Comments on disabled regen in the cold

[cinergi]

Right, and regen = charging. The heating function was added by popular request. I'm suggesting a tweak to save energy.

I think you meant to say don't go into a cycle of keeping the battery heated until the charging starts -- in other words, don't heat it from 7pm to 3am if my charge is set to start at 3am. From 3am onwards, heat, charge, and keep it heated.
I'm thinking a window of time, separate from charging, is needed. I may want it to charge on plugin, but don't bother heating it over night until it gets close to when I leave for my commute. And stop heating after X (settable) hours.

 

[donauker]

Right, and regen = charging. The heating function was added by popular request. I'm suggesting a tweak to save energy.

Popular request? The heating function was there from the beginning and it's intent is to warm the battery to a safe temperature before charging from the grid begins. The tweak to save energy is simply not setting the car to charge. If charging is needed then the battery must be heated if below 32F.

 

[bolosky]

I detect a firmware feature request: option have the battery NOT heat until after the charge is completed. That way you can dial it in to charge in the wee hours, and have a nice toasty and freshly charged battery when you head out in the morning.

I have a slightly different request: change the firmware so that you tell the car when you need it. Then, it can decide when to start charging based on available current, state of charge and how much preheating it will need to do. Then, it lets the car sit until it's needed and then does a just-in-time charge. This is good for your battery by letting it sit around at a lower SOC, and also saves energy by not having to keep it heated for very long before you're ready to go. It could even be clever enough to reduce current if it's got time and it thinks that would be better for the battery. If you plug in at a very low SOC, maybe it would know enough to get you up to a safe level quickly, then sleep and charge later.

The only problems I see with this are if you need the car when you didn't expect it won't have as much charge, and having to optimize charging later to save battery lifetime/heating energy vs. time-of-day electricity rates.

I believe that I heard that some othe EV (maybe the LEAF) has something like this. It would be great for Tesla to have it, too.

As it is, I have to guess when to start charging, and I picked 4AM because it's pretty late but still early enough that I'm pretty sure it'll be full before I leave in the morning even if I used a bunch of battery the previous day. It also has the added advantage of having the noisy fans running when I'm not around the car.

 

[Doug_G]

I think you meant to say don't go into a cycle of keeping the battery heated until the charging starts -- in other words, don't heat it from 7pm to 3am if my charge is set to start at 3am. From 3am onwards, heat, charge, and keep it heated.

Yes, that's exactly what I meant. My proposal has the advantage of minimal user interface. Your scheme sounds great but try representing that clearly in the tiny VMS user interface. I think it's more likely that a simple scheme would be implemented. All my idea might require is a "heat now" button. Just my 2 cents...

 

[cinergi]

On the other hand, basic insulation might be enough to prevent needing a setting at all ...

 

[gday]

Unfortunately insulation keeps things hot too (not so nice in the summer). The trick is to calculate the added A/C cost in the 8 months of the year with insulation vs. the reduced heating cost 4 months of the year. For what it's worth the information I recieved regarding my AC Propulsion eBox which uses similar lithium cobalt cells is that:

1. Storing/operating the cells below 0C damages them
2. Charging near 0C will damage the cells (probably why the ess warms the battery to 6C prior to charging)
3. Regen below 10C will damage the cells due to the high inrush current spikes

A catch-22 is that you don't really want to warm your battery using a heater powered by the battery if the battery is already below 0. So you either cross your fingers or get the car to a warm garage for a while.

I shut off regen entirely (via a control on the dash in the eBox) if below 10C.

 

[jkirkebo]

A catch-22 is that you don't really want to warm your battery using a heater powered by the battery if the battery is already below 0. So you either cross your fingers or get the car to a warm garage for a while.

A setting to always keep the battery at 20C would be nice to have on the Model S here in Norway. With proper insulation it shouldn't use too much energy from the battery to do this, even at -20C. This way, the car would always be able to charge, regen or output maximum power.

The Think City with the Zebra battery does this, although it keeps the battery at about 300C.

 

[Doug_G]

A setting to always keep the battery at 20C would be nice to have on the Model S here in Norway. With proper insulation it shouldn't use too much energy from the battery to do this, even at -20C. This way, the car would always be able to charge, regen or output maximum power.

I would think that the Model S battery might be harder to keep warm. It has a lot of exposed surface area.

 

[vfx]

What about a timer setting "Full by" where it backtimes a full charge based on what time you put input.

 

[jkirkebo]

I would think that the Model S battery might be harder to keep warm. It has a lot of exposed surface area.

A 100W warming blanket lined on the bottom of the battery box would probably be enough. Worst case 200W. This is 2.4-4.8kWh per day parked in really cold climates, or ~3-6% of the large battery pack capacity.