Do you have some rechargeable batteries lying around that need a capacity check? Today, we’ll take an Arduino Nano and a few other electronic parts to build a AA battery tester that will give us fairly accurate “real world” readings on NiMH batteries. This little device will come in handy for the next project on the list, so be sure to subscribe for more how-tos!

How To Install The Correct Arduino Nano Driver https://goo.gl/zWB4BD

Parts List (Affiliate links):
Breadboard & jumpers: http://amzn.to/2uq6KNW
AA battery holder: http://amzn.to/2eHNEOa
Terminal blocks: http://amzn.to/2uq1IRD
1R10W Ceramic Resistor: http://amzn.to/2eHKk5H
Arduino Nano (clone): http://amzn.to/2uQAd4Z
1.5R10W Power Resistor: http://amzn.to/2eIieHc
IRF3205 MOSFET: http://amzn.to/2eInMBG
10KR Resistor: http://amzn.to/2uPLjXQ
Nokia 5110 Screen: http://amzn.to/2eHS0VC

Original concept and Arduino sketch by Adam Welch https://goo.gl/eN85W9

Music: “Robots R Us Remix” by Anders Enger Jensen
https://goo.gl/KEEzoY

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Production videos on Mondays (when available)
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Tech teardowns, repairs, and reviews; sketches; how-to; games; and lots of other interesting geekery. Thanks for watching, and be sure to like, share, and subscribe!

TRANSCRIPT:

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greetings programs Atari here you there

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and as an object of curiosity I’ve been

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looking for a way to check the capacity

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on these little rechargeable double-a

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batteries for reasons and I stumbled

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upon Adam Welch’s battery capacity

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tester a built out of a Arduino Nano for

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a couple years ago Adam was salvaging

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lithium-ion batteries from old laptop

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batteries and so forth and I didn’t mean

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anything quite that robust so I took the

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basic design of the basic sketch and

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I’ve adapted it into a double-a checker

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so I’m going to use the same basic parts

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and I’ll provide links in the doobly-doo

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for your convenience but first we’re

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going to look at the circuit and we’re

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going to see how it works we start with

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the battery that we want to test from

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the positive terminal we need to run the

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circuit into a current shunt a current

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shunt is a resistor of a known value

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that we can use to test the effective

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voltage drop from one side to the other

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here we’re going to use a 10 watt 1 ohm

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resistor so it’ll be easy to measure

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you’ll need to run a probe line from

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each side of the shunt into an analog

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i/o pin on the Nano so that we can

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compare the two values from the shunt

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will run the circuit through some kind

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of a low this can be a power resistor a

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motor a fan or even a lamp so long as

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it’ll run on one type of my bolts from

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the load we’re going to attach our

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MOSFET and what the MOSFET is going to

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do is going to take a signal from the

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Nano and toggle the circuit every few

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seconds so we can take readings over

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time so to wire this and wait wait let

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me let me back this line up just a

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little bit so you can see more clearly

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so why are this let’s run the circuit

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from the load into the drain pin on the

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MOSFET we’re going to run a signal wire

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from one of the digital pen Bulma nano

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into the gate pin on the MOSFET to

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control the circuit and then we’ll run

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the source pin from the MOSFET to a

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common ground

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the ground will connect to the analog

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ground pan on the nano through a 10 kilo

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ohm resistor to protect the

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microcontroller from any kind of voltage

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spike this is highly unlikely in this

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device but it’s a good practice anyway

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then back into the negative terminal fat

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[Music]

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now let’s take a look at the sketch code

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Adams Arduino sketch is fairly simple

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basically we’re just going to invoke the

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library that drive the LCD to find a few

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variables and perform Ohm’s law

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calculations until the battery drains

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out here you can see where we’ve defined

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our pins analog low and high for the

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shunt and the digital signal pin for the

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MOSFET this section defines all our

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variables for the calculations later

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chump resistance reference voltage

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agency make sure that you check your

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reference voltage between the five volt

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and the ground pin otherwise your

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calculations may be off and that will

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give you faulty data back I got a

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reading of four point six eight volts

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from my Nano but your mileage may vary

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for double a nickel metal hydride

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batteries they really shouldn’t be

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allowed to deplete less than seven to

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eight hundred millivolts so we’re going

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to stop our tests about 900 millivolts

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just to be safe this isn’t going to

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allow us to get the crazy high capacity

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ratings of the manufacturers advertise

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but we are going to get a better

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real-world kind of figure now here’s

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where we start our actual program we

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have some serial output so we can read

