DIY 18 cell charger station for ?30

BaconButtie

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Having just acquireda large number of used Dell laptop batteries (154 in total) I was left with an even larger number of 18650 cells to charge and test, in excessof 900 cells.
As I only have a Nitecore D4 for charging and an Opus BT-C3100 to charge/discharge the cells, I started looking at a way to charge a greater number of cells. As money is a bit tight I was seeking the cheapest way possible.
I found these on Banggoodhttps://www.banggood.com/DIY-Digital-8-Section-18650-Dual-USB-LED-Power-Bank-Case-Shell-Kit-p-1177621.html?rmmds=myorder&cur_warehouse=CN
I liked these as they could charge 8 cells and had dual input to charge at 2amps and for under 5 each wasa bargain.

Then I thought of how I could power them without using 4 USB chargers...... As I mess aboutwith computers I thought that a PC ATX power supply has a 5v output so one was ordered from eBayfor 10.

I then stumbled across this whilst looking for a pinout schematic of the PSUhttp://dangerousprototypes.com/docs/ATX_Breakout_Board Only 14 including an acrylic case.
Lashed it all together and hey presto, an 18 cell 2a charging station. If it works ok, which is seems to after charging 18 cells with itthen testing them on the opus it looks like all cells are charging properly. I may order another 4 of the cell holders to give it a 48 cell capacity as the PC PSU has a max of 15a on the 5 v rail so have enough grunt to power all the chargers.




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Nice, I can appreciate a DIY charging station.

Just a word of caution... I have some of those USB DIY power packs same as yours, and they routinely overcharge the cells past 4.2v There may also be some inconsistency between units.

What I do like them for are bump charging cells that are below safe voltage. Some charges wont start it they see a low cell voltage, and I use these to get the voltage up slowly. That said, be mindful if you are doing that as you really want to keep the charge rates low so I would only do that with all spots populated.

I have some that ended up failing on me as well, and now I just use them as cell holders. I soldered leads to the rail so I can use them with my hobby charger.

You could always use these to get the bulk of the charge into the cell, and terminate using something a bit more precise like a hobby charger. I think its worth the investment if you can afford one down the line. You can them have very good control over charge current, termination voltages, internal resistance testing, and other useful items including discharge testing.
 
"Just a word of caution... I have some of those USB DIY power packs same as yours, and they routinely overcharge the cells past 4.2v There may also be some inconsistency between units."


Wise words indeed, I have monitored both the chargers and they run at 5v 2.1a until they get to 90% charge then they switch to 5v 1a for the remaining 10% until fully charged. I have now charged 48 cells with them and none have over or undercharged when tested with the Opus so as it stands, things look quite stable but I shall keep a check on it.
 
Sounds good.

Are you using the Opus for voltage readings or do you have a separate digital multimeter?
 
Nice finds & build.
You might want to take care when you load them with cells - all the cells are directly paralleled in there, ie if you put cells with differing voltages in, large currents will probably flow?
 
CrimpDaddy said:
Sounds good.

Are you using the Opus for voltage readings or do you have a separate digital multimeter?

I use a digital multimeter to check voltages before and after charging. I have ordered an Imax B6AC hobby charger so I will most likely use that with the PC PSU and the battery trays, without their charger circuits, to get more control over the charging variables.
So far the cells charged with the existingrig have all reached 4.19v and 4.21v.
I used the opus as a quick check to see if they were fully charged then tested all cells with the DMM.


Redpacket said:
Nice finds & build.
You might want to take care when you load them with cells - all the cells are directly paralleled in there, ie if you put cells with differing voltages in, large currents will probably flow?

I do try to keep the cells grouped together that have about the same voltage, all within .5 of a volt of each other.
 
I do a lot of parallel charging and its totally fine if you are mindful of the cell voltages before going into the cradle... its one of the main reasons I like to use my hobby charger because I can throw 20 - 30 amps at it, but when you have 30-40 cells in parallel its no different than charging with a bunch of TP4056 boards, just less wiring and complexity.

I generally like to keep the cells within a couple tenths of each other.
 
CrimpDaddy said:
I do a lot of parallel charging and its totally fine if you are mindful of the cell voltages before going into the cradle... its one of the main reasons I like to use my hobby charger because I can throw 20 - 30 amps at it, but when you have 30-40 cells in parallel its no different than charging with a bunch of TP4056 boards, just less wiring and complexity.

I generally like to keep the cells within a couple tenths of each other.

