Prius Use In MN Winters - battery maintainer or new battery or both?

Hello all,

I've lurked here for years but just last week my '08 Prius left me in the parking lot stranded and I have a question that I don't think has come up before.

Backstory: we bought the Prius second hand in 2010 at a great price in Portland OR where we have been for many years. The Prius did great there and the weather was just right for optimal gas mileage. We lived in the NE so there would be days/weeks where I would ride my bike to work instead of driving the car and the commute was only 10 miles or so one way anyway. Time eventually killed the OEM 12V and I had a new one put in by Les Schwab (generic battery about Feb 2014) with a good warranty in case I needed to change it out later.

Fast forward to last month where we pulled stumps up and moved to MN near St Paul. Our cars were shipped out from Portland but it took a month. When we got them they were dirty but OK. I drove the car sporadically and all seemed fine. It has been sitting in the driveway for about a week since MN weather has been snowy and cold.

Last week though while waiting for my daughter to come out of her school and me being in a long line of parents in parked cars (all on our smartphones of course) I decided to turn off the engine instead of just idling (I do think I left the headlights on for a few minutes by accident) and plugged in my phone since it was pretty low on power. Then when it was time to move forward - dead battery It was about 32 degrees out. There wasn't enough power for the 4 ways to flash after a few minutes.

So then AAA came and gave me a jump. I went to the Toyota dealer and their handheld battery tester said the battery was good and could hold a charge. I left not sure why it went dead as it seemed plenty charged even after the long transit across the US. I did not test it with a voltmeter, though.

Now get this. On Saturday I left it sit in negative temps since I didn't trust it for work and then Sunday AM it wouldn't start again. This time it seemed to have plenty of power but it just wouldn't try. So Monday AM I call AAA again to jump or tow it to the dealer and guess what - it starts! Again, negative temps. I take it to the dealer again and this time I have them hook it up for electrical testing. No codes, mA draw is 27 when off. I let them keep it overnight so they could cold start it in the morning - it started fine. Their suggestion is that I don't drive it enough to recharge the battery in this cold snap and so a battery maintainer was installed to top off the battery overnight. I estimate my commute now 15 miles one way 5 days a week.

So my question is this, even though the handheld battery tester says the battery is fine, I've heard those handhelds don't properly test battery loads so that a battery that is on the verge of dying will report as ok on those things. So how common is it to have your car die in 2 days of sitting in minus degree weather and how far does one need to drive to recharge the battery properly? What is the best way to check this battery and would it make sense to change it out since it might have gone into a deep discharge from the long idle time from the move? I do plan to trickle charge overnight for now and keep it as added insurance in the future.

So that is what I'm wondering - it seems to hold a charge but it keeps showing up as a little low each time when tested. I don't want to sell this car just because I don't drive it enough. And I see plenty of other Priuses on the road here. Is low mileage driving in the MN frigid temps tricky for hybrids?

Thanks,

Kevin

 

Thanks for the feedback! I didn't think of these things so the keyless entry was left on while waiting for the move. By some damage, bisco, do you mean to the 12V aux battery? If so I'd rather switch it out for peace of mind. The car will stay out in the frigid cold while I'm at work and like this week I'll be leaving at 10 PM or so when the temps will tank.

 

I did find that and the current draw is 11.7-11.8V then 11.5V with the lights on and then up to 14.2V when the car is on. I saw on this on elearnaids website about voltages that it should not go below. It says no lower than 11.9 and I'm at 11.7-11.8. I'm still thinking a new battery is in order.

And now I know to be extra careful not leaving on the headlights and cycle on and off the ignition manually...