Backup BMW i3-REx, Tesla, and folding mirrors

[bwilson4web]

Hi,

We have a 2014 BMW i3-REx, 40k miles, as backup for our Tesla Standard Range Plus Model 3. It has been the perfect trainer for our Tesla: one pedal driving; dynamic cruise control; front-rear sensors; efficient EV driving, and; trip planning on a 2 gal tank. Most important, I'd stopped driving our Prius Prime because the i3 was so much more fun to drive. We got $18.3k trade-in on the Prime to buy the Tesla. Just background for my questions.

Every two months I take the i3 out: wipe off the brake surface rust, cycle-charge the traction battery, air the tires, run the engine, give the 12V a charge, wash off the tree sap, vacuum the leaves, and make sure everything is working. When I got in, there was a warning about a low 12V battery that cleared by the time I got on the street. The car is parked on the driveway with the BMW cover. Regardless, I parked it with 80% charge but noticed the manual says to fully charge the traction battery and the EVSE plugged in.

Any thoughts about storing the traction battery with 80% vs 100% SOC?

Past experience showed the EVSE plug are subject to weather damage so I'll just add charge using my 24 ft. J1772 extension as needed in dry weather. I prefer to keep the charge port cover closed to minimize accumulating leaves, pine needles, and other debris.

Has anyone used a solar, 12V panel to tickle charge the 12V battery? No big deal, I'll have to connect directly to the 12V battery.

Some things the Tesla does automatically are manual on the BMW i3-REx. Walking away from the Tesla, it automatically locks the doors and folds the mirrors. Per the manual, I just used the BMW App to lock the BMW and hopefully fold the mirrors.

There is no lane keeping with BMW dynamic cruise control whereas the Model 3 AutoPilot does both. By a mile down the road, BMW driving was back to normal. But I transferred one Tesla habit, reaching the posted speed limit first.

Missing from the Tesla is reading the speed signs. Tesla uses Google map for street speeds which fails when approaching construction zones or areas with different posted speeds.

Bob Wilson

 

[alohart]

Every two months I take the i3 out: wipe off the brake surface rust, cycle-charge the traction battery, air the tires, run the engine, give the 12V a charge, wash off the tree sap, vacuum the leaves, and make sure everything is working. When I got in, there was a warning about a low 12V battery that cleared by the time I got on the street.

If you routinely don't drive your i3 for 2 month periods, you'd risk accelerating the failure of the 12 V battery by repeatedly discharging it farther than might be healthy. Maybe simply disconnect the 12 V negative battery cable to prevent parasitic discharge or charge the 12 V battery at least monthly with a battery charger.

Regardless, I parked it with 80% charge but noticed the manual says to fully charge the traction battery and the EVSE plugged in.

The 12 V battery is charged only when the EVSE is plugged in and active charging is occurring. So after the battery pack is fully charged, the 12 V battery won't be charged until self-discharge of the battery pack results in charging commencing briefly again. The self-discharge rate is so low that active charging isn't likely to occur often and charging won't likely be active long enough to fully recharge the 12 V battery. Some i3 owners have reported their 12 V batteries dying even when their EVSE's had remained plugged in for an extensive period.

So I don't feel that BMW's advice is very good. However, their advice is much easier to implement than disconnecting the 12 V negative battery cable, so I understand why most i3 owners would prefer to just plug in their EVSE's and hope for the best.

Any thoughts about storing the traction battery with 80% vs 100% SOC?

Even though an indicated 100% charge is actually ~95% of the absolute full charge, a Li-ion battery cell will statistically degrade more rapidly at a high charge level compared with a lower charge level, especially at higher ambient temperatures that your i3 is experiencing during Alabama's summer months. Because of this, I always store our i3 with its charge level ~50%. If I unexpectedly needed to drive it and needed more range, I could drive to the nearest DC fast charger to quickly add the charge necessary for the drive, or if I had more time, I could plug in our EVSE at home.

Any EV owner who would like to reduce the battery pack degradation rate as much as is reasonably possible would not allow the battery pack to remain at a high charge level for an extended period. This is another reason why I would not plug in our EVSE to charge the 12 V battery while our car is in storage.

 

[vreihen]

So I don't feel that BMW's advice is very good. However, their advice is much easier to implement than disconnecting the 12 V negative battery cable, so I understand why most i3 owners would prefer to just plug in their EVSE's and hope for the best.

