Battery drain test

[joshwilson3]

I just got an AC Delco 60 series group 75 battery for my 89 Vette. I figured it would be a good time to do a battery drain test.

I then connected my multimeter in series with the negative, and then also did the positive as well. And the draw was at .14 milliamps. So, I figured that was good.

I had an Autozone test light I figured I would also use to test. I checked it out across the battery to make sure the bulb lit up. Then I did the drain test, connected one lead to the positive wire, and the other lead to the positive pole on the battery.

Well, the bulb lit up. It wasn't dim at all, but just slighty less than when I had it hooked up to the battery. I then pulled my meter out, and it was still measuring .14 milliamps. I figured at that figure the bulb shouldn't be liting up?

So, I pulled all the fuses in the fuse box. The bulb still lit up and I was still getting the same .14 milliamps drain. So, I then disconnected the alternator with no change.

So, does it sound like something is wrong with the test? I did notice that when I hook the battery up, the inside lights come on. I don't know if that is supposed to happen. But the thing is, when I connect the test light or meter in series to one of the cables, the inside lights don't come on.

 

[joshwilson3]

Ok, I think my multimeter must not be working well on the milliamps. I went and checked my 89 firebird. It read .13 or .14 milliamps. And the test light DID NOT light up.

I went back to the Vette, and it was still reading .14 milliamps and the test light turned on. So, I think .14 is too low a reading to be correct, especially with the test light coming on.

So, I went out and pulled ALL of the fuses at once. The meter still read .14 milliamps. And then I checked it with the test light. The test light flickered one time, I heard a click, then the light went out and stayed out.

So, I started putting fuses in one at a time and checking the test light. The light ended up coming on when I put in the check/courtesy fuse. I then pulled that fuse back out and started putting in the rest of the fuses one at a time. And then the light turned on again when I put in the LCD fuse.

So, it looks like the battery drain has something to do with something associated with the check/courtesy and the LCD fuse. Any ideas?

 

[vetteoz]

I recall there are some direct feeds that do not go through the fuses.You have to tape up the door switches when doing the drain test

 

[93Rubie]

First off, you WILL NEVER get rid of battery drain if unless you disconnect your battery.

Your many modules in the car PCM, ABS, BCM, etc...always draw some voltage from the battery this is called parasitic draw. As long as it is under 50 milliamps you are ok, many Cadillacs have close to 50 milliamps. I am guessing the Vette is higher as well, as we have many on board modules.

Hope this helps. If your concern is to keep the battery charged up during storage I recommend a battery tender/trickle charger to keep voltage in spec. this also keeps your Keep Alive Memory...well Alive. That stores things like Fuel Trims, operating conditons, etc...things that are learned by the car over time. Depending on if your ride is OBDII or not will determine just how much the car "learns" over time.

 

[joshwilson3]

First off, you WILL NEVER get rid of battery drain if unless you disconnect your battery.

Your many modules in the car PCM, ABS, BCM, etc...always draw some voltage from the battery this is called parasitic draw. As long as it is under 50 milliamps you are ok, many Cadillacs have close to 50 milliamps. I am guessing the Vette is higher as well, as we have many on board modules.

Hope this helps. If your concern is to keep the battery charged up during storage I recommend a battery tender/trickle charger to keep voltage in spec. this also keeps your Keep Alive Memory...well Alive. That stores things like Fuel Trims, operating conditons, etc...things that are learned by the car over time. Depending on if your ride is OBDII or not will determine just how much the car "learns" over time.

I know it's gonna have a drain on it. My concern was that my meter was reading .14 milliamps, and the test light would light up. I still think .14 milliamps is too low, so I think there is either something wrong or my meter is screwy in the amps setting. As I figured when I unplugged the radio, the drain should go down, but it always reads .14 milliamps.

And when I tested my 89 Firebird, it read .13 or .14 milliamps, but the test light DID NOT light up. So, something is causing the test light to turn on with the Vette, but the Firebird isn't drawing enough to turn the test light on.

I can't do one of those trickle charges as my car sits outside. Unless I want to remove the battery and reinstall it all the time. I guess I may just go get a different multimeter and recheck it to see if I get a different milliamps reading, but I figured I should have around 20 milliamps or so, not .14 milliamps with the test light turning on.

 

[joshwilson3]

I recall there are some direct feeds that do not go through the fuses.You have to tape up the door switches when doing the drain test

Are you talking about the door switches by the dash under the Windlace? I've never read that before. Why do you need to tape them? With the battery connected, when I shut the door the inside lights go out. So, shouldn't those switches be out of the circuit with the doors shuts?

And when I tested my Firebird, the test light didn't turn on and I didn't do anything special with the door switches.

 

[93Rubie]

Is your meter manual ranging or automatic?
If it is manual make sure you have it setup properly.
I reread your post, and it sounds like have your wires setup right, as long as everything is in series, your test should be ok.

 

[Newfydad]

It is automatic and it is digital. I'm gonna test my dads Yukon and see if I still get a .14 milliamps. If the third car gives me around .14 milliamps then I'm gonna get a different meter. I still think I should be getting around 20 milliamps. The thing I thought is weird is that when I disconnected the radio, there was no change in the drain. Plus, that light bulb was shinning bright, almost as bright as when I connected both leads of the test light to the battery.

