Battery tester

Do you have a good old fashioned hardware store around? Emphasis on old.

My favourite appliance is a 1.25V MES bulb which is screwed into one coiled end of a length of stout iron wire the rest of which is bent to touch the base of an AA battery held against the bulb. I can tell by the brilliant <> dull gleem of the bulb what the state of an alcaline or rechargable is.

But I have looked for a spare 1.25V bulb to no avail. 1.5V is easy, though...

Oh, I understand :-)

But no, I am staying at a new neighbourhood.

On a sunny day (Wed, 10 Nov 2021 17:01:12 +0100) it happened "Carlos E. R." <robin snipped-for-privacy@es.invalid wrote in snipped-for-privacy@minas-tirith.valinor:

It alk depends on the battery chemistery.

For a simple AA or AAA 1.5 V type I, provided it is charged, I sometimes just use the multimeter on the 10 A scale and so short the battery for a second. If it says 100 mA you know it is a throw away, should be much more than 1 amp Internal resistance. Do not do that with a liion or or lipo or lifepo4 at 3V or more .... Ebay has nice power resistors, many for a few $, this I use to test those batteries:

you can put them in series or parallel any way you like (alligator test leads), values are all the same I use that to test high power lipos What also is nice is a clamp on DC current meter: a bit more expensive, but at very high current test leads and meters have way to much resistance.

Pack of fifty little 1.5 volt bulbs:

It says LED, but I can clearly see the filament in the photos. I'm tempted to buy them, but what do wi do with the other 49?

Check these out!! Yes, maybe expensive on your Dollar Scale. However it works great!!

I've sometimes used an auto headlight for load, but my trusty Radio Shack Battery Tester works well for common cell types; its ranges are marked

Alkaline button cell: 1.5V 1 mA (implied load 1500 ohms) Lithium coin cell 3V 1 mA (3k ohms) AAA cell, N cell 1.5V 50 mA (30 ohms) AA cell 1.5V 150 mA (10 0hms) Photo 6V Rectangular 9V

12V 22.5V (those last ranges don't identify the load; possibly they just use a single resistor at circa 3k ohms, which would be appropriate for the 9V at least).

So, there's a wide-ish range of load resistances to consider.

Carlos E. R. wrote: ==============

** Measures voltage. ** It is a rechargeable type - so not easily tested. And not with that meter at all !!

Cell capacity of NiCd or NiMh cells can only be tested by timing a discharge cycle. Tell you friend to buy new cells.

..... Phil

Well, yes, that is the question. Who has published tables of what current on a given resistor should each type of battery yield?

Give me that and I will build a perfect tester, thankyou.

Not the case, single base.

I have charged the batteries (Panasonic Ni-MH, AAA, 550mAh) on a separate charger, and also tried with fully charged batteries of my own.

Originals:

1.345 V 1.334 V

Mine:

1.384 V 1.386 V

But the phone itself indicates both battery sets are empty.

I can read the voltage, but not the capacity. A rule of thumb was that the battery should provide 10% of the A·h rating at nominal voltage, but I don't have a set of resistors here.

And I don't know if the tiny voltage difference is important. I have a table printed on a commercial tester on Amazon:

1.2 1.5 3V 9V Good > 1.25 > 1.3 > 3.0 > 7.3 Low 1.25-0.9 1.3-1.15 3.0-2.0 7.3-6.3 Replace < 0.9 < 1.15 < 2.0 < 6.3

According to that, both sets are very good.

I would have to do a full discharge test to find out if the A·h is good.

Yep and yep.

...

I can see it in Amazon, but no detailed description that lets me find out why it would be a good one or not. Only a single photo. And two weeks delivery time.

This seems to be 10% of the A·h rating of 550mA·h, which I recall reading somewhere that was the guide.

Thanks :-)

Hello Carlos, , Instead of light bulbs, Do you have an assortments of resistors?

To know which resistance value to use, calculate R = V / I V is the battery/cell's nominal voltage I is the test current. For this go here:

your battery in the table, look at its "Typical Capacity (mA hr)" --

-- divide this number by 10.

For example, given a "AA" carbon zinc, V = 1.5 V, I = 1100 / 10 = 110 mA R = 1.5V / 110mA = 13.6 ohms. Next closest standard resistor is 15 ohms.

cheers, RS

Yes, but not here. Temporary place.

YES! This is the data I wanted. Thanks :-)

I wondered about doing the load circuit with a controlled transistor. An adjustable, controlled, current drain. I have not yet thought about it.

Carlos E. R. wrote: ===============

** Don't bother.

Loads used with non rechargeable cells are like resistors. While rechargeable types have steady voltage outputs till exhausted.

..... Phil

Not thinking of that... just of having a variable current drain for different battery types, at relatively high power, more than what a potentiometer stands.

Carlos E. R. wrote: ===============

** Then try.

Constant current is unrealistic for single use cells and meaningless for the others.

** So use a few fixed resistors and a switch.

How many hours of you life do you intend wasting on this exercise ?

..... Phil

My guess(tm) is what you want is a battery capacity discharge tester, which measures the remaining capacity of the battery in ma-hrs. You can't do that with a voltmeter. If the LiIon battery were perfect, it would have the same voltage everywhere between zero charge and 100% charge. That's not very useful.

What you probably want is a graph of the battery that looks something like this. This is a single (cheap) 18650 LiIon cell:

The capacity in ma-hrs (or amp-hrs) is where the voltage begins to drop. The energy stored in the cell is the area under the curve. Both capacity and energy curves will change as the battery ages. Your unspecified model DECT phone batteries will have a similar curve.

I created the graph using a West Mtn Radio CBA III which is no longer being produced:

My test setup looked like this mess: The clamp is to make sure I have a good connection to the cell terminals. The basic procedure is to charge the cell or battery to

100%, clamp it into the tester, set the test conditions (mostly discharge current), and wait for the computer to produce the graph.

There are also devices on the market which will produce a single number for the battery capacity in ma-hrs. I have a few of these and find them nearly useless. There's no way a single number can be used to describe the graph curve.

Good luck.