opinions on this. Some people are passionate about 80% to maximize their battery life. Some people insist that they've paid for a full battery and they're going to charge to 100% every day. These are usually the people who don't plan on keeping the car past the warranty expiration. The truth is somewhere in the middle, where you're probably OK charging to 100% (especially with Toyota/Subaru being so conservative, as you said), but you'll probably maximize life by sticking with 80-90% on a regular basis, as you suggested you may do.

I fall in the middle camp. I have a Chevy Bolt EUV right now, but I would follow the same plan if I get a Solterra. I very rarely need a full charge to get through a day, so I typically charge to 80%. If I plan on traveling more than 100 miles or so the next day, I'll set the charge limit to 100% so that it's full in the morning -- and then set the departure time for morning so that it's not sitting at 100% for a long time, but that's probably being overly cautious.

I do, however tend to leave the vehicle plugged in all the time so that the Battery Management System can do it's thing to keep the battery in a decent temperature range. This is a good idea in the cold temperatures in winter where I live and also in the hotter temperatures in summer down south.

One other related item... some people are under the impression that the Solterra is equipped with an LFP (Lithium Iron Phosphate) battery. There is no actual evidence of that, but if that were true, then charging up to 100% has very little negative effect on battery life. The Solterra battery has the poor cold temperature performance of a LFP battery, but it doesn't have other characteristics, such as cell voltage, of a LFP battery. Plus, I think if Subaru was using LFP, they would be bragging about the improved life cycles, safety, and sustainability of their batteries. Would be nice if we could find this out for sure.
 

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With the buffer above 100% SOC in Toyota's design, I am in the "charge it to 90% most of the time" crowd for my Solterra (arrived 48 hours ago). If the buffer wasn't as large, I would probably be in the 80% crowd.

I plan on keeping my Solterra for 20 years, until about the time I should probably stop driving, so ultimate battery longevity is for me, thus my 90% limit with an additional buffer above.

That said, it will get a 100% charge for cell equalization about once per month.

Here's to hoping for decent battery life and retained capacity.

Just one more opinion.
 

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Vancouver, BC 2023 Solterra Tech Pkg
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I charge to 80% normally, and to 100% if I am going on a longer trip and need the extra range. Also will charge to 100% occasionally just to balance the cells. The 100% charge will be timed to complete just before driving off. It is my understanding that this will best prolong the life of my battery.
 

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Discussion Starter · #5 ·
I charge to 80% normally, and to 100% if I am going on a longer trip and need the extra range. Also will charge to 100% occasionally just to balance the cells. The 100% charge will be timed to complete just before driving off. It is my understanding that this will best prolong the life of my battery.
This is probably the method I will stick with, except I don't think I have the patience to try and time my 100% charge to end just before leaving. I'll put a little faith in their battery management software and the presumed hidden top buffer to avoid a completely full battery from causing degradation. I guess I will see if the lower range readings stop giving me a little bit of range anxiety over time as I have more proof I really don't need a full charge most of the time.
 

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Discussion Starter · #6 ·
I do, however tend to leave the vehicle plugged in all the time so that the Battery Management System can do it's thing to keep the battery in a decent temperature range. This is a good idea in the cold temperatures in winter where I live and also in the hotter temperatures in summer down south.
Both my wife and I got a Solterra, and we have one level 2 charger installed, so unfortunately we need to share and can't just both stay plugged in all the time. I guess at least one of us should stay plugged in more often in the winter just in case.

One other related item... some people are under the impression that the Solterra is equipped with an LFP (Lithium Iron Phosphate) battery. There is no actual evidence of that, but if that were true, then charging up to 100% has very little negative effect on battery life. The Solterra battery has the poor cold temperature performance of a LFP battery, but it doesn't have other characteristics, such as cell voltage, of a LFP battery. Plus, I think if Subaru was using LFP, they would be bragging about the improved life cycles, safety, and sustainability of their batteries. Would be nice if we could find this out for sure.
I saw all the speculation on LFP batteries. Sadly I'm sure it was all wishful thinking, and I'm not going to assume it has an LFP battery just to make me feel better about charging to 100% all the time. :p
 

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Vancouver, BC 2023 Solterra Tech Pkg
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This is probably the method I will stick with, except I don't think I have the patience to try and time my 100% charge to end just before leaving. I'll put a little faith in their battery management software and the presumed hidden top buffer to avoid a completely full battery from causing degradation. I guess I will see if the lower range readings stop giving me a little bit of range anxiety over time as I have more proof I really don't need a full charge most of the time.
With L2 charging it gives you a pretty accurate estimate when charging will complete. So I just work backwards from that. It doesn't have to be exact of course, and not to worry if you are off by a few hours once in a while. I've been on trips before where the hotels offered free overnight charging. I would charge to 80% the night before, and then in the morning continue charging to 100% when I wake up. By the time we have breakfast and get packed up to go, it is finished charging.

Having said that am not sure if our app allows you to start charging remotely or changing the max charge. The Hyundai app did and did not have to go out to the car.

What matters more to the battery, is not to leave it at 100% for days on end, or below 20%.
 

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Discussion Starter · #8 ·
With L2 charging it gives you a pretty accurate estimate when charging will complete. So I just work backwards from that. It doesn't have to be exact of course, and not to worry if you are off by a few hours once in a while. I've been on trips before where the hotels offered free overnight charging. I would charge to 80% the night before, and then in the morning continue charging to 100% when I wake up. By the time we have breakfast and get packed up to go, it is finished charging.

Having said that am not sure if our app allows you to start charging remotely or changing the max charge. The Hyundai app did and did not have to go out to the car.

What matters more to the battery, is not to leave it at 100% for days on end, or below 20%.
If they actually release an update to easily show us the SoC% in the car (or even app!) it would make it a lot easier to estimate charging time!
 

