Basically, you need a card that will withstand enough write cycles to last you however long you want it to last. The maths is relatively straight forward, but I have simplified below. Its not magic, finger in the air stuff. How long a device is warranted for can be calculated.
TeslaCam will write 1GB of data approx every 4 minutes.
So cards will fill approx at this rate of use.
32GB 128mins 2 hours
64GB 256mins 4-1/4 hours
128GB 512 mins 8-1/2 hours
256GB 1024 mins 17 hours
Other factors are at play also - most flash memory slow the fuller they get, and will possibly slow to the point that the car will complain - the dreaded Too slow error. Thankfully Tesla reacted to this to improve matters by deleting stale Sentry footage (dashcam was always removed after approx 1 hour), but it is still possible if you hoard footage.
Manufacturers will often quote cycles or hours use. If hours are quoted, its often based upon HD video at 26Mbs. TeslaCam writes slightly faster than that, but using 80% of quoted hours is a good approximation.
If a manufacturer quotes cycles, the following numbers are a good approximation
300 - 32GB:25 days; 64GB:50 days; 128GB:100 days; 256GB:200 days - typical common USB stick
1000 - 32GB:83 days; 64GB:166 days; 128GB:333 days; 256GB:666 days - typical endurance card
If a manufacturer quotes hours, the following numbers work as an approximation - 8760 hours in a typical year
5000 - 4050 hours - 5-1/2 months
10000 - 8100 hours - 11 months
20000 - 16200 hours - 22 months
HOWEVER - reality may be much better
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These figures are based on use of TeslaCam 24/7. Most people will not run their dash/sentry 24/7 - it has a significant power draw which adds up to significant energy loss from battery and/or electricity cost. So a typical use may only have Teslacam active for relatively short periods of time.
We have 2 no 128GB Endurance SD cards and rotate them for offline viewing, easy to do with SD cards. We also use TeslaCam significantly less than 24 hours a day on average - again, easy to do as TeslaCam can be location aware when linked to favourites/home. So I am expecting our SD endurance cards to each last 4 or 5 years - 8 to 10 years the pair. Not bad for £30 each.
