Torque Pro App vs Multi-meter for Volts

[mtbtim]

Torque Pro App vs Multi-meter for Reading Volts

Hey Dudes and Dudettes,

After reading some threads recently on charging systems and how many volts you should be registering if your charging system is working sufficiently, I decided to look into my own charging system a little further. With an OBD II bluetooth sensor reader and using the Torque Pro app on my Android phone, my volts via the Torque Pro app are showing anywhere from 12.6 - 13.2 volts.

Thinking something might be off with the Torque Pro app, I brought my rig to a local O'Reilly Auto Parts store and asked them if they could check my charging system. According to their multi-meter tool, my charging system is putting out 13.8 volts. That's approximately a 1 volt difference from what the Torque Pro app was telling me.

So, what gives? I'm wondering why there's such a big difference. Is there anyone out there using Torque Pro too that can give me some enlightenment on why this is?

 

[hwnfisherman]

There might be a + or - voltage accuracy spec for the app.

 

[Konkordmusk]

Torque Pro reads voltage off of the 12v+ OBD pin. Possible voltage loss there, should be minor, +/- 0.30v. The rest of the loss can be attributed to an accuracy parameter the app has. I do not know of a way to increase accuracy. I've tried.

 

[alumarine]

How do you know the O'reilly meter was right?

I have a number of meters and they vary up to .5 volts.
The voltage will vary depending on rpm's and load.

I'm sure the app is just reporting what the ecu is telling it.
It's not "measuring" anything.

 

[JRZEE2000TR4LTD]

Not sure how the torque app works, but the scan gauge II uses hexadecimal numbers to "interpret" the values it's reading and uses those numbers to properly display the reading ie decimal placement, proper scaling and such. I think I read one member (Robb235?) on here used the hexadecimal #s from the Scanguage website on his Torque app. I also did this with my scangauge and if you change the right # in the hexadecimal # you can modify the displayed value.

 

[mtbtim]

How do you know the O'reilly meter was right?

I have a number of meters and they vary up to .5 volts.
The voltage will vary depending on rpm's and load.

I'm sure the app is just reporting what the ecu is telling it.
It's not "measuring" anything.

I don't know, but the numbers it showed me made more sense since it seems my charging system is working well enough to keep the battery charged. I'm basing this by how strongly my rig turns over after sitting a few days. But, I did replace the battery a couple months ago, so maybe the subpar charging hasn't affected it enough to start showing signs of getting weaker.

I have read in the FSM the alternator should be putting out 13.7 - 14.7 volts. Since my battery seems fine for now, I'm thinking O'Reilly's meter showing my alternator putting out 13.8 volts is more accurate than the Torque Pro app showing it's putting out anywhere from 12.6 - 13.2 volts. If the Torque Pro app is right, I'd think I would be detecting weaker starts in the mornings by now but I don't really know. Maybe the charging system is doing just enough to keep the battery from dying a quick death.

 

[Konkordmusk]

I don't know, but the numbers it showed me made more sense since it seems my charging system is working well enough to keep the battery charged. I'm basing this by how strongly my rig turns over after sitting a few days. But, I did replace the battery a couple months ago, so maybe the subpar charging hasn't affected it enough to start showing signs of getting weaker.

I have read in the FSM the alternator should be putting out 13.7 - 14.7 volts. Since my battery seems fine for now, I'm thinking O'Reilly's meter showing my alternator putting out 13.8 volts is more accurate than the Torque Pro app showing it's putting out anywhere from 12.6 - 13.2 volts. If the Torque Pro app is right, I'd think I would be detecting weaker starts in the mornings by now but I don't really know. Maybe the charging system is doing just enough to keep the battery from dying a quick death.

If you're concerned about your charging system, I can help check it out on July 2nd!

 

[mtbtim]

If you're concerned about your charging system, I can help check it out on July 2nd!

That would be awesome. I'd like to buy one of those multi-meters or charging system testers but the quality ones are pretty pricey unless somebody has a recommendation on a good one for an affordable price.

 

[Konkordmusk]

I have around 5 of the Craftsman ones...and my baby, my Fluke 87v.
The Craftsman ones do just fine, they take a lot of a abuse and have a limited warranty. They're fairly accurate as well, and budget friendly.

 

[mtbtim]

I have around 5 of the Craftsman ones...and my baby, my Fluke 87v.
The Craftsman ones do just fine, they take a lot of a abuse and have a limited warranty. They're fairly accurate as well, and budget friendly.

You know, I just remembered I have this Innova OBD II scan tool that I bought from O'Reilly when I was on a road trip a couple years ago and throwing check engine codes. It was expensive. I think I paid around $150 for it. I've never used it for anything other than checking and clearing codes but low and behold the thing tells me my battery voltage and it will perform an alternator test. The alternator test showed it was putting out 13.9 volts which matches what the O'Reilly voltage tester showed yesterday. I also checked the voltage this morning via the Torque Pro app and it showed 13.2 volts.

