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Re: Old BMS General Thread
Posted: Wed Jul 28, 2010 3:36 pm
by GregsGarage
retepsnikrep wrote:Looks interesting Greg. I am a bit confused about how it all works though.
That makes 2 of us!
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.
Re: Old BMS General Thread
Posted: Wed Jul 28, 2010 3:43 pm
by retepsnikrep
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
Re: Old BMS General Thread
Posted: Thu Jul 29, 2010 9:01 am
by GregsGarage
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.
Re: Old BMS General Thread
Posted: Thu Sep 01, 2011 11:25 pm
by isaac_alaska1
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
Re: Old BMS General Thread
Posted: Fri Sep 02, 2011 4:34 am
by retepsnikrep
1/8w should be fine
Re: Old BMS General Thread
Posted: Fri Sep 02, 2011 8:21 am
by GregsGarage
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.
Re:
Posted: Wed Jan 18, 2012 4:25 am
by hybridsae
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
, 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.
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.
Re: Old BMS General Thread
Posted: Wed Jan 18, 2012 8:22 am
by GregsGarage
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.
Re: Old BMS General Thread
Posted: Thu Mar 15, 2012 6:00 am
by isaac_alaska1
Re: Old BMS General Thread
Posted: Thu Mar 15, 2012 10:43 pm
by GregsGarage
Cool videos, glad the bms could do its part.