battery voltage questions
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battery voltage questions
I have been monitoring my battery voltages, and now I have questions...
I have an analog voltmeter and the Scangauge display, plus a DVM that I use directly on the batteries. The battery voltage is always a tenth or two higher than what the Scangauge or the analog meter reads. The analog meter (it's a high end Autometer computer controlled gauge) is tied into the white wire that is part of the ODBII bundle, it is ignition key controlled.
My batteries are of indeterminate age. They are resting at 12.7 volts after sitting overnight, which I would normally say is an excellent resting voltage indicating a full state of charge. When I turn the key on for a cold start, KOEO voltage drops to 11.9. After starting, voltage goes up to 12.3. After a minute or two, voltage goes to 13.3 - 13.5 when the alternator starts charging. After driving for a long time, voltage gradually climbs to around 13.8/9 or so.
The only other voltage I can really monitor is FICM, which is normally at 49 volts.
What do you think?
Brian
I have an analog voltmeter and the Scangauge display, plus a DVM that I use directly on the batteries. The battery voltage is always a tenth or two higher than what the Scangauge or the analog meter reads. The analog meter (it's a high end Autometer computer controlled gauge) is tied into the white wire that is part of the ODBII bundle, it is ignition key controlled.
My batteries are of indeterminate age. They are resting at 12.7 volts after sitting overnight, which I would normally say is an excellent resting voltage indicating a full state of charge. When I turn the key on for a cold start, KOEO voltage drops to 11.9. After starting, voltage goes up to 12.3. After a minute or two, voltage goes to 13.3 - 13.5 when the alternator starts charging. After driving for a long time, voltage gradually climbs to around 13.8/9 or so.
The only other voltage I can really monitor is FICM, which is normally at 49 volts.
What do you think?
Brian
Senior User
Joined: Sep 2010
Posts: 306
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From: Southwest Desert, AZ
Gauge of wire and length could cause a slight voltage drop, although you aren't loading it the scangauge, you're just monitoring it. Glow plugs stay on for 2 minutes after starting. Mine does the exact same thing. Voltage at 13.3/13.5 while crusing. Just for peace of mind, I've installed an onboard battery charger and always keep it plugged in unless driving it obviously(makes for a hell of an extesion cord otherwise). I live in the Sonaran desert and the heat is really hard on batteries. Your's seems normal to me.
My $0.02 worth.
My $0.02 worth.
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Joined: Apr 2012
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From: Orlando, FL
Sounds about normal. Contrary to popular belief wires are not a true short between 2 points. There is a small amount of resistance. This is determined by three main things.
1, Material (Copper commonly used as are aluminum and gold)
2. Guage of Material (How thick the wire is)
3. Length of Wire.
If is why most people have to use video amps for runs over 50 feet.
1, Material (Copper commonly used as are aluminum and gold)
2. Guage of Material (How thick the wire is)
3. Length of Wire.
If is why most people have to use video amps for runs over 50 feet.
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well, there must be some serious loading going on to pull the batteries down that much, but glow plugs and exercising the injectors would account for that. I actually found the date codes on the batteries today - they are 2006 date codes, still hanging tough! I have good luck with batteries some times, I have a Dodge Ram with the original batteries from 2003, still perfect... take a charge fine, and start the truck after 4 - 6 weeks no problem.
Brian
Brian
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Joined: Oct 2006
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From: Francestown, NH
+1. Those numbers look normal and what you want.
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