Long-term Storage Results

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alohart

Well-known member
Joined
Nov 1, 2014
Messages
3,081
Location
Honolulu, HI
There have been several posts requesting information about how to store an i3 long-term. I stored our i3 for slightly more than 5 months and have some observations to report.

On 14 April, I folded in our i3 BEV's side mirrors, lifted our i3 onto jack stands to prevent possible tire flat-spotting and dry rot (possibly at the expense of increasing the risk of rusting the fully-extended shock absorbers' shafts in our humid, salty air), disconnected the negative cable of its 12 v. battery (to prevent it being fully discharged and destroyed by parasitic loads), closed but did not latch its frunk (so I could open the frunk upon our return without using the emergency release cord and reconnect the 12 v. battery), placed its antenna and front and rear windshield wiper blades inside the car (no antenna hole in our cheap car cover, and blades suffer after being pressed against glass in the same position for several months), locked the car with the emergency key in the fob, and placed a car cover over it to prepare it for in-place storage in our condo parking garage parking space. Our parking space is not exposed to direct sunlight or rain, but it is exposed to warm, salty, outside air since the parking garage has open sides.

I purposely decreased our i3's high-voltage battery pack's charge level to ~55% (estimated from the charge level bars since I don't have the latest software that displays the charge level percentage) from 88% (reported by iRemote) by running the A/C on max with the high-beam headlights on for ~3 hours while I washed our car, lifted it onto jack stands, and prepared it for storage. I believe that storing a Li-ion battery pack at a high charge level is detrimental to its long-term health. I would have preferred to have stored the battery pack at ~40% but I ran out of time to discharge it further. I did not measure the voltage of the 12 v. battery, but I assume it must have been fully charged at ~12.7 v. Unlike a Li-ion battery pack, an absorbent glass mat Pb-acid battery is better stored at full charge.

The following morning, we boarded a plane to start our long journey to Sweden where we would spend the next 5 months. I left without being concerned about how I stored our i3 despite not following BMW's recommendations because I have been storing our Honda Insight hybrid and former Mitsubishi i-MiEV in the same way since 2008 with absolutely no ill effects. But I wouldn't really know how our i3 fared until we returned in September…

On 24 September, I put our i3 back in service. I took off its car cover, replaced its antenna and windshield wiper blades, opened its frunk, and measured its 12 v. battery's voltage: ~12.5. While not fully charged, it had plenty of charge to boot our i3's computers. I assumed that the 12 v. battery would be charged when the high-voltage battery pack was being charged prior to driving, so I did not charge the 12 v. battery with my battery charger. I reconnected our car's 12 v. battery's negative terminal and entered our car via Comfort Access.

I then pressed the "Start" button to put our car into "Radio" mode so that I could read the high-voltage battery pack's charge level. I was somewhat surprised that the charge level was shown as ~35%, ~20% lower than when I had parked the car more than 5 months earlier. Unfortunately, I could not force iRemote to refresh, so it continued to report the battery pack's 88% charge level as of 14 April before I discharged it to ~55%.

The i3 must be displaying an estimate of its battery pack's charge level after the 12 v. battery has been reconnected which might be based on its battery pack's voltage and temperature. This estimate might not be particularly accurate due to the poor correlation between charge level and voltage in the middle of a Li-ion battery pack's charge level range. I characterized this as an estimate because I am not aware of any reason why the battery pack's charge level should be less than when I parked our car more than 5 months earlier. Li-ion battery packs have a very low self-discharge rate at the storage temperature of our car which probably averaged ~75º, and the battery pack should have been electrically isolated during storage, so it couldn't have been discharged by external loads.

When I plugged in our JuiceBox EVSE, the voltage at the 12 v. battery's terminals increased to 14.3 v. which confirmed that the 12 v. battery is charged while the high-voltage battery pack is being charged. Our EVSE reported that 10.5 kWh of energy was added to fully charge our i3's battery pack. That is insufficient energy to increase the reported 35% charge level by 65% up to 100%. I forgot to check iRemote immediately after I started charging our i3 so that I could see what it thought the charge level was, but I did check it a couple of hours later and noticed that it had come to life and was reporting the charge level as charging was occurring. When charging completed, our car reported a 100% charge level while iRemote reported only 88% charged, its ~45% charge level increase (from ~55% to 100%) being more consistent with 10.5 kWh of energy added than if the battery pack's charge level had started at ~35% as the car reported. I'm guessing that these discrepancies are due to the incorrect 35% charge level estimate before charging. When the voltage of the battery pack reached what the battery management system considered full, the charge level reported by the car probably recalibrated from ~88% to 100%. That iRemote and the car don't always report the same charge level has been observed by many i3 owners and remains unexplained as far as I know. After driving for several days and charging several times, iRemote seems to be reporting charge levels that are in close agreement with those reported by the car.

