What voltage would you use for a vehicle power supply?

[RooflessVW]

Hi,

I am finally putting together a power supply solution for diagnostics/ flashing and wanted to ask the collective: what voltage would you use?

13.8? 14.2?

 

[dogememe]

i'd say anything from 12.8 to 14v is fine

 

[martinq]

13.5-13.8 is closer to ideal, anything higher and you risk overcharging your battery.

What's the application?

 

[DCDG]

Don't you need to be careful with vehicle diagnostics? I was under the impression some modules and switches may operate at lower voltages. I watched a video on YouTube the accidental misuse of a powerbrobe sending 12v to the wrong side of an AC relay and it took Out the control head for the climate control. Don't know if these two things are any what related just saying be careful where one sends 12+ volts

 

[RooflessVW]

13.5-13.8 is closer to ideal, anything higher and you risk overcharging your battery.

What's the application?

I am going to be adding some keys and making some changes to my Defender, but there is no real specific application. Just want to be able to support the battery while performing coding / flashing / diagnostics. I have run the battery down pretty quick on my VWs even with a "smart" charger connected.

13.8 was my initial thought.

Don't you need to be careful with vehicle diagnostics? I was under the impression some modules and switches may operate at lower voltages. I watched a video on YouTube the accidental misuse of a powerbrobe sending 12v to the wrong side of an AC relay and it took Out the control head for the climate control. Don't know if these two things are any what related just saying be careful where one sends 12+ volts

I will be supplying power to the vehicle battery.

 

[Timmastertech]

There is no one set voltage that everyone is happy with anymore, which is why most programming power supplies are adjustable. My portable power supply is a Midtronics 55 amp that was the standard 15+ years ago outputting 13.8 volts but its not sufficient for newer stuff. In the shop i use an adjustable DSR 100 amp power supply.

 

[f355spider]

There is no one set voltage that everyone is happy with anymore, which is why most programming power supplies are adjustable. My portable power supply is a Midtronics 55 amp that was the standard 15+ years ago outputting 13.8 volts but its not sufficient for newer stuff. In the shop i use an adjustable DSR 100 amp power supply.

Yes on this. Make sure it is big enough. I know the independent BMW/Mercedes shop I go to has one that is over 100 amps and has large heatsinks and internal fan. I think he said BMW now recommends 100 amp minimum?

 

[SubLGT]

https://cloreautomotive.com/oe-specified-voltage-environment-for-reprogramming/

............updated table of OE-specified voltage environments for module reprogramming, developed and updated in partnership with our colleague Tanner Brandt, Diagnostic Technician, Technical Trainer, and Founder of Auto Diag Clinic.

What to do if voltage drops too low during programming:

https://cloreautomotive.com/the-gre...wA&jobid=244fb735-faa3-4386-83b3-5edc05b2e97b

 

[RooflessVW]

https://cloreautomotive.com/oe-specified-voltage-environment-for-reprogramming/



https://cloreautomotive.com/the-gre...wA&jobid=244fb735-faa3-4386-83b3-5edc05b2e97b

Thank you! Bookmarked.

 

[JackWildfeuer]

13.5-13.8 is closer to ideal, anything higher and you risk overcharging your battery.

What's the application?

The bigger issue is exceeding zener diode voltage limits and electrolytic capacitor values throughout the car. Many of them can be as low as 16V.

Most 12V lead acid battery manufactures recomend voltages up to 15.5V for 3-6 hours regularly like once a month for longest battery life so almost no one is going to over charge a battery by exceeding 13.8V while doing diagnostic work. If you look at traditional linear shop battery chargers before they all went digital with switchers inside they are going to be way higher than you think they will be. It is not about battery it is about the cheap built to the edge or cost electronics.

Think of it like Apple using a 13V voltage regulator transistor but applying over 19V to it. Short of you spilling your coffee or wine on the laptop it it was a well known and planed point of failure. They would easily make it out of warranty but not that far out of waranty!

There is a reason you plan ahead for current limitting and isolation if needed for a bench transformer.

 

[ripcord]

I saw a dongle to plug into your ODBII port while changing batteries that is powered by a 9v battery.... pretty sure it was on the jungle site.

 

[RooflessVW]

I saw a dongle to plug into your ODBII port while changing batteries that is powered by a 9v battery.... pretty sure it was on the jungle site.

?

 

[berniedd]

?

It's not a charger, it's to keep the power on while changing the vehicle's battery to retain the car computer's stored data (radio settings, engine behavior for owner's driving style, idle settings, etc)

 

[RooflessVW]

It's not a charger, it's to keep the power on while changing the vehicle's battery to retain the car computer's stored data (radio settings, engine behavior for owner's driving style, idle settings, etc)

And what does that have to do with this thread topic?

 

[spasm3]

Could you measure the alternator output at idle, and go with that, in case it's vehicle specific?

 

[BMWTurboDzl]

Hi,

I am finally putting together a power supply solution for diagnostics/ flashing and wanted to ask the collective: what voltage would you use?

13.8? 14.2?

I would use dealership PSU as a guide.
https://www.deutronic.com/produkte/produktsuche/

 

[RooflessVW]

Could you measure the alternator output at idle, and go with that, in case it's vehicle specific?

On some cars you sure could. My LR doesn't have an alternator though.

I was at the dealer yesterday getting a part and was able to confirm the voltage in the link posted by @SubLGT.

Most manufacturers on the chart have a target of ~13.5, with a few outliers.

 

[RooflessVW]

I would use dealership PSU as a guide.
https://www.deutronic.com/produkte/produktsuche/

My LR dealer is using Traction SSU2-50B in the showroom and Traction BSU2-90 in the shop. Both are 13.4V units.

 

[BMWTurboDzl]

My LR dealer is using Traction SSU2-50B in the showroom and Traction BSU2-90 in the shop. Both are 13.4V units.

Have you looked for a used one for sale? The "home built" models I've come across on BMW forums seem kinda crude to me. I was looking for a used one w couple of years ago but had no luck.

 

[RooflessVW]

Have you looked for a used one for sale? The "home built" models I've come across on BMW forums seem kinda crude to me. I was looking for a used one w couple of years ago but had no luck.

I am using an RV power supply