Huge Electric Bill - REX

[GranTourer]

To my unpleasant surprise the majority of last month's electric bill was on peak rates (I have a smart meter). I did start using pre-conditioning due to the cold weather, but surely that couldn't be the reason.

Next I double checked the low cost charging times were set correct (they were). Then one day I stuck around to see what the EVSE was doing when I plugged in. Well, usually it clicks on for a brief moment, clicks off, and then clicks back on sometime around 4am just in time to have a full charge for my morning departure.

What I've found is that if I've been using the REX (which I have a lot lately) it completely ignores that I wish to low cost charge and immediately starts charging and doesn't stop till it reaches 100%. So if I get home at 6pm and was on REX, it pretty much completely recharges on peak rates (before 9pm).

My workaround has been to not plugin when I get home and to take a trip out to the cold garage after 9pm to plugin. This is such a hassle and completely defeats the purpose of scheduling low cost charging!

I'm not following BMW's reasoning for this charging behavior. Maybe someone on this forum knows why it does this? Has anyone else using low cost charging noticed this? I would think if it was a battery health thing it would bring the charge to 10-15% immediately but not a full charge. I mean it doesn't do that when I come home with a few electric miles to spare.

 

[surfingslovak]

What I've found is that if I've been using the REX (which I have a lot lately) it completely ignores that I wish to low cost charge and immediately starts charging and doesn't stop till it reaches 100%. So if I get home at 6pm and was on REX, it pretty much completely recharges on peak rates (before 9pm).

My workaround has been to not plugin when I get home and to take a trip out to the cold garage after 9pm to plugin. This is such a hassle and completely defeats the purpose of scheduling low cost charging!

I'm not following BMW's reasoning for this charging behavior. Maybe someone on this forum knows why it does this? Has anyone else using low cost charging noticed this? I would think if it was a battery health thing it would bring the charge to 10-15% immediately but not a full charge. I mean it doesn't do that when I come home with a few electric miles to spare.

Yes, I have observed this behavior as well. The rationale is that when the battery is at 6%, leaving it at that low state of charge for a prolonged period could be harmful, and ultimately lead to shorter battery life.

I believe that the desired behavior is to give the battery a quick boost, and stop at a state of charge, which is high enough to protect it from any long-term damage. The onboard charger used to be smart enough to stop at about 15% to 20%, and wait for the start of the low-cost charging period according the preset schedule.

That changed with a firmware upgrade last summer or fall. I agree that it's counter-productive when someone is trying to optimize charging around the TOU utility tariff.

 

[ironsia]

See John Higham's post on this on the FB i3 group, posted 9hrs before this. He say's that the updates to KLE and software bring back the original intended behaviour.

 

[surfingslovak]

See John Higham's post on this on the FB i3 group, posted 9hrs before this. He say's that the updates to KLE and software bring back the original intended behaviour.

Yes, I was hoping for that also. I have the latest KLE and I'm helping Beta test the upcoming firmware, but not everything has been resolved. My i3 was at 5% when I rolled in yesterday evening, and it proceeded to charge to full even though low-cost charging was specified, and the TOU schedule was not supposed to start until five (5) hours later.

 

[jadnashuanh]

Rough idea of costs to precondition from the wall when it is below freezing seem to be about 2Kw based on what I can see from my volt/amp meter. Now, I haven't watched it for the full timeframe, but have spot checked it over several sessions and it starts out drawing about 20A @ 240vac, and then bounces between 12-20 for awhile, then when almost done, seems to drop to about 5A. Averaging that all out over the time it's preconditioning seems to come to about 2Kw. Considering that that is almost 10% of the full battery capacity, it makes sense to try to do that while connected to the EVSE verses using the battery to do it. NOw, it may not be as aggressive while on battery - have not tried to check that.

 

[GranTourer]

See John Higham's post on this on the FB i3 group, posted 9hrs before this. He say's that the updates to KLE and software bring back the original intended behaviour.

Yes, I was hoping for that also. I have the latest KLE and I'm helping Beta test the upcoming firmware, but not everything has been resolved. My i3 was at 5% when I rolled in yesterday evening, and it proceeded to charge to full even though low-cost charging was specified, and the TOU schedule was not supposed to start until five (5) hours later.

I also have the revised KLE and a firmware update (14-11-504). I hope that BMW will fix this in a soon to come firmware update.

 

[GranTourer]

Rough idea of costs to precondition from the wall when it is below freezing seem to be about 2Kw based on what I can see from my volt/amp meter.

Thanks for the info.

 

[noakey]

To my unpleasant surprise the majority of last month's electric bill was on peak rates (I have a smart meter). I did start using pre-conditioning due to the cold weather, but surely that couldn't be the reason.

Next I double checked the low cost charging times were set correct (they were). Then one day I stuck around to see what the EVSE was doing when I plugged in. Well, usually it clicks on for a brief moment, clicks off, and then clicks back on sometime around 4am just in time to have a full charge for my morning departure.

What I've found is that if I've been using the REX (which I have a lot lately) it completely ignores that I wish to low cost charge and immediately starts charging and doesn't stop till it reaches 100%. So if I get home at 6pm and was on REX, it pretty much completely recharges on peak rates (before 9pm).

My workaround has been to not plugin when I get home and to take a trip out to the cold garage after 9pm to plugin. This is such a hassle and completely defeats the purpose of scheduling low cost charging!

I'm not following BMW's reasoning for this charging behavior. Maybe someone on this forum knows why it does this? Has anyone else using low cost charging noticed this? I would think if it was a battery health thing it would bring the charge to 10-15% immediately but not a full charge. I mean it doesn't do that when I come home with a few electric miles to spare.

