Test Batteries? Battery Tester?

[Grun]

What is a good way to test to make sure my batteries are charged, aside from using the charger? I have Ni-MH, and Li-Ion types.

 

[diff_lock2]

I would like to know too, other than a multi meter... and voltage checks.

Make it cheap too!

 

[MrAl]

Hi there guys,

Funny you should ask, because i have a new chip that will be available
sometime this week that will analyze a battery using the standard PC
(same computer you use to access this forum). In fact, it will do
four batteries at the same time. Price? $4.50 USD not incld shipping.
Complete circuits on the way (pc board, all parts, connectors) on the
way but im not sure how long that will take just yet.
You have to supply your own battery holder (Radio Shack) and your
own discharge resistors (cheap everywhere, like 5 cents each) of which
you need 1 per cell to test.
The software comes free with the chip too and is made for Windows,
but i could get a dos version going too if needed.

Here's a screen shot, but a lot has been added to it since then such
as a Thermistors page which sets up cheap thermistors for use in
measuring temperature of the cells.
http://upload3.postimage.org/171576/photo_hosting.html


The motivation for this project was that i was tired of getting sad
under rated cells locally so i wanted a way to test them and see just
how bad they really are and bring them back if need be. I decided
to start selling the chips so that other people could do the same too
because i always hear people talking about how their cells dont seem
to be charged fully or something. Some people dont want to have
to construct their own board (1 chip, about 6 resistors and one
low cost 78L05 regulator) so i started thinking about getting
boards made up and populating them myself and then selling
the whole board finished and ready to plug into the computer
port.

 

[Power Me Up]

Although what Al is offering sounds very useful (I've got my name down for one already) it may not be what you're actually looking for. What his tester will do is to discharge the cell under test and tell you how much charge was left in it. A bit like tipping a bucket upside down to see if there was any water in it. If you just want to see if a cell has much charge left so that you know whether to charge it before use, it's not really what you want.

You could take a look at the ZTS Multi Battery Testers:
http://thomasdistributing.com/shop/...ee-deluxe-protective-carrying-case-p-564.html

Although they are fairly expensive...

A cheaper solution would be to get a resistor that would put a similar load on the cell as whatever it is you normally use them in and test the voltage whilst connected to that load. Keep in mind that with NiMH cells, this still isn't going to tell you a huge amount because of their flat discharge curve...

 

[MrAl]

Hi again,

PowerMeUp:
Well thanks for pointing that out, but there may be a way to estimate the
charge in a cell that has been recently charged too. If the cell normally
takes 2.5 hours to charge and on the next charge it only takes 2 hours
then that means it had (2.5-2) times the normal capacity/2.5 for that cell
left in it. Of course this means the cell has to be charged to find out,
and it should be charged and discharged for the first test to see what
the starting capacity is.
I'll try to include as much application information as time will permit with
the software.
Also, because of the ability to profile a given cell, it may be possible to
get the capacity information from a short discharge using a known resistance
and compare the discharge profile with other discharge profiles to see what
the estimated remaining capacity is. I dont know if this works yet, but since
the digital techniques are still relatively new and the data is so much more
accurate than old techniques of using an analog meter, there may still be
things about these cells that can be determined and used in everyday life
that we dont know about just yet.
I'll certainly be looking for these kinds of correlations myself too and of course
anything i or anyone else finds will get put into the software for everyone to
be able to use.
I was thinking of adding an "experiments" application note too, that would
guide people trying to find out more about cells in general in ways of testing
their cells and looking for hints as to capacity and estimated remaining cycle
life. These are things i would like to find out too.

As a side note, they do make 'capacity' chips but they have to be built
right into the device the cells are powering so they can monitor the
current the device is drawing on a 24 hour basis. There is also the chance
that they might come out with new chips too that work even better.

Oh yeah, the Li-ion types can be estimated from their terminal voltage reading.
There's a chart somewhere on CPF made by i think Silverfox if you can find it.
If not, ask him to show you where it is.

 

[Carpenter]

Check out the ZTS testers. They take a reader based on actual capacity left in the cell, not just a voltage reader based on no-load.

 

[raythompson]

I second the ZTS testers. I have one and it works as advertised.

 

[MrAl]

Hi there,

The "ZTS" tester sounds interesting...how much does it cost and how
accurate are the capacity readings?

 

[Power Me Up]

The "ZTS" tester sounds interesting...how much does it cost and how accurate are the capacity readings?

They're about $28 from Thomas Distributing. I included a link to one in my previous post in this thread, but I'll include it again below:
http://thomasdistributing.com/shop/...ee-deluxe-protective-carrying-case-p-564.html

They give readings in 20% increments - i.e. 0%, 20%, 40%, 60%, 80% and 100%

The one I've got seems pretty reasonable - it's not always totally accurate, but certainly a lot better than just reading the voltage with a multimeter or using basic battery tester. You can put each cell through several tests to make sure that the readings are at least consistent.

 

[NiOOH]

I've constructed myself a small gadget that I'm using to estimate state of charge. Mind that I'm talking about estimation. No device can give exact figures for the remaining capacity without a full discharge.
Anyway, what I use is a 1 AA/AAA cell holder connected through a switch to a 4 ohms high power resistor. In parallel, there ar leads to plug my DMM. This is enclosed in a small project box. Plug the DMM. With the switch in off-position I measure the OCV. Then close the cirquit through the resistor and measure again . Since I know the discharge characteristics of my cells I can estimate to within 20-30% the remaining capacity. I'm also using this setup to identify high IR cells.

 

[MrAl]

Hi again,

28 dollars seems reasonable. 20 percent increments arent that bad either.

NiOOH, testing like that sounds interesting. Perhaps you can provide more
details and i might be able to incorporate that into the software.

 

[lctorana]

...what I use is a 1 AA/AAA cell holder connected through a switch to a 4 ohms high power resistor...

+1

Except my rig has a built-in 1.5v meter, and C & D holders as well, and a 1.2v 220mA bulb is my switched load. Concept is identical.

You measure the OC voltage, and then the loaded voltage.

Test works for Alkaline, NiMH, NiCad, Zinc-Carbon & Zinc-Chloride cells - only your expectations differ.