Error with Rex maintenance cycle function

Owned my ‘15 abt 9 mos. Rex maintenance cycle has run periodically in that time as needed & once charge level dropped below 75%. Recently though the maintenance cycle started to run but bc I was only running short errand trips, I wasn’t allowing the cycle to complete before shutting off power. After a few of these short trips, I began seeing the message “maintenance cycle not possible.” Despite recharge and drain of charge as well as deliberately longer treks out on sub-75% charge, still getting error message re maintenance cycle. Now down to 12% charge and wondering if I can count on Rex functioning at all once my charge is nearer to 0. Any ideas? Thanks.

Is your car coded to be able to run the Rex at will below 75% charge? If not, I would consider doing that so you could give it some exercise. It makes it a much more useful car that way, anyway. Either that or drive it down to five miles, then drive around the block near your home until it comes on.

I wasn’t allowing the cycle to complete before shutting off power.

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Whenever that was happening to me, I just sat in the store parking lot, or driveway for the 5 or so minutes it took for the REx to complete the maintenance cycle.

You could try starting the REx using the emissions testing sequence - do a search on Youtube. This will allow you to manually start the REx as a check.

On self-coding the REx to run before the HV battery charge falls to the programmed low limit - some things to be aware of, per an i3 owner from the SF Bay area who posted his experience with BMW/NA on the i3 FaceBook page:
1. The REx engine is separately warrantied by BMW for 15 years or 150,000 miles in the USA.
2. Self-coding the REx to bypass the low-limit auto start voids the 15 year warranty. (The i3 ECU stores complete data on every time the Rex runs).
3. If the REx fails, out-of-warranty repair/replacement costs are in the neighborhood of $13,000.

Many thanks for the very helpful responses!
With your great input I’m realizing it was a combination of two mistakes giving me problems—cutting short the maintenance cycle and over the week or two of not charging, allowing fuel level to drop below minimum for running maint cycle at all.
Smacking my forehead over here...
Thanks again.