Old BMS Hardware Thread

[GregsGarage]

I will get the arduino to respond to a change in the watchdog led state. This will give us data once a second.

[GregsGarage]

Just came across this, a temperature sensor interface for connecting up to 7 of the DS18B20 "1 wire" sensors. http://www.phanderson.com/stamp/onewire.html. It's not something I am going to try at the moment, but might look at it later as it is looking like I will have 4 battery boxes, so need more than the 2 temp sensors which are availble on the master at the moment.

Greg

[retepsnikrep]

You can have as many temp sensors as you wish, the DS18B20 sensors can be used if we incorporate the code into the master. I used them before in an earlier version. See the software thread for an update on this.

[retepsnikrep]

I will be using the controller cutback output (removing RV2 andC5) to modulate the water pump for the Zilla, should save noise and power and gives me geek points.

Derek

Edit; Also removed the opto, disabled the led and changed the current limit resistor to 470. Ooh I'm such a butcher!
Made a tiny board out of veroboard (yuck) bunged on a logic level mosfet,resistor and a shotky diode then screwed it into the controller cutback terminals.
It works!

Can you gives the schematic for this please.

[GregsGarage]

Made the first steps last night in integrating the BMS to my controller. I got a Arduino to send a battery current limit command to the controller. The idea is that when the bms triggers the controller cutback, that will be connected to the Arduino which will then send a reduced battery current limit to the controller. The Arduino will keep reducing the current limit until it stops getting a controller cutback warning or gets to a limit of 1 amp (zero amps disables the battery current limit function in the controller).

That's one half of the equation, also need to get the Arduino to read the data stream from the controller and send it to the bms.

Greg

[dillond666]

I have made a crude screenshot of the circuit used to drive the coolant pump for my Zilla controller.
The master mk1 board was de-populated at the controller cut back output to give a bare output except for a 470 ohm current limit resistor.
Controller cutback was on output 4 which is physical pin 25.
http://dillond1.pwp.blueyonder.co.uk/coolant.png

Derek

[retepsnikrep]

Derek

IMO you would be better to keep the opto to prevent interference from your pump motor getting back into the Master board.

Greg

Sounds good but we have discussed having another processor in the system before and I'm still not over keen on the extra stage/step. I don't allow my BMS to control my insight inverter directly, as soon as I get the audible alarm I just turn the electric assist down or off. My PHEV assist is manually operated via a joystick anyway. The video display unit shows how the cells are faring and you soon build up an appreciation of when they are getting sluggish.

My BMS does control the mains charger however via the main power relay and the voltage opto. The Zivan charger has it's own control logic and i must install that lifebatt lithium eeprom soon.

Over discharge is only a problem if you ignore the audible visual warnings.

Unattended charging is the danger area, and needs most control and failsafe devices. That's why I started expanding the project to include the remote display unit and the smoke alarm which could also be interfaced to the BMS and allow a warning via the remote display after Greg's incident

I hope this doesnt sound like I'm trying to tell people how to suck eggs.

[dillond666]

Derek

IMO you would be better to keep the opto to prevent interference from your pump motor getting back into the Master board.

Peter,
The only reason I didn't use the opto is because I couldn't be bothered sorting out a separate 5v supply for the logic level mosfet.
Extreme laziness(1reg 2caps), but if it becomes an issue I'll do as you suggest (the proper way).

Derek

[GregsGarage]

Sounds good but we have discussed having another processor in the system before and I'm still not over keen on the extra stage/step. I don't allow my BMS to control my insight inverter directly, as soon as I get the audible alarm I just turn the electric assist down or off. My PHEV assist is manually operated via a joystick anyway. The video display unit shows how the cells are faring and you soon build up an appreciation of when they are getting sluggish.

I am in agreement about having an extra processor in the system not being ideal. I am in a bit of a dilemma of the best solution. The controller is set at 19200 baud. It could be changed to work at 9600 baud but that would prevent the RTD Explorer program from working, which is a very useful tool for setting up the controller. It is not possible to change the serial settings on RTD explorer. The version 2 of the master won't do communication faster than 9600 baud, but the Arduino Mega has 4 hardware serial ports that can all be set a different baud rates from each other. Last night I was working on the code to get the Arduino to store the serial stream from the controller and send current limit commands in the same "sketch" ( Arduino programs are called sketches). Previously I have done sending and receiving data in separate small sketches. Will hopefully do some testing tonight and see if it all works.

I am starting to think that maybe I should see if I can use the Mega for the Master. The 4 serial ports will easily handle the display using a Tellymate shield, comms with the controller, serial data for the remote display and data from the slaves. The hardware interface can be built on a prototyping shield stacked on top of the Mega. If that works well a dedicated circuit board (shield) could be built to stack on the Mega.

The software would have to be rewritten, but the basic layout of the current Master code is suitable for the arduino, I think it will be a matter of going through the code line by line and changing the code so it is suitable for the arduino, but the basic logic would be the same, I will even keep variable names the same. The Mega also has much more memory available, so , for example, cell data received from the slaves can be stored directly in an array. The extra resources may even make the program a bit simpler. I will work on it this week and see how I get on.

I do want the Master to have ultimate control of reducing power output and shutting down the vehicle if necessary in the event of a low battery. It's o.k. for someone experienced to know he has to stop, my goal is a vehicle that the inexperianced can drive without being able to harm the cells.

The Zivan charger has it's own control logic and i must install that lifebatt lithium eeprom soon.

Me too.

And I to completely agree on all the charging points, don't want a repeat of the Fiat!

BTW, did you know that the lcd monitor we got for the dash display works fine on 5 volts.

Greg

[retepsnikrep]

Greg

I will also look at the master code and try and convert a cut down version of it for the plain pic. I would like to standardise the pics as this has caused an issue with needing different programming hardware. If I rewrite the master code for Pbpro then we will have the 19,200 baud rate reqd option.

If I manage to convert the Master code to plain picbasic pro variant the chip will need to be pulled from the board for upgrading with the current Master board V2.

Perhaps master board V3 will have ICSP for both watchdog and master chips

What other functions or ports/interfaces would we like for Master V3?

Peter