Here is my meter. I got it at Walmart in the automotive section:

Either the meter is broken or you are reading it incorrectly. I suspect the meter. The reading of .14 milliamps is 140 microamps which, as you know, is nothing. I would suggest opening your meter and have a look at the fuse. I cant see your picture clearly enough, but most digital meters in that price range have an unfused 10 amp input/scale and also a fused 'milliamp' input/scale with a maximum input of somewhere around 200 or 250 milliamps. It is probable that you blew the fuse and the 140 microamp reading is just some kind of residual reading the meter is picking up out of the air. The internal meter fuse is very fine so unless you have really good eyes, you should just replace the fuse or give it a continuity test.

Good luck
Rod

 

[Newfydad]

I forgot to mention, when measuring current: as long as you are fairly certain the current will be less than 10 amps (much more than 10 amps will probably burn out your meter as that input is usually un-fused), it is good practice to measure on the 10 amp scale first. Then if the current is very small, you can go to the 'milliamp' scale if necessary. It prevents confusion and mistakes caused by a blown internal meter fuse.

 

[joshwilson3]

I forgot to mention, when measuring current: as long as you are fairly certain the current will be less than 10 amps (much more than 10 amps will probably burn out your meter as that input is usually un-fused), it is good practice to measure on the 10 amp scale first. Then if the current is very small, you can go to the 'milliamp' scale if necessary. It prevents confusion and mistakes caused by a blown internal meter fuse.

Yeah, my meter has an unfused setting, and a fused 10amp setting I believe. I had used the unfused setting when I was testing first, then I did the fused setting and got the same reading for both.

I popped it open and pulled the fuse. I think it is blown for some reason as yesterday was the first time I put the red lead on the fused port. The line inside the fuse was laying on the glass, and looked like I could see the end of the line. I took my meter and did a continuity test, and it failed. I also did an ohm test to see if I could get a reading, and nothing showed up on the meter.

So, I'll replace the fuse, and recheck on the fused setting. Though, since I was first testing on the unfused milliamp setting, shouldn't that have bypassed the fuse?

 

[Newfydad]

No, I think you have it backwards. Unless your meter is an oddball, the 10 amp configuration is UNFUSED and the 'milliamps' is FUSED. If you used the 'milliamp' configuration and the current was more than about 250 milliamps, it probably blew the fuse right away without you even knowing it. I'm guessing its a 250 mA (1/4 amp) fuse.
=================================================

Yeah, my meter has an unfused setting, and a fused 10amp setting I believe. I had used the unfused setting when I was testing first, then I did the fused setting and got the same reading for both.

I popped it open and pulled the fuse. I think it is blown for some reason as yesterday was the first time I put the red lead on the fused port. The line inside the fuse was laying on the glass, and looked like I could see the end of the line. I took my meter and did a continuity test, and it failed. I also did an ohm test to see if I could get a reading, and nothing showed up on the meter.

So, I'll replace the fuse, and recheck on the fused setting. Though, since I was first testing on the unfused milliamp setting, shouldn't that have bypassed the fuse?

 

[joshwilson3]

No, I think you have it backwards. Unless your meter is an oddball, the 10 amp configuration is UNFUSED and the 'milliamps' is FUSED. If you used the 'milliamp' configuration and the current was more than about 250 milliamps, it probably blew the fuse right away without you even knowing it. I'm guessing its a 250 mA (1/4 amp) fuse.
=================================================

You could be correct. I don't know a whole lot about these things.

This is the fuse: 315mA/250V 5X20 mm

Here is the instruction manual: http://www.equus.com/downloads/manuals/93-0041.pdf

If it is not raining tommorrow, I'll get a new fuse and then recheck it on the DC10A setting first and see what that does.

Thanks

 

[navy2kcoupe]

Sounds as if there's enuf current there to light the test light when it's in series with either the
positive or negative lead of the battery. That's gotta be enough current right there to blow
the fuse on the lower setting........
Andy

 

[navy2kcoupe]

Depends on the type of bulb used. I usually use an old brake light socket with the brake light bulb installed. If you have the fuse out of the meter, look on the metal ends of it and see what the numbers (if any) say. That should tell you the size (current rating) of the fuse and you'll at least know how much current it will take to blow it. As for the meter and fuse, it's entirely possible that the fuse is only for the low current measuring portion. Back in the day when the meters were analog,the fuse was placed in there so that the windings of the meter movement wouldn't become "the fuse". Puting too much current thru the meter windings would cause the windings to "blow" and that required replacing the meter. Fuses are DEFINITELY cheaper!
Andy

 

[joshwilson3]

Depends on the type of bulb used. I usually use an old brake light socket with the brake light bulb installed. If you have the fuse out of the meter, look on the metal ends of it and see what the numbers (if any) say. That should tell you the size (current rating) of the fuse and you'll at least know how much current it will take to blow it. As for the meter and fuse, it's entirely possible that the fuse is only for the low current measuring portion. Back in the day when the meters were analog,the fuse was placed in there so that the windings of the meter movement wouldn't become "the fuse". Puting too much current thru the meter windings would cause the windings to "blow" and that required replacing the meter. Fuses are DEFINITELY cheaper!
Andy

The fuse is rated at 315 mA. So, if the drain is over 300 mA, then I say I'm screwed as I believe it should be 50 mA or less. Though, the fuse could of gotten blown in the past as I've had it for a while.

I'll replace the fuse and recheck on the DC10A setting and see what that does. I'm really hoping the draw isn't alot, cause that would mean just another thing I'll have to figure out before winter. I know there is draw on the check/courtesy and LCD fuse with regards to my test light. On the Firebird, the test light didn't light up.