Old BMS General Thread

Threads relating to the BMS system begun by Peter Perkins

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Re: Old BMS General Thread

Postby GregsGarage » Wed Jul 28, 2010 3:36 pm

retepsnikrep wrote:Looks interesting Greg. I am a bit confused about how it all works though.

That makes 2 of us! :shock: But I am slowly getting there. Can you see the files I put on there and download them? As long as you can do that it means we have one place to keep everything.
Greg Fordyce

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Re: Old BMS General Thread

Postby retepsnikrep » Wed Jul 28, 2010 3:43 pm

It's not clear where the code is. Took a few minutes to find it. I can download it but it does not view correctly in notepad. Not sure this is a problem with this system or a general problem with my uploaded text files. Keep at it, find out how it all works then i'll join up in due course. How reliable is it? Going to last? Why not have your name up there as well as mine or just get rid of the names? You are executive officer after all :)
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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Re: Old BMS General Thread

Postby GregsGarage » Thu Jul 29, 2010 9:01 am

How about trying to view the code in wordpad instead of notepad? Launchpad.net is hosted by the Ubuntu Linux distribution and is the system they use for developing and maintaining code. So should be around for a good long while.
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Re: Old BMS General Thread

Postby isaac_alaska1 » Thu Sep 01, 2011 11:25 pm

i'm starting to order parts for my master board, and it looks like in the parts list all of the resistors are 1/4 watt resistors. i have access to a bunch of drawers of ressistors, but they're all 1/8th watt resistors. are there any resistors that for sure need to be 1/4 watt? or could i stick with 1/8 watt for all of them and be fine?

i'm probably gonna have tons of questions about all of this as i've never built up one of these systems before, so thanks in advance for all of the help!



-isaac

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Re: Old BMS General Thread

Postby retepsnikrep » Fri Sep 02, 2011 4:34 am

1/8w should be fine
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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Re: Old BMS General Thread

Postby GregsGarage » Fri Sep 02, 2011 8:21 am

Got this PM from Issac.

isaac_alaska1 wrote:hey, i'm ordering up a bunch of components to build up a couple of master boards. the EEprom that's listed in the parts list i have is now obsolete, and i'm not positive what i should replace it with. the part number listed is AT24C512B-PU25. what constraints do i have to keep in mind when replacing it with something else? obviously the leg spacing and layout needs to be the same, and i would think that the memory size needs to be the same, and probably the speed and memory layout. is there anything else that i need to make sure matches up before i replace it?

-isaac


This would be more of Peter's area I think. Any thoughts Peter?

EDIT: Please post answers to the Master Board Version 2 topic.
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Re:

Postby hybridsae » Wed Jan 18, 2012 4:25 am

GregsGarage wrote:Been testing the slaves some more, in groups of 4 cells, charging with a lead acid charger and finishing with my dc power supply as the charger doesn't quite get there with the voltage. These cells were already charged but out of balance. The first set I charged one of the cells was very badly out and took about 12 hours to balance. I had been doing some crude balancing with a 5W bulb across the highest cell and left it connected to this cell overnight by accident :shock: , hence the out of balance condition.

Today I have just balanced another 4 cells in 1/2 hour using this method with just the on/off mode of charger control. :D In truth the charger never had to turn off and wait for the cells to bleed down. By the time the lowest cell had turned on the load resistor the highest cell hadn't reached the AbsMaxCellV value. I am pleased with this result and hopefully should see my charger today as well.

The charger is designed for lead acid but provides the CC-CV profile that these cells require at a slightly lower voltage. I will adjust the AbsMaxCellV to 3.65 volts and the MaxCellV to 3.55 volts. This should give me a 98% charge, but if it works it could mean that a standard lead acid charger designed for sealed lead acid cells could be used with these particular litium cells, which I think would be a very neat and useful trick.

Edit: The cells balanced to within 40mv.


What would you recommend for balancing batteries? I noticed that you have implemented some sort of balancing technique used here for high power. I am having difficulty finding balancing circuits to implement into my design with such high power. I am unsure how exactly your slave redistributes the power to the other cells and balances the charge. Do you use the slave boards or the master board to do this? Also, are you able to balance the batteries while the vehicle is running during charge or discharge? I looked through the thread thus far and couldn't truly find out where you describe how the circuit balances the batteries. Maybe it's in the software programming side of things and I missed it.

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Re: Old BMS General Thread

Postby GregsGarage » Wed Jan 18, 2012 8:22 am

Each slave circuit can dissipate 1 watt of power from the cell it is attached to. Near the end of the charging we turn on the load resistors for the cells that have reached the load cut in voltage so the rest of the cells can catch up.
Greg Fordyce

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Re: Old BMS General Thread

Postby isaac_alaska1 » Thu Mar 15, 2012 6:00 am

i found this! it's pretty sweet. i also found videos of the sled pull and the acceleration runs.

http://www.youtube.com/watch?v=poVdxFoeack&feature=BFa&list=PL57F5BB9497F8EB4C&lf=plcp

http://www.youtube.com/watch?v=-YQG54ZKW8g&feature=BFa&list=PLCD23D9FCC044B253&lf=plcp

http://www.youtube.com/watch?v=6-CD05OIT4s&feature=BFa&list=PLCD23D9FCC044B253&lf=plcp


A couple videos that were taken at the competition, that's me in the crazy wild pants haha...

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Re: Old BMS General Thread

Postby GregsGarage » Thu Mar 15, 2012 10:43 pm

Cool videos, glad the bms could do its part. :D
Greg Fordyce

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