2013 Prius C had trouble starting due to cold weather…

Where are you parking: a secure garage, carport, driveway, or on the street? Anything but the last, I would get a decent smart charger. Owner's Manual recommends 3.5 amps or less. I think anything in the 3~4 amp range would be suitable.

My situation: our 2010 is idle for multiple days, sometimes as much as a week. Any day the car's not going to be used, I hook up my charger (CTEK 4.3), let it run to completion and leave it connected, till the car's next used. Current battery had it's 6th year in service, last September. Testing with a Solar BA5, it's supposedly still in-the-pink.

 

I do the same but use "batteryMINDer" 1500s. I usually have two vehicles hooked up at any particular time.

amazon.com/gp/product/B00D7HZ6FC/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Unfortunately, the daughter's Prius C is parked on the street...in Minneapolis . I installed a new 12V this fall. Hopefully it holds up. Honestly, I'm more convened about car theft and/or cat theft than anything else.