Why not design your own charger?

HKJ · 2019-10-29T19:00:06.000Z

My new board arrived today:

A lot of small modifications: A light filtering on the ADC inputs, protection for wrongly connected temperature sensor, diode to avoid back feeding an unpowered charger (It will still back feed a little through the ADC), a few changed connections and adjustment of some footprints and placement.

With a 3D printer I could also make a frame for it, it makes it much safer to test near near wires, metal battery holders etc.
I had already designed the frame with parameter control, i.e. I only had to type in the distance between the screw holes and print it.

theguy · 2019-10-29T19:22:43.000Z

wow, awesome

HKJ · 2019-10-31T16:39:35.000Z

With the new board I decided to make the box:

But I was a bit too fast, I forgot a connector for the temperature sensor. I will probably use a stereo mini jack for that.

But with the box I could do some temperature test.

Two termocouplers into the hole for the led and into a box with computer interface.

One coupler is place at the top above the hot spot, the other is placed below the inductor (It is the hottest part).

First a 1A test with NiMH. The temperature 40°C at the box, it is made of PLA that can handle up to about 50°C
It is warmer at the inductor, but that is no problem or maybe I need to check the box below the inductor?

Lets try maximum charger current, i.e. 1.5A. The box gets very close to maximum allowable temperature.

My options are: Adding some went holes in the box or require a more heat resistance material for the box when using 1.5A charge current.
I could also wait for a inductor with slightly thicker copper windings, it might stay cooler.

Another small issue, I had planned on using a 5mm smart (neopixel) led as indicator, but it do not have the colors in the same sequence as the WS2812 I use on the circuit board. I could just change the program, but I do not like the two LEDS showing different colors. I will probably modify the box to use the small WS2812 breakout board (It is the 2812 version, not the 2811 version as marked on the board).

cturtle · 2019-10-31T18:02:19.000Z

Man alive! This thing is really coming together. It has to be one of the cleanest looking DIYs I’ve seen at this point. How are you getting your graphs? Copy serial output to Excel?

HKJ · 2019-10-31T18:15:15.000Z

cturtle:

How are you getting your graphs? Copy serial output to Excel?

Something like that. The thermocoupler box* can give the same type of listing as the charger. When saved to a file I have a program that uses JFreeChart to make the charts (I gave up on Excel for charts long time ago).

*This is another of my projects, it is finished and a articles with gerbers and software is written, but I have not published it yet. There was a few snags during the design and making of that box.

HKJ · 2019-11-05T10:30:57.000Z

The charger can be used directly from a serial terminal, but I do not plan on it and have written some software to control it. It is done in Java, this means it will work on Windows, MAC and Linux.

Initial screen for connecting to the charger or loading a old csv file for analysis.

The charge control screen, the number of parameters to enter will change depending on selected mode.

The battery I test here is a old eneloop that at one time was used for my charger tests, bet was retired a few years ago.

It is possible to see the log in numeric format

The data can be reduced in a couple of ways.

Adjusting the practical aspects of the charger, i.e. calibrating and setting a few configuration items.

tempo · 2019-11-05T10:33:40.000Z

how fast can it discharge?

HKJ · 2019-11-05T10:42:46.000Z

tempo:

how fast can it discharge?

It will take years to discharge a cell on it, it is only a charger and as long as it is powered the leakage current is very low.

HKJ · 2019-11-05T10:52:33.000Z

cturtle:

How are you getting your graphs? Copy serial output to Excel?

With this software it is very easy to make these charts:

The chart can be saved in any size and will include the curves selected on the screen.

Mr.Poppy · 2019-11-05T21:57:09.000Z

group buy… in for 1 “HKJ Charger”

HKJ · 2019-11-06T11:02:01.000Z

Mr.Poppy:

group buy… in for 1 “HKJ Charger” :sunglasses:

I do not want to make any more chargers than I need, but if somebody want to arrange any group buy of parts or assembly service they are welcome.

If anybody want to play with the software it is here: Download of zip file

It includes the software and a couple of charge logfiles (CSV). All actual hardware control will be disabled, because no hardware is connected.
It is possible to look around in the software, load the logfile and play with the chart and table display.
It is the exact same version software that I use at the moment, I have neither added or removed anything for this demo version. I have tested that it starts on Windows and Linux.

To use/test it a working Java version 1.8 or newer must be installed.

HKJ · 2019-11-07T09:46:14.000Z

I modified the box to add the hole for the temperature sensor and change the led:

That is probably the final box.

The led required a bit of work, I could also have cut a track in the lid to get the led a bit closer to the surface, but decided not to.

kennybobby · 2019-11-07T12:15:00.000Z

Excellent work on your build and thank you for sharing the files. i really like how you integrated the LED in the cover.

Just wondering if you have ever had a cell swell up or explode while testing?

HKJ · 2019-11-07T12:21:01.000Z

kennybobby:

i really like how you integrated the LED in the cover.

With a 3d printer you have a lot of freedom when designing stuff.

kennybobby:

Just wondering if you have ever had a cell swell up or explode while testing?

No, I have had cells vent a couple of times, but that is rather undramatic, i.e. I usually never notice it before I remove the cell.

HKJ · 2019-11-17T10:52:57.000Z

Not much have happened with the charger.

I have mounted all the PCB’s, the one in the frame is still in the frame and working.

The software has got a few updates and I have made it more general. This means it can read any CSV file with a voltage and current column and show it, if the file include a timeStamp column counting seconds it can calculate capacity and energy if they are missing in the file. The software do not care if the file is from a charger or discharger, it will work with both.

The link in post #44 points to the updated software now.

HKJ · 2019-11-29T15:55:52.000Z

In my latest battery review: Test/review of Enerpower+ 18650 3000mAh (Gray) 2019
I uses this charger for a last minute test (Se bottom of review).

I needed a 4.35V charger and logging of the result, it was very easy to do.

HKJ · 2019-12-04T16:15:23.000Z

I am working on the article about the charger, but I do not know when I will be finished.

I did have time to a few software update, The IR curve can be calculated for any charge/discharge curve with pulsing current. The chart can either be saved to disk or copied to clipboard, both in a couple of resolutions.
Use the link in post #44 to get the software.

It is fairly easy for me to add support for other chargers/dischargers as long as they generate a CSV file. To get support email me a couple of CSV files together with a list of charger and software used and I will look at adding it. My email is info@_something_with_lygte

HKJ · 2020-01-05T17:29:46.000Z

Testing charge algorithm for LiFePO4 batteries with this charger: Charging LiFePO4 batteries, algorithms

AkosLukacs · 2020-01-30T13:39:26.000Z

Nice job.
How good is fasttech’s acrylic battery holder? Asking because on the last photos you used the aluminium battery holder.

HKJ · 2020-01-30T13:59:45.000Z

AkosLukacs:

How good is fasttech’s acrylic battery holder? Asking because on the last photos you used the aluminium battery holder.

The acrylic holder is generally fine, the issues I have:

It is slightly difficult to mount batteries in it, there is not enough space beside the battery for my fingers.
It will not fit 32xxx batteries
The front can melt when running hot.

Ad 3) I do still use them, but have replaced that piece of plastic with something that can handle high temperature. This means the inside of the battery connection piece sometimes melts and I have not found any place to buy spares, I do not believe the aluminium will handle this better.