Lukas LK-290 Interruption while starting engine

telero

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I've had the Lukas LK-290 installed with a Mobius used as a dashcam for a while. I occasionally had issues with the Mobius powering off and not coming back on until I unplugged the USB cable from it and plugged it back in. I decided to get a Blacksys CF-100 so I have something that is actually to be used as a dashcam as well as providing a rear facing camera as well.

Once I installed the CF-100 I started noticing more how the LK-290 was working. Since the CF-100 has voice prompts that tell you when the camera is doing something, such as stopping the voice recording and starting the 2 channel recording.

I had the LK-290 set up to cut-off power at a 12.2V, and usually when I would get in the car after a short period of parking the CF-100 would still be on in parking mode. The issue I would notice is that after starting the car the CF-100 would after a short time announce that it was stopping voice recording, starting 2 channel recording, and that the GPS was connected. This seemed to indicate that starting the car was interrupting the power coming from the LK-290, likely due to the voltage dropping while starting the car. I tried setting the cut-off voltage down to 11.8V, but it still cut out and the camera would restart after starting the engine.

I started thinking more about how the ACC vs continuous power connection for the LK-290 might work, as I hadn't really thought about it very much prior to this. The manual seemed to confirm that if the ACC line to the LK-290 has power, the cut-off that applies to the continuous power feed will be ignored. I don't know if that was specifically meant to take into account voltage drops while starting, or if it was to allow the recording to continue at lower voltage while the car was manually placed in the on/ACC mode.

Since I don't really care about the ACC function of the LK-290 and really only care about the voltage cut-off to preserve the engine starting power of the battery, I thought about removing the ACC connection altogether. I also considered what it might take to allow the continuous power to function through a voltage drop caused by an engine start. I initially thought about looking to see if a small capacitor could be used to help the voltage to the LK-290 stay above the minimum cut-off during the engine start.

Then I thought about how my car is actually working. I have a push-button start vehicle rather than a physical key-activated ignition. I started to wonder if the ACC was not being activated until after the car was started. I tested a theory of pressing the start button without the clutch to turn the car on in accessory mode. The CF-100 was already on before that, and stayed on as expected. I then engaged the clutch and pressed the start button again. This time the CF-100 did not announce the voice recording was stopping or that 2 channel recording had started. It appeared to stay on and not reboot during the engine start.

I haven't had a chance to test with physical key-activated ignition vehicle, so I'm curious if it works any differently there or not. Normally the key is turned through an ACC/On position before getting to the starter, so I wonder if the ACC voltage is already present prior to an engine start that would cause a voltage drop the would normally go below the cut-off setpoint.

It does appear that my push-button start doesn't activate ACC voltage prior to the engine start, and although powering the car on prior to starting does seem to solve the problem, the two button pushes are not ideal (mostly because I'm just not used to doing it that way and will probably forget most of the time). This brought me back to my prior idea of not relying on the ACC connection and just trying to insert a small capacitor into the continuous power line. Although a small capacitor/diode circuit wouldn't really be all that hard to put together, I did come up with another idea while researching the capacitor...

I did some searching around here first, but hadn't seen anyone mention using a small rechargeable power pack as essentially a UPS. I also couldn't really find many of the rechargeable power packs that said if they could be charged and provide power at the same time. I did eventually find a device that is essentially a small 12V UPS. It would normally be powered by a 120VAC to 12VDC transformer, then provide a 12VDC output. I don't see any reason the input of this UPS couldn't be connected to the 12V output of the LK-290, and the output could be connected to the CF-100. For me this would do a couple of things. I shouldn't have to use the ACC mode prior to starting the car (I shouldn't even need the ACC line connected), and I could set the LK-290 cut-off voltage to be higher. If it works as I'd expect, the car battery would charge the UPS battery and the UPS would power the CF-100 at the same time. When the engine was on the LK-290 would be on as expected. Once the engine was turned off the car battery would continue to charge the UPS battery and the UPS would continue to power the CF-100. Once the car battery hit the voltage cut-off the of the LK-290, the LK-290 would turn off it's output to the UPS, but the UPS would continue to power the CF-100 until it's battery was drained. Once the car was started again the LK-290 would turn on it's output and again charge the UPS battery and the UPS would power the CF-100. The benefits of this would be having the LK-290 cut-off voltage higher, while still having a longer parking mode available.

So, I'm curious if anyone thinks this is a particularly good or bad idea. Also has anyone tried this and I just couldn't find it while searching? Does anyone have any experience similar to what I found with a key-activated ignition vs. push-button start?

Here is the UPS I found: 12V Mini UPS
There are several similar looking models, this one just seemed reasonably good and priced well.
 

Calgary Dash Camera - Robert

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I would defiantly say a battery pack is your best option, if not you can put together a capacitor circuit.

I know that the Lukas battery packs charge while in use.
 

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