Would one of these motorcycle/ATV battery terminal disconnect switches make disconnecting the 12V battery any easier?

https://www.amazon.com/Jtron-motorcycle-terminal-Anti-leakage-Disconnect/dp/B07C4Q859P

There's several other options for various batteries and terminals, if this one doesn't look like it will work.....

 

[jadnashuanh]

I bought my i3 in June of 2014...one of the first in the country (built in April). When new, it regularly indicated about 80+ miles/empty when the battery was full. It's now over 5-years old, plugged in each time I get home and left there until I leave, last time I got in there, the range indicator said 80+ miles to empty. I'm on the original 12v battery, but that may be borrowed time. It seems to function fine, though. Another winter may finally have it kick the bucket.

My tentative plan is to sell both of my cars when the new X5 hybrid shows up next year. Enough battery capacity to do 95% of my driving, but unlimited, quick refills when it isn't. It will also get plugged in each time I return home. I'll miss the smaller size, but not all that much. Rear wheel steering should make the x5 better in tight spaces.

 

[gt1]

Regarding the HV battery, I'm with alohart. 40-50% SOC is the best for the long term storage.

 

[bwilson4web]

Still having problems with the mirrors not folding even when the car is fob locked. I'll breakout Bimmercode this weekend and see what is going on. At the same time, I'll hookup the solar, 12V tickle charger.

Bob Wilson

 

[alohart]

Would one of these motorcycle/ATV battery terminal disconnect switches make disconnecting the 12V battery any easier?

https://www.amazon.com/Jtron-motorcycle-terminal-Anti-leakage-Disconnect/dp/B07C4Q859P

There's several other options for various batteries and terminals, if this one doesn't look like it will work.....

Almost any battery disconnect switch designed for automotive, not screw-on terminals should work. However, it's not very difficult to loosen or tighten the negative cable clamp with a 10 mm box-end wrench, although access is tight with the frunk box in place.

 

[alohart]

Still having problems with the mirrors not folding even when the car is fob locked. I'll breakout Bimmercode this weekend and see what is going on.

This has been a troublesome change for our i3 as well. I have made the coding changes with mirror folding working consistently for several months until the mirrors begin not folding consistently. I have reverted the coding changes and reapplied them which has resulted in folding working consistently so far. No software updates occurred when the folding inconsistency began.

These are the changes that I made in the BDC Body Module:

Standard mode:
Fold mirrors when locking vehicle with Comfort Access: set to aktiv
Comfort closing delay: set to No Delay

or

Expert mode:
Fold mirrors when locking vehicle with Comfort Access
3056->KOMFORTSCHLIESSUNG_PA: set to aktiv, werte: 00
Mirror folding delay (100 ms increments, default: 0F, or 1.5 seconds)
3056->KOMFORT_SCHLIESSEN: werte: 00

 

[derekgates]

Still having problems with the mirrors not folding even when the car is fob locked. I'll breakout Bimmercode this weekend and see what is going on. At the same time, I'll hookup the solar, 12V tickle charger.

Bob Wilson

Hmm. I coded the folding mirrors via Bimmercode and when I leave the car I hold my hand on the handle for an extra 2-3 seconds which invokes the mirrors to fold in as well as locking the doors. If I only hold my hand for a second the doors will lock but no mirror fold in... it must be a few more seconds. With that 'extra touch' the mirrors rarely, if ever, fail to fold in. My 335is, without comfort access, requires holding the 'lock' button.

Are you experiencing a different result?

 

[bwilson4web]

. . .
Hmm. I coded the folding mirrors via Bimmercode and when I leave the car I hold my hand on the handle for an extra 2-3 seconds which invokes the mirrors to fold in as well as locking the doors. If I only hold my hand for a second the doors will lock but no mirror fold in... it must be a few more seconds. With that 'extra touch' the mirrors rarely, if ever, fail to fold in. My 335is, without comfort access, requires holding the 'lock' button.

Are you experiencing a different result?

I'll give it a try.

Bob Wilson

 

[alohart]

I coded the folding mirrors via Bimmercode and when I leave the car I hold my hand on the handle for an extra 2-3 seconds which invokes the mirrors to fold in as well as locking the doors. If I only hold my hand for a second the doors will lock but no mirror fold in... it must be a few more seconds. With that 'extra touch' the mirrors rarely, if ever, fail to fold in.

This is the behavior when the mirror folding delay has not been reduced. The default is 1.5 seconds plus the usual data bus response delay. I reduced the delay to 0.0 seconds but still must hold the door handle touch briefly for the mirrors to fold, presumably because of the response delay.