Multi-Cell Slave-Version 2

Threads relating to the BMS system begun by Peter Perkins

Moderators: GregsGarage, retepsnikrep

GregsGarage
Posts: 870
Joined: Tue Apr 01, 2008 5:27 pm
Location: Galashiels, Scottish Borders
Contact:

Multi-Cell Slave-Version 2

Postby GregsGarage » Fri Feb 03, 2012 9:34 pm

This thread is for Version 2 of the multi cell slave board. Design features are going to be as follows.

PCB, case and connectors are all going to be considered for this design. The previous versions didn't have much thought for a case and I never found an off the shelf case that I liked. The case being considered is from this range. And mini-fit connectors

Combined surface mount and through hole components. Surface mount on the top side of the board and through hole on the bottom. Through hole components should be limited to connectors and load resistors.

Change from 12F683 to 12F1822 which has an internal voltage reference. A priority of the design is going to figure out how to implement the v-ref without using any external pins. The data sheet suggests it is possible with the proper config settings, but not sure how this is going to work in pbp.

Peter has suggested pwm output on the load. I am thinking that it would be a good idea to put a cap near the load if we do this, but not sure how it should be connected, so it's in the schematic unconnected at the moment. Personally I am not sure what will be gained by doing this, guess I just need convincing on this point. :wink:

A working ICSP header for each slave circuit.

Probably lots of other things that I can't think of at the moment. Anyway I have attached a pdf showing 4 cells. It's still a work in progress, let me know if you spot any errors.

Is everyone happy with the schematics as pdfs? The file sizes are much smaller and clearer than jpegs.
Attachments
4cellSchematic030212.pdf
4 cell schematic 3 Feb 12
(48.37 KiB) Downloaded 820 times
Greg Fordyce

Daewoo Matiz
http://www.evalbum.com/4191

User avatar
retepsnikrep
Posts: 1387
Joined: Sat May 26, 2007 4:50 pm
Location: North Yorkshire England
Contact:

Re: Multi-Cell Slave-Version 2

Postby retepsnikrep » Sat Feb 04, 2012 5:51 am

Can you rotate the schematic 90d right I can't read it like that to check it properly. pdf's are fine.

C1 should be a 100nf or 0.1uf ceramic/poly part not 100uf

C2 if we include it should go just where you have it between each +/- for each cell. If we do include it then it needs to be suitably rated for say 500-2000hz pwm switching of the load and the ripple/noise that will create. We should include it IMHO as cost will be minimal and it helps the rest of the slave circuit anyway, we don't have to use pwm but it's then an option.

R1 should be less say 330 or 220R as well so we drive the transistor hard.
We have a voltage drop in both the diode and transistor as well to consider

To correct an earlier design flaw we really should be using the npn opto U1 to pull the line down into RA2 rather than pull it up, it means R4 needs to go to the + instead and connect to C on the opto. C then connects to RA2 and E to GND
Regards Peter

Two MK1 Honda Insight's. One running 20ah A123 Lithium pack. One 8ah BetterBattery Nimh pack.
One HCH1 Civic Hybrid running 60ah A123 Lithium pack.

GregsGarage
Posts: 870
Joined: Tue Apr 01, 2008 5:27 pm
Location: Galashiels, Scottish Borders
Contact:

Re: Multi-Cell Slave-Version 2

Postby GregsGarage » Sat Feb 04, 2012 1:04 pm

Here's the changes.

I like the changes to U1, makes more sense to do it that way. Let me know of any other changes we should make.
Attachments
4cellSchematic040212.pdf
4 cell schematic 04Feb12
(50.74 KiB) Downloaded 637 times
Greg Fordyce

Daewoo Matiz
http://www.evalbum.com/4191

GregsGarage
Posts: 870
Joined: Tue Apr 01, 2008 5:27 pm
Location: Galashiels, Scottish Borders
Contact:

Re: Multi-Cell Slave-Version 2

Postby GregsGarage » Mon Feb 06, 2012 11:40 pm

I think we should get a 4 cell board done in a 5x5cm size. They can be done for about a tenner for 10 pcbs, total cost including shipping from China. Consider them as a prototype board so that we can work out any bugs before committing to a 8 cell or even 16 cell board. Here's a schematic, basically the same as the one I had before but with the connectors. Once we have a working 4 cell board it should be quite simple to just copy and paste the design for larger cell layouts.

What do you think? Spot any errors before I start working on the pcb layout?
Attachments
4cellSchematic060212.pdf
4 cell Schematic 06 Feb 12
(57.5 KiB) Downloaded 657 times
Greg Fordyce

Daewoo Matiz
http://www.evalbum.com/4191

User avatar
retepsnikrep
Posts: 1387
Joined: Sat May 26, 2007 4:50 pm
Location: North Yorkshire England
Contact:

Re: Multi-Cell Slave-Version 2

Postby retepsnikrep » Tue Feb 07, 2012 7:06 am

Fair enough for the test boards 4 cells. Have you tried the icsp when there is and adjacent slave above and below the test slave in case it interferes in some way.

