Battery Vehicle Society

have been using the bms here at the "society of automotive engineers, clean snowmobile challenge 2012" on the electric snowmobile we put together. it's doing a great job so far, and in the range event it alerted us to shut down just when we needed it to. the abs min cutoff was set to 3.0 volts, and we were doing half mile laps. when our driver came by and said the alarm was going off, the lowest cell read 2.7 volts. right at the edge of where they need to be cutoff. quite pleased that it works as well as it does.

next i guess i need to get the remote display and data logging working, as well as fix a few other bugs. How hard is it to enable data logging? i know i can push the button and change the pc bit, but i don't know how to get the data off once it's on there.

thanks again for the awesome BMS, peter!

-Isaac

There is no store of logged data onboard.

Turning on the TxBit bit just enables the transmission of parts of the data via the TX/RX link.

Turning on the PcBit also enables logging via a lead direct into a laptop

Data logging is covered in these threads but is based around an excel spreadsheet running the PLX-DAQ macro plugin.

So do some digging on that.

With your setup you should have a warning sounding at say 3v and the inverter throttling back progressively so that it is imposible for the vehicle to drain the cells beyond ABSMINV. If you over discharge or otherwise stress your lipo you are in very dangerous territory

Has there been any move to get the BMs to talk to the motor controller, perhaps via CAN? I know it's been mentioned but I don't know how all that works. That would push this to the next level. (of course, I'd need to get the current version working before beginning another journey )

*edit*
I guess a much easier strategy would be to control a digital resistor using an output from the pic. I've never messed with this either, but common sense tells me there would be a lot less coding and testing involved

isaac_alaska1 wrote:Has there been any move to get the BMs to talk to the motor controller, perhaps via CAN?

Nope, good luck.

I thought about digital pots as well so that's an option. You can get I2C ones as well so could hang one off the DS18B20 line

Great idea. I also want to implement more temp sensors. I'm looking at trying to do 72 of them, and read from a different sensor every time the program loops. (full pack reading in just over 1 minute)

Also want to figure out how to monitor individual cells if a parallel fuse blows, but that's in the future

Also! I have been invited to Greenland to demonstrate the machine at "summit camp". Our team took first overall in the electric category

Isaac, I have been working heavily on the data logging recently. You can simply connect the BMS to a laptop with a serial to USb cable and set pcbit to 1 or 0, i forget which one it is.

You can use a program called hyperterminal just to demonstrate that their is communication occuring. Peter also showed me to an excel spreadsheet document called PLX-DAQ and again in a similar way you can log the data from the BMS through that.

The SEROUT out command can be adapter for the information you wish to display.

Once this is complete and you can confirm the BMS outputs data, we have then made our system wireless using the Xbee Pro ZB from Digi. It really is a plug and play device (3.3v supply) and has a line of sight range of 1500m. You can buy a board called the explorer USB Xbee board which is compatible with all the Xbee transmitters and woo-hoo you have telemetry.

This is awesome!! Do u have a list of hardware I'll need? I'm on a time crunch (the machine leaves in two weeks,) but if I could get this working that would be perfect! Right now I'm adding a pair of 19k rpm fans to the BMs box to kee the loads cool during balancing. I can only imagine the scream they are going to make...

heres the link for the xbee...
http://www.digi.com/products/wireless-w ... overview... you'll need to pro with the 1mile range! you'll also need an antenna that works on 2.4GHz frequency with SMA attachment such as this one. The bigger the gain, the further you'll get. This one should work fine:
http://uk.farnell.com/pulse-engineering ... dp/1900062

you'll need two xbees... they can work as transmitters or receivers.. and obviously two antennas. each one needs a 3.3V supply. but for the telemetry on the laptop side you can use this plug and play adapter with voltage regulator and youre away:

http://www.hobbytronics.co.uk/xbee-explorer-usb

you'll need to drop down the 5V supply from the board to a 3.3V supply with a potential divider mind

What power balancing resistors are you using? what sort of balancing current are you drawing?

Thanks for that! I'll check those as soon as I'm on a computer instead of my phone... Haha. I'm using 7.5 ohm resistors with 4.1 volts on each cell. Probably should have gone with a larger resistor value as suggested, but I wanted to see if this would work