In storage for 5 months in winter

[eurosteve]

Hi

I'm looking at the Bolt as a next car after my 08 Prius (170K miles). Since I spend 5 months a year away from my home in NY, I would be leaving the Bolt in my garage over the winter (Dec-May). Currently, I hook up my Prius to a trickle charger (for the 12 volt battery), add stabil to the gas and I leave. With the Bolt I could leave it unplugged at somewhere around 50% (it's spelled out in the Bolt manual what the exact charge level they recommend is) or I could leave it plugged in with one of the smart chargers I'm seeing so I could check on its state of charge etc via wifi while I'm away. While I'm gone temps will go before 32 degrees F on occasion since my garage is not heated.

Any recommendations on how to leave the car over the winter? Am I buying the wrong car - would leaving it 5 months each winter be problematic? Thanks for any thoughts on the matter.

Thanks
Steve

 

[eurosteve]

No input on this? I guess there's little experience with letting EV cars sit for long periods of time.

 

[PV1]

Keeping the 12 volt battery charged has always been the issue with storing EVs. The main drive battery shouldn't lose much of any charge as long as something keeps the 12 volt system charged (this varies by car, but powering 12 volt loads is what drains Tesla batteries).

The rule of thumb on the i-MiEV forum has been to store with about 30-40% charge in the drive battery and hook up a 12v float charger. The extra "quick guide" book I got with my Bolt says to leave it plugged into J1772, which I can't recommend at all unless the thermal management system actively heats the battery while parked and turned off. If that's the case, definitely enable the Hill top reserve before plugging in. 90% charge is way better than sitting at 100%.

 

[eurosteve]

Hi - Thanks for the info. I guess that will be the decision I'll have to make - whether to leave it plugged in or not. Even if I leave it plugged into a 110v outlet I should be able to look in on it using the MyChevy app (and wifi)? Whether to leave it at 30-40% (unplugged) or at 90% (plugged in) is the decision. In either case I would connect the 12v battery to a smart trickle charger to keep it charged.

Any thoughts on whether leaving the car in storage each year for 5 months will do any damage to the lithium battery over time? Is there any concern about leaving it in an unheated garage in upstate NY (with occasional below freezing temps) will do any damage?

 

[PV1]

Leaving the battery fully charged or fully discharged are what harms lithium ion batteries, especially at high temperatures. Also, charging while the battery is below freezing can do some considerable damage to capacity, but the Bolt's liquid thermal management should prevent that. Storing at low temperature with charge between 1/4 and 1/2 should cause no degradation, as long as it doesn't go completely flat.

Unfortunately, I can't get more detailed than that as I simply don't know how the Bolt behaves fully yet. I'd say that if you have time during cold weather (preferably below freezing), leave the car sit for a week and see if it automatically tries to heat the battery while turned off and unplugged. Take note of the charge level on the dash or app at the start and finish of the test. That right there should indicate whether or not it needs to be plugged into J1772. If charge level stays the same (bars or %SoC, not miles) then you should be fine to simply put the 12 volt battery on a float charger and leave the car with about 40% charge. If it goes down considerably (more than 5%/1 bar), then it'll need to stay attached to a charging station or cord with Hilltop Reserve on (no float charger should then be necessary).

 

[dan2112]

You can always set the "hill top mode" that only charges to I think 80% and keep it plugged in. But as long as the 12v system is happy - the car should be ok - just don't keep the battery at extremes (100% or 10%) for a long period. Not sure if the car automatically "tops" off the 12v battery when plugged in.

 

[devbolt]

See page 259 of the manual:

Four Weeks to 12 Months

. Discharge the high voltage battery until two or three bars remain on the battery range indicator (Battery symbol) on the instrument cluster.

. Do not plug in the charge cord.

. Remove the black negative (−) cable from the 12-volt battery and attach a trickle charger to the battery terminals or keep the 12-volt battery cables connected and trickle charge from the underhood remote positive (+) and negative (−) terminals. See Jump Starting - North America Page 295 for the location of these terminals.

 

[eurosteve]

Thanks everyone for your help with this. I guess I should lean toward following the manual's instructions. I'm left with the question of whether leaving it unplugged in below freezing weather will result in any damage. If the car tries to warm up the battery when it's very cold it would likely completely discharge. I wonder if Chevy has a Q&A about this sort of stuff - if I wanted to email them this question.

 

[redpoint5]

Thanks everyone for your help with this. I guess I should lean toward following the manual's instructions. I'm left with the question of whether leaving it unplugged in below freezing weather will result in any damage. If the car tries to warm up the battery when it's very cold it would likely completely discharge. I wonder if Chevy has a Q&A about this sort of stuff - if I wanted to email them this question.

The battery can be safely stored down to something like -40 F. There is no need to heat the battery during storage unless the battery approaches this temperature. The real killer is heat. I would plug in if the car is subjected to high heat in a garage.

12v battery maintenance is the same as for any vehicle; keep it as fully charged as possible.

