To remove or not to remove the dashcam in hot weather

[Dashmellow]

It is interesting to see 70mai's stated rationale for using a lithium-ion battery rather than a super-capacitor, although they admit that lithium batteries do not fare well in extreme temperatures. They also state that they are looking into using super-capacitors due to extensive user feedback.


What is the supercapacitor solution? What are the Pros and Cons of the supercapacitor and the lithium battery?

"The application of the super-capacitor is the combined use of button batteries and the super-capacitors. The super-capacitor itself can store very little power. It will shut down immediately after power cut, risking the possibility that critical footages cannot finish recording in extreme conditions.The application of the lithium battery is using lithium batteries as a backup power source. Even when the power is cut off, the dash cam will still be able to finish recording the emergency video. The drawback is that lithium batteries do not discharge well under extremely high or low temperatures. We believe that the priority of the dash cam is capturing footage even in extreme conditions, so we chose the lithium battery solution and equipped it with precise safety protection logic. However, based on extensive user feedback, 70mai will explore the super-capacitor solution in future products."

 

[hieppg]

70mai mirror dashcam S500, which was released 5 months ago, has super capacitor instead of a battery. Its predecessor mirror cam D07 has battery. Hope 70mai will adapt this into other lines of dashcams.

 

[grubisic]

The application of the super-capacitor is the combined use of button batteries and the super-capacitors. The super-capacitor itself can store very little power. It will shut down immediately after power cut, risking the possibility that critical footages cannot finish recording. . . . .

I think this is key to understanding the dash cam problem. There is no one camera without (at least a small button) battery, and without risk.

 

[Vortex Radar]

I don’t buy the 70mai explanation. Use an appropriately sized super cap, not a capacitor for ants, and you’ll get sufficiently long power for a proper file save after power is cut. This issue has long been resolved by other manufacturers.

 

[Nigel]

I don’t buy the 70mai explanation. Use an appropriately sized super cap, not a capacitor for ants, and you’ll get sufficiently long power for a proper file save after power is cut. This issue has long been resolved by other manufacturers.

I think their problem is that when they "lock" a video file, instead of moving the current file to the event folder, they write a whole new file, I assume from buffered memory, and I suspect that takes rather longer than a normal sized super capacitor lasts!

In the event of an accident serious enough that the battery is disconnected, by damage, or because BMW fire their pyrotechnic battery disconnectors so that they can make extra profits from the repairs! I can understand that you might want to record the events over the next 10 minutes, a battery dashcam can, a supercap dashcam is not going to record more than 10 seconds extra, probably more like 2 seconds. So I think they have a good point, but they need to use a battery suitable for the conditions, and a quick.google shows that many people are having to replace their 70mai batteries. Currently super capacitors are the best solution, and loss of power at the important times is unusual, and when it happens is normally because someone turns the ignition off, but if they were to find a battery that can cope with the temperatures then it may be a better solution than super capacitors.

If you are using a dashcam parking mode battery then there is no issue anyway, unless things get unplugged in the accident.

You can also use no battery or capacitor, and use a file format that doesn't get corrupted, but then it stops recording a few seconds earlier than the supercap dashcam stops recording, and that seems to be too early.

 

[Dashmellow]

I don’t buy the 70mai explanation. Use an appropriately sized super cap, not a capacitor for ants, and you’ll get sufficiently long power for a proper file save after power is cut. This issue has long been resolved by other manufacturers.

There seems to be another flaw (more like an omission actually) in 70mai's argument in favor of lithium-ion batteries. Lithium-ion batteries should never be charged when they are below 32º Fahrenheit (0º Celsius). There are numerous scenarios where this would be likely to occur in normal use and it is not something the average consumer would be likely to know about.

 

[GPak]

Super Capacitor (SC) size is a difficult balance. They cannot simply increase the size because:
SC cannot hold energy, it is basically empty after DVR shutoff or soon after, therefore, every time we start the car, we have to wait until SC is fully charged adding to the time it takes to start recording.
With new power hungry 4K multi-channel DVRs it is even more difficult and already stretch.
I do not have much experience with DVRs but two I have A229 Plus and Mini 2 are quite showing
Have you noticed how long it takes to start A229 Plus/Pro compere to Mini 2? (± twice as long)

Also one would expect that relatively big size (energy capacity wise) SC would help to smooth any momentary voltage interruptions or fluctuations, but no, quite opposite is the case.
With Mini 2, I can use relatively slow relay-based UPS to switch the main power to backup and vice versa flawlessly, but A229 Plus is so sensitive that it re-starts even with faster solid-state 0.07 millisecond UPS.
I am guessing because they have to compromise between the time it takes to charge SC and the min size required to operate.

 

[grubisic]

Have any of you tried disconnecting the power off the camera with SC (simulate the crash phase) and measure how long the footage after disconnectig the power will be saved?

 

[Nigel]

Have any of you tried disconnecting the power off the camera with SC (simulate the crash phase) and measure how long the footage after disconnectig the power will be saved?

Most shut down as soon as they detect a voltage drop, so you may get only 1 second.

Normally this is not a problem, because they don't get disconnected.

Sometimes the cheap dashcams become disconnected because they leave the windshield in a bad impact, but then there is no reason for recording any more, because they are pointing at the floor or sky!

It is very rare to see any footage where a camera has shut down due to loss of power, and extra recording would be actually useful, the accident has already happened, more footage might be interesting, but it is not important.

The only ones that are a potential problem are the ones without battery or super capacitor, because then you can lose 2 or 3 seconds before the impact, and people often want that 2 or 3 seconds.

 

[GPak]

Have any of you tried disconnecting the power off the camera with SC (simulate the crash phase) and measure how long the footage after disconnectig the power will be saved?

Here is rough measurements on A229 Plus 2CH, original never updated FW.
(I guess, I am going to wait for another couple of years until FW is all ironed-out and finalized, including switching between 60fps (day) and corrected HDR (night)).

Power switch ON, it takes about 35 second to hear “Recording 2ch started”
Power switch OFF, it shuts down instantly (within milliseconds) and in about 6 seconds all lights are off.
I guess recording also stops instantly or so and 6 sec takes to properly close the DVR.

I think SC is sized at least for a double of that time perhaps for 15-20 sec, for added margin, just in case it takes longer to properly stop recording and shutdown, we definitely want that last video before "crash" to be safe and not corrupted.

 

[Nigel]

Power switch ON, it takes about 35 second to hear “Recording 2ch started”

Too long!

That is a good reason to hardwire a dashcam, so it doesn't need to boot up from scratch every time.

Does anyone know how long the A229 Plus 2ch takes to start recording from off/parking mode with a hardwire kit?

It may also be a good reason to update the firmware, I think boot up times were improved.

 

[GPak]

Too long!

That is a good reason to hardwire a dashcam, so it doesn't need to boot up from scratch every time.

Does anyone know how long the A229 Plus 2ch takes to start recording from off/parking mode with a hardwire kit?

It may also be a good reason to update the firmware, I think boot up times were improved.

Just tested it:
It takes about 10 second to hear "Recording 2ch started" from off/parking mode, much better.

Both tests are done with standard HK4 hardwire kit, thru attached GPS module which is ON, WiFi is off.
Using power supply providing 12.7V.

In my first test, I just wanted to show how the charging SC effects overall boot time.