Hybrid batteries vs subzero temps?



I’m on the cusp of buying a new car and have been thinking about a hybrid. We regularly get extended periods of subzero weather up here during the winter. I have a block heater for my current car ('94 Saturn) but have never heard whether one is necessary for the hybrid’s batteries.


A heater is not necessary for the batteries in a hybrid vehicle. You may want one for the gasoline engine, just as you have now, but you don’t need a heater for the batteries.


OK, just re-read my question and realized that I conflated two questions. My real questions are: 1) Would a hybrid need a block heater, and B) Are the batteries in a hybrid as sensitive to subzero temperatures as my Saturn’s are when not driven for several days when it’s -20?


Batteries that supply relatively small amounts of energy compared to their capacity (full discharge over the course of many minutes to hours) are not affected by cold very much. Acceleration will suffer a little but at below 0, you probably won’t want very much acceleration anyways!

I have worked with installations that actually refrigerate UPS batteries in service to extend service life. They work just fine.

BTW, a properly charged battery will not freeze very easily. A heavily discharged battery can freeze more easily, so keep the batteries charged.


A battery can lose up to 50% of its capacity when the ambient temp is -20 deg F.

That just means you will be running the small engine more often when it’s really cold.


I have a neighbor who has a hybrid…and I work with a guy who owns one…Never had a problem with their batteries…and we get several days below 0…in fact last winter we had a couple below -10.


When I see some of those hybrids tooling around I think to myself, what kind of snow build-up will occur on those wheel wells, and does it have sufficient ground clearance for deep snow


I too would like to know how well hybrids - specifically the Prius - deals with rougher roads – whether deep snow or mud or bumps. Seems like they’re built more for the city, but I really want one!


My neighbor owns a Prius…Does pretty good in the snow here in New Hampshire. One thing the Pirus has pretty skinny tires which are GREAT in snow.

I’ve never driven in the Prius, so I can’t comment on the ride…But Camry Hybrid is EXCELLENT.


Hi All,

 Yes, batteries loose power at cold temperatures, Hybrid NiMH or Lead Acid starter battery. But a Prius, or other hybrid has a 4 or more times physically larger battery used for starting the engine. And since the battery is NiMH, which is much more powerful than a lead-acid battery, pound for pound, or cu in for cu in the car has many many times the engine starting power of a traditional car.

  So, engine starting reliability in cold weather is one of the bigger advantages of a Prius or other HSD car.


Great theory but that’s not how the hybrid electrical system works. There is a separate engine starting battery that is 12VDC and is of conventional lead-acid design. The high voltage battery pack that powers the electric motors does not connect to the engine starter.


That is why the 12v lead-acid accessory battery and the hybrid traction battery is located in the passenger compartment (or at least is heated/cooled by passenger compartment air) - the batteries perform better at what humans consider “room temp.”

That being said, as long as your 12v accessory battery is up for the job (like on a regular car, only it needs to only power some electronics which let the hybrid battery start the car), you should be fine. I can’t say that I’ve heard of any battery-related problems with the Prius in cold weather climates (Minnesota, Alaska, Canada, Norway, etc.). You may want to purchase an engine block heater so that the car may start providing you with more cabin heat earlier, but that’s about it.


No, the 12v lead-acid battery is just there to power the electronics. The electronics connect up the big NiMH hybrid battery, and it is the hybrid battery that’ll start the gasoline engine (just like it would in regular driving on/off cycles).

On Toyota hybrids, there isn’t even a conventional 12v-powered starter motor. Honda hybrids have an emergency 12v-powered starter, but it is only used in the uncommon instances of a completely drained hybrid battery (or other electrical system anomalties).


Tires are not skinny, at least on my '07 Prius. they are 185/65-15. A 65 profile tire is not skinny.
For the curious, go to www.priuschat.com for all the info you could possibly want.


A 65 means nothing with skinny. The 65 is percentage of width (185mm) the tire protrudes above the rim.

185 is skinny.


What you say makes no sense and is directly opposite everything I have seen or read about hybrid electronics setups. Why would they need to use a conventional battery for only the electronics? They use the same starter motor as the engine only cars so why convert from the battery pack voltage to 12VDC to run the starter motor when they already have a starting battery to power the electronics (as you claim)? Makes no sense.


The hybrid battery directly powers a motor-generator, which spins up/starts the gasoline engine, which it would do for normal start/stop during your drive, besides when you first start the car.

Yes, the 12v battery is recharged off of the hybrid battery in a step-down converter while the car is on. The 12v battery powers the lights, fan, radio, computers, etc. (I’m ignoring the 42v “hybrid” pickup trucks that GM has…)

The 12v battery does not directly start the gasoline engine. IF there is a conventional 12v starter motor, it is rarely used. The 12v battery only needs enough power to boot the computers, then the computers link up the hybrid battery, and the hybrid battery will start the gasoline engine.

Reason? 1 = Safety. When the vehicle is off, the high-voltage hybrid battery is isolated from the electronics of the rest of the car. 2 = battery life. It’s much easier to replace a standard 12v accessory battery, than it is to replace a hybrid battery, should you accidentially leave a light on or a door ajar overnight. 3 = convention. Most car electronics today are already designed to be run on 12v DC.