Rechargeable and non-rechargeable battery testing - Page 1
Forum section: electronics / beginners

author: Greorge
author_rank: Regular Contributor
timestamp: February 09, 2014, 11:43:53 pm
content: Have some 1.2 NiMh batteries AAA AA DHave Alkaline 1.5 AAA AAAlso Lithium 1.5 AAReading Voltage alone is only part of the story as many say that batteries should be tested under loadOn one of the U-Tubes it was mentioned that all of the above batteries can be tested with 100 ohms resistor attached across probes.Is it adequate solution or there is something much better to get true pictureAlso any resistor 100 Ohms can be used? Even the tiny in size?Or it has to have larger body?Have difficulties to find answer using search here on our Forum( I must develop better search technique for future searches, but now excuse my question, especially if it was answered few times before )

author: Mr. Coffee
author_rank: Regular Contributor
timestamp: February 10, 2014, 12:24:02 am
content: 100 ohms is probably a good all around value to put across the battery to test battery voltage, but different batteries have different voltage response to that. Bigger batteries can hold their voltage up across 100 ohms much better than small batteries, but may still not hold up under a heavier load...that is, they may show a good voltage but be getting weak.You really have to look up what the ampere/voltage curve for a given size and type is supposed to be before being able to interpret the test results. A decent battery tester should have its meter scale already calibrated for the different sizes.As far as resistor wattage goes, the power consumed will be E^2 divided by R. For example, for a 1.5 volt battery and a 100 ohm resistor would be (1.5x1.5)/100 = 0.0225 watts, so even a 1/4 watt resistor (in 100 ohms value) would work. Fresh batteries do have slightly higher than "nominal" voltage though. More like 1.6 to 1.65 volts for a fresh alkaline "1.5 volt" battery.

author: gotwood
author_rank: Contributor
timestamp: February 10, 2014, 01:24:46 am
content: you put the appropriate resistor across when testing....then there is a certain percentage the voltage should be of the rated voltage ...this says good or not

author: IanB
author_rank: Super Contributor
timestamp: February 10, 2014, 01:36:54 am
content: The most important thing isknow your battery. Different brands of battery behave differently, especially NiMH rechargeable batteries. The difference between brands is more significant than whether you test them under load or not.So just use a simple voltmeter, but learn what to expect from each battery when fully charged, half charged, and discharged.Learning the characteristics of your own batteries and making note of them will tell you far more than any general advice you find on the internet.

author: Greorge
author_rank: Regular Contributor
timestamp: February 10, 2014, 01:51:57 am
content: QuoteI get it.Should I want to include 9V battery then :( 9 x 9 ) / 100 = 0.81 WSo 1W resistor 100 Ohms will just make it (probably 3 or 5 W would give safety margin)As to smaller batteries as you said even tiny resistors should be good enough.Smallest capacity rechargeable battery I have is 600 mAh 1.2 garden light one but it is AASmallest AAA I have is 750 mAh, so probably different size Ohms resistor would be better.Almost looks that some kind of adjustable resistor would be more appropriate.Don’t want to go over the top, as all I want to know if battery is 70% loaded, or something like that and can be used for a while yet or it is closer to 50% and should be recharged/replaced sooner than later.

author: Greorge
author_rank: Regular Contributor
timestamp: February 10, 2014, 01:58:02 am
content: QuoteThis is what I do all the time, but got impression that I am missing the boat.Right now my 1.2V NiMh get up to probably too much at 1.32V charged,down to 1.1V when I often top them up.Or I let them to stop working devices, when they go down to 0.9 or 0.8V

author: mariush
author_rank: Super Contributor
timestamp: February 10, 2014, 01:59:05 am
content: V = I x R .... I = V / R = 1.5v/ 100 ohm = 0.015A = 15 mA ... battery will discharge slooooowly with a 100ohm resistor.P = I x I x R = 100 x 0.015 x 0.015 = 0.0225 wattswith 9v batteries .. you're looking at 90mA and 0.81w dissipated... 90mA is kinda in the sweetspot for 9v batteries along with 25mA (most multimeters use <10-15mA) ... see datasheets and pretty graphs in themhttp://data.energizer.com/PDFs/522.pdfhttp://www.adafruit.com/datasheets/MN1604_US_CT.pdfA member of this forum already tested a bunch of batteries at low and high drain:* low (200mA ... toy, CD/MP3 player, torch etc) :http://www.batteryshowdown.com/results-lo.html* high (1A ... digital cameras with flash etc ) :http://www.batteryshowdown.com/results-hi.html

author: Greorge
author_rank: Regular Contributor
timestamp: February 10, 2014, 02:38:12 am
content: Many thanks, will have to study all the info

author: IanB
author_rank: Super Contributor
timestamp: February 10, 2014, 04:16:18 am
content: Quote from: Greorge on February 10, 2014, 01:58:02 amNiMH cells are fairly predictable in the discharged state, but the voltage can vary a lot when charged.For instance, Eneloops: These will be at about 1.47 V hot off the charger, but leave them to sit for a week or two and they will be down to 1.35 V or so. Most NiMH will be somewhere around 1.3 V to 1.35 V when fully charged and unused.When discharged, nearly all NiMH cells sit at 1.20 V when empty and unloaded. Anything less than 1.20 V is the result of recent discharge, or prolonged discharge beyond empty such as leaving a device switched on after the battery has run out.

author: Greorge
author_rank: Regular Contributor
timestamp: February 11, 2014, 05:31:55 am
content: Quote from: IanB on February 10, 2014, 04:16:18 amDidn't think that NiMh battery is 'beyond empty', when below 1.20 VDoes it mean that NiMh battery 0.8 V or less is damaged and not suitable for re-charge?

author: IanB
author_rank: Super Contributor
timestamp: February 11, 2014, 06:03:16 am
content: Quote from: Greorge on February 11, 2014, 05:31:55 amAn NiMH battery with a resting voltage of 1.20 V is 'empty' in the sense that it has almost no useful energy stored in it. If you tried to put a load on the battery when in that state you would see the voltage decrease rapidly and the output current drop towards zero.No, a battery measuring 0.8 V or less is not necessarily damaged and can quite well be recharged. However, you may find it needs reconditioning before it performs at its best. Reconditioning may be performed by putting the cell through a few controlled charge/discharge cycles, however the best way in my experience is to apply a 16 hour 0.1 C timed charge to the cell, then discharge it slowly down to 0.9 V, then charge it again.

author: Psi
author_rank: Super Contributor
timestamp: February 11, 2014, 06:23:06 am
content: i like to test AA's with a quick direct short on my DMM 20A current range.Is it a good idea... definitely not.Does it show which batterys are better than others beyond a shadow of a doubt = You better believe it(If it reads over 5A for a drycell or 10A for a rechargeable i consider it charged)Note: Never do this to lithiums or big batteries, ya really shouldnt be doing it with AA's but at least AA's don't complain much