adrian_sm said:Xrain said:If multiple parallel strings of batteries are used, then each string must be individually fused. If individual fuses are used this will provide a total fusing equal to the number of fuses multiplied by the fuses rating. Any wires conducting the entire pack current must be appropriately sized to this total fusing or an additional fuse used to protect the wiring.
Multiple parallel fuses in a single string are not permitted.
We had originally arranged our headway pack like any other sane person would, but we were told that we weren't allowed to arrange them this way.
I would ask for clarification on which rule stops you from wiring the packs in the way you would like, because I can't find it in the rules you linked to. http://students.sae.org/competitions/snowmobile/rules/rules.pdf
I didn't see anything mandating that you use parallel strings. Only an IF you do, fuse them this way.
I think the UL listed charger will be the rule that annoys you the most. As all the RC style chargers I know of will not be UL listed, so this may force your hand in how you charge the packs. You may end up just having to get whatever UL listed charger you can find then having some non-UL listed monitoring, like from here, which should be able to do your HVC & LVC.
Good luck.
texaspyro said:Frankly, the rule makers are REALLY clueless dumbasses. Their rules are down right dangerous. I would recommend bailing out of the competition and going it your own way... properly.
Xrain said:All of the EV rules are in Appendix G, That specific rule is Appendix G, FH-2.4: Fusing
John in CR said:Xrain,
I think you've overlooked a key advantage of those nanotech packs. Lower weight is great, but compute the size of your 8kwh nanotech pack and you'll cream in your pants. For the real racing part the more than 50% smaller volume of the Nanotechs compared to the dead-ways would give you so much more flexibility in battery placement.
E-racer said:How I would win an electric snowmobile challenge. Convert this:
- doctor bass http://endless-sphere.com/forums/viewtopic.php?f=14&t=16775#p246707Bill Dube The owner of the Killacycle heat the 1210 A123 cells to around 70 celsius before each run.. That lower the cell internal resistance a lot and decrease the voltage drop of the pack. These cells have been tested to 250 celsius before they become weak so it’s no worry.
Provisions for charging must follow the same rules as other high-voltage wiring: no exposed connections, proper strain relief, etc. The battery enclosure must remain closed during charging.
auraslip said:I was thinking more about your pack, and the fact that your buying rc lipo from an alibaba site.
Perhaps more people post about problems than they do about good products, but batteries in general have a pretty high DOA. I'm sure the top of the line nanotech stuff is QC'd properly, but even the 20c hobbyking stuff has seen a few of people complaining about bad cells. The fact that you are buying even CHEAPER cells from an ALIBABA site worries me. I hope you have researched that brand very well! ALSO be sure to look of lipo break in and priming procedures.
As far as bulk charging with HVC protections: I would do bulk charging on each parallel group with the HVC on the bulk charger. Since you can't watch the cells as they charge, I would check all cells to be sure they are bottom balanced before you charge. Then I would set the HVC in the charger much lower than you need it(for example 3.9v instead of 4.2v). This shouldn't effect range much, and will (hopefully) keep the cells from overcharging.
Provisions for charging must follow the same rules as other high-voltage wiring: no exposed connections, proper strain relief, etc. The battery enclosure must remain closed during charging.
Can you watch the battery charge? You could get some battery medics/battery loggers and be your own single cell HVC. OR check out ggoodrums lvc/hvc boards http://www.tppacks.com/products.asp?cat=26
Bmsbattery sells 2000w chargers for $200 each, and they are voltage tunable. I don't know if they are UL registered.
Ironic that in a competition to create an entire electric vehicle, they don't trust you to make a charger for it..Xrain said:The UL listed requirement is more they just don't want us creating/modifying our own charge
Like I had proposed earlier, Chargery BM6's that will monitor each paralleled cell group, and alarm if anything goes wrong (and you can route that alarm output to do anything you like).
liveforphysics said:BMS is such such such a terrible idea for a race vehicle....
Don't you just need an HVC/LVC (which can be done with a simple voltage divider and a uController that cuts the controller enable or opens a relay etc) and a way to monitor the paralleled cell groups? Like I had proposed earlier, Chargery BM6's that will monitor each paralleled cell group, and alarm if anything goes wrong (and you can route that alarm output to do anything you like).
auraslip said:Like I had proposed earlier, Chargery BM6's that will monitor each paralleled cell group, and alarm if anything goes wrong (and you can route that alarm output to do anything you like).
Yes! Make this your bms. Route the output of the LVC alarm to a relay that breaks the main packs connection to the controller. Dead simple.
I've been thinking about doing the exact same with the "smart" programmable bms that bmsbattery.com sells. If you do it this way, you can use a bms rated for any amps. Use the BMS just to make or break the relay connection.
John in CR said:What exactly does the cold start entail? Do you have to leave it totally unplugged overnight to reach ambient temp? Is there any prep time before the start? What about charging afterward. I'd consider making use of an electric blanket...low weight, limited temps, UL approved. If it can't be plugged to the wall, but can recharge after the cold start, then I'd consider just running the electric bike off the pack overnight, maybe with a timer and temp sensor cutoff to make sure it doesn't get too toasty. Starting all of the events with the pack a nice temp will pay big dividends.