That's really good. I just had a $200 4 year old battery fail... So I'm a little jaded. Very few EV zero turns out there running on 4-5 years yet
It'll be interesting to see how quickly they fail out of warranty. It's a little bit hard for non-engineering or non-manufacturing customers to understand that a low failure rate near warranty period is actually a sign that you have poor process control. Perfect process control means perfect consistency of product, and therefore better consistency in time to failure, ignoring differences in user profiles.
If you can get your process controls dialed in so well that you know exactly how long a product will last, with zero variability, you can set the warranty just shy of that. Of course then you'll see 100% product failure just after warranty expiration, but if this allows the warranty to be extended from 3 years to 10 years, that's not always bad.
But the poorer your process controls, the more margin you need to allow, as the random failures start ramping in farther and farther ahead of the mean. Wide distributions are bad for marketing and engineering, as they remove the seller's ability to safely advertise longer warranties, due to uncertainty of when first random failures will occur. Longer warranties are always better for sales, ask Hyundai.
So we set warranty at a point where the number of random early failures is acceptable, both financially and reputationally. With a 3-year warranty, we should expect
some failures starting in year 4, but hopefully the distribution is wide enough that the number remains very low. I guess we will see!
Now that I've made a point to ask, I'm sure my cousin will let me know as soon as he has his first failure. He's an early adopter, bought one of the first Tesla Model 3's, and has a full fleet of Ego OPE. His batteries get moved from mower, to snowblower, and other machines, so they get more use the average household with e-mower alone.
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