Old BMS Hardware Thread

Threads relating to the BMS system begun by Peter Perkins

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steiner
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Postby steiner » Wed Jul 15, 2009 11:45 pm

Peter,

I am working on laying out the multi-slave board. I am referencing your drawing "25DigitalSlave 160509". My question pertains to C1 which is a 100nF Poly capacitor. Is there anything specific about about this capacitor for the circuit to work properly? I haven't used poly capacitors before and wasn't sure what their strength is. They seem to be considerably more expensive than the equivalent ceramic capacitor.

If you have any modifications to the multi-slave board since this drawing, I would be interested in seeing them.

Rick

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retepsnikrep
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Postby retepsnikrep » Thu Jul 16, 2009 10:28 am

I had a big bag of 0.1uf poly capacitors so I used them.

You are welcome to try ceramic.
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.

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SV2000 chip

Postby GregsGarage » Tue Jul 28, 2009 11:42 am

Peter, do you have any more SV2000 serial to video chips?

I am going to order a Arduino based board and try and make a Master based on that. I am going to stay as close as possible to your design for the master, it will make "porting" the code easier. I am looking at this board, http://www.nuelectronics.com/estore/index.php?main_page=product_info&products_id=1 along with this board http://www.nuelectronics.com/estore/index.php?main_page=product_info&cPath=1&products_id=3
These protoboards can be stacked, handy as I will probably need more than one, and will mount the watchdog, SV2000 and various optos and transistors etc to interface to the vehicle.
Greg Fordyce

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

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retepsnikrep
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Postby retepsnikrep » Tue Jul 28, 2009 2:56 pm

I don't have any spare video chips at the moment. I suggest order yourself a couple from the supplier.

I now have my Master and the slave blocks on the bench. I may try a reprogram to the Pulse code tomorrow.
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.

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Postby GregsGarage » Tue Jul 28, 2009 3:17 pm

I will order myself a couple of the video chips. If anyone else wants one, pm me, it will be a day or two before I order them.

Hopefully the pulse code works well. Any update on the multi slave pcb's?
Greg Fordyce

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

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retepsnikrep
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Postby retepsnikrep » Tue Jul 28, 2009 3:29 pm

GregsGarage wrote:Hopefully the pulse code works well. Any update on the multi slave pcb's?


Time and money causing delay, I don't have enough of either :roll: I must also get the Master working correctly in my setup before I move onto that.

Rick is looking at the multiple slave pcb though.
Rick any update on your tinkering?
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.

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Postby GregsGarage » Tue Jul 28, 2009 3:57 pm

I understand the time and money problem. :cry:

I have just ordered the freeduino board and 2 protoboards, so thats the money gone, now if I could just find some time! :shock:
Greg Fordyce

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

steiner
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Postby steiner » Fri Jul 31, 2009 1:48 am

Yes, I have been working on the multi slave pcb. It is about finished. I have made a few changes though that you may or may not want. I am using a much larger bypass resistor (10 watt 3 ohm). I have had good luck with it on the analog balancer that I built. It only requires about 15 minutes to balance the cells. It obviously creates a great deal more heat and requires a cooling fan. The other change that I made was to simply move the location of the LED that signals the bypass resistor is on. I wanted it in parallel with the bypass resistor so that if the mosfet failed into the on state, the LED would still be lit. This is the configuration that you have on your slaves but it looks like you changed it to be in series with the output of the micro on your "25 digital slave".

I still want to work on some software that would let me know if the bypass resistor is on when the system is not charging. A failed mosfet is what concerns me the most about the complete system. I have seen it occur twice now (different design but same basic concept) and nearly caught one vehicle on fire. I contemplated building a seperate board just for the bypass resistors and mosfets that would be disconnected after charging but decided that would be a pain. The cooling fan is activated by temperature and will at least keep the resistor from getting too hot. As the system is right now, at least it will give an audible alarm when the individual cell reaches 2.5 volts which if caught in time would keep from damaging the cell.

Is there any chance you could send me a jpeg of your latest schematic for your master and multi slave board? I remember you mentioning you added a few items.

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Postby retepsnikrep » Fri Jul 31, 2009 4:30 am

Rick

More heat on the board = more chance of fire does it not?

I found in use over several years with lithium cells 250ma load was suffcient even for 200ah cells to balance them during the charge phase.

Also if your higher load fails on apart from the heat it could kill the cell quite quicky due to over discharge. With the 250ma load I would get 160hrs to notice it on my 40ah cells. Plus Master should show the problem up in time.

I put the led in series to save on the extra resistor, I was going for minimal component count.

It's your board of course, so please proceed as you wish.

The multi slave cell board is as per that last schematic.

www.solarvan.co.uk/bms/32DigitalSlave230609.jpg

The Master is also as per the earlier schematic which has been laid out and supplied.

I have tinkered with a newer Master but it has not got beyond schematic stage, it still needs some work and may change direction completely as I add more functions specific to my Honda Insight phev project.

www.solarvan.co.uk/bms/Master231008V2.jpg
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.

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It's alive and working in the Insight!

Postby retepsnikrep » Fri Jul 31, 2009 10:53 am

Bloody hell finally. I've woken from the Insight noise nightmare.

After scoping it today still lots of noise on Master Bus and Temp Sensor Bus. (These snake round the pack passing the high current wires so are just ripe to pick up the emi) I didn't rewire my slaves in the end with twisted pair etc as I wanted to try the supression first.

Added a varistor between Gnd and Master Bus Input pin.

http://uk.farnell.com/jsp/search/produc ... KU=1057154

Instant massive reduction in noise.

Then added a 0.1uf poly between Master Bus Input pins which smoothed it right off. (Might need to add a minute amount of voltage compensation due to extra capacitance on bus)

Also added same varistor between Temp sensor data line and Gnd all noise gone off there as well. :wink:

Went for short test drive and BMS responded normally as if it was in EMI free environment on bench with no errors. :shock: I need to do some work on Master software now to tidy it up. I also need to do some checking to make sure the Master logic is working correctly, over/under alarms, temp alarms etc etc. Charger control seem to be working OK but I need to adjust the voltage set points in Master etc.

One pic shows setup in Insight IPU compartment.

www.solarvan.co.uk/bms/ItsAlive002.jpg

Ignore the Google warning.

Board on right is the Master.

Board on left is my testing/connection point for Insight BCM/MCM METSCI & BATTSCI RS485 bus work.

I think I could probably use the serial data system now instead of the new pulse width voltage system. So I might go back to that to try it!
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.


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