The hidden service menu reports a maximum battery pack capacity of 18.7 kWh with firmware version I001-14-07-503 which was installed when our i3 was built on 1 August 2014. Our maximum battery pack capacity has varied from 17.9 to 18.9 kWh, so the 5 month storage doesn't seem to have reduced our battery pack's capacity.

Other than the loss of our battery pack's charge level data, the only other effect of disconnecting the 12 v. battery seems to be the loss of the current date and time which an iDrive warning message requested to be reset. The presets are all as they were before storage. The guess-o-meter reported unreasonably long range estimates after the initial charge since it had likely lost its recent driving history data, but it is back to normal several days of driving.

So it appears that my storage regimen has had no deleterious effects and was certainly a more energy-conscious and safer approach than keeping our EVSE plugged in and consuming at least 10 watts of power continuously for 5 months as BMW recommends.
 
Hi there.

Thanks for the detailed write up. Been wondering how your car would fare. Honolulu sure sounds like a warmer place to overwinter compared to Sweden!
 
Semmtexx said:
Been wondering how your car would fare.
So far, so good. I don't expect its long slumber to have any negative consequences, so I'll do it again next year :)

Semmtexx said:
Honolulu sure sounds like a warmer place to overwinter compared to Sweden!
Our poor Honda Insight used to overwinter in Honolulu but must now spend each winter on jack stands shivering in our garage in Sweden. It must think we hate it :)
 
alohart said:
Semmtexx said:
Honolulu sure sounds like a warmer place to overwinter compared to Sweden!
Our poor Honda Insight used to overwinter in Honolulu but must now spend each winter on jack stands shivering in our garage in Sweden. It must think we hate it :)

Indeed!!
Brrrclink brrrclink go the poor chilly tappets!
:)
 
Mr. Isbell, Thanks for the writeup. Looks like the battery management system keeps the cells synchronized better than Honda's battery system. I remember you from the InsightCentral forum. My Insight sits next to the i3 but doesnt see much use anymore. Maybe I'll use it in the winter. I think the i3 is a true successor to the Insight. The Insight was a technical revolution when it came out, and I think the i3 is too.
 
Thermactor said:
Looks like the battery management system keeps the cells synchronized better than Honda's battery system.
To cut Honda a little slack, it's far easier to keep the battery cells of an EV balanced since top-balancing while plugged in is easier than while driving.

Thermactor said:
I remember you from the InsightCentral forum. My Insight sits next to the i3 but doesnt see much use anymore.
We still have our Insight at our apartment in Sweden where it's a great Euopean road trip car. But driving it seems positively archaic compared with our i3.

Thermactor said:
I think the i3 is a true successor to the Insight. The Insight was a technical revolution when it came out, and I think the i3 is too.
I agree! I'm concerned that our i3 won't be as reliable as our Insight has been. There have certainly been far more reports of i3 problems than there were when the Insight was first sold. Time will tell…
 
Maybe we should start an i3sight forum for i3/Insight owners. Art is absolutely right that the Insight is a fabulous long-range car ⎯⎯ it seems to hit a sweet spot loping along an undulating highway ⎯⎯ but then it turns downright grumpy around town (especially a stick in such a hilly place as San Francisco), which of course is where the i3 starts whooping it up. Between the two of them, best of both worlds.
Having said that, I expect that the i3 will turn out to be astonishingly reliable, if for no other reason than it has far fewer moving parts. Yes, it is bleeding-edge, first down the line, which bodes ill, but I have faith that BMW thought it through and has executed pretty darn well. Most of the whining on this forum is over pretty minor stuff (a lot of which can be improved through software updates), as well as dealership cluelessness, but nothing that foreshadows any long-term major reliability issues.
 
Very useful article that I will follow soon for a 4 month away period.

QUESTION: (Should this reach you) ... What type of jacks did you use and what are the contact points on the i3?
 
Randy101 said:
Very useful article that I will follow soon for a 4 month away period.

QUESTION: What type of jacks did you use and what are the contact points on the i3?

BMW use standard jack points front and rear on the i3. You can buy rubber pad adapters that locate on the car's jacking points when used with a trolley jack. Don't lift the car anywhere else on the chassis.

As you're lifting the entire car, consider investing in jack point stands, these are quite different from axle stands.
 
Links here: http://www.jackpointjackstands.com

Arkan trolley jacks, 2-3 tonne are very well made and I rate them.
 