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With the buffer above 100% SOC in Toyota's design, I am in the "charge it to 90% most of the time" crowd for my Solterra (arrived 48 hours ago). If the buffer wasn't as large, I would probably be in the 80% crowd.

I plan on keeping my Solterra for 20 years, until about the time I should probably stop driving, so ultimate battery longevity is for me, thus my 90% limit with an additional buffer above.

That said, it will get a 100% charge for cell equalization about once per month.

Here's to hoping for decent battery life and retained capacity.

Just one more opinion.
I’m new to electric so a lot is confusing for me - especially the charging! I don’t keep the charger attached to my car everyday. I charge it up to 100% and then thought I don’t need to charge it again until it dips at least below 80%. I often drive 100 mi. in one trip, but when I’m home, my local driving doesn’t amount to much. Some days I don’t drive at all. Right now, I haven’t plugged it in for days. Is this not good battery management? I can’t see plugging it in when it’s sufficiently charged for local driving. But, of course, I want battery longevity. The manual makes it clear that charging it every night to 100% is fine except there are A LOT of posts here saying that’s not a good idea. Totally confusing for a novice!
 

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I’m new to electric so a lot is confusing for me - especially the charging! I don’t keep the charger attached to my car everyday. I charge it up to 100% and then thought I don’t need to charge it again until it dips at least below 80%. I often drive 100 mi. in one trip, but when I’m home, my local driving doesn’t amount to much. Some days I don’t drive at all. Right now, I haven’t plugged it in for days. Is this not good battery management? I can’t see plugging it in when it’s sufficiently charged for local driving. But, of course, I want battery longevity. The manual makes it clear that charging it every night to 100% is fine except there are A LOT of posts here saying that’s not a good idea. Totally confusing for a novice!
I think if you keep it most of the time between 20 and 80%, you'll be fine. Plug in when gets down to 20-ish (unless planning a long trip), set it to stop charging at 80%.
 

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I think if you keep it most of the time between 20 and 80%, you'll be fine. Plug in when gets down to 20-ish (unless planning a long trip), set it to stop charging at 80%.
Thanks. Sounds awfully familiar to the advice I got for my iPhone 🙃
I’m thinking that overtime more will be understood about the Solterra battery.
 

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I’ll be leaving mine closer to 90% during the peak of California fire weather and major storms, in case we choose to evacuate. Otherwise, no reason to worry about keeping it high, any more than an ICE-powered vehicle. You wouldn’t go get gas every day after driving a short distance, so don’t worry about that.

But I still like the 20%-80% rule and for long trips, bringing it down to 20% will get your vehicle into the zone where it will accept the fastest charging rate, minimizing your time spent at the charger.

ABetterRoutePlanner is your friend, especially once their Solterra/bZ4X modeling improves.
 

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I’ll be leaving mine closer to 90% during the peak of California fire weather and major storms, in case we choose to evacuate. Otherwise, no reason to worry about keeping it high, any more than an ICE-powered vehicle. You wouldn’t go get gas every day after driving a short distance, so don’t worry about that.

But I still like the 20%-80% rule and for long trips, bringing it down to 20% will get your vehicle into the zone where it will accept the fastest charging rate, minimizing your time spent at the charger.

ABetterRoutePlanner is your friend, especially once their Solterra/bZ4X modeling improves.
That’s a good point. I don’t live in California but I’d be in a bad situation if I let the battery run low and then lost my electric to recharge the car. When I was a gas car owner, I never let my tank get too low. Kind of makes sense to do the same with electric as long as it doesn’t hurt the battery. That’s my main concern.
Interesting note: “for long trips, bringing it down to 20% will get your vehicle into the zone where it will accept the fastest charging rate, minimizing your time spent at the charger.” Haven’t thought about that. So much to learn!
 

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With the current zero mile point in the Guess-o-Meter, if there were plenty of charging stations available close-by in an area, I would probably take it down to 5% (or whatever would leave me enough to definitely get to the next station in case it’s busy or all broken, etc.) then recharge to 50% or enough to get to the next charging point. You will spend less time at the charger if you are charging it in the zone where the car charges at the fastest rate. Above 50%, the current Solterra/bZ4X charging curve is basically a joke. I would never sit there long enough to charge to 80%, especially on hot days.

This also assumes the charging stations are not very far off of your route.

This “charge to 50% often” routine will get far easier as more stations come online and the density of chargers is better.

Definitely an interesting optimization problem for long trips (more than one full-charge range for the day).
 

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I also want to thank everyone for sharing here. It is so helpful to hear how people deal with charging or plan to. In SW OH there is 1 DC fast charge location with 11 units 24 mi. away (more 60 mi.). There are several L2 public stations xloser. An L2 EVSE is installed inside our garage. We also have solar panels and I plan to maximize charging when they are producing. Since we are retired charging during the day is easy. Except at moments like right now when the panels have 3 in. of snow on them and are producing 0 KW. I could, if needed, charge using the grid.
 

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I reached out to my aftermarket support at the dealership regarding this question. He had also heard of the 80/20 rule, but has no official information from Subaru. He recommended it as a best practice at this time.

I updated my car to charge to a maximum 80% on L2/L1 chargers from the Settings menu. I don’t let it dip below 20%, and charge to 80% for daily driving.

Of note, when you set it to charge to 80% and have the charger lock enabled, you must unlock the car using an unlock button on the driver door or remote in order to remove the charger (even after charging is suspended). When I charged to 100% the first time, I did not need to press the unlock button (it released when I used the touch sensor in the door handle).

I plan to charge to 100% infrequently for a long drive that I perform (usually) 2x per month (the reason I needed an extended range battery).
 
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