Old BMS General Thread

[GregsGarage]

I was thinking along this line. This particular BMS board just connects to the negative terminal and a fly lead connects to the positive terminal so it fits just about any size cell. They can also be remote mounted as the 6 way connector also has a space for the cell negative.

This board uses screw terminals, some people don't recommend the rj style connectors for a vehicle on the grounds that they will fail prematurely due to vehicle vibrations.



EDIT: The above image may only work if you are logged into the thundersky group when trying to view. Pictures can be found on the following link. Might have to be a member of the thundersky group to view them though.
http://tech.groups.yahoo.com/group/ThunderSky/files/Stybrook2009Format/

[retepsnikrep]

Boelle

You have designed yours for 6v cells have you not?

Good to have different designs available please upload them.

Possibly a good idea to have a web site/forum dedicated to this project but I don't have the time to do that as present.

Not sure about the perforated board idea, I'm presently seeing how many cut down digital slaves we can fit on an A4 board using standard components. Non Surface Mount. I'll keep you updated.

The multi slave large board can just be populated with as many copies as you need, so say it holds 30 slaves but you only have 25 cells then just build up the first 25 and add two jumper wires and you have 25 cell board.

[GregsGarage]

Not sure about the perforated board idea, I'm presently seeing how many cut down digital slaves we can fit on an A4 board using standard components. Non Surface Mount. I'll keep you updated.

The multi slave large board can just be populated with as many copies as you need, so say it holds 30 slaves but you only have 25 cells then just build up the first 25 and add two jumper wires and you have 25 cell board.

I have had a better look at the schematic and it sure does suit itself to being perforated. Replicate J2, J3 and J10 for each slave but with the connecting traces intact. To allow individual mounting on cells, use just one cell mounting hole to keep the size as small as possible and fit more onto an A4 board. That should allow at least 20 on a A4 board, I reckon more is possible. J5 would require a bit of thinking. Maybe solder the flyleads straight to the board? Then we have a single board that can be built and sized to everyone's exact requirements. You can keep them together for remote mounting, breaking off any unused boards, or break them down to individual boards as required. You only need to solder one J2, J3 and one J10 per individual board, so if they are kept together you just leave the pads empty and the circuit board traces make the connections.

You probably wont be able to fit quite as many on an A4 board making them perforated but probably worth the trade off. I am a big fan of reducing part counts and I like the idea of a single board design. Should be quite easy to then go to smd and get someone else to make these for us.

Greg

[retepsnikrep]

I think putting lots of slots in the board to facilitate snapping off unsused parts will massively increase board price. But I'm not sure? Anyone care to comment on that.

We already have the pcbs for the digital slaves for people who want to build up individual boards, they can omit a couple of caps, led etc and change the odd resistor value to reduce the component count if reqd.

I've no idea how to go about sourcing built up boards using SMD, anyone car to comment on that?

I'm not totally against smd, and it may mean we can really pack stuff onto a board which perhaps handles 50 cells. Just i'm not familiar with it and wanted it to be possible for people to build them themselves if reqd.

I'll speak to my pcb man to see what he thinks about numbers of cells per board smd V standard.

[retepsnikrep]

Looking at a big board with 51 wires comming into it direct from the cell terminals for 50cells, the voltage at the board connector and fusing are a bit concerning.

1) Should we have any fusing in these wires?

2) Where should it be? On the board? In the wire near the cell? Polyfuse or a proper holder onboard/inline

3) These fuse will have to stand the 500ma max drain per wire ao can be quite a low value and the wires reasonably thin.

4) Should we go for a slightly smaller board (A5) with say 25 cells. these could then be stacked as reqd. They may be a bit easier to locate as well than a massive A4 thing? Hmm

We can probably compensate for voltage drop in the cell/sensing wires with some dvm measuring and an extra line in the software to add 10mv or something when the load resistor is on.

D connectors won't give enough isolation from the pins to the shell for the high voltages ASFAIK

So I'm thinking sil 0.1" pins on the board bottom edge for some sort of ribbon connector.

As there is no reset jumper for the Pic (we have removed both the jumpers) care will be needed during the programming cycle and a removable 50 way connector at least gives us a way of interrupting the supply if we have a reluctant pic which needs reseting. If the dig slave software is set to work at 4mhz anyway this probably won't be an issue. But that limits comms to 2400 baud scan rate of 50 cells/sec. Might be able to improve that with some more work on software.

Actually thinking about this we could just make up a 4.5v supply (3xAA bats) on a two pin jumper connector and then remove the HV connector and work down the sil 0.1" line with our simple supply plugging it onto the first two pins and them moving along a pin at a time, powering each pic in turn during the programming cycle. Much safer as well


The current Master software using the 28X1 only supports upto 128 cells, the new 28X2 would increase this to 1024 cells enough even for the biggest pack!! Should be a simple chip swap and a few constants to change in the Master program to deal with that.

[retepsnikrep]

Have to think about forced cooling if a 25 cell board has all the bypass loads active it will disipate 25W from the load resistors.

4 boards 100 cells = 100w

Load resistor spacing and clearance on the board will also be an issue, do they do 2w smd 15R resisors?

[GregsGarage]

I haven't found a supplier but have found a data sheet for 2w smd resistors, so they do exist.
http://vishay.ru/docs/60031/m.pdf
Trick maybe finding someone who stocks them. Other option is to solder in a conventional resistor later.

Fusing could be done with a axial lead fuse (Rapid part no. 26-1023 for example). Attach one end to the wire and the other to the cell terminal. Do this by attaching a ring terminal to the fuse lead and then covering it with heat shrink from the ring terminal to the wire.

The trick is going to be finding an optimal number for 1 board. Too many and you have thermal issues, larger voltage potential on one board and thermal issues. You also have longer leads to cells than if you had smaller boards located closer to the cells and I doubt the cost savings of putting more on one board will be very significant. A5 size probably makes more sense than A4 size.

Greg

[retepsnikrep]

Don't forget Greg I will have 50 made up digital slaves spare if we get some big boards made up They might be available cheap

You can do your one end bolted and flying lead on the other trick for your 100ah cells if reqd.

[boelle]

Boelle

You have designed yours for 6v cells have you not?

No the version i do is just a plain copy of yours, just in SMD and with mount holes that can be cut off if smaller cells than 200 ah is used

[boelle]

I think putting lots of slots in the board to facilitate snapping off unsused parts will massively increase board price. But I'm not sure? Anyone care to comment on that.

working with the sunstone software the board itself is the most expensive part, have not checked whatever the size of board do much differnense

I've no idea how to go about sourcing built up boards using SMD, anyone car to comment on that?

I'm doing a 100% copy of yours just as smd version. the 123 file from the sunstone software should be able to get us a ready to install board

Just i'm not familiar with it and wanted it to be possible for people to build them themselves if reqd.

people can do that, they just orders the parts and the board and do the mounting themselves. is just a simple option at sunstone to have them mount the parts or not