brawnyrebel wrote:
Please do continue. I have a nice fluke multimeter that i need to figure out how to set up to read the current between the battery and disconnected negative cable. I am with you up to this point and really appreciate it.
Well, you axed for it, so here goes.
I don't know what model Fluke (in your case, and for other folks...), Radio Shack, Walmart, Sears or other brand you have, and I don't care. Makes no difference. So if you don't have the operators manual, then ask Dr. Google. She can probably take you to a web site that can give a better explanation of your brand and model, than can I, about the operation of your meter. My Fluke 77 has two connection ports for the positive lead. One is 300mA, ac or DC, the other is 10A ac or DC. You want DC in all cases here. What you need to know, is that a fresh 1.5V D cell has the capacity to push more than 10 amps through a short circuit. "Short circuit" has nothing to do with length of any kind. It means resistance to the flow of current. I would encourage you to spend some time playing with your current function and some 1.5V batteries ranging in size from AAA to D. You will soon be comfortable with your understanding of polarity and scale or range. Polarity is not of concern as the only thing that happens with a digital, is that you get a negative sign on the read-out. I am going on and on about this because, in my previous post I tried to instill in all who read it, the absolute necessity of understanding the simple concept of "short circuit devise" when you have your meter set up to measure current.
Your meter __WILL NOT__ survive even momentary, accidental contact directly across the posts of a healthy, fully charged 12V bike battery, which will probably have enough "capacity" to push 300 to 400 amps through a short circuit until it explodes; and it will explode!!!
If you connect your meter leads to a 3A or 2A battery and it does not read current, then you need to first double check that it is set correctly to read DC 10 amps or so. If it is correctly set up, then take your meter cover apart and replace the fuse(s) inside. If the fuse is already missing, then buy 1/2A fast blow for the low current circuit and a 10A fast blow for the high current circuit. This may not be the correct fuses, but it should not cause major destruction in the event of a short. While you are at it, find out which fuse is correct, go buy some spares, and keep one or two inside the meter. The fluke should have a receptacle for a spare fuse or two, inside.
Now that you are clear in your mind what _not_ to do with the meter, you are ready to track down the problem.
Bear in mind, I am not familiar with your bike, only with testing procedures. What you will do is to leave your meter out of the circuit while you pull fuses out one at a time and then check to see if the drain/leak current is gone.
Mission accomplished!
I hate to over simplify things sooo much, but that really is all there is to it.
To start, disconnect the negative cable clamp as indicated, and put your meter between the battery negative post and the negative cable clamp as described previously. Do you read any current? The only bikes with a small current drain are those equipped with clocks or chip memory of any kind. That maintenance current should be on the order of 500mA (1/2A) or less. If you do in fact have a leakage current, then set your meter on the bench for a moment. Next, you want to pull one fuse out and then put your meter back between the battery negative post and the negative cable, and check for current again. When you are doing this, you can leave previous fuses out till you isolate the circuit with the problem. When you go from having leakage before pulling a fuse, to not having leakage after pulling the fuse, you are on the right track. Put the other fuses back in at this point and check for current leaks again. It is not outside the realm of possibility to have multiple problems on old bikes.
If you don't get any response from pulling fuses, then it could mean someone has jury rigged something and it is not even fused, for example.
It is not rocket scientist stuff, really. You can pull single wires out of their connectors anywhere and as many as you need, if that's what it takes to find out which branch is at fault. Just make a accurate journal entry or list of what you undo so you can redo at the end of the session.
I absolutely guarantee, _all_ of the current supplied by any battery will pass through both of the battery posts/caps at the same time. You/I chose to monitor the negative one for safety reasons only. Further, I guarantee that you will not get any current leaking through the side of the plastic battery case or through magic of any kind. Also, I promise, all the current _will_ go through your meter if you are careful to do as I say when connecting the meter to the battery and cable clamp. Makes no difference where the current ultimately goes, it will return to the battery through your meter.
To the best of my knowledge, there is no such thing as a current storage device of any kind. Current will not flow out of your battery and get trapped , like in your frame or something, and show up somewhere else later. Current flows or it don't, and the placement of your meter/test circuit insures it will all go where you can watch it.
Now, the only other mystical property that needs investigating is the concept of "intermittent leaks/problems" and this is a very important concern, possibly for another session.
You got all that?
That sounds like a lot to ingest, but I like to be thorough.
Now youse guys, go ahead and flame me, I'm ready.
Post edited by: JimatMilkyWay, at: 2007/02/03 13:29
