Problem with starting a car

The performance of a battery is temperature related.

If the battery is in good condition, making sure it is charged (a small battery charger connected overnight) does help and if you can keep the battery and engine warm - I use a small 400W heater under the bonnet which makes a massive difference - it is on a timer to come on about 3 hours before I need the car.

Do test the battery and charging systems but they are working hard ie lights heater wipers all on and if you only do short trips the battery gets discharged over time, then include the temperature effect and it won’t start...

Cold weather starting is a combination of two factors. The primary factor is the chemical process in the battery, whereby the available energy in the battery drops dramatically over a narrow range of temperature. For example from 25F to 0F there is a very substantial drop in not only power, and current, but also a drop in voltage. So cold cranking Amps (CCA) is a metric which helps reflect that change in performance. Usually when there is a problem with a engine turning over slowly or now turning over, it goes back to the effective power available at that temperature. Bigger batteries and different design batteries supply different power at cold temperatures.

In extreme cold, one can not only charge the battery, but also put a heating pad around the battery. The higher temperature results in higher chemical reactivity and higher battery performance.

The second issue is mechanical. Cold engines, especially those with thicker or oil laden with particulates, have substantially more drag. Diesel engines typically fall victim to this as many utilize heavier grades of oil, and they also tend to have more particulates (soot) in their oil. At 68F a quart of motor oil is capable of suspending a pound of dust, soot and other particulates. At 0F that figure is less than two oz. of dust, soot and other particulates and the resulting suspension has the consistency of some peanut butter products.

So a well charged and good condition battery is the first line of defense. The second line of defense is clean oil, perhaps a lighter weight.

Operating a variety of engines is arctic and near arctic conditions, most of the time the problems are these two issues.

It is also true that it may take more power to turn over cold engines (due to belts and other sources of drag), but aside from the battery and oil those issues are tertiary.

So what do people do in arctic areas? They run block heaters to keep the engine warmer, which aids ignition by having a warmer engine, and also keeps the oil thinner to reduce drag. They also run blankets on their batteries, and have on-board chargers to keep the battery topped off in charge.

I have personally drained oil in an airplane, and taken it inside, so that it can be poured into an engine prior to the next start. Normally the engine is pre-heated with a hot air blower. One aircraft engine I had utilized pre heater units on each cylinder head, which dramatically assisted in cold engine starts.

Additionally, I have pulled the battery out of an airplane in arctic conditions, and kept it inside, until shortly prior to a flight. It can be charged inside, so that when it is brought out it is warm and up to peak starting potential.

One aircraft (Cessna C-208) actually made it real easy to pull the battery after a flight. It was a turbo prop so it had a different oil, and a different drag with cold oil. But a warm battery made an appreciable difference.

On my plow tractor, if the temperatures are getting real cold, I will hook up a trickle charger, and then put the block heater on a wifi switch. The block heater comes on about 4 hours before I think I will need the tractor. The batteries last about 8 years and the engine starts fine even when the outside temperatures are -20F. I have used the same diesel plow tractor for 40 years.