AA rechargable battery life tester


With accumulation of AA rechargable cells I've bought over
the years. Would be nice to make some kind of life tester.
I have been toying with the idea of some kind of resistor,
for load. Also run a small clock on the cell. Start the
clock at 12:00 and leave it to the next day. When the clock
stops, that tells me for how many hours the battery was
delivering power. 5:00 on the clock means 5 hours of power
delivery.
The reason being so I could tell which batteries to trash,
and which ones are still useful. Is any such device already
made?
Reply to
Stormin Mormon
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how about a flashlight?
Reply to
Cydrome Leader
This smart battery charger made by PowerEx (Maha) measures capacity and is available through Amazon for about $55:
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Battery capacity measurements can vary quite a bit depending upon the discharge rate (profile), but PowerEx has a good reputation for their products. Here=92s a PC-based system if you want to spend $800:
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are much more expensive battery tester/analyzers made for labs (science/industry) Here=92s a decent article on rechargeable batteries:
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Reply to
Denis G.
The battery test function on this Harbor Freight multimeter:
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the current the battery can push through a 370 Ohm resistor. They suggest a good 9V battery can do 25mA and 4mA for a 1.5V cell.
I've noticed some old cells that show the right voltage open circuit but show up as high resistance on this test.
This serial port datalogger can record the voltage as a battery discharges through a resistor.
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free included software doesn't let you shut off the load at an endpoint voltage, so it's not good for rechargeable Lithiums. AFAIK individual NiCads don't mind discharging to zero. When multiple cells are in series the first one down will be charged backwards by the others, which is damaging
When I get to that project I'll use an old laptop running QBasic under DOS and control the load with a printer port bit. They have USB versions but I can't program them directly.
Another possibility:
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coupling the input is possible but risky.
Dec 7 note: NH just named a new bridge for Pearl Harbor.
jsw
Reply to
Jim Wilkins
Seriously good information. Thanks. I might buy myself one for Christmas.
Reply to
Stormin Mormon
I remember the original carbon zinc cells, would read fine with VOM, but could be dead to any load. I made a load tester with a PR-2 bulb, and a piece of 10 gage wire. Make a loop around the bulb, cnd then curl the wire in to a C shape. Lead tip of the bulb on the battery, and end of the wire on the other end of the battery. I can do a quick, practical test of AAA through D cells.
By the brightness of the bulb (or light at all) I can quickly tell if a battery is new, used, or useless.
Reply to
Stormin Mormon
I have one of these
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similar to
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You can set them to discharge and charge a battery multiple times and they will tell you the capacity in milliamp hours. They work on NiCd, NimH, Lithium ion, Lithium Polymer, lead acid, charge from 0.1 to 5A... just check the specs. Connect to PC, cable and software included.
In my opinion they are a great charger for the money.
RogerN
Reply to
RogerN
I made something like this with a relay, wired to self latch, a Hobbs hour meter and an assortment of light bulbs for loads. I used NO and NC push button switches for start and stop. I use it to test the capacity of 12 V. gel cell batteries. when the output voltage drops below about 8 V. the relay drops out and, of course the meter stops. First time SWMBO went past the shop and saw the red pilot light and heard the meter ticking over, she accused me of building a time bomb! You would need to find a relay and clock that would run on 1.2 V. Gerry :-)} London, Canada
Reply to
Gerald Miller
Relay yes, but the clock/timer could & should run on external voltage, so it can be any voltage. . But... don't try a digital alarm clock...
Reply to
David Lesher
Very interesting. I think I know what's inside but I couldn't build one for twice that price. Can you use it as a general purpose data logger?
jsw
Reply to
Jim Wilkins
Feed the base of a simple transistor through a bias resistor with the battery voltage such that it turns the transistor off when you reach your desired voltage. Run whatever part of the circuit through the emmitor/collector of said transistor, and you have what you are looking for at a buck or two max.
Jon
Reply to
Jon Danniken
When I discuss electronics in this machining forum I assume the audience consists of those who understand it and don't need my simple advice, and those who don't and won't build the circuit anyway. I can't teach circuit design and soldering by correspondence. It's the same with chemistry.
You have the right general idea but need a circuit that shuts the load control off abruptly, such as a comparator with hysteresis. Remember that the battery voltage will rise when the load is removed.
jsw
Reply to
Jim Wilkins
/ /Very interesting. I think I know what's inside but I couldn't build /one for twice that price. Can you use it as a general purpose data /logger? / /jsw
I just tried right now, the data doesn't start logging until a charge or discharge has began. I have the Thunder AC 6 and downloaded the software for the skycharger, works fine. I'm not sure if the charger doesn't send data until it's started or if the software just doesn't start recording.
This place has a lot more chargers along with reviews
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I found info on one of their reviews on how to calibrate the voltage readings on my charger.
RogerN
Reply to
RogerN

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