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Brett's Arduino 8x Smart Charger / Discharger
#1
Hey all,

Just thought I would start a new thread.

Finally I have had some success on building my new prototype 18560 charger / discharger. I am using 3.3ohm resistors for the discharge, TP4056 modules to charge and it is controlled by an Arduino Mega micro controller. My first manufactured PCB version almost done check out the photo's. I have 1 out of 8 module setup. 

I have already found some mistakes in my design:

9v power jack has backwards orientation. Soldered a cable instead 
The mounting holes for the Rotary Encoder module are wrong. Might be able to drill them.
The RobotDyn Arduino Mega Mini Module I used in easyEDA has the ICSP header 1.27mm to the left. only using 1 wire for the SD Module so can jumper wire it.
Also thinking of adding a relay switch to the 5V 10A charger power input.

Still ironing out some issue in the code at the moment. 

The sequence is:
• Check for a battery to be inserted
• Get the battery barcode via a barcode scanner
• Charge the battery
• Check the milliohms of the battery
• Rest the battery for the set duration (if the battery was charged)
• Discharge the battery
• Recharge the battery
• Competed cycle uploads the battery information to my database – wait for battery to be removed then it restarts the cycle back to check for a battery to be inserted.


Checkout my database stats page of currently processed batteries: http://vortexit.co.nz/battery_statistics.php

My youTube channel: https://www.youtube.com/channel/UC3F60pB...sHjqQOAO9Q

So I thinking hopefully next revision releasing the PCB design and code once it is fully working. 

Gregor Scott, BlueSwordM, yngndrw And 7 others like this post
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#2
Nice job! Im nearly finished a very similar project to this. How important is it that you let the cell rest after charging before discharging for capacity checking? I have mine set to immediate as of right now
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#3
(03-26-2018, 03:51 AM)Stephen Ryan Wrote: How important is it that you let the cell rest after charging before discharging for capacity checking? I have mine set to immediate as of right now

I would probably wait about 5 seconds just so the voltage settles. Other wise, you might read the cell when it's slightly higher and it'll throw your capacity readings off a little bit.
So, the end of charge the cell could be at 4.21V, and the settled voltage is 4.19V. This doesn't seem like a lot, but it could make the difference into which bin you put your cell. (ie. 2200mAh vs 2100mAh as the cell could be 2230mAh vs 2160mAh, respectively with all numbers). Granted, it might not matter in the end overall, but just saying  Wink
Stephen Ryan likes this post
Proceed with caution. Knowledge is Power! Literally! Cool 
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Certified 18650 Cell Reclamation Technician

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#4
(03-26-2018, 03:51 AM)Stephen Ryan Wrote: Nice job! Im nearly finished a very similar project to this. How important is it that you let the cell rest after charging before discharging for capacity checking? I have mine set to immediate as of right now

Awesome mate. Yeah I rest for 1min but I can change it to whatever I want. Like Korishan said it is good for them to settle also lets the temperature drop a bit for the discharge cycle.
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#5
Hey brettwatty, 

thank you very much for the presentation of this project.
In a small group we also imagined something like this, our layout is very similar: 8x charger / discharger, scanner, database!

We would like to support your project. How can we help?
The day of 100% renewable energy will come. It won't be long now.
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#6
Hi.
Nice !! and very finished looking Smile cool 

I'm in stage of upgrading my 20x tester to do pre-charge and i need that cells ,after 2-3 week rest after first charge, coul'd be recharged to max. But .. TP4056 are made that way, that they do not charge until <4V so .. i need to pre-discharge prior the pre-charge Smile Did you use this kind of stages in your code ? Smile
I'm thinking of calculating the drop while in 1 amp and then discharge the cell until it is  voltage+ drop < ~3.9 then the tp4056 would start charge... and then run real discharge test
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#7
(03-26-2018, 10:37 PM)EGOksy Wrote: Hi.
Nice !! and very finished looking Smile cool 

I'm in stage of upgrading my 20x tester to do pre-charge and i need that cells ,after 2-3 week rest after first charge, coul'd be recharged to max. But .. TP4056 are made that way, that they do not charge until <4V so .. i need to pre-discharge prior the pre-charge Smile Did you use this kind of stages in your code ? Smile
I'm thinking of calculating the drop while in 1 amp and then discharge the cell until it is  voltage+ drop < ~3.9 then the tp4056 would start charge... and then run real discharge test

Hey mate, I am not currently doing that but can do. I might look into that. Thanks

(03-26-2018, 10:16 AM)tango Wrote: Hey brettwatty, 

thank you very much for the presentation of this project.
In a small group we also imagined something like this, our layout is very similar: 8x charger / discharger, scanner, database!

