Author Topic: Battery testers and duff batteries  (Read 569 times)

Wowbagger

  • Dez's butler
    • Musings of a Gentleman Cyclist
Battery testers and duff batteries
« on: April 03, 2019, 06:45:35 pm »
I seem to have acquired an awful lot of AA and AAA batteries over the years, but have few which seem to be able to hold a charge for long enough to keep my Garmin Oregon 600 alive for more than a few hours.

I have been looking at battery testers in order to try to sort sheep from goats, as it were. Amazon do a few, of which this seems to be flavour of the month, and there's this, from Ansmann.

Does the panel have any experience of This Sort of Thing? Do they work, or are are they just yet more tat to accumulate?

Thanks in advance.
Oh, Bach without any doubt. Bach every time for me.

Re: Battery testers and duff batteries
« Reply #1 on: April 03, 2019, 07:44:49 pm »
What you need is a smart battery charger that can do a discharge test - charge the battery to full, then run it down by applying a load and measure how long it takes to drop below some voltage threshold.

This kind of thing:
https://www.ebuyer.com/843686-intelligent-aa-aaa-battery-charger-with-usb-port-fast-charge-and-smart-test-t1charge

(No experience with this particular model. I have an Opus C3100 which can do this kind of thing, but it's more expensive and I've only ever used it with lithiums)

Kim

  • 2nd in the world
Re: Battery testers and duff batteries
« Reply #2 on: April 03, 2019, 07:52:11 pm »
Weirdly, I don't actually own a battery tester.

Thinking about it, it's because the vast majority of the batteries I deal with tend to be:

- NiMH AA/AAA cells, which if in doubt I just bung in the charger (which can measure their capacity, for an official verdict of whether they're duff).
- Li+ batteries with their own charge controllers.
- Primary lithium cells in low-current applications (CR2032s and similar), where an off-load voltage reading is meaningful enough to ascertain trustworthiness.
- Alkaline cells in applications where they get used until they're leaking, or at least unable to operate the device.
- Sealed lead-acid cells, ditto.
- Zinc-air cells which barakta has pingfuckited, and are now completely self-discharged on account of having been hiding behind a chair leg for the last three weeks.

If I had a box of alkaline cells that I really wanted to sort through, I'd augment my multimeter with a suitable shunt resistor  (you can't just measure off-load voltage, as it tends to 'recover').  This is basically what a battery tester is.  If I were dealing with radio mic batteries or something, I'd invest in one.
To ride the Windcheetah, first, you must embrace the cantilever...

Re: Battery testers and duff batteries
« Reply #3 on: April 04, 2019, 12:46:59 pm »
there are two distinct issues which a battery tester might be expected to address;

a) whether a battery has a charge in it that is worth having and/or
b) whether a rechargeable battery is any good (i.e. has a decent capacity and a low self-discharge rate)

a) can be addressed by using a variable load and seeing if the voltage holds up as Kim says.  You can quite easily design and make a box of tricks with a variable load in it, and a resistor network that allows a fraction of the test current to be bled off into a circuit using a 9V battery, a transistor, an LED and a few other odds and ends.  This can be used to give a visual assessment of if (or how brightly) the LED illuminates when the battery is placed under load.


b) can be addressed by doing a capacity test as grams suggests.  However an acid test is to charge the batteries and then to leave them a couple of weeks and see if they still have a charge left or not; IME cells are more likely to start to self-discharge than they are to 'lose capacity' per se.


Cells that start to self-discharge are deadly; if the cells are discharged in series with good cells, the bad cells soon go reverse polarity and you see that 'the battery has gone flat'. You charge everything up again which has the effect of shagging the good cells (which were only part discharged). In the meantime the bad cells have also suffered more damage by being sent reverse polarity. Total uselessness is not far away.

FWIW I have owned countless NiCd and NiMH cells and they have all failed the second test after a relatively low number of cycles, regardless of charging method, type of charger, and/or type of cell.   Most of these batteries also leaked electrolyte in their death throes which has completely ruined some expensive (but infrequently used) gear.    I am pretty sure that in many uses  both I (and the planet) would have been better off using disposable cells which are not made with such toxic ingredients.

cheers

fruitcake

  • some kind of fruitcake
    • Bailey
Re: Battery testers and duff batteries
« Reply #4 on: April 06, 2019, 11:46:31 am »
I have found an intellient charger to be very useful in analysing and refreshing Ni-MH cells. It has allowed me to continue using using some of the AA powered devices I might otherwise have replaced. This is the charger I bought.

https://www.ebay.co.uk/itm/391495597965

This model may be a rebadged Technoline. It looks similar.

