Possible RFID car battery drain solution

Apologies for not putting this in a particular thread, so many to choose from and I’m currently


So several of us have been worried about drawing too much power from access controllers rigged into cars, and we were talking about ways of mechanically turning the reader off, or relays etc
The fear being a car left for a week or 2 could be dead

Was talking to a friend, and he just opened Pandora’s box I think

“Why don’t you just install a solar trickle charger?”

Why didn’t I think of that before?!?

I could maybe make a custom thing to install on my dash closet to the window, would loose a good deal of efficiency, but I only need to offset the reader

Or maybe a thin film on the roof of my car

I’d want to do it clean… but that shouldn’t too hard

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I highly doubt it’ll drain the battery in a week. There are other things in a car that constantly use more power than the xAC will ever do.

Still, if you’re worried, there’s an easy solution: install a switch outside somewhere :slight_smile:

I think some of these solutions get a bit messy and unnecessary. You may as well detect a low voltage condition and have the thing switch to a small auxiliary battery pack, not with a current hungry relay either. But that’s all a bit crap. If it were me, rather than cobble together a bunch of non-optimal PCB modules, I’d design it from the ground up. Low power microcontroller - no boot loader stuff where you can’t optimise the low power modes - coded in C/assembler, correct use of low power sleep modes etc, low Ron FETs for switching duties. Household door locks can go on for a long time on a few AAs or even a coin cell!

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This sounds amazing, only issue will be getting people up to scratch on those topics - many of the people working on these projects are relatively or completely new to hardware / software design…

Hmm, I wouldn’t be too sure about that.

I’m guessing you don’t park in a garage.

On Amazon you can get long range wireless power. Like wireless phone charging, but much bigger. I was going to look into using that so I could just park over it and trickle charge the battery as it’s my secondary car and I don’t drive it much. But I blew it up on the bench just testing it… I did get it to wirelessly transmit 12v at 1.5 amps which is way more than I’d need.

That’s impressive!
What range did you get out of that?

Well apparently I had it too close (2 in) and that’s why it blew. It could take up to 40 something volts and it was working, But then I tried to take the input voltage above 30V and at 35V and 2 inches it popped the receiver chip.

THis is what I bought… supposed to do 12V @ 2A up to 4 in.


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I rewired my ignition cylinder so the Accessories position that the key usually rests in after starting the car supplies the 12v to the access controller. From there I have the reader hidden behind a panel in the car so I just hold my NeXT to it and the car starts right up. I rerouted the ignition cylinders starter wires to a relay connected to the access controller so trying to crank the key does nothing. This way you need to have the key and a registered chip in order to start the car. I also routed all the lines to a more hidden spot and made sure the wires in the steering column looked stock so if anyone trys to hotwire it they’ll just get confused and give up. Granted this only works for starting the car and not unlocking/ locking the doors or anything.

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Gotta say, this will result in confusion EVERY time you take your car to get maintenance done :joy: