That's a good question. Everything eventually connects in to the ECU, so there's no reason the customer shouldn't be able to read this data. As for writing data

That's a good question. Everything eventually connects in to the ECU, so there's no reason the customer shouldn't be able to read this data. As for writing data, I'm not sure how difficult it would be, but it can probably be done. Personally, I'd leave battery controls to people smarter than me. Consider that the battery costs around $8,000, and that severe over- or under-charging is a massive hazard to both the battery's lifespan and the driver's life.