Old BMS General Thread

[MalcolmB]

Just wanted to say a quick thanks for this thread. Like a lot of people I've been following your progress closely and am very impressed with what you've achieved. Just wish I had more time to experiment more myself.

Don't want to sidetrack you at all but I just came across this link on ES to a new BMS chip that I thought you both might find interesting: http://www.linear.com/ad/6802.jsp

[retepsnikrep]

Just wanted to say a quick thanks for this thread. Like a lot of people I've been following your progress closely and am very impressed with what you've achieved. Just wish I had more time to experiment more myself.

Don't want to sidetrack you at all but I just came across this link on ES to a new BMS chip that I thought you both might find interesting: http://www.linear.com/ad/6802.jsp

Malcolm, it was inevitable that as soon as we got some results something better would come along, that chip looks interesting, is it actually available yet, hmm I hope someone will produce a simple bms for everyone using it, the more the merrier. I believe the bms on this thread still has some advantages though

1) It's open source, freely available and doesn't use SMD parts so can be assembled by almost anyone without the need for laser eye surgery.

(Derek's has already adapted it for his 12v pb system)
(Greg's using it in analogue mode in his Fiat with his own charging setup)

2) It's expandable within the limits of opto coupler leakage and pic memory space. 128 cells presently and 256 cells when 28X2 Picaxe part is released. (In fact the limit is only because I choose to retain the cell voltages within the Master Pic for later processing instead of on the fly) with modified Master software or in Analogue mode who knows how many Slaves would work in parallel.

3) It got a nice display and associated Master board with lot's of auxilliary functions. (Display will be colour in Master MK2 with pretty graphs etc )

4) It's reasonably cheap IMHO, now the donkey work has been done.

5) It's shown that almost anyone including me a full time plod, with no electronics training of any kind, but 45 years of accumulated spare time tinkering can produce a BMS if they put their mind to it

[MalcolmB]

Peter
Like you say, the linear chip is still in development, I just thought it would be of interest.
The number of hits this thread has been getting says everything about the level of interest in your solution. I'm a great fan of the open source movement and also believe your BMS has many advantages. I'm especially looking forward to seeing the display in action – a moving bar graph showing individual cell voltages is one of the features I'd love to have on my mini, it would be a very practical piece of eye candy

[qdos]

I whole heartedly agree Malcolm this thread is one of the busiest and to my mind is exactly what the BVS should be about. I too am very much a fan of Open Source and try to use open source where ever I can it's much more flexible and dynamic all in all a much better philosophy to follow. A classic example of non open source and what it achieves is the Chevron GM deal on the Impact/EV1 and the battery hijack

The thread here is superb and the way the whole thing has developed very quickly with working examples just proves the whole approach is the right one Imagine if it was closed shop neither Peter nor Greg would be running their BMS systems right now I'm fairly sure they would be kicking around trying to solve problems and getting disenchanted probably too. I'm also quite sure there's a number of us less skilled observers on the sidelines here keen to have a go and order some too I know I am certainly hoping to. Just got to get the rest of the machine sorted out in the meantime

[retepsnikrep]

Thanks for the support gents

Just about finished the second block, only power cables remain.

I've ordered a load of Anderson high current connectors so it's a true plug and play setup.

Reflashed all 50 slaves (takes about 15 minutes) with a slightly faster version of the Digital Slave software.

Blocks are now sitting on the bench chugging round the expensive led lights might try and balance charge them both today

Display graphs will have to wait until Master Board MK2 or a daughter board to accept the more sophisticated display chip. That's a winter upgrade

Latest photo

www.solarvan.co.uk/bms/FinalBlocks01.jpg

[retepsnikrep]

Interconnected the battery blocks and started the charger to be greeted by two sparks and smoke. (Not from the battery blocks)

1st spark was caused by the current inrush into the charger filter capacitors from the battery pack, must watch that and power up psu/charger to charge internal caps before making the connection or leave it permanently connected or have some sort of pre-charge resistor.

2nd one with smoke came from back of charger/psu and heart sank but PSU still worked, opened it up to discover a tiny piece of copper swarf had fallen through a vent hole onto the output terminals. It had obviously vapourised but left a tiny piece to help identify the culprit.

Then about two hrs into the 200ma balancing charge, cells starting to come up to full V and balancing leds switching on and off. I test charger in line cheapo cut out relay by simulating a fault and charger trips out correctly but won't restart , hmm relay is operating but no power getting to charger so looks like the under specced mains e-bay relay has failed. I have a much better one standing by, but ran out of time until Friday.

I did finish off the pack data/bcm connections and started tidying up some of the other wiring on the old Insight battery pack box, which has been emptied of nimh cells and now holds the odd bits of extra electronics reqd and the Master board for the new pack.

