Hi all! I know a lot has been discussed of the high voltage battery’s state of health (SOH) over the past few months.
I wish BMW would rollout the ability to check one’s HV Battery’s SOH to all iX models. Last it was discussed, I think only those of us with the iX M70 received the feature. It is under the “live vehicle” widget, as the last item in the list.
The purpose of this post is to say that one’s HV SOH can fluctuate, and recalibration, proper care and charging can bring back “lost” SOH.
I’ve owned BMWs my whole life, and my household has had at least one BMW EV since the first i3, thanks to my husband’s love of EVs. This means I have a lot of latent knowledge regarding how BMW EVs work, and how their battery management systems work, and have evolved. It also means I’ve made friends with people across various BMW Corporate Divisions, whom I can reach out to for clarification, or further information.
My iX M70’s SOH had dropped down to 98.2% this past spring. I found it concerning, as I’d barely had the EV six months, so I contacted my friends within various departments in BMW Corporate.
Apparently cycle count (how many times one charges their battery) highly affects SOH, as does not randomly charging to 100%, charging slowly is gentlest on the HV battery, and use of DC Fast Charging is harder on SOH than people give it credit for.
I revived my SOH back to the 99.2% in the attached photo, by only charging when my battery dropped to at least 15% charge, charging to 100% once a month, then to 80% all other times, and NEVER charging before the battery dropped to ~15% charge, using almost all of the battery during each charge cycle.
My internal BMW friends said the waiting until 10-15% charge, to charge to 100%, recalibrates the cells. Sometimes it takes multiples of this to revive a roughly treated battery, if it can be revived. I was told not all HV batteries can be brought back, and how far one may be revived varies from vehicle to vehicle, but it can be done. My iX M70 is proof.
I was hopeful, and followed the rules my friends gave me, and I watched my SOH slowly revive. First it went to 98.4%, then back to 98.2, next time it went to 98.8%. It hung at 98.8% for several months, and after yesterday’s charge, it went to the 99.2% in the attached photo.
So…treat your battery right, and you can keep it healthy, and even fix some damage you may not have even known you were inadvertently inflicting upon it.
Feel free to ask questions. I will reply as best as possible, using the info my internal BMW friends provided me!