We would like to support your project. How can we help?

No worries mate. Yes all I need is time and money either I have much of hahaha. Hopefully will have something presentable in the next few weeks and I can do some demo's. Cheers Brett
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#8
I got the other 7 modules in last night. Got the whole charger / discharge working. I found some small bugs in the code will need to fix them. I had an issue with the 10W 3.3ohm resistors getting so hot that they were melting the wire insulation. I will need to order some silicone 20awg wire. I the interim I wrapped some kapton tape around the wire insulation. 
Has anybody had issues with the TP4056 chargers over charging the batteries I have 1 charging at 4.27V another 4.30V luck I have a voltage read out during the charge cycle. I can easily replace them.

Here are some photo's
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#9
(03-27-2018, 09:22 PM)brettwatty Wrote: I got the other 7 modules in last night. Got the whole charger / discharge working. I found some small bugs in the code will need to fix them. I had an issue with the 10W 3.3ohm resistors getting so hot that they were melting the wire insulation. I will need to order some silicone 20awg wire. I the interim I wrapped some kapton tape around the wire insulation. 
Has anybody had issues with the TP4056 chargers over charging the batteries I have 1 charging at 4.27V another 4.30V luck I have a voltage read out during the charge cycle. I can easily replace them.

"Preset 4.2V Charge Voltage with 1.5%
Accuracy " - so it could be 4.2V+- 0.07245V
better test .. and get some tp4056 IC's to replace or replace whole pcb

No heat-sink on irlz44 ? they must be toasting ? Smile mine with the small heat-sink are very hot ... i use a fans to keep everything to touchable temperatures.. and 1ohm10W resistors to..
Tried just now after code update to not use the fans, but the heat is quite high Smile

P.S: liked your decision to add the irlz44 as polarity protection Wink  Rely nice idea ... i keep doing this mistake of adding in wrong polarity's .. and after that MEGA gets crazy .. the load on all slots starts jumping from 400mA to 1.5A Smile
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#10
Big Grin 
(03-27-2018, 10:02 PM)EGOksy Wrote:
(03-27-2018, 09:22 PM)brettwatty Wrote: I got the other 7 modules in last night. Got the whole charger / discharge working. I found some small bugs in the code will need to fix them. I had an issue with the 10W 3.3ohm resistors getting so hot that they were melting the wire insulation. I will need to order some silicone 20awg wire. I the interim I wrapped some kapton tape around the wire insulation. 
Has anybody had issues with the TP4056 chargers over charging the batteries I have 1 charging at 4.27V another 4.30V luck I have a voltage read out during the charge cycle. I can easily replace them.

"Preset 4.2V Charge Voltage with 1.5%
Accuracy " - so it could be 4.2V+- 0.07245V
better test .. and get some tp4056 IC's to replace or replace whole pcb

No heat-sink on irlz44 ? they must be toasting ? Smile mine with the small heat-sink are very hot ... i use a fans to keep everything to touchable temperatures.. and 1ohm10W resistors to..
Tried just now after code update to not use the fans, but the heat is quite high Smile

P.S: liked your decision to add the irlz44 as polarity protection Wink  Rely nice idea ... i keep doing this mistake of adding in wrong polarity's .. and after that MEGA gets crazy .. the load on all slots starts jumping from 400mA to 1.5A Smile

Yeah the bloody TP4056's I have are not even close to +- 0.07245V. 
Thinking of adding a fan on the side.  
I am using IRF540N N-Channel FETS rated at 28A max never get hot for me I only used them because a have a bag of 100 left over from another project. 
I have SI2306DS SOT23 for the polarity protection rated for 2.8A @ 4.5V VGS I will eventually use IRLML2502TRPbF-1 SOT23. 
My board is designed for either THT or SMD components for all the resistors and FETS.
Polarity protection is a must for me so many TP4056 fried because of dumb mistakes and last thing you want is a -4.20V on an Analog input  Big Grin .
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