Once in a while, I use it in discharge refresh mode, which measures capacity on a controlled discharge down to 0.9V and then recharges the battery.  It repeats that process until it detects no increase in capacity.

I then write the measured capacity on the cell using a Sharpie. This allows me to see which cells are good for use in digital cameras (i.e. those with at least 2Ah capacity), as oppsoed those only good for torches and bike lights (those with less capacity) or those fit for the battery recycling bin at the supermarket.   

Although I use the smart charger for analysis in this way, I charge batteries with a charger rated at 45mA. This is the charger that gets daily use. It seems to charge them better than the lowest setting on the intelligent charger, resulting in less heat and longer run time.

Re: Battery testers and duff batteries
« Reply #5 on: April 07, 2019, 12:02:34 am »
I also use a smart charger for capacity checks (Powerex MH-C9000 in my case).

a) Use good cells
b) Check the capacity when new, and pair up cells of similar measured capacity.
c) Don't use too many pairs.
d) don't wait for the battery warning before changing cells

I've found the black Eneloop Pros best. The current ones are 3 years old, and are reading about 2410mAh, vs 2480-2500 when new (sold as "minimum 2450").
I have 3 pairs on the go - one in the GPS, two in a battery case in the saddlebag. I swap at the next convenient stop after reaching 1 bar on the gauge. the used pairs go in the case head to tail so I don't mix them up with unused pairs, which are head to head, and I try to remember to recharge straight away, but there's the second spare pair available if I don't.
I charge at 1 amp, and run the capacity check every half dozen cycles (charge, wait an hour, discharge at 0.5A, charge).


I've not had any success in reviving failing batteries, so I've used the charger measurements to separate out the cells that seem to be reasonable, throw away the duff cells, and assigned the apparently good ones to unimportant domestic duties, such as the clock on the wall, the TV remote, or the wireless mouse.

StuAff

  • Folding not boring
Re: Battery testers and duff batteries
« Reply #6 on: April 07, 2019, 11:13:17 am »
+1 for using a smart charger rather than another bit of kit. The refresh & test modes on a Technoline BC-1000 (or similar) take an age to do their thing, but they'll sort good from bad.

road-runner

  • is in Slovakia.
Re: Battery testers and duff batteries
« Reply #7 on: April 07, 2019, 11:54:23 am »
Thank you for raising the topic, Wow, as I am having a challenging time with batteries that fail to hold their charge (unused) for more than a couple of days, silver Ansmann AA 2850mAh being the worst in my experience. In case you are interested, black and grey/green Amazon basics 2400mAh are both good, and my oldest, blue Jessops 2000mAh are the best I have used. I have 8 of each sort. Perhaps I should add that I am not anti Ansmann as my 9v PP3 Ansmann rechargeables hold their charge very well.

I do find YACF has produced a good few "look what you made me do" moments and today is no exception as I have just ordered a Technoline BC-1000. Thank you one and all.

Cudzoziemiec

  • Solar powered, tea fuelled cycle-wol
Re: Battery testers and duff batteries
« Reply #8 on: April 07, 2019, 02:29:47 pm »
I've not had any success in reviving failing batteries, so I've used the charger measurements to separate out the cells that seem to be reasonable, throw away the duff cells, and assigned the apparently good ones to unimportant domestic duties, such as the clock on the wall, the TV remote, or the wireless mouse.
Just to note that dead batteries can be recycled at most supermarkets, though I've no idea what actually happens to them.
An ungovernable laughter, a joyous agitation which makes the summer stretching before you seem like an unrolling canvas on which you might draw those first rude pure strokes that are free. (Capote)

hellymedic

  • Just do it!
Re: Battery testers and duff batteries
« Reply #9 on: April 07, 2019, 03:36:18 pm »
Our local authority collects batteries for recycling.