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the test data as it comes out then we

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set our digital signal pin to love when

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it goes high it will close the circuit

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and we’ll be able to collect some that

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then we begin our loop first we check to

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make sure that the battery is a drained

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out cap then we send a signal for the

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MOSFET to close the circuit by switching

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the digital pin to hot we’ll measure the

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voltage on both sides of the shunt then

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divide the difference by the known

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resistance of the shunt and get the

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actual current going to the circuit

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little quick convert

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and units on the current and multiplied

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by time to get the measured capacity of

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the battery at that point and then

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display it rinse and repeat

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once the voltage drops below our

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specified threshold then we’ll jump down

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to the Kota that displays the final

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results of the test and turns off the

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circuit now that we’ve got an idea of

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the design in the code let’s see what

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parts were going to need and build this

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first we have our breadboard this is

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well I guess a collectible at this point

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this is a RadioShack 2 7600 one

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breadboard that has the integrated power

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terminals but you can use any old

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breadboard just as well where are

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shunned we’re going to use this 10 watt

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1 ohm ceramic resistor to connect the

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battery we’ll use this single cell

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double-a battery hole of course I’ve

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already soldered a couple of leads off

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the terminals so that I can actually use

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it for the load I’m going to use this 10

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watt 1.5 ohm power resistor but you can

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again use a fan or a lamp or whatever as

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long as it’s 1.5 volts on that we’re

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going to need a handful of these little

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terminal blocks to connect the lead

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wires together so we’ll throw those and

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an even high RF 3205 MOSFET to handle

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the switching in the circuit 10 kilo ohm

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resistor as voltage protection for the

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Nano of course we have the Nano or in

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this case a cheap Chinese clone now I

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found out the hard way that these will

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likely need a different driver as they

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use a different onboard chipset than the

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FTDI the genuine Arduino music

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I’ll put an article on airborne surfer

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comm explaining how to install those

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drivers just in case you

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bottom piece to the puzzle is this Nokia

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5110 screen module and I’ll show you how

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to wire that in as excessive things

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together on the breadboard you’ll need

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the library for this module and I’ll put

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a link to that in the write-up on

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airborne surfer comm as well and of

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course we’ll need some assorted jumper

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wires to connect everything that’s

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necessary so let’s get this thing

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together first let’s get the lead wires

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from the battery holder screwed into one

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of these terminal blocks so we can

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attach it to the red book just like the

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circuit we drew earlier the positive

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terminal is going to connect to the

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shunt resistor and to the high analog

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pin which is a zero on the net at the

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other end of the shunt and I could

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jumper to the low analog pin a1 on the

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Nano for the load I like to have a

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little space here because of all the

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components that are going to be

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installed in really close together so

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I’m going to attach a separate terminal

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block to each of the loads leads plug

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the men like so take a second and see

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that you’ve got your spacing right on

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the breadboard because we’re going to

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need to install everything according to

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the pins on the MOSFET the left end here

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is the gate then the drain then the

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source and the whole thing is dependent

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on how you wire this part plug the

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MOSFET into the breadboard

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so that the drain pin lines up with the

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lead coming from the low run a jumper

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from the digital signal pin the 10 to

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the gate 10 on the MOSFET for the ground

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I like to buy myself a little space by

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running a jumper from the source pin on

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the MOSFET to an adjacent clear line on

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the breadboard now we have a sort of a

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ground bus if you will that we can

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connect all of our common grounds to go

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ahead and run a jumper from the ground

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bus back to the negative terminal

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battery

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now add your 10 kilo ohm resistor from

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the ground bus to an adjacent row and

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from there back to the ground pin on the

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Nana lastly we need to connect the

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screen module make sure you’ve got

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plenty of space on the breadboard and

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test fit it to be sure then just connect

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the digital pens to the appropriate end

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on the screen as shown here now that

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we’re all wired up let’s test this thing

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out I’m going to throw a standard

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alkaline battery from the horror fright

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on here just to make sure everything

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works doesn’t really matter the

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chemistry though we’re really just

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concerned with the voltage and the

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capacity for testing purposes and tastic

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looks like everything works so now I can

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solder everything to the circuit board

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and have a proper tool now this little

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device is going to come in handy on the

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next project I’ve got the lined up so be

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sure and hit that subscribe button and

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don’t forget to click the bell

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notification icon so you’ll be able to

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see exactly what I’ve got up my sleeve

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in the meantime let me know you like

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this video we’re leaving a comment down

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in the doobly-doo and I don’t see you

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again in a few days Tallyho y’all