Power Supply for Diagnostics

[Puffy]

Hi All,
I have a g42 M240i and was checking fault codes with Ista. I kept getting a voltage low warning. Did some research and BMW recommends connecting a 70 Amp power supply before diagnostic work!! I was thinking of trying a generic 240V to 12V DC 50A power supply and setting the voltage at 13.8 for this. Anyone tried this? 50A Power Supply

 

[Spanky]

840W seems like A LOT. Probably best to have when you're programming chips and so on, but still seems like overkill. The biggest shop PSU I've seen is like 30A.

Anecdotally, I've done many long flashes (DME & TCU) over K+DCAN with just a 6A charger and never ran into trouble. While not advised, I now often do short writes completely on battery with the faster WiFi dongle and some large consumers turned off (Lights, AC etc.). But, I have a fresh battery which does add peace of mind.

If you're getting voltage warnings from the car doing basic diagnostics then your battery is likely showing signs of weakness and a replacement should be considered. A high quality, lowish output, charger should be more than enough when paired with a fresh battery that is at a healthy SOC.

 

[Puffy]

Yep it does sound mad. 1st BMW I have connected to but never had this with other cars. I am just using a generic obd2 to enet cable, and ista seems slow and does a complete read. I'm pretty sure a lighter weight tool for diagnostics and maybe flashing in future wouldn't dim the neighbourhood. Will check the battery. Might still try a power supply but what wifi dongle and software would you recommend?

 

[Spanky]

Dodgy cable could certainly play a role in speed, putting undue stress on battery. ISTA is the diag standard for a BMW, so look at a proper cable if you wanna keep using that.


I've been using the MHD Universal Wifi dongle for DME and TCU flashing. Can also do code reading, and logging via MHD & CAFlash. The Universal dongle also works with Bimmergeeks ProTools & Bimmerlink, when you wanna code modules, at least on E-Series.

For day to day though, I use basic BT ELM dongle paired with Car Scanner Pro (Android app). It's set up to automatically connect, has a very customisable UI, and can still read codes and do nice logs.