Heated Battery Blanket and Battery Insulation
 

I'm considering installing a battery blanket for my car, but not for the usual reasons.

In temperatures below -25°C with a battery that is only 1-3 years old, my car can throw engine codes for low fuel injector voltage immediately after the ignition is turned on. These codes allow the engine to crank, but prevent it from starting. A new battery always solves the issue.

I think it happens when the battery voltage dips much below 12.0 volts under load when the ignition is turned on, which only happens with a very cold, slightly old battery. I keep a small charger on the battery in the winter, but it doesn't really help.

A heated battery blanket should solve the issue, but I sometimes have to leave the car sitting out in the cold for hours without plugging it in, though rarely longer than 8 hours.

So, some questions:

1) Does anybody know how long a lead acid battery takes to cool down to near-ambient temperature, with or without an insulated battery blanket installed?

2) Has anybody experimented with wrapping additional insulation around a battery that has a heated blanket to help keep it warm between drives?

I've also been toying with the idea of installing a capacitor bank in the 10-100 F range, to help prevent the voltage from dipping too much even when the battery is cold. I see there are some units on Aliexpress with good specs for a reasonable cost, but not sure whether or not they'll explode or burn my car to the ground, or if there are other potential downsides.

Not sure how long your trips are, but a lot of insulation around the battery might keep it from warming up fast enough once the engine bay is hot.

If you have access to plugging in, then a 120/230V heating pad under the battery might be an option.

I charge a lot of group 34/78 optima batteries.
If they're really dead they can over heat when charging. I'll throw them outside when it's cold freezing temperatures can take a hot battery from over 100f to under room temperature in less than an hour. That's sitting the battery outside.
Under the hood out of the wind, next to a hot engine who knows.

I get around that by getting the biggest lead acid battery I can make fit. I made a free 2 year old group 31 battery fit in my Dodge Dakota, biggest they normally run is a group 27. Started right up no problem 2 mornings at 0f. That's really gd cold in degrees c.

One thing you might try is a small capacitor bank in parallel with the battery. It will take some of the peak impulse when the car first starts (or when it cranks), preventing it from dipping too low.