Old BMS General Thread

[GregsGarage]

The reason for 24 volts is that my controller requires 24 volts on its inputs so it has a seperate DC-DC converter. This is not as big a nuisance as it first seems because the inputs on the controller are not isolated from the traction pack, the GND terminal is connected to B- internally in the controller. I am isolating all my inputs and outputs going to and from the controller and my managent module, from the vehicle, to keep the traction pack earth floating and seperate from the vehicle chassis.

I am using regen. The Kelly controller has 2 ways of doing this. It can have variable regen through a 0-5v hall sensor, I had thought of using the clutch pedal. The other option is fixed regen, which can be adjusted with the PC configuration software. I have gone this route and wired it to the brake switch. When I first touch the brakes I get around 50 amps of regen which slows the car nicely. There is a spot between when the brake switch activates and the brakes actually engage that gives regen without using the brakes.

I will investigate the current sensor options later, for now I will borrow the e-meter from the Volvo after I have finished the wiring.

EDIT: I have programmed all the slaves with V1.08 and connected the charger for a full pack charge. Hopefully it all works as planned!

[retepsnikrep]

Very odd about the corrupt downloads of 1.07 & 1.08 just have to put that down to a glitch.

My copies here worked ok, but when I downloaded 1.08 from this thread I also got 3 bytes as program size? I just deleted a couple of spaces near the #ENDREM statement, tried again and it worked correctly.

Perhaps there was some invisble ascii character there causing a problem. or a corrupt download or obscure editor bug

[GregsGarage]

Peter, the software glitch was weird, just glad someone else could duplicate it.

Nearly finished charging, here are the values I have settled on. These seem to be working well with my charger, A Kelly 72v 15a for maintenance free lead acid batteries;

CPU 250 khz

Max Cell Opto On = 3.80V
Max Cell Opto Off = 3.65V

Load On = 3.65V
Load Off = 3.60V

Min Cell Opto On = 2.40V
Min Cell Opto Off = 2.50V

The charger is now cycling on and off. I can see were your master could really come in handy, it could switch the charger off, for good, after the lowest cell has reached a preset value. I can see my setup cycling the charger all night if I let it.

At least now I can seal up my battery boxes.

[retepsnikrep]

Sealing up the boxes,
Bloody hell I hope it works all right!! Can we have some photos please before you put the final nail in the coffin or screw in the lid whichever you choose

I hope you have some sort of temp monitoring in the boxes? Can I suggest you include a DS18B20 I2C device in each box in the middle of the pack, the Master (when you build one) can interogate these and tell you the temps. If you do it now and bring the leads out you won't have to open them up again later.

http://194.201.138.187/epages/Store.sto ... cts/ICO011

You could use a simple plug in timer to prevent endless cycling.

Dial in the estimated charge time each night, then even if it cycles a few times near the end it would help to balance them anyway, when your time period has elapsed it shuts off and prevents further charging/cycling.

Please keep a close eye on the cells and BMS boards during this initial period so you can see if anything is awry, Pic lock ups I suppose is my greatest concern.

[GregsGarage]

O.K. Maybe sealing up is too harsh a word. The temp sensor idea is good. I will order some. Have to open up the boxes again to put them in but that will give me a chance to check everything.

I like the timer idea. I can implement it in my management module so that the timer starts after the first time the HV opto triggers and then doesn't let the charger restart after it times out. That way I only need to now how long it takes to balance from when the charger first trips the opto, it won't matter about the DOD so I won't have to guess about overall charging time.

[retepsnikrep]

At the Moment the Master only interogates one temp sensor but it is able to address several, once I get round to writing that bit of the software that is!! Greg, do you want me to send you a Master board yet? I have the chips for it as well if you want them?

Just been attaching the Slaves to my first block of cells. The Slaves are not interconnected yet and neither are the cells any more than 10 in series, about 35V, I won't interconnect the main cell buses on the blocks until the wiring/slave testing is complete and covers are ready to put straight on afterwards.

www.solarvan.co.uk/bms/BlocksBms01.jpg

Whilst checking current consumption of each Slave as I attached it I found a couple of annoying mistakes.
One had a wrong resistor and one had completely the wrong IC soldered in WTF

I must have been asleep, some sort of op amp thingy from my old stock, just shows you need to check and double check everything. I'll have to make another Slave now as I won't be able to unsolder that without wrecking the board

I haven't programmed any of the Slaves yet, I'll do that when they are wired up, if I then program them in sequence with the Master attached I should see them respond immediately and the Master will display the fact they have come on line. Well that's the theory.

