Dash cams, and the parking mode nobody explains

What this section covers

A dash cam is the only accessory here that has to work perfectly on the one day you need it and can be ignored completely on the other 364. That asymmetry is why the buying advice in this category is so bad: almost everything written about dash cams ranks image quality, and almost every dash cam failure is about heat, power or a memory card, none of which show up in a sample clip.

So the pages here are organized around the three things that actually decide whether your camera has footage on the bad day. What temperature the maker will commit to in writing. Whether parking mode is a real feature on your car or a spec-sheet line item that needs a fuse box and an afternoon. And what card is in it, because a camera writing continuously for three years will kill a general-purpose microSD long before the camera itself fails.

What to buy, in order

If you have never owned one and want the shortest route to a camera that works, buy in this order:

• A front camera with a published heat ceiling. This is the single filter that removes most of the market, because most makers do not publish one. The under-$100 page ranks the ones that do.
• A real endurance card. Not the card from your camera bag. See the card page, where the gap between the two mainstream endurance cards is 70,080 rated hours against 10,000.
• A hardwire kit, but only if you actually want parking mode. Read the battery arithmetic first. It is a half-hour job under the dash and it is genuinely optional.
• A rear camera, last. Being hit from behind is the most common not-your-fault collision, and it is also the one your insurer least often disputes. Front first, rear when the budget comes back.

The heat problem, which is the actual problem

A car parked in summer sun runs roughly 60 to 70 C inside, and the strip of windshield where a dash cam lives is hotter than the cabin average because it is behind glass in direct sun with no airflow. That is the environment the device has to survive, every day, for years.

Two things follow. First, a camera with a lithium battery in it is a camera with a consumable in the hottest part of the car; batteries swell and lose capacity in heat, which is why the good cameras use a supercapacitor instead. Second, the published operating ceiling is the most useful number on the whole spec sheet, and most makers do not publish one at all.

Parking mode is three different features with one name

When a listing says “24-hour parking mode” it could mean any of three things, and they draw wildly different amounts of power:

• Motion or impact triggered. The camera sits in a low-power state and wakes on the G-sensor or on movement in frame. Lowest draw, and it misses the seconds before the trigger unless it buffers.
• Buffered recording. Same as above but the camera keeps a rolling few seconds in memory, so the clip includes the approach rather than starting at the impact. This is the one worth having.
• Time lapse. One frame every second or so, continuously. Covers the whole parking period, produces footage that is legible for a hit-and-run plate and useless for anything subtle.

All three need power with the ignition off, which the 12V socket does not supply in most cars. That is what the hardwire kit is for, and it is the real cost of parking mode: not the money, the afternoon. The install guide walks the whole job, and the battery page does the division that tells you how many nights you get before the car will not start.

What we do not do here

We have not mounted any of these cameras in a car. Every competitor in this category leads with a testing claim, and we cannot make one honestly, so we compete on something else: the manufacturer specifications, compiled with their sources attached, and the arithmetic those specifications support. Where a maker does not publish a figure, the spec table on the page says “Not published” and the product loses points for it. The methodology page sets out the whole thing.