I am thinking if i can divert the passenger side footwell heater into my glove box to at least get going a little faster.
I've always wanted a heated glove box, would be much more useful than heated seats or heated steering wheel, don't like cold gloves.
It might be better for you having a #2 car battery of the AGM type, and then get a charge splitter so you can use that extra battery for the camera and not risk depleting the main car battery.
AGM batteries are fine charging in the cold, and also reasonably cheap, although they should not last as long. Some of them do seem to last much longer than some LiFePo4 batteries though!
All quality LFP batteries have or should have sub-freezing charging protection (google to help)
Agreed, charging in freezing temperatures is dangerous and they should have protection against doing so. People using standard USB powerbanks need to remember that these do not normally have the required protection for charging in sub-freezing temperatures.
Adding a heater to a battery is not an ideal solution, with some drawbacks.
I tried that once, came to the conclusion that the centre of the cells was not going to be warm before my normal journey was complete, and so it was a waste of effort! Furthermore, the temperature sensor is never in the centre of the cells, it is always on the outside, so if you heat them too fast, the sensor will allow charging to start while the centres of the cells are still at dangerously low temperatures. They need to be pre-heated.
I would not expect a long life from dedicated batteries for the following reasons:
All your reasons are good reasons why the cells will lose capacity relatively quickly, but losing capacity doesn't mean that they are dead, cells are normally rated for lifespan based on replacement when they drop to 80% original capacity, but for dashcam use, many people will continue using them long past that, cells tend to only die after dropping below 60% original capacity (Not sure if that is correct for LFP?)
Most of the dead power banks people report appear to have component failure in the charging circuits rather than failure of cells, possibly due to inadequate cooling while charging, or maybe they are cheapish components being pushed too hard. They are handling a lot of power to achieve the high charging rates, so that would not be surprising.
These dashcam powerbanks don't spend much time at 100%, I suspect most people almost never reach 100% on their normal commute with the larger capacity batteries. They can spend a lot of time empty, but if you use a HWK with 11.8V cutoff then the "empty" condition is not too bad for lifetime either. LFP is able to cope with a bit of charging abuse. Overall, the cells are not being treated too hard.