Randy101 said:
What type of jacks did you use and what are the contact points on the i3?
To lift our i3, I bought a lightweight aluminum floor jack and placed a BMW jack point adapter on its flat lifting surface:

31c43rSECvL._SL500_AC_SS350_.jpg


To keep our i3's tires off the pavement, I used ESCO 10498 jack stand bases each with a pivot top designed to fit BMW jack points:

71095d1484790949-sold-e53-ball-joint-tool-fullsizerender-42.jpg
 
What will be the 12v and main battery discharge rather (monthly?) if the locked car is simply left standing in place for 4 months. If I know the drain rate, i may be able to have someone do periodic charging to bring the car to 50%. With the loss of 3G I'm no longer able to remotely monitor levels.

Alternatively, if the car would be plugged for 4 months, what is the degree of harm the main battery charged at 100% will experience?
 
Randy101 said:
What will be the 12v and main battery discharge rather (monthly?) if the locked car is simply left standing in place for 4 months. If I know the drain rate, i may be able to have someone do periodic charging to bring the car to 50%. With the loss of 3G I'm no longer able to remotely monitor levels.

Alternatively, if the car would be plugged for 4 months, what is the degree of harm the main battery charged at 100% will experience?
In my experience, the high-voltage battery pack self-discharges ~1% per month during storage, so you shouldn't worry about the high-voltage battery pack discharging too much while your i3 is stored for 4 months. I store our i3 with the charge level between 40% and 60% which reduces the battery cell degradation rate compared with storing it at a higher charge level. I can't quantify the harm caused by storing it fully charged. Tests of Li-ion battery cells with chemistries similar to those used in i3's indicate that the degradation rate increases with the charge level and temperature, so why store an i3 fully charged when doing so isn't necessary?

The health of your 12 V battery would determine when it would discharge enough to either damage it or to set all sorts of DTC's as happens when a 12 V battery fails. When an i3 is locked, its burglar alarm is armed, so the burglar alarm would join the keyless entry system, the telematics module, the clock in the entertainment system, and other parasitic 12 V loads that would gradually discharge the 12 V battery. I would be very surprised if it would not be essentially totally discharged if you left your i3 parked and locked for 4 months.

That said, I know of 1 report of an i3 that sat parked for over a year yet was able to start. The owner stated that an EVSE was not plugged into his i3. He wrote that the charge level of the battery pack had decreased noticeably which led him to believe that an i3 would periodically charge its 12 V battery by turning on the DC-DC converter. I have not found any documentation that supports this. Some i3 owners have installed 12 V battery monitors that store the 12 V system voltage over time. None of these owners have reported the DC-DC converter periodically turning on to charge the 12 V battery.

So when we store our i3, I always disconnect the high-voltage disconnect under the removable cover to the right side of the frunk box before disconnecting the negative cable of the 12 V battery, both of which are quite easy to do. I then fully charge the 12 V battery with a battery charger so that its charge level remains high during storage.

There is no evidence that leaving an EVSE plugged in for 4 months would keep your 12 V battery charged. The DC-DC converter charges the 12 V battery only when the high-voltage battery is actively charging (actually, it remains on for up to 30 minutes after the battery pack is fully charged). Indeed, several i3 owners have reported dead 12 V batteries even though an EVSE had been plugged in during storage.

Having stored our i3 5 times for periods of 3 to 9 months each time, I have always been able to take our i3 out of storage without any problems. I don't think I could say that if I had left the 12 V battery connected during storage.
 
Nice response, but: "so why store an i3 fully charged when doing so isn't necessary?" Because there is no such thing as a fully charged i3 battery, perhaps? I would trust the battery management software to take care of it. Of course, you might be on to something with the 12 volt battery... especially one of unknown age.
 
JohnKelly said:
Nice response, but: "so why store an i3 fully charged when doing so isn't necessary?" Because there is no such thing as a fully charged i3 battery, perhaps? I would trust the battery management software to take care of it.
The U.S. i3 Owner's Manual states:

"The service center can advise you on what to consider when storing the vehicle longer than three months."

The first time I planned to store our i3 for 6 months, I asked the service manager at our BMW dealer what he recommended. He told me that the 12 V battery was of greatest concern because vampire loads would discharge it, so he recommended disconnecting the negative battery cable. This isn't unique to an i3; all modern vehicles have vampire 12 V loads that gradually discharge the 12 V battery.

