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| Alkaline battery tester |
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| wolf9545:
I have been building electronic projects for a while but have never really designed anything so please bare with me. I want to make something like this: https://www.amazon.com/ANSMANN-ENERGY-BATTERY-TESTER-ALKALINE/dp/B000KHVKV6 but I don't want to spend the almost $100 just to test some batteries. I would like to be able to test AA, AAA, C, D, coin cell and 9V batteries. I wanted to test the battery under a load because I know you will get a better idea of the current capacity. I figured I would make something like the harbor freight multi-meters that have a battery tester function. They just pass the battery through a 360ohm resistor and display the mA on the meter. More info for anyone that doesn't know: http://www.instructables.com/id/Add-Battery-Test-to-a-Multimeter/ I ended up buying this meter: https://www.amazon.com/gp/product/B00D2M623C/ref=oh_aui_detailpage_o04_s01?ie=UTF8&psc=1 and I put a 360ohm resistor inline with the tester side. That way I can get a reading of 25mA for a 9V, 4mA for a 1.5. What I am wondering is if there is a better way to check the batteries? I found this circuit: https://www.eeweb.com/blog/extreme_circuits/battery-tester-circuit-schematic. Would I get a better idea if a battery is good or not? If I read the article and schematic right I would connect a volt meter to the circuit and watch the numbers. If I am testing a 1.5V battery I would see if 1.5 stays steady on the meter or drops. Sorry about the massive amount of links. |
| rdl:
Checking a battery under load is probably the best way, but it seems like the load should be scaled to fit the capacity of the battery. |
| sasa:
Calculating internal battery resistance will give a bit more reliable info of the status and future life of the battery. For a bit more concrete info: https://learn.sparkfun.com/tutorials/measuring-internal-resistance-of-batteries |
| Kleinstein:
With alkaline cells just measuring the voltage is usually good enough. However this does not work with the old style dry cells: they show some 1.52 V all the way till the end. So to test the dry cells one would need a load. An alkaline cell starts at some 1.6 V with a low internal resistance (e.g. < 0.1 Ohms for AA). When about empty they have some 1-1.2 V and still a low resistance maybe in the 0.1-0.5 Ohms range. In contrast the dry cell may start at 1.53 V with a reasonably low impedance (maybe 0.5-1 Ohms) - when empty its at something like 1.5 V but the internal resistance goes really up and can reach 100 kOhm (depending on how empty). So testing would be ideally without an with a certain load (e.g. 10 mA). So one would get both the open circuit voltage and the output resistance. |
| wolf9545:
Thank you for all your help. Sorry I am replying so late, I never got any notification that people replied. I did find this circuit: https://www.eeweb.com/blog/extreme_circuits/battery-tester-circuit-schematic and I am waiting for the components to arrive. I like the idea of a constant current to act as a load. Like the description says I will then look to see if the meter stays on a steady voltage for the battery or it decreases. I wish I could use a digital volt meter so all you would have to do is read the digits. I could not find any that worked on 1.5V. I ended up getting a analog meter that goes up to 20V. |
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