16.1 Kwh battery

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sibumi

Member
Joined
Jul 6, 2024
Messages
6
I just bought a used bmw i3 REX. and after checking the battery capa max it shows 16.1 kwh. I think that is very little. The new battery i think is 22 kwh. The cas has 10 years and 45k miles. Is that measurement from the secret menu reliable?
 
Congratulations on your purchase. The usable capacity when new is 18.8 Kwh due to a buffer to protect the battery. So 16.1 Kwh is more or less in line with normal degradation, considering it's age and milage, as it means about 14% loss of capacity. As you have a Rex model, you have infinite range as long as you keep filling the gas tank.
 
Thank you Dutchi3. The only think about the REX is that i am not sure how to use it. By default it starts when the battery is very low, under 20% and i read that is not recommended to let the battery go under 20%. On the other hand i read as well that the REX is for emergencies, not to use regularly. Is that truth?
Thank you
 
Thank you Dutchi3. The only think about the REX is that i am not sure how to use it. By default it starts when the battery is very low, under 20% and i read that is not recommended to let the battery go under 20%.
If you license the BimmerCode smartphone app (~$40) and buy an OBD to WiFi or Bluetooth adapter, you could enable the iDrive choice that would allow you to start the REx engine whenever the charge level is <75% (Hold State of Charge). That way, you wouldn't have to wait until the charge level decreases to 6.5% for the REx engine to start automatically which can be so low that by the time the REx engine warms up and begins generating electricity, full propulsive power might not be available. This capability is standard for i3 REx' everywhere but in North America, so you'd not be doing anything that BMW didn't intend. This restriction is only to satisfy California Air Resource Board requirements for a range-extended EV.
 
If you license the BimmerCode smartphone app (~$40) and buy an OBD to WiFi or Bluetooth adapter, you could enable the iDrive choice that would allow you to start the REx engine whenever the charge level is <75% (Hold State of Charge). That way, you wouldn't have to wait until the charge level decreases to 6.5% for the REx engine to start automatically which can be so low that by the time the REx engine warms up and begins generating electricity, full propulsive power might not be available. This capability is standard for i3 REx' everywhere but in North America, so you'd not be doing anything that BMW didn't intend. This restriction is only to satisfy California Air Resource Board requirements for a range-extended EV.
Thank you alohart for your reply. I am in Europe, so i can start the Rex anytime, but my doubt is if it would damage the battery to use always the gas. I mean just refuel again and again.
Another thing that i noticed is that when the REX is working the battery range decrease slightly. Is it normal? Depends on the way i drive?
Thank you alohart
 
Thank you alohart for your reply. I am in Europe, so i can start the Rex anytime, but my doubt is if it would damage the battery to use always the gas. I mean just refuel again and again.
No, the battery pack doesn't know whether electrons enter from a charging station, the propulsion motor-generator during regenerative braking, or the REx generator, so the battery pack doesn't care about the source of those electrons.

When you turn on the REx engine manually, it would only maintain the current charge level and couldn't be used to increase the charge level. So if you always drive with the REx engine running, the charge level could never increase above 75%, the highest charge level at which the REx engine could be manually started, but would be lower if you turned on the REx engine at a lower charge level.

Battery cell charge level balancing occurs more rapidly at a 100% charge level but continues at a somewhat lower rate at lower charge levels. I'm not aware of any documentation that states the lowest charge level at which cell charge level balancing could occur. Some i3 owners feel that it might not occur at charge levels much below 80%. If it doesn't ever occur, the cell charge levels would gradually deviate from each other resulting in a lower usable battery pack capacity. This would not cause permanent cell damage but is only temporary until the charge levels of all the cells are balanced again. You would have to charge the battery pack with a charging station to increase the charge level to where cell charge level balancing would occur and then allow your i3 to rest. However, it's a slow process, so if the cell charge levels deviate significantly, it could take many days with an i3 off, not charging, and not preconditioning to balance the charge levels completely.

So it's probably best not to always drive with the REx engine on. Occasionally, the battery pack should be fully charged followed by resting for hours to allow cell charge level balancing to proceed.
Another thing that i noticed is that when the REX is working the battery range decrease slightly. Is it normal?Depends on the way i drive?
The REx generator doesn't maintain the battery pack's charge level precisely. If one drives fast, up a steep incline, with the cabin heater on high, etc., the generator might not be able to maintain the battery pack's charge level, so the battery pack range estimate would decrease until the REx is able to increase the charge level back to the charge level at which the REx generator was turned on (that should increase the battery pack range estimate slightly). Also, ambient temperature could change the battery pack range estimate as well as how one has been driving for the past 30 km or so.
 
No, the battery pack doesn't know whether electrons enter from a charging station, the propulsion motor-generator during regenerative braking, or the REx generator, so the battery pack doesn't care about the source of those electrons.

When you turn on the REx engine manually, it would only maintain the current charge level and couldn't be used to increase the charge level. So if you always drive with the REx engine running, the charge level could never increase above 75%, the highest charge level at which the REx engine could be manually started, but would be lower if you turned on the REx engine at a lower charge level.

Battery cell charge level balancing occurs more rapidly at a 100% charge level but continues at a somewhat lower rate at lower charge levels. I'm not aware of any documentation that states the lowest charge level at which cell charge level balancing could occur. Some i3 owners feel that it might not occur at charge levels much below 80%. If it doesn't ever occur, the cell charge levels would gradually deviate from each other resulting in a lower usable battery pack capacity. This would not cause permanent cell damage but is only temporary until the charge levels of all the cells are balanced again. You would have to charge the battery pack with a charging station to increase the charge level to where cell charge level balancing would occur and then allow your i3 to rest. However, it's a slow process, so if the cell charge levels deviate significantly, it could take many days with an i3 off, not charging, and not preconditioning to balance the charge levels completely.

So it's probably best not to always drive with the REx engine on. Occasionally, the battery pack should be fully charged followed by resting for hours to allow cell charge level balancing to proceed.

The REx generator doesn't maintain the battery pack's charge level precisely. If one drives fast, up a steep incline, with the cabin heater on high, etc., the generator might not be able to maintain the battery pack's charge level, so the battery pack range estimate would decrease until the REx is able to increase the charge level back to the charge level at which the REx generator was turned on (that should increase the battery pack range estimate slightly). Also, ambient temperature could change the battery pack range estimate as well as how one has been driving for the past 30 km or so.
Amazing explanation, thank you so much.
Another doubt is about the charging cable. I just bought a cable to connect direct to the sockets in my house. Here in London we have 240W.
Is it ok to charge with this kind of cable or should it be used only exceptionally?
 

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Is it ok to charge with this kind of cable or should it be used only exceptionally?
This "charger", actually a EVSE (EV Safety Equipment) not a charger, should be fine to charge your car as often as you want. I recommend that you use a dedicated outlet that has proper diameter wiring for sustained 3.3kW power delivery, and proper earthing.
 
This "charger", actually a EVSE (EV Safety Equipment) not a charger, should be fine to charge your car as often as you want. I recommend that you use a dedicated outlet that has proper diameter wiring for sustained 3.3kW power delivery, and proper earthing.
thank you Dutchi3, there is something that I dont get, Is it not possible to open the door without shutdown the engine?
 
Working as designed, not much you can do about it. Maybe with coding, but it would be an unsafe situation.
The car logs the incident, too -- at least mine does. My service rep gave me some ribbing about being "naughty" trying to get out with the car running in drive.
 
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