My eta is end of october for instalation.

EDIT Oh, I bought one of those microscopic 433mhz data transceiver kits with an alleged 50-100m range. I like the idea of a remote wireless monitor for the BMS in the house. Probably a simple 16x2 lcd in a little box driven by a picaxe 08M chip just relaying the info from the Master onboard the car. It can easily have a remote alarm function as well, so it's basically a little pager type thingy. On screen pack voltage etc etc. Another winter project and a simple serial link to the house PC so I can start accumulating charge data for analysis.

[mikep_95133]

Hi Peter,

I've followed your Solarvan for quite a while. Years I think. I preach BMS over here as there is so little invested in it. I'm glad you are open source. These types of projects have been great in my experience.

I have some of the yellow TS 40ah cells for evaluation and testing. At 1C they show 103-105% capacity relative to nameplate. Next test is at 1.5C. Then they go into my truck for a thorough beating 250 amp max draw on a 3 phase system currently using flooded Saft nicads.

I'm a long time builder and tester of hardware. Are you selling the boards or is that DIY also? I'd like to get onboard by first offering my abilities for creating tests and taking data. My load tester is good for 130v or 60amps not to exceed 2500watts. My bench 'charger' is just like yours. A rack mount power supply that is CC/CV capable at 10a and 60vdc of output.

If the project is total DIY I'm fine with that. I may make the boards smt just because I'm proficient at it. But I'd rather just populate what ever you have and get these cells into my truck so the fun can begin.

Thanks so much for your time and efforts.

Mike

[retepsnikrep]

Charger relay repaired and balancing charge now underway.

I'm going to leave it on all night under the care of the BMS. I have adjusted the psu output to 150ma that means it should stay on all night, as the cell loads turn on, it will burn off the 150ma and no cell will be able to reach the cut off voltage, however the low cells should come up to meet all the full ones. I'm not worrying about implementing minute charger control at the moment, I'll just use two modes.

1) Daily, Charger set to max current output, and turns off when first cell reaches cut off voltage, gives a small amount of balancing at end of cycle.

2) Weekly, Charger set to 150ma and allowed to run all night to bring up the slightly out of balance ones.

Another couple of naff Youtube videos to amuse you

"Look at all the pretty lights!!" (Bungle from Rainbow)

http://www.youtube.com/watch?v=Wgyg41GIGxU

http://www.youtube.com/watch?v=xSXLVTJJtvA

Got to put some shelves up tomorrow

Edit

One more photo of pack and display.

www.solarvan.co.uk/bms/BMSTour3.jpg

[retepsnikrep]

Hi Peter,

I've followed your Solarvan for quite a while. Years I think. I preach BMS over here as there is so little invested in it. I'm glad you are open source. These types of projects have been great in my experience. Mike

Mike

Sorry I wasn't ignoring you I had the other post nearly done when your reply came up. Thanks for your support.

Questions are how many boards do you need? Where are you?

I think I have about 20 Slave pcb's left from the initial 100. I have one Master pcb left as well.

If you want to develop a SMT version that would be great as many will consider this now as an option. Please make your smt version open source as well, and compatible if possible with mine. I do have a couple of suggestions for the SMT Slave version MK2

1) An extra led on the Slave Master bus output so you can see when it is operating.

2) I've forgotten the other one at the moment.

Peter

[mikep_95133]

Hi Peter,

I've followed your Solarvan for quite a while. Years I think. I preach BMS over here as there is so little invested in it. I'm glad you are open source. These types of projects have been great in my experience. Mike

Mike

Sorry I wasn't ignoring you I had the other post nearly done when your reply came up. Thanks for your support.

Questions are how many boards do you need? Where are you?

I think I have about 20 Slave pcb's left from the initial 100. I have one Master pcb left as well.

If you want to develop a SMT version that would be great as many will consider this now as an option. Please make your smt version open source as well, and compatible if possible with mine. I do have a couple of suggestions for the SMT Slave version MK2

1) An extra led on the Slave Master bus output so you can see when it is operating.

2) I've forgotten the other one at the moment.

Peter

I don't need many slave boards as the cells are only being put in for testing right now. No one over here has documented their use. You are the only source of the 1st generation TS cells. I'll take all 20 boards and the master. That will get me going. Right now I have 7 cells. But there will be uses for more over time. Right now I need to see if these second generation cells will supply enough current in a single string.

I'm in California.

I've noticed that since your boards are spaced above the vents, then the whole board is useful for components. That makes the board layout very easy for the parts count that I see now. Open sourcing the layout is fine by me, that's why I'm here.

Mike