Should we have cell fusing on the pcb? Normally I would recommend it is at the cell terminals.
Regards Peter

Two MK1 Honda Insight's. One running 20ah A123 Lithium pack. One 8ah BetterBattery Nimh pack.
One HCH1 Civic Hybrid running 60ah A123 Lithium pack.

GregsGarage
Posts: 870
Joined: Tue Apr 01, 2008 5:27 pm
Location: Galashiels, Scottish Borders
Contact:

Re: Multi-Cell Slave-Version 2

Postby GregsGarage » Tue Feb 07, 2012 9:02 pm

retepsnikrep wrote:Fair enough for the test boards 4 cells. Have you tried the icsp when there is and adjacent slave above and below the test slave in case it interferes in some way.

I used a led to simulate the slave bus opto of the next slave (I ran out of optos), that is the one below when looking at my latest schematic. I can't see anything in the slave above (previous) that should affect ICSP. The only way to be sure is to build 3 adjoining circuits, which is another reason I am proposing the 4 cell prototype board.

Should we have cell fusing on the pcb? Normally I would recommend it is at the cell terminals.

Cell terminals must have fusing for the system to be safe. We could possiblly copy an idea of Cedric's and put a fuseable trace on the pcb. I am not sure if there would be room for this, or how to go about sizing it. If anybody has links to info on fusible pcb traces, please post them. But they wouldn't be a substitute for fuses at the cell terminals.
Greg Fordyce

Daewoo Matiz
http://www.evalbum.com/4191

GregsGarage
Posts: 870
Joined: Tue Apr 01, 2008 5:27 pm
Location: Galashiels, Scottish Borders
Contact:

Re: Multi-Cell Slave-Version 2

Postby GregsGarage » Sun Feb 19, 2012 11:05 pm

I've started working on a pcb layout. I changed the component designators on the schematic to the system I have used previously. At the moment I am putting smd components on the top layer and through hole on the bottom. D1x, R1x, Q1x and C2x will all be through hole and the same components used on previous versions. SMD resistors and cap will all be 0805 size for ease of soldering.
Attachments
4cellSchematic150212.pdf
4 cell schematic 150212
(59.4 KiB) Downloaded 608 times
Greg Fordyce

Daewoo Matiz
http://www.evalbum.com/4191

User avatar
retepsnikrep
Posts: 1387
Joined: Sat May 26, 2007 4:50 pm
Location: North Yorkshire England
Contact:

Re: Multi-Cell Slave-Version 2

Postby retepsnikrep » Mon Feb 20, 2012 5:51 am

Looks good my only comment is should we keep slave and master bus seperate so slave bus on right and master bus on left.

Will it be possible to use sil 0/1" pins and sockets to stack the boards, it should be if we put them in right places.

That will mean the icsp pins/pads need to be at one edge of the board so they are still accesible in a stack of say 5-10 boards. No point diassembling the stack just to get to the icsp pads.
Regards Peter

Two MK1 Honda Insight's. One running 20ah A123 Lithium pack. One 8ah BetterBattery Nimh pack.
One HCH1 Civic Hybrid running 60ah A123 Lithium pack.

GregsGarage
Posts: 870
Joined: Tue Apr 01, 2008 5:27 pm
Location: Galashiels, Scottish Borders
Contact:

Re: Multi-Cell Slave-Version 2

Postby GregsGarage » Mon Feb 20, 2012 5:44 pm

retepsnikrep wrote:Looks good my only comment is should we keep slave and master bus seperate so slave bus on right and master bus on left.

That would make pcb layout much easier, but my thinking is you can make up cables to connect from one slave to the next. So the connectors are one in and one out. I think it would make for neater wiring this way.

Will it be possible to use sil 0/1" pins and sockets to stack the boards, it should be if we put them in right places.
At the moment I can't think of a way to do this, but I will keep it in the back of my mind.

That will mean the icsp pins/pads need to be at one edge of the board so they are still accesible in a stack of say 5-10 boards. No point disassembling the stack just to get to the icsp pads.
I better put some holes in the boards for stacking. :shock: With a standard 2.54mm spacing it won't fit on one edge, we either need to use both sides, a connector with tighter pin spacing or a stacked configuration (2x3 like an atmel ICSP header). Remember these 4 cell boards are just going to be a prototype. The goal is to make 8 and 16 cell boards, but we can still try and fit as many features on these that we can. :wink:
Greg Fordyce

Daewoo Matiz
http://www.evalbum.com/4191

GregsGarage
Posts: 870
Joined: Tue Apr 01, 2008 5:27 pm
Location: Galashiels, Scottish Borders
Contact:

Re: Multi-Cell Slave-Version 2

Postby GregsGarage » Tue Feb 21, 2012 9:36 pm

Just had a setback with DesignSpark. It has started crashing on me, seems to be some problem with the libraries. One of the things I liked about it was the wizards for creating components. Another thing I liked over Kicad was that it lets you add or change components directly to the pcb without updating the schematic, but it won't (or at least I can't figure out how to) push the changes back to the schematic. Now everything is a mess, the schematic and pcb are out of sync with each other. :evil: Anyway I am starting over with Kicad. :(
Greg Fordyce

Daewoo Matiz
http://www.evalbum.com/4191


Return to “BMS thread”

Who is online

Users browsing this forum: No registered users and 5 guests