 

[boltage]

Owner's manual is here:
https://my.chevrolet.com/content/dam/gmownercenter/gmna/dynamic/manuals/2017/Chevrolet/BOLT%20EV/Owner%27s%20Manual.pdf

See page 259 for storage.

 

[LeftieBiker]

There should be no need to disconnect the 12 volt battery if a maintainer is used. I'd leave the charge at about 50%, not the low state suggested by the manual. That way if the car needs to warm or cool the battery, it can.

 

[eurosteve]

As reported above, the manual states to "discharge the high voltage battery until two or three bars remain on the battery range indicator." Can anyone tell me approximately what SOC this equates to? It sounds very low. Also, can anyone tell me if the car has the ability to turn something on to warm up the battery if it gets too cold - even if it isn't plugged in?

 

[devbolt]

As reported above, the manual states to "discharge the high voltage battery until two or three bars remain on the battery range indicator." Can anyone tell me approximately what SOC this equates to? It sounds very low. Also, can anyone tell me if the car has the ability to turn something on to warm up the battery if it gets too cold - even if it isn't plugged in?

2 or 3 bars would be between 11 and 19 percent SOC.

The car doesn't do any battery conditioning when SOC is less than 30%.

The problem is that the manual doesn't discuss what is the proper long-term winter storage, just what the proper long-term storage is, regardless of outside temperature. Battery conditioning appears to be mostly there to make sure the car is drivable when it's extremely cold or warm. If the car has been sitting all winter, the battery will need to be charged before it can be driven, anyways, and will get conditioned as part of being charged.

Someone on another forum suggested a way to keep the car plugged in for long-ish term storage, but still have battery conditioning available to keep the battery happy and the 12V battery maintained: You edit the electric rate schedule so that off-peak is only available from 2am to 2:15am, and you tell the car it can only charge during that short window. However, over a 5-month period, there's enough cumulative time to fully charge the car. I don't think shortening it to a 5-minute window would help, either.

 

[SparkE]

As reported above, the manual states to "discharge the high voltage battery until two or three bars remain on the battery range indicator." Can anyone tell me approximately what SOC this equates to? It sounds very low. Also, can anyone tell me if the car has the ability to turn something on to warm up the battery if it gets too cold - even if it isn't plugged in?

2 or 3 bars would be between 11 and 19 percent SOC.

The car doesn't do any battery conditioning when SOC is less than 30%.

The problem is that the manual doesn't discuss what is the proper long-term winter storage, just what the proper long-term storage is, regardless of outside temperature. Battery conditioning appears to be mostly there to make sure the car is drivable when it's extremely cold or warm. If the car has been sitting all winter, the battery will need to be charged before it can be driven, anyways, and will get conditioned as part of being charged.

Someone on another forum suggested a way to keep the car plugged in for long-ish term storage, but still have battery conditioning available to keep the battery happy and the 12V battery maintained: You edit the electric rate schedule so that off-peak is only available from 2am to 2:15am, and you tell the car it can only charge during that short window. However, over a 5-month period, there's enough cumulative time to fully charge the car. I don't think shortening it to a 5-minute window would help, either.

I posted that, but I am not sure NOW if it was correct. I have read elsewhere that the battery conditioning is only active when charging is immediate (either charging, or not charging because 'full'). But that actually could have been posted on a Spark EV forum. I don't know which is true. I would love to hear from somebody with a separate meter for charging (or a measuring tool) if battery conditioning happens if delayed charging is configured.

 

[eurosteve]

Thanks for all of the help with this. I've posted in an "Ask Chevrolet" thread on another forum to see what they say. Seems unlikely that storage between zero F and 32 F sometimes would be damaging to the battery - as long as the thermal management system doesn't kick in to deplete the battery. But it would be nice to have something definitive from Chevrolet.

 

[LeftieBiker]

Thanks for all of the help with this. I've posted in an "Ask Chevrolet" thread on another forum to see what they say. Seems unlikely that storage between zero F and 32 F sometimes would be damaging to the battery - as long as the thermal management system doesn't kick in to deplete the battery. But it would be nice to have something definitive from Chevrolet.

Since thermal management apparently only works above 30% charge, you need not worry about that happening. It would warm the battery until 30% SOC was reached, then stop.

 

[eurosteve]

Thanks for all of the help with this. I've posted in an "Ask Chevrolet" thread on another forum to see what they say. Seems unlikely that storage between zero F and 32 F sometimes would be damaging to the battery - as long as the thermal management system doesn't kick in to deplete the battery. But it would be nice to have something definitive from Chevrolet.

Since thermal management apparently only works above 30% charge, you need not worry about that happening. It would warm the battery until 30% SOC was reached, then stop.

I saw that someone else posted that thermal management only works above 30% SOC (maybe in this thread). Do you know if that's a fact or if this is something that is believed to be true? If this is a fact, then I think I have my answer about the battery running down.

 

[LeftieBiker]

I don't have access to the manual, but I think that's the original source for the claim. (I don't drive a Bolt.)