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Comment by tzs | Hacker News Reader

How well do Prius Primes (or other PHEVs) handle long periods where one's daily mileage is well under the EV mode range and one is able to charge at home every night? I think it has been 5+ years since I've driven more than 25 miles in a day and even longer since I was away from home overnight.

I've read ICEs can have problems if you go too long without running them. Will the Prime's software automatically run the ICE on occasion to keep it in good shape?

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The VW PHEV’s will run the combustion engine regularly, mainly to avoid the fuel going stale. I assume the Toyota does the same.

My friend's Jeep will give them a notice that it needs to switch to gas when it hasn't been used for a while, so it seems like a pretty common thing across manufacturers.

Also, have they sorted out the 12V battery management for this low use scenario?

Our family has an older Hybrid Camry from around 2010 and it will destroy 12V batteries with too much local driving and parking. A typical regular ICE does better in the same conditions.

From the behavior, I assume it's because they only charged the 12V via a weak alternator when the ICE runs, rather than also keeping it charged via DC-DC conversion from the larger electric traction power system.

They haven't solved it.

I just returned from a 21 day trip and my 12v was dead because I left the Prius off the charger. It's fine as long as it's on the charger (my guess is it trickle charges it), but if you leave it off the charger, the traction battery doesn't maintain the 12v.

That's too bad. It shouldn't necessarily even need to charge the battery when parked, so much as have smarter battery management logic to get the car into lower power consumption states when parked and to more aggressively maintain the 12V charge when operating.

We resorted to installing a big master cutoff switch on the negative battery terminal in the trunk of the Camry. So if there is no plan to use the car again in the next few days, we electrically isolate the battery.

Then, we have to go through a longer "boot up" process to reactivate the car for its next use. Use the mechanical key to open the trunk, restore power, then enter the cabin and go through multiple cycles with the START button to let all the computers power back up...

The engine still kicks on once in a while. Notably now in winter, it kicks on if I have multiple seat heaters and the steering wheel heater on. But my use case also has two days where it's over the battery range so I know it'll kick on.

You can manually control it if you want and I do it once in a while when I need more acceleration since max power is delivered with both drivetrains.

We had this situation when we lived in a big city, before we moved somewhere that we drive longer distances regularly. We’d often go over a year without filling up. The engine runs occasionally to keep the gas from going stale, and in the winter the engine will kick on for the defroster. We never had any issues with it, and still have the car now.

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