Does it harm the hybrid battery to not be driven for a few months?

The HV battery holds up quite well. Just make sure it's fully charge (6 blue bars or higher) before you leave. It should be fine when you come back.

 

Our car sat when new for about 15 months. The 12 volt was (understandably) dead, but the hybrid battery has been champion, so far.

 

no worries.

 

Don't do that too often, although yours has held up well it is definitely not a good thing to do, i would advise that you get a friend or relative to start & run it for at least 10 mins a week just too keep all good

 

That actually is not a good idea.......as 10 minutes might not be enough to recover the 12 V up to full charge and the HV battery doesn't need it.

The 12 V needs to be nearly full and kept that way. A battery "tender" is best for that.

The HV battery needs no special attention, because of different chemistry, and as long as the charge level is within the "normal" operating range you don't need to worry about that either.

 

Are you suggesting it'll lose charge in a week? Are you in the business of rebuilding batteries?

 

No I am not suggesting anything like that - its prolonged periods, I have personally seen the effect in a Gen2 Prius that had been off the road for 6 months

The charge level of the HV Battery can & will drop out of that normal range over time as all batteries no matter what chemistry have a self -discharge rate so much depends on its inner state at the time it was last used. The battery tender is a good idea for the Lead acid 12V but has no effect whatsoever on the HV Battery if the vehicle is not running. The 12v is their to run the ECU's & ancillaries & is charged by a dc to dc converter fed from the HV battery but the converter is only engaged when the vehicle is in actual use

 

OK so maybe in addition to a tender for the 12 V, one should start the car periodically to keep the HV from going completely dead........but once every 6 weeks or so should be plenty for that; certainly NOT once a week.

If you don't let the gas engine come completely up to operating temperature, excess moisture tends to accumulate in the crankcase, intake manifold and the exhaust system.

 

The Toyota advice regarding the traction battery for stored vehicles is to make the vehicle READY for 30 minutes, every two months. This gives the gasoline engine an opportunity to bring up the traction battery charge by spinning MG1. That produces high voltage three-phase AC which the inverter converts to high voltage DC, used to charge the battery.

 

if that's the case, why does it stay at 2 purple in stop and go?

 

As I said depends on the inner state of the HV battery pack at the time of last use

 

Really......honestly........???
Brain not in gear this morning yet ???

It is because you are USING some of that charge as well as putting some into the battery.
That does not happen when you are in PARK.