Electric cell recycling/sorting machine

Electronics and electrotechnical stuff
tony_arduino
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Re: Electric cell recycling/sorting machine

Post by tony_arduino »

Ok, I thought I'd better gather some actual data, rather than speculating. I took samples from two bucket fulls of batteries awaiting recycling. If anyone wants to look at statistical significance, then sample one was about 790gm from an approx 18kg bucket, sample 2 was about 580gm from an approx 15kg bucket. By my reckoning this would give us results in the region of +/- 15% in terms of representing the whole bucket full. The trouble is I now reaslise that although I took random (gloved!) handfuls of cells, I didn't dig into the bucket significantly, so not really a random sample! Anyway as a start here is a CSV with the data Battery Survey

I was a bit surprised at the number of relatively undischarged cells. The open circuit voltage is not a very exact measure of charge left, but voltages between 1.5V and 1.65V apparently indicate less than 10% discharged for alkaline cells. (energizer-alkaline-appmanual(Eveready Battery Co. Inc.): "an OCV reading of 1.5 volts or greater for a single cylindrical 1.5 volt Alkaline or Carbon Zinc battery indicates essentially an undischarged battery or one that has been discharged less than 10%.")
I like re-using/re-purposing/recycling old pieces of technology and have boxes of 'useful' looking salvaged parts. One day I might actually make something original ;)
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Orngrimm
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Re: Electric cell recycling/sorting machine

Post by Orngrimm »

Indeed. Yes... The sample will be interesting!
The base question here is: How do you plan to measure the left energy in those cells?
Voltage alone is zero indicator on that level... Only to say: Maybe full or propably used
Basically what you need is a current-meter in the super low regions 0.01-50mA.
Then, hook it up to the line connecting your battery to be tested to a resistor of around 30 Ohm. This would give 50mA with a full battery and 0.02 mA (or 20 Microamps) with a dead one @ 0.6V.
Stupid idea...

Another and more simpler Method would be to measure the voltage directly over the Resistor and handle the resistor as Shunt which measures the voltage to a dead short.
In other words: We combine the shunt and the load.
To measure the voltage would be much simper than Measuring the current indirectly thru a gauge.
Just be sure the resistor can handle a fully charged battery in case... I would take like 500 Ohm or so to have a much higher resistance as load (Re) than the internal resistance (Ri) of the battery. With Ri = Re the power on Re would be the highest, but the efficiency would be 50% only.

This measurement could even be done with a small arduino if you provide a good external Analog reference or use a A/D-Converter which is of higher quality than the crappy ones of Atmel inside... a nice 16bit or so. Like a ADS115 (https://www.aliexpress.com/item/32817162654.html) or something alike.
Slap on a nice Arduino which logs the Voltage data over time to a SD-Card or via USB to a PC and you have your voltage-graph.
Keep the sampling to like 1 per second for simplicity later. Lets say, you go with exactly 1sec / sample.

A joule is conveniently also based on the second: Watt times second.
We know that Current = Voltage * Resistance
Watt = Current * Voltage
When we substitute Current by the formula, we get Watt = Voltage * Resistance * Voltage = Voltage2 * Resistance
Now, as the timeframe per measurement = 1 sec and we have the Watt in this sec, we also can say = Joules or WattSeconds

If you calculate the Watt (or the Ws, same here) per line (of 1 sec) you can sum it up and you have the total of joules or Ws left in the battery.
Simple! :D
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tony_arduino
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Re: Electric cell recycling/sorting machine

Post by tony_arduino »

I would agree that for Lithium cells, voltage doesn't tell you a lot about the capacity left, but looking at the discharge curves for Alkaline cells, the voltage drops rapidly to below 1.5V then flattens off a bit - I am betting that those cells showing 1.57V and higher, are basically unused (perhaps a bit of self discharge), it will be interesting to prove it though.

