driesdepRunning Tesla Model 3's computer on my desk using parts from crashed cars
Very cool. Over a year and a half ago I installed a towing brake controller in my Tesla Model Y. Found the location of the plug, how to access and the pinout online (confirmed via a voltmeter..) so the car's side felt straight forward. But then I needed to find a brake controller that can work with the higher voltage (14.4v vs the normal 12v). Then built a cable from the brake controller to the connector that plugs into the car that I found on eBay. I velcro'd the controller under the dashboard. It works pretty well. I towed my small camper several times with it last year with no issues. Yay! However my little project is nothing compared to this post. Love people hacking away. So cool.
>then I needed to find a brake controller that can work with the higher voltage (14.4v vs the normal 12v)
Put a voltmeter on the battery terminals of a regular car at 2000rpm and note the voltage. You'd be surpised (the alternator can produce as high as 15V on some cars).
Automotive transients can be wild. I did a bringup with a board that had specified 100+v range specified for transients and finicky quality requirements on the output. The power supplies took up most of the (very large) board.
14v is not a transient, if your voltage was 12v with the car running, there's something wrong with the charging system (DC-to-DC in an EV, alternator/generator in an ICE)
13-14v is normal in all 12v automotive systems as the charging voltage
If I recall correctly, a fully charged lead acid battery has an open circuit voltage of 13.6V.
So the alternator has to put out at least something higher than if it’s planning on recharging the battery after 500 to 700 amps have been pulled from it for a few seconds to start the engine.
I typically fault anything above 15.6V as “that’s a bit high, your alternator might be on its way out” when working on automotive / caravan / camper van appliances and accessories.