Greg, I've forgotten how many cells/slaves do you have?
Are they all wired up and working correctly?
Any problems with the Paralleled High/Low V buses?

[retepsnikrep]

Hhere are the values I have settled on. These seem to be working well with my charger, A Kelly 72v 15a for maintenance free lead acid batteries;

CPU 250 khz

Max Cell Opto On = 3.80V
Max Cell Opto Off = 3.65V

Load On = 3.65V
Load Off = 3.60V

Min Cell Opto On = 2.40V
Min Cell Opto Off = 2.50V

Greg, remember the voltage has to be > or < than the values you have choosen for the program to respond.

I think "Max Cell Opto On = 3.80V" is a little high for my liking, I would suggest 3.70-3.75V max to allow a bit more error headroom and prolong life.

[GregsGarage]

Peter,

Go ahead and send me the master board and whatever chips you have. PM me the cost and I will send it via paypal.

I am looking at the spec sheet and see that a number of sensors can be included on 1 wire. I would probably go for 5, 1 for each battery box and 1 for the motor. Might look into whether these would work with my board as well.

Also, do you have any ideas about adding a motor speed sensor to cut off the motor if it over revs. Not something I need for this project, but just thinking ahead.

I chose the 3.80 volt max to help keep the charger from cycling on and off to fast. Its a bit close to the edge but should help the rest of the cells get there faster. It doesn't stay at that level for long though as the load resistors start to bleed off the voltage straight away back down to 3.65 volts.

I will post some pics, but probably next week, lots to do still.

[retepsnikrep]

This topic on the Picaxe forum covers the issue of multiple temp sensors on one line, it's quite complicated and I have no idea at present how long it will take me to implement this in the Master software.

It probably won't be until I get my Insight install completed.

http://www.picaxeforum.co.uk/showthread ... ht=DS18b20

Re Motor Speed. The Master board speed (MPH) input basically counts pulses for 250ms, you could just attach some form of pulse generator to your motor shaft and use this input as rpm instead of speed with various simple changes to the Master software, obviously you would lose the mph function. But if you don't use a gearbox and have a fixed drive ratio then this could become the rpm and mph combined

You could use the Master Board Interlocks Input J14 as an rpm counter input, and use the Count / Pulsin command. You lose the interlocks function, but it's not implemented in the current software anyway at present, too much other stuff to do.

Or you could build a more normal analogue rpm circuit which produces a changing voltage 0-5v says depending on revs and then use one of the spare ADC inputs on the Master Board (There are three spare 0-5v Adc Inputs) to detect this signal and act on it when > max V (rpm).

A simple rpm chip with analogue output is the LM2917N and guess what I've found one in my junk box on an old Maplin rev counter kit pcb

http://www.maplin.co.uk/Module.aspx?Mod ... 0&DOY=16m9

Good luck with it I'll bung it in the box as a freebie

You could also use an independent Picaxe 08M chip to do the job

http://www.picaxeforum.co.uk/showthread ... 2A+counter

[retepsnikrep]

I am using regen. The Kelly controller has 2 ways of doing this. It can have variable regen through a 0-5v hall sensor, I had thought of using the clutch pedal. The other option is fixed regen, which can be adjusted with the PC configuration software. I have gone this route and wired it to the brake switch. When I first touch the brakes I get around 50 amps of regen which slows the car nicely. There is a spot between when the brake switch activates and the brakes actually engage that gives regen without using the brakes.

This worries me a bit, I would have used hall sensor and clutch pedal as a second brake, that's basically what I have on the Insight, but I have a steering wheel cowling mounted proportional control lever instead of a pedal. This negates the need to touch the brake pedal as well avoiding any mechanical braking and wasted energy.

http://www.solarvan.co.uk/insight/switch015.jpg

You do not want 50A of regen into your nice fully charged batteries when you first touch the brake. Also with the proportional control you can dial up the amount of regen they can stand, so when they are lower you can use more electric braking and vice versa.