Optimum garage temperature for your EV

[oilerlord]

Just curious to get everyone's input on this. Winter is upon us, and our heated garage is set at a constant 54F. My goal is maximizing the battery's lifespan, and thus keeping it at the "best" temperature while parked. I don't leave the car plugged in all the time.

 

[michael]

That is perfectly fine.

 

[LeftieBiker]

Yes, "cool but not cold" is great.

 

[oilerlord]

Thanks, I think so too. I've read the optimum charging temperature range for lithium ion batteries is between 50-86F. I figure staying on the lower end of the scale allows for temperature rise into the middle of the range while charging, and puts less demand on thermal management. After 100K miles, this may only save a few percentage points but it all adds up.

I'd also assume charging on L2 at 13 amps generates less heat than at 30 amps. However, because it takes ~9 hours at 13 amps and only 3.5 at 30 - in terms of minimizing the detrimental effects of heat, which is better? Moderate temperature for a longer period or higher temperature for a shorter period?

 

[LeftieBiker]

IF the temp doesn't reach the point where acceleration of degradation occurs, then I don't think it matters. DC Fast Charging is generally considered to be fine in cool weather and not so good in hot. I'm not sure that different L-2 rates matter at all...

 

[user 1485]

I have my Bolt EV in a garage at about 54 F too. Remember the Bolt is capable of heating and cooling the battery to keep it in the optimum range. I have monitored this over the last month using either a car diagnostic scanner or my ChargePoint charger. I see that if you leave the charger plugged in, the car charges but, about every eight hours afterwards, the car pumps some heat into the battery. Its a few kWh. I have not yet looked at it with the charger unplugged.

 

[oilerlord]

IF the temp doesn't reach the point where acceleration of degradation occurs, then I don't think it matters. DC Fast Charging is generally considered to be fine in cool weather and not so good in hot. I'm not sure that different L-2 rates matter at all...

No doubt that thermal management will kick in if/when ambient temperatures are a health risk to the battery. I just figure there's no harm in treating the the battery as if was an old Leaf with no BMS. In terms of temperature rise, I'm not sure if different L2 rates matter either but my thoughts are that the pack will remain somewhat cooler charging at 13 amps than it would at 30.

Generally speaking, and other than notable exception of charging a very cold pack, it's pretty much a given that a battery in an EV that gets driven in northern climates and is parked in a temperature controlled garage will last longer than the one in warmer states that isn't.

 

[IMAdolt]

IMO it would depend a lot on how your garage is heated/cooled, if it's a burden on your homes energy costs to heat or cool your garage to a stable temperature it's likely more efficient to use the battery TMS to do the work even if it's plugged in and not charging.

If You're the kind of guy who likes a not freezing or boiling hot garage for whatever reason that's a different storey.

 

[devbolt]

We park our Bolt in the driveway, outside. Overnight temps during the winter are typically in the mid to upper 40’s, though we do get a few trips to the mid to lower 30’s. I leave the car plugged in at night.

 

[LeftieBiker]

I just figure there's no harm in treating the the battery as if was an old LEAF with no BMS.

I think you mean "no TMS." The BMS keeps the pack equalized and limits maximum charge and discharge levels.

 

[michael]

Thanks, I think so too. I've read the optimum charging temperature range for lithium ion batteries is between 50-86F. I figure staying on the lower end of the scale allows for temperature rise into the middle of the range while charging, and puts less demand on thermal management. After 100K miles, this may only save a few percentage points but it all adds up.

I'd also assume charging on L2 at 13 amps generates less heat than at 30 amps. However, because it takes ~9 hours at 13 amps and only 3.5 at 30 - in terms of minimizing the detrimental effects of heat, which is better? Moderate temperature for a longer period or higher temperature for a shorter period?

The final temperature is likely to be about the same either way. The battery is v.ry well insulated I'm confident, so the temperature rise depends only on the thermal capacity of the battery pack and the energy loss

In other words, if the battery is, for example, 95% efficient during charge, you would generate 60 kWh * 5% = 3 kWh of heat either way. If the battery is well insulated, most of this heat stays in the battery as heat. Of course, this is an approximation only, but you get the idea

So I'd definitely go with higher power, just in time for departure. Battery stays cool longer and is warmed up in time for your drive.

 

[winterescape]

IMO it would depend a lot on how your garage is heated/cooled, if it's a burden on your homes energy costs to heat or cool your garage to a stable temperature it's likely more efficient to use the battery TMS to do the work even if it's plugged in and not charging.

If You're the kind of guy who likes a not freezing or boiling hot garage for whatever reason that's a different storey.

I do not feel that you are likely making any measurable improvement in the life of your Bolt battery by heating your garage in the winter and would agree that the likely amount of energy wasted in doing so is not trivial. Having said that, you are near the recommended "59F " that is mentioned as being "optimal" for long term storage of lithium Ion batteries.

