Hi Jason! I thought about it some more, especially about the initial (high) current that flows when you put the fuse (ampere meter) back in. This could damage your ampere meter.
I'd build the following device: * Use an old (burned!) fuse and solder two (fat) cables to the terminals. * Connect the cables to a switch supporting at least 10 or 15 Amps. A usual light switch may be just right. * Use some screw-type terminals to connect the tips of the measuring lines of your ampere meter. * When you put in the fuse, the light switch must be conducting. Your ampere meter should not be connected (pull out one cable on ampere meter side). * Then connect your ampere meter. It will show about half of the current that's currently flowing * Turn off the light switch. The ampere meter will show the full current that's flowing. Be aware that some fuses might also be placed under the hood and maybe even in the trunk. You can also do it the other way round. Connect the light switch between one battery pole and its cable. Then add the ampere meter and turn off the light switch. Then start pulling fuses. If the current is rather high, your ampere meter might get damaged, or you must use it only for a short time (turn switch back on after reading the value and disconnect the measuring line). The switch might also need to support more amps with this setup. Regarding the current that's allowed to flow: Let's say you have an 80Ah Battery. So, if there is 1A of current being sucked from a full battery, it's (ideally) going to live for 80 hours. I'd expect a car to start after 4-6 weeks without a problem, so the maximum current drawn should be (in that case) 80Ah/(4*7*24)h .. 80Ah/(6*7*24)h = 0.119 .. 0.079A (which is about 120 to 80 mA). Of course, your battery might be damaged so much, that it doesn't have 80Ah anymore, but only 20 or so. Lead batteries don't like being discharged completely :( Please note, I haven't had a lot of electronics in my education, but I'm half-way confident that there is not too much nonsense in above calculations and instructions :) best regards, Markus On Jun 17, Jason C. Lamb <l...@gweep.net> wrote: > Markus, > > Thanks for the suggestions. This is the route I started down. I have a > camp-on ammeter, and am able to measure significant amperes across the > negative terminal when the car is running. I watch it go down to ~2 > amperes when I shut off the car. I then start pulling fuses and can see > some reduction, but my fear is that using a camp-on ammeter my readings are > not that accurate (correct me if I am wrong). And after several nights of > not picking the right fuse I am getting a little annoyed. > > If I disconnect the battery completely, it holds a charge. > > I think you might be right, an in-line ammeter might be more accurate and > help me narrow down the cause. > > Anyone have an idea on what the typical draw should be on a car battery so > that it can hold a charge for days at a time? I would guess milliamps? > > > FYI This is a 2007 Honda Odyssey, and has a good amount of electronics. > > > > Jason C. Lamb > 617-512-6064 > l...@gweep.net > http://www.linkedin.com/in/jasonclamb > > > -----Original Message----- > From: Markus Gaugusch [mailto:mar...@gaugusch.at] > Sent: Thursday, June 16, 2011 2:08 PM > To: OWFS (One-wire file system) discussion and help > Subject: Re: [Owfs-developers] Monitoring Battery Voltage > > On Jun 16, Jason C. Lamb <l...@gweep.net> wrote: > >> I am fairly new to 1-wire, though I setup a temperature probe about 4 >> years ago with excellent success. Today I am looking to 1-wire to >> monitor the voltage on my car battery. It seems to drain over night. >> I can measure the voltage at night using a multi-meter (13.1 VDC) and >> by the morning it is 0.2 VDC. The problem I am not sure if the >> voltage drop is slow and steady, or there is a defect in the battery that > is causing a sudden drop off. > > While this is not a 1-wire solution, I'd rather pull some fuses of > suspicious consumers (like radio) and see if the problem persists. If you > know which fuse is relevant for the battery draining you can find the > problem more easily. > > Additionally, you don't need a voltage meter but an ampere meter to measure > the current. Voltage won't tell you how much power is consumed (it will only > tell you when the power is over, that's it). > > But: This is more dangerous, as you have to put the ampere meter in-line > with the consumer, and not parallel like a voltage meter. Some devices suck > significant amounts of power, so be prepared for some sparks to fly! > > I'd probably pull out a fuse, and put in an ampere meter instead. Another > suspect (apart from the radio) is any consumer in your doors. The cables > there tend to loose their insulation over time and can cause more or less > significant current flow. > > > best regards, > Markus > > ---------------------------------------------------------------------------- > -- > EditLive Enterprise is the world's most technically advanced content > authoring tool. Experience the power of Track Changes, Inline Image Editing > and ensure content is compliant with Accessibility Checking. > http://p.sf.net/sfu/ephox-dev2dev > _______________________________________________ > Owfs-developers mailing list > Owfs-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/owfs-developers > > > ------------------------------------------------------------------------------ > EditLive Enterprise is the world's most technically advanced content > authoring tool. Experience the power of Track Changes, Inline Image > Editing and ensure content is compliant with Accessibility Checking. > http://p.sf.net/sfu/ephox-dev2dev > _______________________________________________ > Owfs-developers mailing list > Owfs-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/owfs-developers > > > -- __________________ /"\ Markus Gaugusch \ / ASCII Ribbon Campaign markus(at)gaugusch.at X Against HTML Mail / \ ------------------------------------------------------------------------------ EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
