Battery question

[James Morse]

09 Rabbit. Diehard battery. 12.6V sitting, 14.2V running. Is that normal or should sitting V be higher?
It de-charges after sitting for, let's say, a couple/3/4 weeks, and seems like unless there's draw somewhere it shouldn't (?) You have clock, a bunch of stuff but that's low draw it seems like it should last longer.
12.6V after trickle charging all night. Might charge higher after driving but kind of doubt it. Trying to keep this vehicle going while her old Lexus getting fixed and just wondering if I'm seeing reasonable numbers and battery probably ok and it just discharges from sitting so long, but, seems like it should last at least a month sitting but maybe I'm wrong.

 

[fastpakr]

You can use a volt meter to chase down the source of the parasitic drain.

 

[James Morse]

Voltmeter - and? Test where, the fuse box and ground?

So you think it's draining too fast. Seems to me, battery should be good to start the engine for 6 mos or something. Cars sit on lots all the time for months.

Wires to hatch are broke per usual on these. I don't think that affects it, just mentioning in case it does. Vehicle hasn't been a high priority, the broke wires stop hatch auto-open, fuel door, and wiper so you do kind of want them.

It's always something isn't it.

 

[fastpakr]

It shouldn't be draining down quickly to the point that it won't start (assuming the battery is in good condition).

If you've got a meter, try this:

How to Find and Fix a Parasitic Battery Drain

Quick, simple, and it works! In less than 5 minutes, we show you how to find a parasitic battery drain. Find out what's killing your battery.

shoptoolreviews.com

 

[don4331]

I thought garlic was what you used to address vampire drains

 

[James Morse]

thanks

 

[James Morse]

I have only old Beckman voltmeter. Seems like this (below) would be good. Not the cheapest multi I can get, but, the included stuff is good to have. Or you can get just the multi.
Kobalt 10 Amp 50-1000-Volt Digital Specialty Meter (Battery Included) in the Test Meters department at Lowes.com

 

[fastpakr]

The Beckman meter won't do the trick?

 

[RonD]

You need to test Battery's "at rest" voltage after it has been sitting over night or at least 6 hours without being charged

12.8v is a newer battery
12.5v is a 3 year old battery
12.3v is a 5/6 year old battery and time to shop for battery sales

12.2v is 50% and goes down after that
So done battery

Car batteries are sold with a CCR(cold cranking amp) Rating
To get Amp Hour Rating multiply CCR by 0.7
So 600CCR x 0.7 = 420 amp hours

So 1 amp draw for 420 hours(17 days) would have a TOTALLY DEAD battery
A battery won't crank engine over below 50%
So 8.5 days before a no crank

Most vehicles now a days have an "all off" draw of 0.07 amps, thats with keyless entry which needs to be on 24/7
420AH / 0.07amp = 6,000hours(250 days)
Or 125 days for 50%, about 4-5 months

So better to unhook a battery that will be sitting longer than 3 months


To test battery, do this first before trying to chase down a drain
After battery has been sitting 6+ hours, unhook 1 cable, test voltage, write it down
Come back 6+ hours later(longer the better) and retest battery, should be EXACTLY the same volts, if its less the battery has an internal short, self draining, this is the usual end-of-life for most car batteries
If this is true then vehicle probably has no extra drain, battery is the issue

If battery voltage stays the same then you do have a voltage drain in the vehicle system

Alternators run vehicle electric system at minimum of 13.5volts up to 14.8volts
14.8volts just after start up to Fast Charge the battery
Then after a few minutes it will start to drop down to under 14volts, 13.8v is average
But 14.2v is OK, might be a sign battery is getting older, or just the way the charging system works on that vehicle

 

[Curious Hound]

There is a remote possibility that the broken wires are a problem. If the car doesn't see the hatch closed, it might not put all the electronic modules to sleep. But I'm not an expert on that vehicle.

 

[James Morse]

Beckman unit just has AC volts, DV volts, resistance, and continuity. No amps.
Thanks for the link and for the test procedure. this is great and I will follow.
Before I start chasing drain first I find out battery status just sitting unconnected, does it still degrade.
Thank you everyone.

 

[James Morse]

12.02V with cable off battery. That's low, I know, but still, if battery is good, and I test in 6 hrs, it should read the same.
Wish battery had a date. I normally keep records for my stuff so I'd know, hers, I dunno. I'd be willing to bet it's just an old battery going or gone bad.

 

[RonD]

Its a bad battery, find a battery sale

You said it showed 12.6v after charging, "12.6V after trickle charging all night"
and now 12.02v..........................

 

[James Morse]

Exactly. There could still be drain, but, to me looks like battery just refuses to hold a charge any reasonable amount of time.
I'm still checking it at 7PM just to see, but, I think you've pinpointed the problem. Thanks.

 

[fastpakr]

What's the date on the battery?