High School team in the Shell Eco Marathon needs your help

[zombiess]

There is a team in Connecticut that is trying to get to the Shell Eco Challenge this year. This team has a vechicle that was running a Hydrogen fuel cell, but has since switched to battery power due to issues with the fuel cell.

Shell has more stringent rules this year and the battery they are running MUST be Li chemistry and it requires a BMS with full cell management, high/low cut off and over temp. BMS must break the battery circuit on a fault.

Rules here, article 57
http://www.shell.com/content/dam/shell-new/local/corporate/ecomarathon/downloads/pdf/sem-global-official-rules-chapter-1-2014.pdf

This group is one of only a handful of high schools in the challenge which is filled with mostly colleges.

The team lead CJ is on this site and I'll send him a link to this post. This group only has 2-3 weeks to finish up their vehicle and could use the help of our collective knowledge.

Top priorities on the list are batteries and BMS because they need them ASAP. If you have suggestions on what to purchase or would be willing to help out somehow, post up.

I'd really like to see this group make it to the event. Building an EV is not an easy task.

 

[DHS]

We were really bummed this year when we didn't raise enough money for the replacement fuel cell. By the time we decided to quit the fundraising efforts and start converting the car to fully electric it was already mid February.

What's different about the battery electric category is that teams are required to build a motor controller and not buy an off the shelf one. We attempted to build the Jeremy Harris style controller but we really didn't have the knowledge and skill for the circuitry. Jeremy has been kind enough to loan us his lebowski style controller and we're truly thankful.

That leaves us with the two big tasks of picking Lithium batteries to power the car and a battery management system to control them. The Eco-marathon is April 9th-12th and we plan on shipping the vehicle April 1st. If anyone would be interested in loaning us their battery pack and BMS (we were planning on a 48v system) it would mean the world to us. Our budget is somewhat limited but if you have something your willing to part with for the right price I'm sure we could work out a deal.

We've come so far with this project and it'd really be a huge disappointment if we had to give up now.

This is an excerpt from chapter 1 article 57 of the rules. "If Lithium-Ion based batteries are used, Battery Management Systems (BMS)
tailored to this chemistry must be installed to control and protect the battery against risk of fire.
The BMS must provide cell balancing and overvoltage protection during off-track charging. For Emobility
vehicles, the additional requirement of cell level overdischarge, over-current and overtemperature
must be provided as part of the on-vehicle system. The BMS must AUTOMATICALLY
isolate the battery, without operator intervention, if a limit or out of range condition is reached on
any of the above parameters. For Li-Ion based accessory batteries, the BMS cell balancing and
overvoltage protection may be contained as part of the off-board charger."

If anyone could point us in the right direction on where to start looking for batteries and a BMS that can be incorporated, that'd be great. Our motor is the crystalyte 5304 hub motor and we planned on using 48 volts.

 

[cycborg]

Do you know what capacity you need? If not, post some specs of the racing conditions (distance between charges, typical speeds, terrain) and vehicle (weight, frontal area, Cd if you have it) and some photos of the vehicle, and we can make some educated guesses.

Also give an idea of how much you are able to spend. Hopefully someone has roughly what you need and is willing to loan it to you, but if not it would help to know what your resources are.

 

[Lebowski]

Ah, so Jeremy got 'my' controller working ?

As far as I remember he has a very old version of the controller chip. One of the things not possible with the old version is to turn off the power to the controller
completely when coasting. This would be possible with the new versions and might help you get an extra few 100 yards or so. If you want you can mail me back the
controller IC (the big 40 pin chip) and I can re-program it if you want. Send me a PM if interested.

Can you maybe post a picture of Jeremy's controller, as I've never seen it...

 

[Nobuo]

Don't worry about the BMS, that's choose the right one and plug, but how to build the battery is another Story. I have not seen any info about how much Ah should have the lithium battery, neither the motor Watts. That's essential to choose the right BMS.

As the rule is not to exceed 48V nominal 60W max, You could go 14 serial lithium-ion batteries. That would be 51 Nominal, but 58.8 max. If you are sure is not allowed 13 serial would be the 48V nominal and 54.6 max.

What about the controller specs?

 

[Ypedal]

This challenge is all about range and lowest possible power consumption, not speed.. the slower you can go and still finish the required laps in time, the better... so higher voltages are not always needed.. entirely depends on motor winding selection, wheel size. etc..

 

[DHS]

Thanks for the input everybody,

We decided to go with a 48v 20ah LiFePo battery pack with a BMS already incorporated. I spoke with the company on the phone and from the information they gave me it seems like their BMS will get the okay from shell.

Lebowski, I don't have the controller yet but maybe Jeremy could post a picture for you. Thanks for the offer but I'm not too worried about the added efficiency, At this point were thankful to make it to the competition. So much going on here right now trying to finish up everything before we have to ship the car. Jeremy made a good point in an email before about the heat sink if you want to give some input here. Basically shell requires teams to house their controller in a clear or see through case, when Jeremy sends it to us we're going to remove it from his housing and mount it in a plexiglass case. Jeremy had his heat sink built into the housing and he thinks running without it wont be much of an issue since we're really not using it to nearly its maximum power. I'm not doubting his judgement, just getting another opinion. I really don't want to fry anything on his power boards!

 

[zombiess]

Ah, so Jeremy got 'my' controller working ?

He is talking about me, I'm a Jeremy too. The controller is my silver shoe box sized one that I'm going to loan them for a few weeks.

I'm trying to assist them with selecting a battery and BMS that will meet the rules. What questions to ask the vendors, looking over specs, etc.

 

[Lebowski]

Any news here ?