1 sec sampling as they are discharging would be a good idea, I see there are a few programs out there to do data logging straight to a spreadsheet hanging off the serial output of an arduino ... might be useful. I might hang fire for a bit until I've got some sort of Joule thief / DC-DC voltage booster, and then discharge them through that so I can look at performance at both ends (I might as well be doing the discharge test into a real system).
I like re-using/re-purposing/recycling old pieces of technology and have boxes of 'useful' looking salvaged parts. One day I might actually make something original ;)
Downunder35m
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Re: Electric cell recycling/sorting machine

Post by Downunder35m »

Although a bit off topic, I feel the need to toss in because the topic is rather interesting:

Back in the day our company had a lot of lead acid batteries.
Mainly used for temporary traffic light systems or lights on big worksites.
One major problem we had was the always different ages and real capacity left in those batteries.
It is vital that something like traffic lights or warning lights stay on during the assigned period of time.

We has bosh charger system for them, was then one of the most expensive things out there.
I guess it was one of the first "smart" chargers.
As we were also working with Bosch on several levels I had no problem getting some nice tech to explain to me how their fancy charger is able to "predict" the capacity of the batteries.
For starters, every battery had an assigned number, you type it in and then connect the battery.
This info was used to store the profiles for this battery.
So far so good and I guess identical to what you are trying.
BUT:
One key feature of the charger was the "pulsed charge" - bad translation but let me explain....
The charge would first check the battery as any charger does, then it puts a load on it and monitors the voltage.
During the entire charging cycle this load check would happen in fixed intervals.
Charger stops charging, gives it a break for a few minutes, then check the voltage drop under load.
The secret algorithm Bosch used are not known to me but I think a similar approach is quite possible with an Arduino.
For us, back then, it was a blessing to know whether or not a battery is still good enough for the task at hand.
As certain types of batteries do benefit from proper charging it might be a nice way to sort your batteries with more accurate, real capacity ratings.
Just an idea though.
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tony_arduino
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Re: Electric cell recycling/sorting machine

Post by tony_arduino »

Downunder35m wrote: Sun Jan 10, 2021 4:12 am ...
For us, back then, it was a blessing to know whether or not a battery is still good enough for the task at hand.
As certain types of batteries do benefit from proper charging it might be a nice way to sort your batteries with more accurate, real capacity ratings.
Just an idea though.
Interesting stuff. For this project I don't really need to know the capacity of the batteries, the system will just suck them dry and spit them out. Basically pouring the contents of lots of batteries into a reservoir, not really caring how much each cell contributed. And powering the system from that reservoir.

But I haven't actually decided it must work that way, if we in fact have a significant number of cells with plenty of charge, then perhaps it would be more efficient to power the system directly from the cells (with a DC-DC step up converter), rather than incurring the losses of discharging the cells into another battery first (the reservoir). It might then be useful to predict how long a given cell was going to power things.

Maybe a hybrid system : those batteries assessed as 'good' because they have a useful charge (eg able to power things for 10s of minutes), could be used to power things directly. Others with insufficient charge (and perhaps that 'good' bunch after they've been used), could be connected to the vampire joule thief to suck out every last drop ...
I like re-using/re-purposing/recycling old pieces of technology and have boxes of 'useful' looking salvaged parts. One day I might actually make something original ;)
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Orngrimm
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Re: Electric cell recycling/sorting machine

Post by Orngrimm »

tony_arduino wrote: Sun Jan 10, 2021 1:05 ambut looking at the discharge curves for Alkaline cells, the voltage drops rapidly to below 1.5V then flattens off a bit
The problem is if you have a dead battery (Lets say, your LOADED voltage (and thats what is shown in these graphs!) of around 0.9V) and you let the battery sit for like a week without any load and maybe even in a warm place, the voltage will recover to in the ballpark of 1.3-1.4V. But it is hollow voltage. No power behind it. As soon as you start to discharge, within like 1mAh it is back to 0.9 or 0.8V.
Source? Electrical engineer by trade, designing medical devices with livetime-batteries with loads close to none (We deal in nanoamperes) where such effects pop up all the time
Thats why i suggested a real discharge under load. The voltage will give you mostly only 3 statis:
1.65-1.45V: New or almost new
1.44-1.0V: Used to an unknown percent
<0.1V: Shorted and leaked cell

