Weird results on a battery drain test

[ausgezeichnet]

I just installed a new redtop optima battery. It and started the car fine. I let it sit for about 3-4 weeks and the battery had dropped to 5-6 volts.

Recharged the battery disconnected the charger and now it reads 12.99 volts.

Removed the negative battery cable got distracted for about 45 min went back and inserted my mutlimeter between the negative battery cable and the negative post on the battery and I get a reading of 12.81 volts. I immediately check the voltage between the two posts on the battery and I also get 12.81 volts.

I wait about 10 minutes do both tests again and I get a reading of 12.65 volts.

Should I be testing Amperage when I insert my multimeter between the neg battey cable and post instead of voltage?

Why would the Voltage drop from 12.99 to 12.65 in about one hour with just the postive battery cable connected.

[ausgezeichnet]

Did a little more digging and confirmed I need to test for amperage draw.

I am getting a drain of .086 A.

Pulled all the fuses and only fuse 17 made the drain drop to .064 A.

Since I was never able to get the drain to 0, I cheeked the positive battery cable and there is another smaller gauge wire attached to it. I think this powers the radio/CD changer which is where I think the rest of the draw is coming from. Does this make sense.

Is .087 A drain some thing to worry about or should I just keep a battery tender on it when it sits for a while?

[911pcars]

Seems like this connection is the same as checking open circuit at the battery post. If any circuit is operational (clock, radio preset, etc.), the VM will read voltage drop. In this case, it's the same as the open circuit reading. I think I'm correct in this regard.

It may be there's an internal short inside the battery that causing the open circuit voltage to decrease. The battery must produce at least 9 volts while cranking, otherwise the engine won't crank. Take it to an auto electric shop and have the battery checked. It may be faulty, in which case Optima should provide a free replacement.

Sherwood

[ovilla]

Could be the battery. I bought a new red top about a month ago and on the second day the thing was dead. Took it back to the FLAPS and they charged it and put it through their load tester, which confirmed that there was a dead cell. Anyway, just a thought.

[RoninLB]

Originally posted by ausgezeichnet

Recharged the battery disconnected the charger and now it reads 12.99 volts.

Why would the Voltage drop from 12.99 to 12.65 in about one hour with just the postive battery cable connected.

it's called surface voltage on the plates. After a recharge I turn the headlights on for 20-40sec to disapate it then take a reading.

[ianc]

Is .087 A drain some thing to worry about

Clock?

ianc

[Wil Ferch]

Spec "standby" draw for an 84 is about 16 milli-amps ( 16mA)..or 0.016 Amps.

You're "over" by a factor of 5 or 6.

Wil

[ausgezeichnet]

Thanks for all the feed back.

I kept the neg battery cable off over night and I still have votage of 12.70 which probally means the inital drop was what RonninLB reffered to as surface voltage.

If I add up hthe drain for the clock, "standby" and radio/cd changer, I've probally accounted for all of the drain. I noticed my radio/cd operates with the ignition off. Can someone reccomend a good circut to wire this into so it only operates when the key is on?

[cstreit]

Chargers often run at 13-14 volts, but the batteries are built to hold 12-13... So some drop after charging is normal... If it drops below 12 after a few days of sitting, then you should worry...

[88911coupe]

My battery seems to be having some trouble but it may just be due to the fact that it was on a trickle charge for about a year. HOWEVER, I'd like to make sure there is not some paratitic draw and have a dumb question regarding how to use my multimeter to check this. Can someone tell me what setting I need to use to test the current draw between the neg. terminal and the neg. cable? I don't want to damage anything. I noticed that the battery had dropped to something like 7 over a few days but I THINK this may have been due to a funky power window switch. After I recharged the batter it's started the car fine for the last few days. Still, I notice the charge (battery in car) has gone from 12.9 or so down to 12.6 or so in about a day. I had the alternator rebuilt prior to installation and notice I'm only getting about 13.9 with the engine running and I've read it should be in the low 14's to indicate it's working properly.
TIA

[911pcars]

13.9 charging volts is borderline okay depending on the typical vehicle accessory load when you drive the car (A/C ON, radio/CD, headlights/taillights, A/C, cooling fans, electric fuel pump, windshield wipers, etc.). Check voltage with all accessories ON. The alternator should supply all the voltage needed to operate the vehicle + recharge the battery (or prevent it from discharging). The charge light usually indicates charge status.

With engine OFF, battery voltage should remain around high 12 volt range.

To check parasitic current drain with engine OFF, check the archives for the complete connection of the ammeter to the battery.

Sherwood

[rattlsnak]

Originally Posted by Wil Ferch

Spec "standby" draw for an 84 is about 16 milli-amps ( 16mA)..or 0.016 Amps.

You're "over" by a factor of 5 or 6.

Wil

exactly.. something is causing the extra drain.

[88911coupe]

I got 13.9 with nothing on, even the radio was off so maybe it's okay. I'll try it again with accessories on. I've checked the archives and have seen several references to "hook up an ammeter" between the neg. term and the cable. I guess I'm confused about terminology, does my multimeter have this function of is an ammeter a separate device? Also, if the multimeter will work for this test which setting do I use on the dial for the MM?

[911pcars]

Originally Posted by 88911coupe

I got 13.9 with nothing on, even the radio was off so maybe it's okay. I'll try it again with accessories on. I've checked the archives and have seen several references to "hook up an ammeter" between the neg. term and the cable. I guess I'm confused about terminology, does my multimeter have this function of is an ammeter a separate device? Also, if the multimeter will work for this test which setting do I use on the dial for the MM?

Yes, try monitoring charge voltage with many accessories ON.

The connection description is accurate. Your MM should be on the current measuring mode (ammeter), set to measure the highest range at first (typically 10A). If the meter is auto-ranging, the meter will automatically read the actual current. If not, you must set the meter controls to read the current range that's most readable for diagnosing.

Hope this brief description helps,
Sherwood

[HawgRyder]

As far as I know...every type of battery ever made will go dead in a certain length of time.
Has something to do with the magnetic lines of force on the planet or something similar.
I do know that the direction of posts of the battery will delay that event.
In the military, we were instructed to store long term batteries oriented across the N - S lines of the magnetic poles (in other words...plates of the battery E - W)
With the Optima being a circular type of cell, I dont see that you could do anything to help.
My take would be to install a plug in parallel to the post of the battery and mount this small plug under the bumper or out of the way place so that you could put a trickle charger on when parked.
The reason I say under the bumper is if you forget to disconnect before driving away, the plug will pull out by itself.
Not the best solution, but a no-brainer for most ppl.
Bob

[88911coupe]

Sherwood, that's what I was looking for. Thanks.