Will Leaving Prius Parked Regularly Cause Battery Issues?

It probably will be best you don't buy a prius with your usage. It'll be cheaper using uber.

A battery will go out of balance if not used regularly.

If you need a car, want to pay the high insurance costs, registration, repairs, maintenance, depreciation etc for 50 miles of driving a week, then just buy a regular non hybrid. You are only driving 3000 miles a year.

 

Sitting unused five days at a time is at the upper limit of what we would consider OK. We recommend our customers charge & balance the battery anytime the car sits unused for more than one week. Charging & re-balancing the cells after the car has sat will ensure the cells are in the normal operating range and ready to receive the high current charge & draw the vehicle will deliver.

 

welcome! corolla, matrix, yaris, camry, civic, fit, mazda 3, etc.

 

I wonder if this holds true for a newish (6 months old) battery. My Prius was in an accident in July and had to sit for about 2 weeks for repairs.

 

I think you are fine. Self-discharge that leads to cell imbalance increases as batteries age. At only six months old, your battery probably did not self discharge much if at all.

 

A NEW Hv Battery that came from Toyota?

Or are you saying "new" rebuilt/used HV Battery that came from Doorman (orange case) or Fraudtech (aka Greentech, green colored case)?

 

Mine sits for 5 days, drives 80miles then sits for 2 days then drives 80miles and is parked. Almost every weekend. Definitely not optimal for the battery and there is a significant difference for the first half of the drive as the car "repairs" itself.

I would say the balancing issue is more of a problem, the shorter the drives. For example if it sat 5 days then you drove to the corner store and back only that would be orders of magnitude worse than sitting for a month then driving cross country.

 

I'm surprised to read the concern over leaving a car parked and unused for one week. Doesn't seem that the self-discharge during that period of time would be significant, or detrimental. Here is what I found on the Battery University site regarding self discharge of Nickel Metal Hydride batteries:
Self-discharge
NiMH cells historically had a somewhat higher self-discharge rate (equivalent to internal leakage) than NiCd cells. The self-discharge rate varies greatly with temperature, where lower storage temperature leads to slower discharge rate and longer battery life. The self-discharge is 5–20% on the first day and stabilizes around 0.5–4% per day at room temperature.[22][23][24][25][26] But at 45 °C it is approximately three times as high.[16]

Low self-discharge
The low self-discharge nickel–metal hydride battery (LSD NiMH) has a significantly lower rate of self-discharge. The innovation was introduced in 2005 by Sanyo, under their Eneloop brand.[27] By using an improved electrode separator and improved positive electrode, manufacturers claim the cells retain 70% to 85% of their capacity when stored one year at 20 °C (68 °F), compared to about half for normal NiMH batteries. They are otherwise similar to other NiMH batteries, and can be charged in the typical chargers.

 

Right, So for a degraded battery that has some cells that are at the high end of the self-discharge scale you referenced, the weaker cells can loose up to 44% SOC in one week. The stronger cells might only lose 8% SOC. The pack can become that much out of balance from sitting for only a week. One week isn't so bad, it's the cars that sit for 6-8 weeks or more that we get phone calls about all the time.

 

Couple things-

• Assuming you live in non-CARB NC, you have a 8-yr 100k miles warranty on the hybrid batt. You need to check orig purchase date, if you had an extra year that'd be nice but probably less than one year
• We have not heard too many 2009's batts going bad yet, but it is starting to maybe look like Gen3 batt (2010+) might be a little better longevity, and then you'd have an extra year or two warranty
• Normally for Gen2 the sitting problem has to do with the small 12v batt. The Smart Key System drains the battery slowly. There is a switch under the Steering column to turn it off, which is a good idea for the period which it sits. Gen3 (2010+) this "issue" is fixed as the car will automatically turn off SKS on sitting.

 

It is also a good idea to put the 12 V battery on a maintenance charger if you know it is going to sit idle for 2 weeks or more.

 

I would say that's a new idea for Prius Chat to suggest 1-week sitting is bad for HV batt. Makes sense that a stressed old batt might have a problem with 6-8 weeks. I'd wonder if there are corrective measures such as giving a good charge before parking, and 5-minute warm-up on re-start.

 

That was a qualified statement. Please don't take statements out of context. That's how urban myths start.

For an aged HV battery, that could be true. It depends very much on the condition of the battery as to how it will be affected by self-discharge.