Why is my battery gauge showing dropped voltage while a DMM isn't?

[justafifteen 10+ year member]

I was cruising around town the other night, bumping a song that really doesn't bump that hard compared to my demo songs. Well, my battery gauge was dropping whenever the bass hit, almost down to the 12v mark (where it sits when you turn the ignition to Accessory).

This is the first time that I've ever seen the battery gauge do this -- I seriously have almost no voltage drop in this car. I can be putting on a demo at night with my headlights on and they won't dim.

Yesterday I decide to bust out my DMM, and test my voltage. Reads 12.65 with the car off, 14.00 sharp with the car on. I put on my heaviest demo song, and it goes down to 13.7. With the headlights on, it goes down to 13.6. Not bad at all, right?

So, is something wrong with my gauge? It's an older car and the tachometer bumps around just from the vibrations, but the battery gauge has never done that.

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[Falcons 5,000+ posts]

if your lights dont dim or anything then your gauge's wires might be bad

 

[sacsking916 5,000+ posts]

I got the same problem. Not 100% sure I figured it out. Mine is the stinger voltmeter and will show mid 12s while driving while the dmm shows 14+. While driving with the system on it was saying 12s but with the dmm hooked up it was barely dropping into 13s.

 

[Chriszle 10+ year member]

Are the voltmeter and dmm hooked up at the same spot when doing these tests?

 

[pieper88 10+ year member]

I got the same problem. Not 100% sure I figured it out. Mine is the stinger voltmeter and will show mid 12s while driving while the dmm shows 14+. While driving with the system on it was saying 12s but with the dmm hooked up it was barely dropping into 13s.

Stinger voltmeters need to be calibrated to your DMM. Theres is a little dial you turn with a screwdriver to adjust it.

 

[Falcons 5,000+ posts]

Stinger voltmeters need to be calibrated to your DMM. Theres is a little dial you turn with a screwdriver to adjust it.

oh yeah i heard about that good job lol

 

[sacsking916 5,000+ posts]

Stinger voltmeters need to be calibrated to your DMM. Theres is a little dial you turn with a screwdriver to adjust it.

It was adjusted when I installed it. Before Saturday I would get 14.3 while driving and all that good stuff. My problem has only been within the last 3 days. But thank you for reminding me about it. I guess I could recheck it.

 

[justafifteen 10+ year member]

Are the voltmeter and dmm hooked up at the same spot when doing these tests?

What voltmeter? I'm talking about the battery gauge in my dash, next to the tach and oil pressure gauges. My DMM is hooked to my battery

The battery gauge wasn't doing it today. It might've just been a quirk, but I'm going to keep an eye on it. I thought my alternator was going bad or something at first

 

[Boomsday 10+ year member]

Install fresh batts in ur dmm, it could be that easy

 

[justafifteen 10+ year member]

Install fresh batts in ur dmm, it could be that easy

Could you explain the reasoning behind this?

Caught the gauge doing it again the other day. I was playing "Lost" by Gorilla Zoe, which as you may know, has pretty long bass lines, not quick punchy ones. Well while the bass was playing, I saw the gauge -- it was doing a heartbeat kind of thing. It'd be at the normal 14v part, and then go down a little bit, but then right back. It looked like a heartbeat (which makes no sense because of the long bass lines I had mentioned). 14v, drop down a little bit, then right back up to 14v -- pause -- repeat