I keep car charged at 80 percent SOC most of the time. I have a 3 mile mountain descent every morning and I lose regen about 2/3rds of the way down the mountain. If I have a lower SOC, say below 70 percent then this does not happen. It’s a small gripe but it forces me to use my brakes when normally I wouldn’t have to. I really wish there was a way to adjust this. It seems at 80% SOC there would still be plenty of headroom to take a full charge for this mountain descent. I hardly ever use my brakes but this is causing me to use them everyday leaving my house. If anyone knows of a solution or work around, I would love to hear it. Starting with a lower SOC works but some days I don’t want to give up more than 20% of my range.
-
Want to remove ads? Register an account and login to see fewer ads, and become a Supporting Member to remove almost all ads.
Regen on mountain descent from house each morning
- Thread starter Pemby
- Start date
E90alex
Active Member
I mean there’s not really many other options here. Start at lower SOC. Deal with using the brakes. Or move.
I arrive at the main road with a negative power usage over the 7 miles or so it takes to get there. I just don't use the brakes. Maybe I am not as steep.
For me being completely off grid requires a higher state of charge, that being said. I usually regain it as I start moving on the main road. This time of year it takes a bit longer.
For me being completely off grid requires a higher state of charge, that being said. I usually regain it as I start moving on the main road. This time of year it takes a bit longer.
boulder.dude
Member
Charging speed decreases at higher SOCs (witness the Supercharging curve). Your battery can’t charge fast enough to absorb the full regen power.
If you're maxing out the battery on the way down the mountain then setting lower initial SOC seems the obvious solution. Lower it to 75% and test for a week. Then go to 70% if that's still getting maxed out.
On a typical day what SOC do you return home with?
Mid to upper 40’s or so. I can lower starting SOC easily and solve the problem. Really would just like to see a slight charge curve change, wouldn’t take much. Recommended charging to 80 percent SOC doesn’t work optimally when you live on a mountain. I know a subset of a subset, but a small change to curve would be cool
E90alex
Active Member
So you use 30-40% range in a day then. You will be more than fine charging to 70%. Even 60 or 50% would be fine for you.
Tesla does not recommend charging to 80% exactly. They recommend staying under 80%.
Occhis
Member
You could use the friction brake blending option to give the effect of consistent regen deceleration at all SOC.
If it quits charging during regen on descent, then you likely arrive at work with roughly the same SOC, as you would if you dial back your home charge a bit and let it have full regen going down.
One you pay for, one you don't. Plus you're using up your brake pads as well. As said before, experiment with the increments. You stand to gain from it.
One you pay for, one you don't. Plus you're using up your brake pads as well. As said before, experiment with the increments. You stand to gain from it.
MrFixit1094
Member
Keep in mind that there are two factors that limit regeneration...
First, If the SOC is 'too high' regen will be limited.
When you start with 80% and lose your regen (2/3 of the way down the mountain) what is the SOC at that point?
When you reduce your initial SOC to 75% (and do not lose regen), what is the SOC when you reach the bottom of the hill?
Second (and more elusive) is HV battery temperature. This is akin to the need to pre-condition when approaching a supercharger. The battery has to be surprisingly warm in order to be able to accept high levels of charge (whether from regen or from a supercharger). Unfortunately, Tesla provides no visibility for this and about all you can do is infer that temperature is the issue when you lose regen without having a 'high' SOC.
If your problem is temperature related, it will get worse as the temperature drops in the winter.
This may also be a function of your battery specifics. Do you have a 'new' Model Y with the structural 4680 batteries? I think these batteries are not as good as the older 2170 cells when it comes to accepting higher charging rates under a given set of conditions.
There are other discussions here where Tesla owners are quite annoyed about losing regen. Regeneration is fundamental to the superb efficiency of these vehicles and if regen essentially goes away in the winter, then you could argue that a Tesla is not much better than an ICE vehicle !.
First, If the SOC is 'too high' regen will be limited.
When you start with 80% and lose your regen (2/3 of the way down the mountain) what is the SOC at that point?
When you reduce your initial SOC to 75% (and do not lose regen), what is the SOC when you reach the bottom of the hill?
Second (and more elusive) is HV battery temperature. This is akin to the need to pre-condition when approaching a supercharger. The battery has to be surprisingly warm in order to be able to accept high levels of charge (whether from regen or from a supercharger). Unfortunately, Tesla provides no visibility for this and about all you can do is infer that temperature is the issue when you lose regen without having a 'high' SOC.
If your problem is temperature related, it will get worse as the temperature drops in the winter.
This may also be a function of your battery specifics. Do you have a 'new' Model Y with the structural 4680 batteries? I think these batteries are not as good as the older 2170 cells when it comes to accepting higher charging rates under a given set of conditions.
There are other discussions here where Tesla owners are quite annoyed about losing regen. Regeneration is fundamental to the superb efficiency of these vehicles and if regen essentially goes away in the winter, then you could argue that a Tesla is not much better than an ICE vehicle !.
Occhis
Member
Using Schedule under Climate in the app, you can preheat the battery before departure while plugged in. This may help retain regen for a longer period, depending on the ambient temperature.
MrFixit1094
Member
This would be an interesting test for the OP... Charge to his normal 80%, but intentionally preheat the battery to see if this retains the regen. If it does, it would be especially effective in the winter when things are even colder, and he might lose regen even sooner during his descent.
Of course, from a net energy standpoint, you will likely expend more energy (albeit from the grid) by preheating than regeneration can recover.
Preconditioning prior to supercharging is all about speeding up the supercharging process. I'm sure it wastes energy, but it cuts down on time spent at a supercharger.
E90alex
Active Member
The battery warning during preconditioning is very minimal to none depending on ambient temperature. Not anywhere near to the level of supercharger preconditioning.
Occhis
Member
Completely agree, just thought a slightly warmer battery might allow for more regen. I think that’s what OP is after, not overall energy cost.