I see this too. I let the charge continue for around 30mins then disable the chargemaster with its key for a few mins then re-enable. Then i3 waits for off peak before resuming as battery charge is outside the danger zone.

 

[Tomasz]

I've learned long time ago not to trust firmware in the car (be it i3 or Leaf) to start charging when I want it to. To solve the problem I went with EVSE that gives me total control - I've set up times on it and now I can plug it in whenever I want and it will charge only off peak.

 

[Lykke]

Preconditioning w. battery heating can be quite expensive. On my 32 amp EVSE, the car periodically pulls 4-5 kW and use about 4 kWh during the last couple of hours on a cold morning. I do not need extra range, so now I just start the preheating from my phone 5-10 minutes before departure which will cost ½-1 kWh

 

[Lincsat]

It appears to me that preconditioning also tops up the charge on the battery. I don't use the car every day and if it's not been used, the charge can drop 2-3%, then during preconditioning, the charge goes back to 100% even if charging is set for off-peak only.

 

[jadnashuanh]

It appears to me that preconditioning also tops up the charge on the battery. I don't use the car every day and if it's not been used, the charge can drop 2-3%, then during preconditioning, the charge goes back to 100% even if charging is set for off-peak only.

When preconditioning while on the EVSE, keep in mind that the power is essentially coming out of the batteries, and the on-board charging circuits are replenishing it probably faster than it is going out to warm or cool things off, so, yes, the thing will use electricity and top off the batteries in the process. I've seen it drawing around 12-20A during the beginning of a preconditioning cycle, but it eventually drops off to somewhere in the 5A range near the end, but never to zero A and this is with the battery previously fully charged. You can do the math...power=volts*amps. I figure a typical preconditioning cycle where I live this time of year may take as much as 2Kw, but that equates to maybe 8-miles if you weren't drawing it from the wall.

FWIW, I do not typically see the battery SOC drop over a 2-3 day period. If you have comfort access, do not lock the car, and frequently walk past it, that could 'awaken' it regularly, and that may draw some power. Best to lock it.

 

[alohart]

FWIW, I do not typically see the battery SOC drop over a 2-3 day period. If you have comfort access, do not lock the car, and frequently walk past it, that could 'awaken' it regularly, and that may draw some power. Best to lock it.

Isn't the DC-DC converter between the battery pack and 12 v. battery off except when the car is in the Ready state? If so, the Comfort Access system, burglar alarm, and all other 12 v. loads could only drain the 12 v. battery and would not result in any loss of range immediately upon entering the Ready state. Of course, as the 12 v. battery is recharged, some loss of range might occur, but that would not be immediate and would be minimal if even noticeable.

When I read reports of predicted range dropping while the car is parked, I figure it must be due to a drop the battery pack's temperature between when the car was parked and when the predicted range was read again. Like you, I've never noticed a drop in range while my car is parked which can be several days at a time.

 

[jadnashuanh]

Yes, all of the operational 'normal' car functions are powered by the small 12vdc battery. That battery is not automatically recharged except when plugged in to an EVSE OR you're actually in the ready state. I do not know if, under extreme conditions, if that battery level SOC dropped enough, that it would try to recharge it otherwise, but I doubt it.

There IS an emergency mode activated when recharging the vehicle when that battery is depleted too far...the logic to control the main recharging is controlled by the computer(s) run from the 12vdc battery, and if that is too low to reliably run the computer(s), there is a path that is activated to charge up that 12vdc battery directly until it can reboot the computer(s) and then take over. During that time, the main batteries are not being recharged.

The i3 is a complex, computer-controlled device, many years in development, so, to me, it's not unusual for it to have some novel solutions to uncommon circumstances. Since it was essentially a clean slate design, they had the luxury of thinking out of the box. As a result, you need to be open to new things if you wish to understand why it is reacting in the way it does. FOr me, for the most part, it operates pretty close to a conventional car, but there is a LOT going on in the background, and it may be achieving that in a totally novel manner.

 

[noakey]

Yes, all of the operational 'normal' car functions are powered by the small 12vdc battery. That battery is not automatically recharged except when plugged in to an EVSE OR you're actually in the ready state. I do not know if, under extreme conditions, if that battery level SOC dropped enough, that it would try to recharge it otherwise, but I doubt it.

There IS an emergency mode activated when recharging the vehicle when that battery is depleted too far...the logic to control the main recharging is controlled by the computer(s) run from the 12vdc battery, and if that is too low to reliably run the computer(s), there is a path that is activated to charge up that 12vdc battery directly until it can reboot the computer(s) and then take over. During that time, the main batteries are not being recharged.

The i3 is a complex, computer-controlled device, many years in development, so, to me, it's not unusual for it to have some novel solutions to uncommon circumstances. Since it was essentially a clean slate design, they had the luxury of thinking out of the box. As a result, you need to be open to new things if you wish to understand why it is reacting in the way it does. FOr me, for the most part, it operates pretty close to a conventional car, but there is a LOT going on in the background, and it may be achieving that in a totally novel manner.

Awesome post jim... i agree this i3 is a complex beast presenting itself as a simpleasure machine to the user's. .. i think it's great to be involved in novel tech...

 

[lownoterider]

I have the same issue, and everything is up to date on my REX. If you plug in after driving on the REX, it just starts charging regardless of what you do.

My dealer assures me I am fully up to date. He's had plenty of opportunities to check.....