Downunder35m wrote: Sun Jan 10, 2021 4:12 amOne key feature of the charger was the "pulsed charge" - bad translation but let me explain....
The charge would first check the battery as any charger does, then it puts a load on it and monitors the voltage.
During the entire charging cycle this load check would happen in fixed intervals.
Charger stops charging, gives it a break for a few minutes, then check the voltage drop under load.
The secret algorithm Bosch used are not known to me but I think a similar approach is quite possible with an Arduino.
Thats state of the art nowadays... You can get single chips doing all that and more. See, a rechargeable battery can be parametrised by many metrics. If you have the luxury to have an identifiable cell (Serial#) you are super lucky. If you even can make sure the chip stays connected to the battery at all times (The idea behind current BMS-chips) you have another advantage:
You can measure the voltage-curve and outputcurrent. Now, you can create sort of spreadsheets where you fill in the voltage at the given external resistance or load. Imagine, every 50Ohm is a new spreadsheet. Now, all you have to do is checking the external load (Re = Uloadedcell / Ioutpout) and you pull up the respective table and you can check where on the curve the current current is. With that you know exactly, the % of remaining energy with THIS battery and THIS load.

Another way (early days) is another metric: Internal resistance.
I made a patent once which goes a bit into this direction:
https://patents.google.com/patent/US8936572B2
There you can see how to measure the internal resistance of a battery by loading it with 2 different external loads. This can happen very fast. The internal resistance is a very good indicator on the livestage of a battery if you know the chemistry of the cell and a bit about the type of this particular cell. See Figure 7 in that case.
Basically the whole patent is about exactly this: Measuring an unknown battery and getting its state of charge.

And while we are at the patents: Group G01R31/3606 may also be of special interest to you:
https://patents.google.com/?q=G01R31%2f3606
It is all about measuring state and % of a batteries and gauging their status. read a bit there and get ideas :D
Stuff like
  • Battery capacity display apparatus and battery capacity display method
  • Apparatus and method for estimating battery state
  • Method and circuitry to calculate the state of charge of a battery/cell
  • Electrochemical cell monitoring and balancing circuit with self-diagnostic feature
  • Battery state estimation method and system using dual extended kalman filter, and recording medium for performing the method
  • Method and apparatus for estimating maximum power of battery by using internal resistance of the battery
and many MANY more...
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Orngrimm
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Re: Electric cell recycling/sorting machine

Post by Orngrimm »

I did a little search for another project at work and stumbled over the energy-Harvesting-Page of Linear.

I took a few minutes to scour over the base parameters and figured from the list at
https://www.analog.com/en/parametricsearch/11503#/
that the
https://www.analog.com/en/products/ADP5090.html
would be very nice for you:
Can be powered dirctly from the "dead" battery if it still can provide 16μW of power at at least 0.38V
Once thru the coldstart, it works down to 0.08V as it seems.
Also, has a direct Battery-Charge-Output as well as a digital "PowerGood" pin which can be used to indicate if there still can be power drawn from the battery or not. Hopwever, i havent checked this exactly, if SYS-Voltage is dependent or independent of ONLY the powersource to be harvested or if the IC starts to use power from the supercap/battery once the input-source is depleted. Would need a bit of reading or a quick test.

In terms of testing: The Eval-kit is available:
https://www.digikey.com/en/products/det ... LZ/5031774

https://www.analog.com/media/en/technic ... 3105fb.pdf could also yield good results...
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tony_arduino
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Re: Electric cell recycling/sorting machine

Post by tony_arduino »

Thanks for that bit of research, I'll have to track some of those down. Haven't had much time, but did get another sample of batteries, the voltage distribution was more in the range I expected. The average recycled Alkaline cell is about 1.2V . The higher voltage Alkalines (1.57 and above) only drop to about 1.5V on load so look as though they really do have charge left. The Lithiums though do drop to well under 1V with load.
I like re-using/re-purposing/recycling old pieces of technology and have boxes of 'useful' looking salvaged parts. One day I might actually make something original ;)
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