Lots of low mileage driving - will this ruin a Prius battery?

No, it won't. The 12v battery has no heavy drain on it at any time in it's life. All it does is power up the system. Unlike a conventional battery which may be cycled due to heavy drain from engine starting loads, it stays at a constant state of charge for its entire life.

The traction battery goes from a low state of charge to a high state of charge within a few minutes of charging, and then can go back to a low state of charge within the same time. It is computer maintained, and does not require any type of drive cycle to keep it in tip-top shape.


That said, the Toyota dealer in Japan will tell you not to buy a Prius if you have the kind of drive cycle outlined by the OP. This is due to fuel in the tank not being used for excessive periods of time. A tank of gasoline should not last for a month or two. Additionally, the OP will not see the benefit of a hybrid, as the ICE will probably be running for a significant part of the car's driven time (1.7 miles each way).

 

Nice theory but in real life it doesn't seem to work out that way.

Flooded cell lead acid batteries "self discharge" when not in use (not charging).
AGM ones do that a lot less.
Certain usage patterns get the battery discharged and then never completely recovers to full.

The evidence is clear and compelling. You can choose to ignore it if you please.

 

OK. Because you just don't seem to get it...I'll spell it out for you.

In a normal car... The battery is used to stat the engine, putting a large drain on the battery. The battery then needs to be charged back up. The state of charge drops measurably, and then recovers. Ever hear of a deep cycle battery? It may take more than a few minutes of driving per day to recover the battery, and it may lose it's state of charge if you never give it time to recover...

Toyota hybrids do not use the 12v battery for any heavy loads. They simply power up the system, at which point the charging system takes over.

If you want to nit-pick, then yes, they do see a fluctuation in their state of charge as they sit overnight, and then regain this charge in the morning, as you turn the headlights on without the system powered up, and then regain this loss in charge when the system is powered up, etc.

The battery state of change will degrade over time, to the point where it will not have enough charge to power up the car. It does this pretty linearly.

None of this is what was being discussed. The battery in a Prius, when used properly, does not see large fluctuations in it's state of charge from day to day. It does not see heavy drains. It sees a small fluctuation. Because of this, you do not need to drive the car for 30 miles, once per week (original question), as the battery is in almost the same condition you left it the night before. It takes less than a few minutes to recoup this charge, and the car does not have to be driven to do it. Mileage, and road speed have nothing to do with charging the Prius battery...you simply turn it on.

This is how the system works in real life. You can choose to ignore it, if you please.

It's also easily visible and provable with a graphing scan tool,multimeter, etc. I can do a first-start to full-charge graph of the charging of the battery, and put it up here if you like? We can see just how many minutes it takes for the battery to completely recover at first power-on after 10 hours of sitting.

 

I get it just fine. I've been dealing with electricity for a bit over 50 years now.

Your stance is ridiculous, short sighted and pathetic for someone who seems to have a pretty good handle on how things work in general.

Nobody claims that the 12 V battery will be damaged by a low SOC .......if the car is used "normally". That includes me.

The fact is, however, that there ARE some usage patterns that WILL not keep it fully charged, which is bad for it.

It seems you are arguing the old "because I haven't seen it happen then it must not exist" fallacy.

I quit. It seems that further exchange is pointless.