The Torque Pro values, even though they are a little off, will still alert me if something is up with my charging system because I know the value range when the system is working right. I find the Torque Pro app usually shows around 13-13.2 volts.

 

[gamefreakgc]

I have around 5 of the Craftsman ones...and my baby, my Fluke 87v.
The Craftsman ones do just fine, they take a lot of a abuse and have a limited warranty. They're fairly accurate as well, and budget friendly.

I can attest, he does have some good multimeters and battery chargers! I'm still thinking about getting one for the AGM battery you got me a while back to make sure it stays in tip top shape. I like playing my music... alot so I think I'm starting to drain it down a bit.

 

[pendragon]

I have an OBDII mini bluetooth adaptor and torque pro for android on a 1999 4runner 3RZ-FE and I don't have any data for O2 voltage or anything related to battery voltage. Are y'all able to access that stuff?

 

[mtbtim]

I have an OBDII mini bluetooth adaptor and torque pro for android on a 1999 4runner 3RZ-FE and I don't have any data for O2 voltage or anything related to battery voltage. Are y'all able to access that stuff?

I just scrolled through the Torque Pro app when making a new display and found a "Volts OBD II" or something like that. So maybe you didn't scroll far enough.

 

[TheDurk]

I just scrolled through the Torque Pro app when making a new display and found a "Volts OBD II" or something like that. So maybe you didn't scroll far enough.

It's definitely there on a 5VZ-FE. The O2 voltage would have to be there, but I suppose it is conceivable the 4 cyl ECU would not report the PID for battery voltage. But it would surprise me.

I'm going to try to compare actual battery voltage and Torque voltage report later on. I'll report back.

 

[rideexileex]

It's not the app "reading" the voltage, it's the OBD2 adapter with a volt meter (A-D converter). It's likely cheap Chinese and gives a rough reading. The the app connects to the adapter and displays what the adapter thinks.

I would trust the voltmeter long before I trust the adapter.

 

[TheDurk]

It's not the app "reading" the voltage, it's the OBD2 adapter with a volt meter (A-D converter). It's likely cheap Chinese and gives a rough reading. The the app connects to the adapter and displays what the adapter thinks.

I would trust the voltmeter long before I trust the adapter.

That's not at all how it works. The adapter has no A-D converter and no voltmeter. It takes PIDs (defined digital values) from the ECM over the OBDII interface and transmits the exact same digital value over BT. Period. If the reading is off, it's the ECM's fault, or it's somehow the nature of circuitry the ECM sees.

Try seventeen adapters, cheap or not, and I bet you get seventeen identical readings.

 

[Brian3676]

Test voltage at the ECU, it will be about the same as the torque app. There is a voltage drop between ECU and battery. The batter is basically the first thing to see fresh power from the alt. Anything past the battery will never read the same as the battery due to the voltage drop. All cars/electronics are like this. To help, some upgrade the wire to bigger gauge. Hence the common and popular "big 3" upgrade you may hear of.

 

[gamefreakgc]

Yes and yes. An OBD reader isn't taking voltage from the battery, rather from the ECU. There will be a drop because of resistance with wires, connectors, and relays along the way. They will all be about the same but the only way to truly test the battery is with a voltmeter on the battery terminals, ruling out all other electrical components.

The only reason an OBD reader would read a low voltage is if your alternator was failing and not giving the ECU enough juice. But I think your engine would shut off shortly after that!

 

[mtbtim]

Test voltage at the ECU, it will be about the same as the torque app. There is a voltage drop between ECU and battery. The batter is basically the first thing to see fresh power from the alt. Anything past the battery will never read the same as the battery due to the voltage drop. All cars/electronics are like this. To help, some upgrade the wire to bigger gauge. Hence the common and popular "big 3" upgrade you may hear of.

If this is the case, why was I able to do an alternator test with my Innova OBD II reader and get a similar value as I got when I had O'Reilly test my charging system via connecting directly to the battery terminals? At O'Reilly they told me my charging system was putting out 13.8 volts. Via the my OBD II reader, it showed 13.9 volts. That comparison showed me the values from the two different locations is pretty darn close.

 

[TheDurk]

If this is the case, why was I able to do an alternator test with my Innova OBD II reader and get a similar value as I got when I had O'Reilly test my charging system via connecting directly to the battery terminals? At O'Reilly they told me my charging system was putting out 13.8 volts. Via the my OBD II reader, it showed 13.9 volts. That comparison showed me the values from the two different locations is pretty darn close.

Because the voltage drop (when the alternator is charging) is not from the battery to the ECU at all. It's from the alternator to the battery and from the alternator to the ECU. The alternator wiring goes first to the fuse box and then to the battery. The ECU takes its power through the EFI fuse in the same box. So the difference in voltage drop from the alternator between the two is in the differnce in the wires from the fuse box to the battery and the fuse box to the ECU. Maybe two feet difference max, or eight vs. ten. Not going to amount to much, probably less than the error inherent in the two measurement systems.