"The possible storage temperature range for Lithium-Ion batteries is is -20°C to 60°C but for prolonged storage period -20°C to 25°C is recommended and 15°C is ideal"

http://www.mpoweruk.com/storage.htm

 

[oilerlord]

I do not feel that you are likely making any measurable improvement in the life of your Bolt battery by heating your garage in the winter and would agree that the likely amount of energy wasted in doing so is not trivial.

While it's entirely possible that someone out there installed a garage heater for the sole reason of keeping their EV battery in the "optimum" temperature range, I think most folks that have heated garages do so because they don't like freezing their ***** off. Put me in the latter category.

I know full well it's inefficient to heat our garage, and that it takes energy and all of the nastiness of GHG's being released from the burning of natural gas. Being warm is worth it to me.

 

[LeftieBiker]

I use an electric heater set to 750 watts in my garage, primarily because I have several EVs out there and I actually use the bicycles in Winter. I try for 45F and settle for anything above 33F though.

 

[Chargeit]

I converted our garage into a man cave. The last couple years our two Spark EVs have been parked outside during winter, and our new Bolt will have to join them. I think it will be OK.

We usually get at least a couple cold spells down into the teens, and as far as I can tell, there haven't been any negative consequences. Just remember to remote start, while they're plugged in, ten minutes before you leave so their inside is toasty warm.

I also don't worry too much (now) that the battery keeps it's original capacity. As long as we can get at least 20 miles out of a charge, they will still be great city cars. Long before then, we'll be ready for another Bolt.

 

[SeanNelson]

In other words, if the battery is, for example, 95% efficient during charge, you would generate 60 kWh * 5% = 3 kWh of heat either way. If the battery is well insulated, most of this heat stays in the battery as heat.

That assumes that almost all of the inefficiency lies in the battery and not in the AC to DC conversion going on in the charger.

 

[michael]

In other words, if the battery is, for example, 95% efficient during charge, you would generate 60 kWh * 5% = 3 kWh of heat either way. If the battery is well insulated, most of this heat stays in the battery as heat.

That assumes that almost all of the inefficiency lies in the battery and not in the AC to DC conversion going on in the charger.

No it does not. I'm talking about battery charging efficiency which is the only part that heats the battery itself. Inefficiency in the electronics is a separate matter. I am talking about the battery alone. Overall charging efficiency is in the range of 90% typically, which includes both charger inefficiency and battery inefficiency.

When the battery charges, the ESR (effective series resistance) causes loss of energy and heating of the battery itself.

 

[SeanNelson]

In other words, if the battery is, for example, 95% efficient during charge, you would generate 60 kWh * 5% = 3 kWh of heat either way. If the battery is well insulated, most of this heat stays in the battery as heat.

That assumes that almost all of the inefficiency lies in the battery and not in the AC to DC conversion going on in the charger.

No it does not. I'm talking about battery charging efficiency which is the only part that heats the battery itself.

Ah, OK - point well taken.

 

[plj]

Remember the Bolt is capable of heating and cooling the battery to keep it in the optimum range. I have monitored this over the last month using either a car diagnostic scanner or my ChargePoint charger. I see that if you leave the charger plugged in, the car charges but, about every eight hours afterwards, the car pumps some heat into the battery. It's a few kWh. I have not yet looked at it with the charger unplugged.

I would be very interested in comparing how the Bolt conditions the battery plugged in versus using it's own battery power. Please share any information you obtain.

My experience in hot weather (90+) is that plugging the charger activated the battery cooling system. That observation led me to believe that the Bolt is more willing to cool (or heat) the battery when plugged in. Evidence of this conditioning would be helpful for our understanding. That makes sense to me--who would want to return to a car with a drained battery. I heard that early Teslas would use a lot of battery power to cool/heat the battery, and customers complained enough that Tesla re-programmed the conditioning to reduce the amount of conditioning when using battery power.

My Bolt salesman, who was well informed, told me to plug the Bolt in whenever ambient temperatures are below 32° and above 90.° Plus, put it in "immediate" charge mode. The first half of his advice is in the manual (page 231): "It is recommended that the vehicle be plugged in when temperatures are below 0°C (32°F) and above 32°C (90°F) to maximize high voltage battery life." Note the manual doesn't say anything about immediate charge mode, but as my experience is that is necessary for the battery conditioning to work.

I suspect that battery conditioning kicks in at different temperatures depending on whether the Bolt is plugged in and in immediate mode, or not. I would be interested in learning more about these set points.

 

[SparkE]

Remember the Bolt is capable of heating and cooling the battery to keep it in the optimum range.

I don't know that this is 100% accurate (regarding "optimum range"). I would say that the TMS definitely keeps the battery out of "the danger zone" (too cold or too hot).