Battery Vehicle Society

Luckily there are no ready built colour ones at the moment, he has only just released the design. And the original is still supported in the latest software, so I will be using 4.0. I expect there will be a few bug fixs on his firmware over the next month. I hope to get something working soon, whatever that means!

I've got the 6802 slaves connected to my Colour Maximite master. Here's a screen shot of the charging just before it finished. Lot's of work to do still but so far it's working well. I'm running both bms side by side and they both read the same, well at least within 10mv, but that has more to do with the resolution, the new system gives 10mv, old system 20mv resolution (btw the 6802 does 1.5mv resolution but I round the value to 10mv).

Nice screen.

That looks like my first Lithium BMS from ten years ago LOL!!

Peter, if you liked that one, how about this?


The background is a .bmp image created in paint that the maximite loads. It then fills in the boxes.

Shame my artistic ability isn't up to much, it could be used to create a nice display.

Latest code can be found at https://github.com/Greg-Fordyce/evBMS/

Tomorrow I am going to work on getting a working charger relay circuit in the MM.

Oh, nearly forgot. The box in the lower left corner with the question mark. I am thinking that with the left and right arrows I could scroll through the bar graphs and display the cell voltage of the highlighted cell in real time. Similar to the existing function in the version 2 master that lists cell voltages, only you can go back and forward (or is that left and right) and still have live readings. To turn off just scroll to the edge. That box may also be used for other warning messages, time will tell.

Edit: fixed broken github link

Nice and fairly simple master code as well.

I need 56 bars (Cells) on screen can it manage that?

I think the whole width across the bottom would look better for the bargraphs.

Text etc above that in that big space.

retepsnikrep wrote:I need 56 bars (Cells) on screen can it manage that?

The CMM (colour maximite) in mode 4 has a resolution of 240x216 pixels, half of the normal 480x430 (or composite pal which has 304x216 monocrome output only) The bars are 3 pixels wide with a one pixel gap so 240/4 = 60 cells. At the moment you could use the code with 56 cells just by changing this value;

The rest of the bar graphs would be drawn off screen, but by digging into the code you can change the start point. What I intend to do is make the code easier to configure by adding variables in this section of code so that in addition to CellNo you can set the bar width, start location and spacing in between to suit your own pack configuration and personal tastes. One of the things that is nice about working with the MM is the speed of development. Run the program and see how it behaves, then drop into the built-in editor, change a variable, etc and run it again until it works how you want it to. I am using a small vga screen from ebay. The other options for a display is to use composite mode (you will only get monochrome output, even with a CMM), or a vga to composite adapter also available on ebay. But to use the editor, I find the vga display works best. Another thing with the composite mode on the MM is that I would get an occasional flicker from the screen that could be annoying when driving. Maybe it's just me, even with the version 2 master I haven't had a good display. Looks like I am cursed when trying to use a composite display with a bms.

Simple charger control added and working with only 3 new lines of code!
Updated github master branch.

Some more work on the master code. Pressing the left or right arrows allows you to highlight a cell in the bar graph and display it's voltage. Scrolling all the way to either end turns off the selection. The "12.7" is amps display (car was on charge when the screen shot taken), a bit rough and ready at the moment. I've also been working on connecting the MM to my controller. I just need to tweak the string parsing routines, but I can read data from the controller. Once that is sorted expect more bar graphs! Code updated on Github. https://github.com/Greg-Fordyce/evBMS/

What's the refresh rate for the cells/screen/system?

I've done a video tour of the bms, at about 1:45 you see the screen refresh rate as I blip the throttle a couple of times. http://www.youtube.com/watch?v=92ZabILEuZg

I've been trying to come up with a naming convention for both versions of the bms. I am thinking Generation 1 for systems with pic based slaves and Gen. 2 for the 6802 based system. Not very original I know but what do you think? If we get to the point of using a MM master on the Gen 1 system then it should help prevent mistakes like someone trying to use my current MM software with the pic slaves. Any new items can be labelled as Gen 1 or Gen 2.

Also if someone wants to gather all the existing 'Gen 1' files into one folder and email it to me I'll put it on the github site. I've thought for a long time that we need a central place for files instead of telling people to trawl through the forum threads for info. Github seams to be working well, is simple to install and not to difficult to learn. Basically it takes all your files and compresses them like a zip archive. When you add or change a file it adds it to the archive and if you want to roll back you just get it to unpack the archive at the snapshot you want.