Correct Voltage on Scanmaster

[John Wilde]

Guys,

I have been having a terrible week so far.
To make things worse I left my lights on all day and gave myself a dead battery.
The car jumped easily and I was able to drive it home.
On the freeway the voltage fluctuated between 13.2-13.7.
This seems a little bit on the low side.
At idle the car would be in the 13.2-13.4 range.
This also seems low.

What would be good bench mark numbers to look for?
I am trying to decide if I should pick up a new battery.

Thanks in advance,

 

[BlackBandit]

That's right around where my voltage hovers. It's been that way since my battery was new.

 

[JOHNDEEREGN]

Guys,

I have been having a terrible week so far.
To make things worse I left my lights on all day and gave myself a dead battery.
The car jumped easily and I was able to drive it home.
On the freeway the voltage fluctuated between 13.2-13.7.
This seems a little bit on the low side.
At idle the car would be in the 13.2-13.4 range.
This also seems low.

What would be good bench mark numbers to look for?
I am trying to decide if I should pick up a new battery.

Thanks in advance,

I would have thought hiway voltage to be higher than idle voltage.... but never checked....

Somebody smarter than I can chime in

 

[John Wilde]

Thanks for the input guys, I would like to hear a couple other people's numbers too. However I don't think there is any downside to a new battery besides lightning the wallet. I need a stimulus package!!!

 

[86brick]

John,

I'm pretty sure mine sees between 13.5 and 13.9. I'd venture to say on most cars with the SM the norm is between 13.5-14.2 depending on the condition of the battery, alternator, RPM, etc.

Sometimes though Scanmaster #'s can be deceiving as it may be seeing losses down the line rather than true battery voltage so if you have a voltmeter that might be a better way to determine if you have a problem.

BTW, I run Red's Volt Booster FWIW although I suppose that would matter more if you were talking about WOT #'s.

 

[SS_Sean]

14.2 - 14.4 on a one wire 120 alternator. No more running the charge wire through the dash.

 

[Razor]

Understand the scanmaster BAT voltage reading is from the Ignition wire input on the ecm. Not directly from the battery. If you want to know battery voltage, put a meter on the battery. You should see 14+ volts at the battery engine running. Or 12-13.5 on the scanmaster.

Its kind of confusing, but the scanmaster displays "data stream" information the computer see's. Its not hooked up to the battery.

HTH

 

[JST A 6]

+1 on all above posts about using a voltmeter but the Scanmaster voltage you're reading sounds about right. It won't necessarily be higher at highway speeds because that voltage is regulated.

 

[TurboDave]

Razor makes an excellent point in that the scanmaster is NOT reading the battery or alternator output. What's being displayed on scanmaster is a voltage converted from a digital word inside the ECM which converts it's power input from and analog voltage to a digital word, after line losses, etc.

Mine normally reads in the 13.2-13.5 range, with occasional dips into the 12.9 range, depending on how much stuff I got running. And that's with a new die hard and a 200A alternator and 2ga. charge wire.

 

[John Wilde]

Thanks for all the great information guys.
I was pretty sure there was at least the draw of the ecu factored into
what the scanmaster was displaying. Based on what I am seeing I think that everything is in working order. However the battery is at least 5 years old.
Do you guys have any recommendations on a replacement?

 

[KevinB]

I'm an autozone freak lol. That what I have in my buick and suv. I have not put a charger on the buick in a year. The batt is even located in the trunk. I use the Duralast Gold.

 

[Roger]

No Optima. My Optima died in 2 days of not being driven. I gave it to my teenager - his car never sits for two days.

I know TR owner who like the cheap China batterys fron the big box stores. I have no issues with the Sears platnum (pricey).

 

[Roger]

No Optima.

My Optima died in 2 days of not being driven. I gave it to my teenager - his car never sits for two days.

I know TR owner who like the cheap China batterys from the big box stores. I have no issues with the Sears Platinum (pricey).