EVMonitor - Windows Based Graphical Display for EVs

[martinwinlow]

For anyone that is interested here are the details of my VB6-based BMMS monitoring program I use on my EV - a Daihatsu HiJet micro-van which has a Netgain Impulse 9" motor, Belktronix controller and 38 x Thundersky LFP160 LiFePO4 cells giving a nominal pack voltage of 120V - see www.evalbum.com/2092 for more details. The program(s) run on a carputer running XP. This thread has come out of Peter Perkins' BMS thread, viewtopic.php?f=3&t=1245

There are actually 2 separate applications. The main one - EVMonitor - displays and records the BMMS (battery monitoring and management system) data. The secondary one - EVPlotter - allows the playing back of the data in the same format as the main program and can be speeded up or slowed down as required.

You can see 2 basic videos of EVPlotter running here... http://qik.com/martinwinlow/videos ... one recorded whilst the EV was charging and the other recorded whilst the EV was on the move.

The main sensing hardware is currently 5 x Paktrakr Remotes and one Paktrakr display which also puts out a very wordy serial string of data containing all the cell voltages etc - in all around 150 separate bits of data. Unfortunately, the PakTrakr uses the first 3 cells of each sub-pack (I have 5 sub-packs in my EV - 3 x 8 cells and 2 x 7 cells) to power itself and this unbalances the pack - albeit only by an additional 10mA or so draw. But, after a few days without charging it is enough to cause the charger to stay on unnecessarily long whilst it balances the pack. More seriously, I have never managed to get the current sensing to work reliably due to electrical noise issues I believe. Consequently, I intend to replace the PakTrakr system with Peters digital Master and Slave BMS which I hope will stop unbalancing the pack and give reliable and much simpler data for EVMonitor to use.

EVMonitor displays the following information updated every 2 seconds (hope to reduce to every second or less):-

All 38 traction pack cell voltages to a resolution of around .01 of a volt
Traction pack current - the Hall Effect transducer is on the negative pack lead so measures battery amps (rather than motor amps)
Speed - obtained via a USB GPS
Power in and out in kWh calculated from pack current and voltage
Each sub-pack temperature - but the sensors are in the PakTrakr remotes on top of the cells so not accurate
Motor RPM (not yet implemented)

EVMonitor also records the above parameters every 2 sec unless stationary when it saves the data every minute. Data is saved to a file on the hard disk of the carputer. Apart from the displayed info above, the system also records location in northings and eastings, speed and direction. A new file is created each day at midnight.

EVMonitor uses an RS232 to USB converter to get the data from the PakTrakr and a USB GPS receiver for speed and location. This is shared using xPort with the navigation software included in the main carputer 'front end', Centrafuse.

The carputer has wifi so I can access EVMonitor via a LAN.

There is a GSM USB modem attached to the carputer to allow it to send status reports both at a pre-configured time of the day as well as on demand by texting the carputer a code word. Eventually, it will also interface with a smoke alarm and anti-theft alarm. The Evmonitor program also monitors the state of charge of the pack and can send alerts via text for under/over pack voltage and under/over individual cell voltages. Obviously, just about anything can be done in terms of monitoring or even controlling the EV systems using a combination of text and/or wifi (or even internet) connection. Cripes, if you put a USB WebCan in the front, you could drive it remotely (OK - you'd have to do something about the accelerator, brakes and steering etc).


Both aps are very much works in progress and have lots of bugs but it still works well enough most of the time. The main bug at the moment is getting the texting to work reliably without errors slowing down or halting the modem. I'll post the latest exe file and VB6 source files in a separate post.