Vectrix "BMS" improvements

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Mik
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For the electrical engineers here: Do you think this might work?

The diagram shows the planned arrangement of the Vectux cells when reconditioning has finished.

Photobucket
High resolution PDF file here.

The design might contain beginners errors, like really nasty design faults that break stuff or make it unsafe.

I am still a beginner with electronics design and would appreciate it very much if the more experienced forum members could have a good look at the diagram and let me know if this could work.

In particular I would like to know if anyone can see a way for any potentially lethal currents to make it out of the battery safety container. I hope that I have placed 150kOhm resistors in all the right places, but it is a bit complex!

I hope I have included enough labels etc. to make it self-explanatory.

The general aims I hope to achieve with the design are:

1) The red (=low capacity) cells are all located adjacent to each other so I can charge them via the on-board switch-mode power supply, using the "surplus" charge in the good cells, and they can also be discharged if needed and re-conditioned without taking anything apart. The maximum voltage leaving the safety container through the 10A rated cables (to the boot under the seat) would be 13x1.5V=19.5V. (The single red cell in the top left corner shows no swelling and has recovered very well with reconditioning, but it can be individually monitored by the BMS to detect it early in case it deteriorates again).

2) The good cells can all be voltage monitored in Modules of 8 or 9 cells, during both riding and charging. No lethal current should be able to escape due to the 150kOhm resistors.

3) After opening the safety container the good cells can be recharged or discharged in modules of 8 or 9 cells. This can be done after disconnecting the (Stock) Andersons connector between the batteries, which limits the voltage to about 60-70V maximum.

4) The weak cells and the modules of good cells all have 30A cable with a 20A fuse right at the cell connector. This should allow for inclusion of a relatively powerful active and automatic BMS later on, without taking everything apart again.

Originally posted there: http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=6853&p=110602#p110602

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Mik
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Re: Vectrix "BMS" improvements

How come no-one comments?

Are those schematics too weird? I have not yet had any training (beyond school) in how to draw electrical schematics, but my home-brew schematics sure help me (if I don't end up zapping myself, that is!)

Here are the latest schematics: They show the final cell (re-)distribution (YES, they are finally all back together into modules again!) and the planned rotary switch array which will tell the DMM which cell voltage to display.

http://www.endless-sphere.com/forums/download/file.php?id=15538

http://www.endless-sphere.com/forums/download/file.php?id=15539

In another 24hrs the last of the 102 cells should have finished being re-conditioned and then I can hopefully concentrate more on the actual BMS.

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moccasin
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Re: Vectrix "BMS" improvements

Nice work! I don't understand any of it, but then, I just bought mine to ride! HAHA!! ;-)

jmap
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Re: Vectrix "BMS" improvements

It seems that you have the problem of being the person here that understands best the Vectrix electronics... So it becomes difficult to others to say anything...

undead
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Re: Vectrix "BMS" improvements

I mainly purchased it to ride, but am very interested from a geek perspective how it all works - have learnt a lot so far by reading various posts on this forum on this, and other bikes.

That being said, Miks diagram is way out of my range of basic electronics!

marsupi
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Re: Vectrix "BMS" improvements

HI Mik,
I'm not quite sure I understand how you're reading voltages for example from tap 1 thru 9 (cell 103--024 thru03-058) are you switching (+) and (-) off via the rotary switches to get individual cell voltage or are you using the whole pack ground reference? I'm not seeing were you have your ground reference for each reading.
As a general comment, the thought of rotary switches is a bit scary to me, though frankly I don't have a better suggestion if you're looking to make this really cheap.

on another note,from littelfuse, thought it might be of interest for this and other projects.
http://www.isispower.com/products.html
http://www.littelfuse.com

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mikemitbike
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Re: Vectrix "BMS" improvements

Hi mik, sorry i had no Time to make a diagramm, but finaly...

the only way is to disconnect the two packs from each other and using the front-pack to charge the rear-pack or otherwise.

http://kastenente.heim.at/zap.jpg

greetings Mikemitbike

Mik
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Re: Vectrix "BMS" improvements

Here are more detailed schematics to illustrate what I am in the process of building.

The main problems so far have been the tight engineering and resultant lack of empty space within the Stock Vectrix. But I'm getting there, just need to build that stuff smaller.

Here is an updated schematic of the planned overall Vectux BMS setup:

http://www.vectrix-forum.de/images/fbfiles/files/Vectux_BMS_Preliminary_Design_2008_11_18.pdf

And here is the schematic for the rotary switch array located in the "modified dashboard" part of the above schematic.:
http://www.vectrix-forum.de/images/fbfiles/files/Vectux_BMS_Switch_Array_2008_11_12.pdf

.

At the moment I am concentration on building the thing I called:

15-pin-Screw-Conn / 8-pin Conn
XXXXXXXXXXXXXXXXXXXXX
8 x 150kOhm Resistor-PCB
XXXXXXXXXXXXXXXXXXXX
40 x IDE cable connecto
r

which is located at the front battery in the first diagram above.

Two prototypes turned out too thick to enable sliding them into the small space available.

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kito
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Re: Vectrix "BMS" improvements

Hi Mik,

You might be interested in this BMS chip. Its for EV designs.

It's not an end user product, but based on the datasheet looks like it could be a DIY project.
It allows monitoring and cell balacing series connected batteries using a stackable chip design.
Its a stackable design so you can monitor long chains from a single SPI serial port.

PN LTC6802-1
http://www.linear.com

Galago
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Points: 118
Re: Vectrix "BMS" improvements

Hi Mik,
Indeed you have done alot of work toward forwarding this wonderful bike.
Keep it up. But PLEASE be careful.... I looked at your schem and
see something that just does not sit right with me.... your 12 volt switch
mode p.s. please look carefully at how you have it connected. Maybe
I am not looking at it correctly or maybe you have just put the dotted line
in the wrong place but it seems that you have your 12volt supply across about
90 percent of the pack..... ???
Galago

Mik
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Re: Vectrix "BMS" improvements

Thank you, Kito and Galago.

I'll have a read about that chip.

Regarding the 12V power supply: It has not yet been connected to the 89 good cells in the string.
The idea is to use a 120-240V AC switchmode power supply which produces 12V DC. Because the first stage inside it is a bridge rectifier, it can apparently be powered by DC as well. The 12V output will then be directed to an IMAX B5 charger or other 12V applications. I hope it will be possible to charge the 13 low ́capacity cells with the (otherwise unuseable) remaining charge in the good cells.....

Once I have built the 16 pole banana-plug grid, then I'll test it with the charger powered by the grid at first.

There are more details about the Vectux M-BMS on Endless Sphere.

Hopefully I'll find some time to write an entry for my V Blog that is more tidy and readable than the posts written "on the fly" whilst developing it!

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kevin smith
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Re: Vectrix "BMS" improvements

am sorry.. but this comment just brought a tier to my eye with laughter out loud ..
me too wan't to just plug n play but am so intreged with all the workings
ok i just wan't to work out why these tecnoghically advanced piceses of kit jsu doesn't do what
they say they will do i/e 68 miles ok lets be more relistic 58 miles per charge..!!!!!!!!!!!!!?????????????

Galago
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Joined: 10/11/2008
Points: 118
Re: Vectrix "BMS" improvements

Mik,
Here is an article that you might be interested to read. I found
it very informative and hope that it may assist you in your quest
for a better battery pack.

http://www.smartsparkenergy.com/pdf/batteq1.pdf

Galago

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