Doug, it’s not battery testing but I follow BigClive on Youtube and he’s had a number of interesting videos about electronics. His one from last Friday is one I am going to employ at my work as part of monitoring a remote section of property against trespassers. He, alone, is responsible for me spending over $250 in the last two years on small electronics gear and upgrading some of my soldering kit. :) https://www.youtube.com/channel/UCtM5z2gkrGRuWd0JQMx76qA <https://www.youtube.com/channel/UCtM5z2gkrGRuWd0JQMx76qA> — Ryan > On May 15, 2019, at 11:01 PM, Mike Miller <mbmiller+l at gmail.com> wrote: > > This is really helpful. It answered a bunch of questions I had but hadn't asked. People were commenting on that YouTube battery-testing video that a 100-ohm resister wouldn't be right for a D battery, but I guess it also wouldn't be right for a 9-volt. > > Looking at more info out there on the web -- it's a problem for me that a lot of people don't seem to know what they are doing, but they are still there, teaching the world. ;-) > > Thanks again, Doug. > > Mike > > > On Sun, 12 May 2019, Doug Reed wrote: > >> Yes, the Ax-Man stores are the place to look if you don't want to ask someone to mail it to you. I believe there are 3 or 4 stores around town. The only stores I am familiar with are in St Paul and Fridley, but I thought there was one more in Bloomington. >> >> The color code for 100 ohms is brown-black-brown. But 100 ohms is too low for testing a 9V battery. 100 ohms is fine for testing 1.5 volt batteries at about 15 milliamp current load which is within the capability of all AAA or larger batteries. >> >> But 100 ohms will attempt to draw about 90 milliamps from a 9V battery. Most 9V batteries are rated for 50 milliamps maximum load. Your 100 ohm resistor will tend to suck them down so they all fail your test. For a similar test effect, you should use a 1000 ohm resistor, perhaps even higher, up to 3000 to 5000 ohms so the load is proportional to the battery capability. >> >> So when you are looking for the resistor at Ax-Man Surplus, the 100 ohm resistor should have Brown as the first band, black or brown or red for the second band, and Brown again for the third band. The bands are counted with the first band closest to one end. >> >> The 1000 ohm resistor would have the third band colored Red instead of brown. Since we don't care exactly what the value is between 1000 and 5000 ohms, the first band can be any of Brown or Red or Orange, or Yellow, and we don't care at all about the second band color. >> >> And I suggest that you look for a resistor that handles one-half watt dissipation or more. Your batteries should never approach that but the larger physical sizes are usually less likely to break from lots of handling. A half watt resistor is physically about 1/8" diameter and 1/2" long with leads about 1.5" on each end. >> >> The size you pick isn't really critical, it is really just for ease of handling. You will probably find multiple examples to choose from, I just suggest you don't choose the smallest size you find. Any resistor larger than 1/2 watt will also work of course, if that is what you find or want. The much larger watt values usually have the resistor value simply printed on the side. >> >> And of course buy more than one of each for when you break or loose one. :-) >> >> Good luck. If my description isn't enough to work from, you can easily find web pages that explain the resistor color code. And you can always bring your voltmeter to the store and use it to check the resistor value before you buy. Or buy a handful of different values that have brown or red on the third band and check them at home. No matter what you choose to do, the parts will probably cost less than the gas to get you to the store. >> >> Doug Reed. >> North St Paul. >> >> -- >> Scientists say the world is made up of protons, neutrons, and electrons. They forgot to mention MORONS. >> >> She had buried three husbands and at least two of them had already been dead. > _______________________________________________ > TCLUG Mailing List - Minneapolis/St. Paul, Minnesota > tclug-list at mn-linux.org > http://mailman.mn-linux.org/mailman/listinfo/tclug-list -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mailman.mn-linux.org/pipermail/tclug-list/attachments/20190515/e706ed70/attachment.html>