What does the SD-card endurance estimator calculate?
An MDVR records in a loop. When the card is full, the newest video is written over the oldest. Every pass over the card uses up a part of its rated endurance. A busy vehicle with a small card passes over it many times a year.
This estimator turns your cameras and hours into three answers: how long one pass takes, how many passes a year, and how many years until the card reaches its rating. It then gives a replace-at date and the cards your fleet needs each year.
Why cards wear out in a vehicle
Flash memory can be written a limited number of times. Continuous recording writes all day, in a hot cab, so the limit arrives sooner than in a camera or a phone. Three kinds of card are sold, and they differ most in how long they last under that load.
Standard card
Made for photos and files
- Built for
- Light, occasional writing
- In a vehicle
- Wears fastest
- Ask for
- Rated write cycles
High-endurance card
Made for continuous recording
- Built for
- Dash cameras and security cameras
- In a vehicle
- Lasts longer, still wears
- Ask for
- Cycles or TBW, and heat rating
Industrial card
Made for harsh conditions
- Built for
- Heat, vibration and long service
- In a vehicle
- Lasts longest
- Ask for
- TBW and operating temperature
- A bigger card wears slower. Twice the size means half the passes a year, so about twice the life.
- Lower bitrate wears slower. Less data a day means fewer passes.
- Heat shortens life. The estimate does not include temperature, so leave a margin in a hot climate.
Inputs you need
| Input | Where to find it | Tip |
|---|---|---|
| Channels and bitrate | Device video settings | Use the recording stream, not the live-view stream. |
| Recording hours | Shift pattern and trip logs | Add the minutes the device records after the engine stops. |
| Card size | The card label | Decimal GB. The usable share is lower after formatting. |
| Rated endurance | Card datasheet or the seller | Write cycles or TBW. If none is published, treat the result as a guess. |
| Install date | Your maintenance log | Needed only for the replace-at date. |
How the estimate is calculated
Sizes are decimal: 1 GB = 1,000 MB and 1 TB = 1,000 GB, as printed on cards.
The lamp compares the replace-at life with the years you want. Green means at least 10% more than you want. Amber means it just reaches it. Red means it falls short. The 10% line is a convention.
Worked example: 4 channels at 2 Mbps on a 128 GB card
- Data: 4 x 2 = 8 Mbps, which is 3.6 GB an hour. Ten hours a day is 36 GB.
- One pass: 128 x 90% = 115.2 GB usable. 115.2 / 3.6 = 32 hours.
- Passes a year: 36 x 300 days = 10,800 GB. 10,800 / 115.2 = 93.75.
- Life: a 500-cycle card gives 500 / 93.75 = 5.3 years. Replacing at 80% gives 4.3 years. A 32 GB card in the same vehicle gives 1.1 years.
This example uses a write factor of 1 and no extra recording after the engine stops. The estimator opens with a write factor of 1.2 and 10 extra minutes, so the screen will not match this example until you enter those values.
How to read the results
- Time for one pass is also how far back you can look. If it is under a day, a clip can be gone before anyone checks. Use a larger card.
- Passes a year is the wear driver. Halving it doubles the life.
- The replace-at date is a planning date. It is not a promise that the card works until then.
- The card grid shows the safe life for each size and rating, so you can compare options before you buy.
A service routine for fleet cards
Check the card every month
Open a clip from each vehicle and check that it plays, that the date is right and that the last day is on the card.
Format on the maker interval
Format in the device, not on a computer, at the interval your card maker gives. Save any clip you need first.
Log each card
Write the vehicle, install date and replace-at date in one sheet. The report from this page is a start.
Replace on the date, not on failure
A card often fails without a warning. Replace at the planned date and keep a spare on the shelf.
Common mistakes
- Judging by days kept only. A card can hold 30 days and still be near the end of its life.
- Using the label size as usable space. Formatting takes a part, so passes come sooner.
- Waiting for failure. A card that stops writing may not show an error.
- Copying a rating from another card. Ratings differ by model. Use the datasheet of the card you buy.
- Ignoring the engine-off minutes. They add to the hours the card writes every day.
Assumptions and limits
Results are estimates. The bitrates, the card ratings, the write factor and the usable share on this page are typical values, not Tracom device or card specifications, so replace them with datasheet values. The estimate assumes the same load every recording day, and it leaves out temperature, power cuts and defects. Many card makers publish no endurance number at all, and then the result is a guess. Check a sample of cards in service before you fix a replacement interval for a fleet.