I have just ordered 20 of thesehttps://www.aliexpress.com/item/2016-Hot-Selling-18650-Power-Battery-Storage-Case-Portable-Light-Plastic-Box-Holder-With-Leads-ED391/32653104810.html
and 20 TP4056 from Aliexpress for a little over 15, will make a 20 bay charger with them, my thinking being that each cell will have its own charging moduleand by using the PC PSU each module will get the full 1a charge rate. I also have some small digital voltmeters from another project that I may include so each bay can be monitored for input volts and total charge volts.
these are the metershttps://www.aliexpress.com/item/Hot-0-28-Inch-2-5V-30V-Mini-Digital-Voltmeter-Voltage-Tester-Meter-LED-Screen-Electronic/32832406640.html?spm=a2g0s.9042311.0.0.tpLYFb and are accurate to 0.01 of a volt according to my bench power supply and my 2 flukeDMMs, so should give a pretty good idea of voltage being used and stored after charge.
 
some of my TP4056 boards do some weird things when I have one of those mini volt meters attached to it.. Both the charge and completed lights are flickering quickly at the same time when it gets near completion... almost like it wont terminate. I started adding a mini momentary push button so I can take a voltage reading vs having the display live.

I also think 1A is pushing it on those boards from a thermal standpoint, they get pretty hot... I changed most of the SMD resistors on mine to lower the current to 0.5 amps.

Either way, many ways to accomplish the same task... but I opted to keep it simple. I got 4 bay 18650 holders for $1.50 USD each, so for $15 i can hold 40 cells and parallel charge that. I have multiple hobby chargers so cells that are higher or lower voltage get dropped into the appropriate charging station.

While its charging, I just use a non-contact IR thermometer and scan the bank for heaters... soon to be upgraded to a thermal imager.

Its the discharge testing that is more complicated, because I want to use hobby chargers, but its unrealistic based on my cell count. That said, if I can do a few a day, ill get though it eventually.
 
Good point with the momentary push button, will look into that once the build is started.
I have been looking into ways to "bulk" discharge the cells whilst keeping a track on the mah of each cell individually but I can't find a viable solution so looks like I am stuck with doing 4 at a time with the Opus. I may purchase another Opus when funds allow, at least I will be able to do 8 at a time :) but with over 900 cells to get through now and another 250+ arriving any day it's going to be a long task.
 
go for the liitokala 500, youll get one for eur 13,- and it does a good job. i do have 10 of them...
 
Charly144 said:
go for the liitokala 500, youll get one for eur 13,- and it does a good job. i do have 10 of them...

Thanks for the heads up on that charger, I found this on youtubehttps://www.youtube.com/watch?v=hIlR089epyQ looks an interesting build and may better suit my needs due to the amount of cells I have to process, currently have over 900 with another 250+ arriving next week so being able to charge / discharge & test 20 cells at a time will greatly reduce the time taken. I already have most of the parts needed to make thecharge/discharge board from other, now redundant projects.
 
Raided the piggy bank and ordered the rest of the parts to make the charge / discharge board in the youtube video. Should be a fun build once all the parts arrive which will be a few weeks as most of them are from Banggood in China so around 20 to 30 days shipping time to the UK. The most expensive part was the discharge boards, 3.48 each, 78,40 total including shipping but that was all I really needed apart from another 20 single 18650 holders which were only 5 as I have all the other parts in my bits box.
 
Those really are a good deal all thing considered... cell holder, charging board, labor... just bring in 5v and done and a decent parallel charging bank.

Lots of options out there.
 
BlueSwordM said:
These kind of powerbanks, as long as they don't exceed 4.23-4.25V, the cells are in spec.

But I do prefer undercharging, which all my DIY powerbanks from this source are doing at a max of 4.19V:
https://www.ebay.ca/itm/DIY-USB-Mob...hash=item3f703ef972:m:mGkHz9qZaExq3dcYCCpVCcA

They can also output at reasonable currents, so useful for testing large parallel packs.

Yep, the two I have cut off at 4.20 every time, i was surprised at how accuratethey were for the cost as ones i have had beforeither over or undercharged.
 
That is because their IC is much more accurate than the other ones that I've encountered.
The ones I now buy are based on the TP4302B. If set on the 4.20V setting, the voltage deviation needs to be a maximum of 0.1V on constant voltage mode.
Meaning that they are very safe.

http://www.kynix.com/Detail/1136476/TP4302B.html
 
BlueSwordM said:
The ones I now buy are based on the TP4302B. If set on the 4.20V setting, the voltage deviation needs to be a maximum of 0.1V on constant voltage mode.
Meaning that they are very safe.

http://www.kynix.com/Detail/1136476/TP4302B.html

Are there any PDF's that are in english? All the ones I'm finding are oriental and google translate isn't reformatting the text so it overlaps. Can't read all the specs that way.
 
Noooope.

And my Chinese friend is on vacation until Sunday, so no translation coming from him until then.
 
hahah. I did find one that showed a web page that at least kept most of the formatting when translated.

2.1A on discharge, and 1A charge. I can't quite figure out how the leds are lit up (as in, what each one means).
 
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