Actually, Honda may be using thinly disguised GM software. Out of Spec reviews drove a Honda journalist test vehicle and at one point it popped up a message on the screen which contained wording, I forget exactly what, which revealed that that the software is actually GM. Those were preproduction demonstrator vehicles, so perhaps the software was tweaked or entirely replaced by the time the vehicle went to dealers for sale. I have a 2001 Honda Insignt and generally it has been a bullet proof car. I had a problem with the battery pack which Honda should have fixed under warranty, but they didn’t. I got the run-around from Honda’s corporate claims people until after the warranty expired. I wound up replacing the battery with a rebuilt pack which lasted over 10 years. I replaced the pack a second time with a rebuilt from Green Tec and that one is still working well. The Insight is 23 years old has about 192,000 miles on it. It still looks pretty good and has lasted longer than any other daily driver car I’ve owned. The insight battery is tiny compared to a full EV battery, made from NiMH cells and quasi-consumable. It is under $2000, replaceable by one’s self, so under $200 per year. I save way more than that on decreased gasoline consumption. I get between 50 and 80 MPG depending on driving conditions.
I have the first generstion 2017 Bolt and I would give high marks to the power train software. GM did an excellent job at reliability and operability. GM did much better job at blending the regenerative braking with the friction braking than Nissan did with a LEAF I had before the Bolt. In the LEAF there was always a small but noticeable change in feel when the system changed over from regen to friction. It is seamless in the Bolt.
Besides power train management of the traction motor(s) and braking, the management of the battery itself is a big question. The battery in my Bolt was replaced two years ago due to the safety recall, but there was no noticeable deterioration of the battery before or after the replacement. I would rate the battery management as very good. We’ll have to see about Ultium. The LEAF I owned had pretty serious deterioration. After six years it has lost almost 30% of its capacity at less than 30K miles. I got the LEAF used and I didn’t put many miles on it because the range was so limited, only about 90 miles when I got it. IThe LEAF was really only good for running around town errands.