Switchable Dashcam powerbank circuit

So I wanted my dashcams to run for 12+ hours whilst parked, and I did not want them running down the main car battery whilst doing so.

There are a few commercial solutions available. Namely the Cell link B, which is basically a UPS for your dashcams. You connect the dash cams to it, and it powers them whilst your ignition is off. When the ignition is on, it charges the pack, and also powers the cameras.


Problem is, that its £180, which is too much.

So, I built a relay solution that does the same things with Ravpower USB power banks.

Here is the diagram:


It looks complicated, but it isnt. All it does, is use 2 relays to switch the USB connection from the vehicle to the powerbank, when the ignition is turned off. Keep in mind you could use a DPDT relay to do the same thing, but with one relay instead of 2.

This is what the end device looks like :


The 2 USB feeds are at the top. The output is on the right, and the two wires on the bottom left go to switched 12v. (there is a 1 amp inline fuse in these).

Keep in mind some devices support “chargethrough”. They say they support charging a device, whilst itself is charged. I find this dangerous unless it bypasses the battery circuit inside, and as we cannot be 100% sure, this is much safer solution.

I get roughly 16 hours on a “20,000mah” ravpower battery pack. I also use quick charge 2.0 chargers to replenish the packs, as short journeys will not put much into them.

Time will tell how long the Memory cards in the cameras last too.


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Ultrafire BRC 18650 LI-ion battery test

So, I run my head torch from a batch of these batteries. They are cheap and have a claimed capacity of 5000mAh


I found that the head torch would drain with two of these batteries installed, in around 30 minutes or so.

I always figured that the head torch just used a vast amount of power, but then I saw this online:

Turns out, most of the cheapo “too good to be true” priced batteries are completely fake, and look like the above! Also important to note, they lack any over-current protection circuitry. Not to mention the fact that they have fire in the name.

I thought I would test the capacity at 0.1a discharge rate and was pretty surprised.

I tested it with a Lipo battery charger with a discharge mode, its not like to be 100% accurate, but close enough.


368 mAh…..

That’s all!

Save your cash and buy something genuine, it will literally be at least 6 times better.

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Simple heater repair

I have an upright heater that has a digital control panel on it, and the power button started playing up and not responding.

I pulled the thing apart and found it has 6 surface mount buttons, and the power one had broken inside:



The power button had lost its click. I knicked the set timer button off the pcb, as I didnt have any spare, and I never use that function anyway. I de-soldered the old button and chucked it in the bin:




Luckily for me, the swich locations are illustrated on the PCB. I soldered in the switch into the power location.

All back together and its working well again. A relatively simple post, but effective nontheless!

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