He also recommended storing with the battery pack's charge level near 50%. There are no high-voltage vampire loads (the battery pack is electrically disconnected when an i3 is off), so the energy in the battery pack isn't being used during storage. The self-discharge rate of Li-ion cells is very low, so there's no concern about the charge level decreasing so low that the cells could be damaged.

I have followed his recommendations several times since with no resulting problems and with a 12 V battery that lasted over 7 years before not holding a full charge.

While a 100% displayed charge level isn't the actual charge level, for a 60 Ah battery pack, the actual charge level is ~96%. That's still quite high. The cell degradation rate of any Li-ion battery cell with a chemistry similar to that used in i3 cells increases as its charge level increases, so the degradation rate is greater at a 100% displayed charge level than it is at a displayed 50% charge level. Why would any i3 owner store her i3 at a 100% displayed charge level when energy in the battery pack isn't needed for anything during storage? If one doesn't care about maintaining one's battery pack capacity at the highest possible level over a long ownership, then by all means store an i3 at a 100% displayed charge level.

JohnKelly said:
Of course, you might be on to something with the 12 volt battery... especially one of unknown age.
This is a problem with any modern vehicle that's stored. I believe that BMW disconnects the 12 V battery during shipping from its factory. Dealers are supposed to check the 12 V battery voltage periodically while a new BMW is on the dealer's lot and charge the 12 V battery when the voltage drops below a certain level. When we bought our i3 new, a checklist which included checking the 12 V battery periodically was in the glove compartment.
 
Before disconnecting the negative connection to the 12v battery, should I using the main battery disconnect, and leave it disconnected for the duration of storage?

An on return first connect the negative 12v and then reconnect the main battery.
 
Randy101 said:
Before disconnecting the negative connection to the 12v battery, should I using the main battery disconnect, and leave it disconnected for the duration of storage?
I always back up my driver profiles to a USB flash drive prior to storing our i3. With no 12 V power while in storage, the driver profiles could be lost. I then restore the profiles after reconnecting the 12 V negative cable. You might need to set the clock afterward.

Yes, disconnect the high-voltage disconnect prior to disconnecting the 12 V negative cable. Make sure the burglar alarm isn't on (i.e., the doors aren't locked) when you disconnect the negative cable. If the alarm is armed, the siren will sound when the negative cable is disconnected which is very loud when one's head is in the frunk while disconnecting the negative cable.

When the negative cable is disconnected, the windows won't roll down when opening the doors. Be gentle closing the doors because the windows will collide with the weather stripping.

If you plan to lock the doors before storing your car, you'll need to use the physical key in the fob to lock the driver door after locking the passenger door from inside the car. Be careful removing and installing the lock cover on the driver door. If not snapped securely into place, it could fall off while driving. Buying a replacement could be expensive because it might need to be painted to match the body color.

Leave the frunk only partially closed during storage, if possible. If you close it all the way, you'll have to open it with the emergency opening cable in the driver door jamb.

It's best to let the high-voltage system go to sleep with the frunk open before doing anything else (wait 30 minutes without opening or closing the doors, hatch, or frunk). I once disconnected the high-voltage disconnect before the high-voltage system was asleep which immediately caused a drive train error. Fortunately, that error cleared when I reconnected everything, but I was concerned that I had caused a problem.

Leave the high-voltage disconnect disconnected during storage.

Randy101 said:
An on return first connect the negative 12v and then reconnect the main battery.
Yes, that's the correct order.
 
I have a question about using a battery tender to maintain the 12 volt while away for 4 wks in here in the Northeast, I wanted to ask if I need to disconnect the high voltage connection to the 12 volt before adding the battery tender.. would appreciate someone here sharing their knowledge on this. Thanks.
 
Ladysman101 said:
I have a question about using a battery tender to maintain the 12 volt while away for 4 wks in here in the Northeast, I wanted to ask if I need to disconnect the high voltage connection to the 12 volt before adding the battery tender.. would appreciate someone here sharing their knowledge on this.
Several i3 owners who have installed 12 V battery monitors have reported the DC-DC converter turning on automatically for an hour to charge the 12 V battery when its voltage drops below a certain level. That's not likely to happen when a battery tender is connected, but who knows what unexpected situation might occur? Also, the HV system turns on when unlocking or opening a door, the hatch, or the frunk. When the HV system turns on, the DC-DC converter could also turn on depending on the 12 V battery's voltage, the i3's integration level (system software version), or maybe even model. I would not want the DC-DC converter to turn on when a battery tender is also charging the 12 V battery for fear that this could damage the DC-DC converter which is an irreplaceable portion of the very expensive EME.

It's so easy to disconnect the HV disconnect that why not do it to avoid potential expensive damage even if that's a remote possibility?
 
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