Battery Vehicle Society

Looking around for more information about the composition of lithium phosphate cells and combustion products, I came across this wiki that I'd not read before: http://en.wikipedia.org/wiki/Lithium_ir ... te_battery

Quote:
LiFePO4 is an intrinsically safer cathode material than LiCoO2 and manganese spinel. The Fe-P-O bond is stronger than the Co-O bond, so that when abused, (short-circuited, overheated, etc.) the oxygen atoms are much harder to remove. This stabilization of the redox energies also helps fast ion migration. Only under extreme heating (generally over 800 °C) does breakdown occur and this bond stability greatly reduces the risk of thermal runaway when compared with LiCoO2.
As lithium migrates out of the cathode in a LiCoO2 cell, the CoO2 undergoes non-linear expansion that affects the structural integrity of the cell. The fully lithiated and unlithiated states of LiFePO4 are structurally similar which means that LiFePO4 cells are more structurally stable than LiCoO2 cells.
No lithium remains in the cathode of a fully charged LiFePO4 cell â€â€

There is also a carsonagenic element to the gas, as with all lithium cells, but the concentration is less than the fumes from petrol.

I have been corresponding with China Hi-power about my fire, discussing possible causes. Most likely seems to be a charger or wiring malfunction. I have asked about strapping the cells as Thundersky recommends for their cells. China Hi-power says it shouldn't be necessary if the cells are operated within their design parameters. I will probably strap my next pack just to be safe.

They have shown a lot of concern for my fire, even phoning me from China several times to discus the fire. I am quite pleased with their response. China Hi-power are going to provide me with another pack at a discount to help me with my next conversion. I have just purchased a Matiz. Planning on putting the bits from my Volvo 440 into the Matiz. The large motor in a smaller car should allow me to lock the gearbox in 4th gear and not have to consider whether to keep the clutch or not. Main battery pack mounted under rear seat in fuel tank area should help keep the batteries safe in the event of an accident. I will probably use a Zivan charger with Cedric's cell protectors, now that his new version is available, suitable for all of the current lithium chemistries on the market. I still have faith in Peters BMS system, but Cedric's are available off the shelf.

Some sort of good news there from Hipower.

Cedric's cell protectors are very good no question.

I would let you have my pcb's free if you did want another try with mine.
As you are an early adopter and supporter it would be helpful to the whole BMS project as well.

How many cells in this new system?

If you need a Zivan get it ordered now, mine took over 2 months to arrive from Italy!!

Thanks for the offer Peter. Nothings set in stone yet so I will keep that in mind.



At least 32, may go a bit higher. Looking for a pack size of at least 10kWh, more if I can afford it. Would like to hit that magic 100 mile range, even if that is only achievable with very careful driving.



I will need to find out if my current Zivan can be reprogrammed for the Hipower cells. Thay are temptingly close to lead acid, but I am not making that mistake twice!

My main concern at the moment is if the NetGain Impulse 9 motor can be shoehorned in. Looks like the length may be alright, just, but the 9 inch diameter of the motor may interfere with the OS inner drive shaft joint. I will probably try and find a second hand gearbox to work with off the car and then I can just swap the engine for electric motor in one go.

The Matiz just came back from the MOT station with a pass. I'll put 6 months tax on it and check out the article in the latest BVR about calculating power required for a conversion. Skimmed it and it looked interesting, so will give it a good read through. I will start a thread in the conversions section once I really get stuck into this project.

Good to hear you've got another project going Greg. I'll be following this closely. The Matiz looks like a good choice and should really shift with a 9" motor.

On the subject of calculations, I came across this excellent book not long ago that covers all aspects of sustainability and the numbers behind it. This is the chapter on cars. Recommended reading: http://www.inference.phy.cam.ac.uk/sust ... 53.326.pdf

Good to see you are forging ahead with another conversion Greg. That's the spirit! Also good to see China Hipower is cooperating so well. I am of course very keen on understanding why your vehicle caught fire. Also very relieved no one was hurt and your house is intact!

I've been trying to contact Stybrook to place an order for their bms for 36 SkyEnergy 180Ah cells I have on order but no one is responding. I sent the email to info@agnimotors. Is there another email for them?

Thanks,
Tom
USA

UK Europe, USA & Canada

STYBROOK LTD

Mobile: +44 (0) 7876 702702
Email: stybrook@hotmail.com

lifted from Agnimotors.com distributor page

Hi Tom,

Stybrook have a bike entered in the isle of mann tt race, the electric one, so are probable busy preping that at the moment. It's on in the next week I think, so they may not respond till after that. Send them another email if you don't here from them by the end of next week.

Greg

Well, while I'm waiting for Stybrook to respond, has anyone been using this bms, and if so, how is it working? It seems to mainly be used in the UK. Evpower in Australia seems to have their own version, but I don't know any details on how it works. The US seems to only offer very expensive systems with more functionality, e.g. Elithion.

I am thinking of using the Stybrook with a Manzanita PFC30 or Elcon charger, and have the signal from the Stybrook turn off the charger. Anyone used an Elcon charger? I can't find much info on them, including if they can be shut off with such a signal. I want a charger that will operate from 240AC or 120AC so I can charge with 240 at home and opportunity charge with 120.

Any further insight on cause of the fire? Any indication cold temperature had a role? I'm thinking of heating the battery boxes and interlocking my charger with a temperature sensor so it will not come on unless the temperatures in the boxes are greater than 5 degree C or so. I"m guessing I would likely only need to heat when the car is parked overnight.

Thanks,
Tom