Battery Draw - Need Advice on What Meter Numbers Mean

[jb3t]

So I'm no electrician but I know a little bit. Here's the deal...

My battery is drawing down and killing my battery over about 5 days. So today I pulled out the multimeter, set it to "10", and connected it to the battery and battery lead. This is what the results were:

- With no fuses pulled, I had a 0.02 draw.
- With no fuses pulled and the door open, I had a 1.01 draw.
- When I pulled the ACC fuse, I had a 0.01 draw.
- When I pulled all other fuses, I still had the 0.01 draw.
- When I disconnected the radio with all fuses in, I had a 0.01 (radio does not work)

Can you guys tell me if the 0.02 is enough to draw down the battery over 5 days? Also, what is the 0.02 and what is is equal to in volts?

I need to hit wikipedia to learn the difference between amps, watts, volts, ohms.

Thanks

[Bigstevex4]

No that's nothing most modern cars pull at least0.05. how old battery

[jb3t]

Originally Posted by Bigstevex4

No that's nothing most modern cars pull at least0.05. how old battery

Battery is very new. Alternator is new.

[Bigstevex4]

Did you try un hooking it see if it keeps charge

[Oldriginal86]

Your battery needs to be at or close to full charge to get accurate voltages during diagnosing draw issues.

[86c20]

start with checking the alt out put. then check batt volt. as far as you readings go if they are right and you did an amp draw that is dead on.

[jb3t]

Battery is fully charged. Also, if I disconnect the battery cable, it works fine. Fires right up.

Can you guys tell me what the 0.02 is? 0.02 Amps?

I will try the alternator thing, though it's brand new.

What's interesting is that I was going through the old records (I just bought the truck and it's been one owner). Looks like it's had this problem for years. Looks like they brought it in a few times with this issue.

[rich weyand]

Quickie on electricity. Think of electric circuits like a garden hose. VOLTS is the pressure of the water. 13.2 volts at the battery is like 50 PSI on a water tap on the house. AMPS is the current, or flow, like gallons per minute through a garden hose. OHMS is the resistance to flow. Smaller hose (smaller wire) more resistance and less flow, big hose (bigger wire) less resistance and more flow. WATTS is amps * volts, and is the amount of work being done.

.02 on a current reading is 20 milliamps, or 20/1000 of an amp. This is the current through a single LED, like a security alarm LED on the dash. Ain't nothin'.

Headlights, when people leave them on, pull about 10 amps, or 60 watts per bulb. 60 watts divided by 12 volt system is 5 amps per bulb.

A battery stores typically 80 amp-hours at 12 volts (nominal; usually reads 13 and change). So, leave your headlights on for 8 hours while you are at work, come out and the battery is dead. 8 hours x 10 amps = 80 amp-hours: that's all the battery had.

.02 amps (20 milliamps) should take something like 4000 hours to drain a battery, or about 5 months. Which is why it pays to disconnect the battery if you will park a vehicle over the winter, because even a single LED on a security alarm or stereo will drain the battery flat.

To drain a battery in 5 days (120 hours), you are looking for a current in the .7 amp range, 35 times bigger than .02.

Reading the adjacent thread, yeah, a trailer brake controller could do that if it was hooked up to the battery (constant on) instead of to the ignition (on only with key).

[jb3t]

Originally Posted by rich weyand

Reading the adjacent thread, yeah, a trailer brake controller could do that if it was hooked up to the battery (constant on) instead of to the ignition (on only with key).

Thanks for the lesson. As I work in the water engineering industry, I fully understand the garden hose analogy. My dad was an electrical engineer but it never 100% stuck with me.

Per the above quote... Regardless, I am at 0.01 with nothing on. I'm scratching my head as I actually pulled every fuse and still had a little draw (0.01). However, based in what you guys said, that's completely normal. Maybe the battery is defective. I'll keep an eye on it.

Regarding the trailer break contraption on my inner fender, I am curious if I can test electrical draw there, I used the meter on the doohickey and nothing.

[franken]

To check current, the battery cable needs to be disconnected, the meter connected to the cable, and battery terminal. The DVM has to be set to DC current, 10A (until you find the current is under 300mA or whatever the lower setting is), and the meter wire plugged into the right port.
Lots of people open the circuit and measure voltage but that's not the way things are done. As Rich explained, you want to measure flow/current/Amps.
The OP needs to explain how and what he's measuring, how the meter is set up and where he's measuring. Numbers without units are meaningless... That said, I'd guess he's got things set up right since the numbers are so low...

[jb3t]

Got my digital multimeter set to 10 amps DC. Hot cable off battery. Red multimeter lead to battery, black to the disconnected cable. Drawing 0.02. With door open (and one light on), it's 1.02. Pull the ACC fuse and I'm 0.01.

My question was answered… I was wondering if that 0.02 is a significant draw. Appears the answer is no.

I am also wondering about my units on measure. if they are OKAY.

[86c20]

you know now that i think about this i have had a problem with my c20 like this a few times. i checked everythign i could and everything was fine what i found was the tumbler would not return all the way some times so the coil was hot at all times.

also if you disconnect the batt for a week and it is fine when you try it that would rule that batt out.

also on my ramp truck i have a short in the head light switch some where that the head lights wil come on and off with the truck off. and it is random as hell. something to think about

[jb3t]

Yea... I may trace the wires to make sure they have not been gnawed by a mouse and shorted out.

[Oldriginal86]

When checking amp draw, the positive cable should be hooked up and meter placed between ground side of battery. I would think measuring with the door open and interior light switch grounded, meter should be reading 12v or more. I think the readings obtained on your meter are erroneous due to meter in the wrong circuit. Try measuring in the negative side and report back with readings. If unhooking the battery and truck will start the next day, you don't have a bad battery, you have a draw just as you suspected. I forgot to say when checking for draw, the meter should be on a voltage setting, 20v scale. You should be looking for a circuit that draws more than.5v. There will always be some draw through the alternator.

[craig113]

https://www.youtube.com/watch?v=B__D...IlF-k-K5YU8XPA

hope this helps

[rich weyand]

You're doing it right, with the meter on amps and inserted between the battery and the removed cable.

Removing the negative cable is safer, because you can't touch the positive to any of the grounded metal all over the place and cause problems.

The .02 draw is not a problem. The 1.02 draw when the door is open is correct -- several bulbs (ceiling, in the doors, whatever) drawing 1 amp more.

It sounds to me like there is a circuit in the truck finding an intermittent ground. I had one of these in a van that drove me crazy. The wiring harness was pulled hard around a sharp corner somewhere, and when the temperature changed, it would short the dome light circuit. On a van you have to bulbs in the middle ceiling, the ones in the cargo area, the ones in the door wells, etc. So I would park it and when the temp fell overnight, the dome lights would turn on and drain the battery. I never did find it. Being a van, it had a defeat for the dome lights for loading in the daytime, and I just left them turned off.

So something could be "turning itself on" by finding a ground somewhere at a chafed wire.

[jb3t]

Excellent... Thanks.

[homemade87]

You don't have a security system do you. Some of those thing will kill a battery after several days when armed .

[jb3t]

No on the security system. There should be nothing on at all.