battery ??'s
Fleet Mechanic
Joined: Feb 2007
Posts: 1,652
Likes: 79
From: Mooresville, NC
I'd shut everything off, pull the NEG cable and insert a DVM between the cable and the NEG battery term post to see what (if any) current pull is going on........
Set DVM to DC current, Amps (or milli, micro Amps if your DVM provides for those readings)
Connect the COM lead of the DVM to the disconnected NEG cable
Connect the A (amps or smaller) lead to the NEG battery term post
.......again, if your DVM goes smaller than A, I'd recommend it vice A (you want the smallest scale possible)
Small/imperceptible current pull is normal (particularly on newer vehicles) but yours should be non-existent (provided you have no "fancy" electronics sitting out on the harness.....
Postmaster
Joined: Nov 2011
Posts: 3,533
Likes: 17
From: SW Florida
Yeah check the standby current draw as mentioned above. A fully charged battery should provide 12.6V, BUT that is for lead acid batteries, which normally provide 2.1V per cell. An Optima uses a gel type thing and may be slightly different.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
The voltage across the terminals will decrease after charging, and increase or "bounce back" after discharging; in fact that's why the "surface charge" must be removed prior to testing. Letting the battery sit overnight is one way, A quick method is to (engine off) turn the headlights on for five minutes, wait ten minutes, then measure. This is the OCV or open circuit voltage of the battery and an accurate indication of the state of charge, provided the voltage is compensated for the temperature.
You'll have to dig around and find out what exactly an Optima battery state of charge is, they are different. A few tenths of a volt doesn't sound like much, but on a percentage basis it is huge. Consider that 12.6 volts is a fully charged lead acid battery, and 12.0 is 25% charged and the engine may well not turn over. Optimas are probably a higher OCV, but I don't know. Give the battery what it wants or you're wasting your money.
Wouldn't worry about the second digit. You should measure for current draw just to make sure. About 50 milliamps is considered OK for modern vehicles.
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Elder User
Joined: Nov 2010
Posts: 731
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From: Ocean County, NJ
i dont know squat about electrical, i'm an idiot. Black lead of dvm goes to neg cable, red lead goes to neg post ? what do i set the meter at ? Innova 3320 https://www.equus.com/Support/Manual
Fleet Mechanic
Joined: Feb 2007
Posts: 1,652
Likes: 79
From: Mooresville, NC
i dont know squat about electrical, i'm an idiot. Black lead of dvm goes to neg cable, red lead goes to neg post ? what do i set the meter at ? Innova 3320 https://www.equus.com/Support/Manual
Set your 3320 to DC mA
3320 auto ranging should automatically go to the lowest scale
Read current draw figure
By the way the 3320 is 1/20th the cost of the Fluke 88 Automotive DVMs I have in the shop and is a decent value
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Elder User
Joined: Nov 2010
Posts: 731
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From: Ocean County, NJ
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Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
With a conventional DVM, has to be connected in series with a battery cable and battery post to measure current draw. Modern vehicles, too, take a half hour or better for all the bells and whistles to go into "sleep" mode after shutdown. There are some good YT instructional videos for this if you want to learn, as parasitic draw has become much more of a problem in recent years. Tons of websites too, on troubleshooting with a DVM.
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Elder User
Joined: Nov 2010
Posts: 731
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From: Ocean County, NJ
thx guys. the red top is good. It only dropped to 12.51, an has stayed for a few days now. Neg wires were alittle corroded an lost .5 v.
the original battery was the problem.
the original battery was the problem.
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