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Old Nov 18, 2004, 10:31 AM   #11
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ed777 wrote:
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What does everyone use for testing theirbatteries?
I have several different, very cheap, digital voltmeters which have a "battery test" facility, which works well on AA cells. It applies a standard resistive load, you read the current passed through that load on the LCD display, and you can judge its condition.

I find that the range designed for AA disposable cells "40mA - Cell OK" works just as well for Ni-MH or Ni-Cd, except that 38mA is as good as you'll get.

So...

1. buy a DVM with battery test facility;

2. put in a known good cell and note the reading for current passed through the standard resistor;

3. Compare dubious cells with that reading.

Good luck!
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Old Nov 19, 2004, 12:35 PM   #12
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Thanks for your answers.

I found a cheap multimeter with battery load tester and tried it out on several batteries, primary and secondary. Naturally I focused on the AA size since that's what my camera uses.

All the new primary batteries registered between 1.45 and 1.55v.An older onewas about 1.30.

The almost-fully charged Nimh (at least I think it is) was only 1.28 and an almost completely dead Nicad was 1.23.

Obviously I will want to test a fully charged Nimh and Nicad, butI don't expect it to be much higher than that 1.28 since it is only rated at 1.25. I guess what I've learned is that there really isn't that muchdifference between a charged cell and a dead one . . . for example, it seems 1.25 will power your camera, but 1.23 won't.

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Old Nov 19, 2004, 9:35 PM   #13
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You should definitely see a difference between a freshly charged healthy cell & a fully discharged dead cell.As stated above a NiMH cell will have useful charge all the way down to 1.100 volts(Nothing useful below that) If you happen to have a unique device that shuts down below a certain threshold voltage then that would be another issue.

style="BACKGROUND-COLOR: #000000"I chose to measure via voltage readouts but thinking about it I suppose (as Alan T pointed out)that as Voltage & Current are related that either should give you useful information.But voltage measurements work well for me.But better still ,as I suggested, buy the necessary resistors,alligator clips,leads etc which cost absolutely nothing and experiment for an afternoon.Then you will be as informed as anyone re practical battery testing.

style="BACKGROUND-COLOR: #000000"Bear in mind that there are variables present.You will get a higher voltage reading handholding two multimeter probes against a battery(more pressure) then you will in a simple AA battery carrier.You may get slightly different readings with different resistors(more or less loading) You may have to leave the batt in the test unit for a minimum period of time to stabilize. But as Alan T was inferring you are after a relative readout that is useful. And that you WILL get. Go for 1.2Ohm (5 Watt) & 2.2,3.3 & 4.7 Ohm (1Watt) resistors.Assuming average batt voltage of 1.2 Volts this will give you a current draw of 1000,540,360,& 250 milliamps/cell respectively.[ Ohms Law]Its also possible that if too higher a resisitance is used (over a certain point) then the battery will not be loaded enough(not enough current flow)& the readout will not be useful.This can be verified with the above setup,but I have yet to buy the 4.7Ohm resistor to find out.Remember that with modernmultimeters re battery voltage 1/1000 of a volt(.001) volts is readable and is relevant.That is the beauty of the system extreme accuracy,extreme fineness.

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Old Nov 19, 2004, 9:47 PM   #14
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Re above post.
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Old Nov 19, 2004, 9:48 PM   #15
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Re above post 2
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Old Nov 19, 2004, 9:50 PM   #16
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Re above post 3.Hard soldered unit.
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Old Nov 21, 2004, 8:54 PM   #17
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photog180, thanks for reply and the detailed pics.

I did some more playing around with the multimeter and I think it will give me the approximatedata I need (even w/o the resistors). But as you say,the nice thing about your setup is with the resistors, you can use it to discharge cells also (probably more important for Nicad than Nimh).

I'm embarrassed to admit that in my testing this weekend, I relied on my old tried-but-true low-tech method of discharging cells: I ran down my Nicads as much as I could in variousdevices, then did the metal-paper-clip-short-circuit thing. I only did it with cells that tested lower than 1.10v, so the clip never got warm, but was effective in discharging cells down to 0.30 or lower after a few hours. With a full charge now, hopefully they'll have been conditioned.I know thatif I'm serious about regularly conditioning cells, I should get one of those Maha intelligentchargers or get the stuff for photog180's setup.


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Old Nov 22, 2004, 3:21 AM   #18
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Hi ED777

Be careful how far you discharge your cells.To my knowledge going below approx .900 volts risks driving the battery into reverse polarity(effectively rendering it useless)

For very useful & authoritative info see this link http://www.batteryuniversity.com/

Happy shooting.
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Old Nov 22, 2004, 4:07 AM   #19
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Also in relation to the Maha chargers(re the search for the perfect charger)I have the Maha C204W & C401FS.Both heat the batteries up to 50 'C in fast charge mode which as far as I'm concerned is too hot.The lightning Pack 4000N charges fast & cool but only discharges at 160mA(too slow) So I've decided to charge with the Lightning Pack & discharge when needed with the 204W (discharges at 400mA)So what is the perfect charger? It would be one that charges like the 4000N,discharges at minimum rate of 400mA(like the 204W) & charges each cell independently like the 401FS.Did I fail to mention that one of the reasons why you would go with the resistor/multimeter setup is to evaluate how completely/successfully an individual charger performs? ED 777 before you buy that charger get thee to the following links:-

http://forums.dpreview.com/forums/re...essage=9974095


http://forums.dpreview.com/forums/re...essage=9974213

http://forums.dpreview.com/forums/re...essage=9974234

http://forums.dpreview.com/forums/re...essage=7524174

If these are not hyperlinked just copy & paste them into your browser. Maybe this will save you some leg work.

Cheers
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Old Nov 22, 2004, 12:19 PM   #20
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Oops, I just discharged my old Nicads to under 0.50 but they seemed to charge up OK. I'll test them out. They're backups for the Nimhs that arecurrently in my camera. The Nicads only lasted about 15 shots before so Ihoped that discharging them would improve their performance. We'll see. But I'll keep that 0.90 threshold in mind.

I actually have an Energizer Universal charger that lets me do Nicads and Nimhs of all sizes. It does Nicads in 3 hrs and Nimhs in 5 (charge rate: 500mah). I assume it works on a timer so I know it's not ideal, but I needed something with flexibility for all the different batteries I have.

Interesting posts about the Maha chargers; I will certainly do more research if and when I decide I needan AA fast charger. I guess there is no perfect charger unless you're willing to spend hundreds for it.


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