[JohninCR]

You may want to reconsider the multiple pack approach. A123's recommended fast charge current is a 4c, so it takes only 15 minutes, and normal recommended charge takes only 45 minutes. Of course you'll need a charger and BMS capable of that, but it's cheaper than the multiple packs of batteries.

Cheaper, lighter, and smaller would be a pack made of the Lipo cells the RC guys use, and the way they use theirs is quite similar. You won't get the same cycle life, and the batteries are more dangerous, but in terms of performance the LiFePo4's can't keep up. It's a cheaper way in + greater performance to weight ratio + can even be charged in only 5-10min. That's what everyone will go to anyway, at least until the safer chemistry batteries catch up to the Lipo's.

John

[Xph]

Thanks for all of the great feedback... It would seem that I can start ordering parts, and that my goals and assumptions seem resonable. I should be close to my weight goal, and within my budget, I will have to see how the acutal performance pans out.. The big variable seems to be the battery and BCM... and it seems that this is the likely the reason you dont see more Electric Karts at the track or Kits for sale...

So I will need to be prepaired to break out the spot welder, soldering iron, and spend some time researching the latest BCM electrical diagrams to get something just right for my purposes...

http://www.batteryspace.com/index.as...&Category=1061

Is looking like a decent place to start shopping. but I will still need some BCM, they offer a DIY kit, but it seems a little short of my needs and a bit expensive

Also looks like I am going to need a bunch of these cells if I want to get to 72v @500A... The issue I see with these is that most are rated for a 30A draw, and they start to get very expensive when you go up to the 50 or 100A... and even at 50A I am still going to need 200 to build a 74v 500A batt... 6K$ for a 74v 500A 50AH batt @ 50lbs and thats without a BCM... I am guessing unless there is a way to raise the Discharge raiting (eg using ultracapacitors http://www.tecategroup.com/store/ind...roducts_id=126)... these are not going to be practical for my inital build out.

But even if I could integrate some ultracapacitors, I think I am going to need to go befriend a local Electrical Engineer or two to get some custom BCM technology to keep my kart from catching fire or worse.

I guess one of my goals wich seems out of reach at the moment, was to stick with off the shelf, just a parts list, wiring diagram and a few mounting brackets... this would have allowed me to prototype a system others could go out and buy to race with me... The only real chance I see of this would be to go back to using heavy Optima syle batteries, but these just arent safe in a karting applicaiton, they are way to heavy. I suppose I could go back to the Dwalt packs, and just limit the discharge to something around 20A per pack using the built in BCM, this would just cap me to around 100A draw with my smaller pack size and I would be under powering the motor.

[Xph]

Hmm I have to say something like this looks intreguing...

http://www.xheli.com/20c11-1v2200mah-lipo-battery.html

its a 20C 11.1v 2200mAh LiPo 6.4oz pack for 30$...

So 70 of those would net me a 2100$ 77.7v 22AH pack... which I could discharge at up to 400A

That should power me through 3 runs of autocross with Ah to spare and what I speculate would be about half the power I would need for a Kart race.

And it would only weigh in at 28lbs + wiring and mounting brackets.

As for battery cycles... If I raced every weekend for a summer for a year, maybe 30 events say... and throw in a practice day every week, so make that 60 days, maybe 3 power cycles a day.. The battery pack should easly out last the life of the Kart.

However, I would still suspect I would need some BCM's for a 70 pack battery, not to mention they are designed to be charged individually, and I wouldnt want to buy 70 chargers...

[SMEECH68]

We are also building a Electric Race Kart for Badger.
We started with a Hasse chassis and I am using a Briggs ETEK motor with 4 12/20 sealed AGM batteries (48 volt system to start) and a Alltraxx controller.
I would like to talk to you about your kart and share idea's as well as race & practice at Badger.

Drop me a email to: dsmith@QuickCable.com
Thank you, David Smith

[nepore]

I think is expensive, but is a really nice project

[neanderthal]

I dont know about using the kelly Every time I see a test on one the actual output is 1/2 to 1/3 of what it is rated for

[AmpEater]

Originally Posted by neanderthal

I dont know about using the kelly Every time I see a test on one the actual output is 1/2 to 1/3 of what it is rated for

I had a Kelly in my custom 3 wheel kart. The 500A version seemed, at least measured by my "butt dyno", to be comparable to the 400A curtis I was running before. But it weighed half as much and was less than half the size. In my application I had no manual brakes, and relied entirely on the regen function, which was suprisingly strong but limited to my batteries capacity to accept charge current. I imagine something like A123 cells could actually lock the rear wheel up if set to full regen. (As a side note, this was an experimental vehicle, I'd never reccomend relying solely on regen for safe stopping, too many things can go wrong that would mean the loss of brakes).

As far as I know, there really isn't any other option for regen controllers out there right now. For something like a go kart of bike where space is at a premium there aren't any controllers as compact as a kelly, either.

You're right on track for your project, the Agni is an excellent motor choice, and A123s are perfect for this sort of project. You could build a smaller pack now without spending too much $$ that could still deliver massive current, and upgrade in the future for longer run times (perhaps buld the packs in a modular fashion, 1x pack for sprints and 2x or 3x for longer races)

It will be a blast

[blank_rv-6a]

Cool to see you guy's having crazy thoughts like me about Karts. Just a off the wall comment or two on regen braking. I haven't done all the calcs but some run front brakes and I think if you replaced the calipers with the rc motors plus have a maxwell ultra capacitor or two you could have a cool extra brake power with added power boost out of the corner. I just joined the site so I need to poke around more but it just seems to me we need to scale up the RC stuff to the kart realm. Perm Magnet sure saves some watts from the power pack. On short duration like 10 to 15 minutes I would think it would fall into the RC mode and a Hacker Brushless A200 weighs only 6lbs for 13hp....Sweet Now to go lurk some more.

[AmpEater]

Originally Posted by blank_rv-6a

Cool to see you guy's having crazy thoughts like me about Karts. Just a off the wall comment or two on regen braking. I haven't done all the calcs but some run front brakes and I think if you replaced the calipers with the rc motors plus have a maxwell ultra capacitor or two you could have a cool extra brake power with added power boost out of the corner. I just joined the site so I need to poke around more but it just seems to me we need to scale up the RC stuff to the kart realm. Perm Magnet sure saves some watts from the power pack. On short duration like 10 to 15 minutes I would think it would fall into the RC mode and a Hacker Brushless A200 weighs only 6lbs for 13hp....Sweet Now to go lurk some more.

I looked up the A200....it's rated at 15000 watts, which is more like 20hp

Now I get why the ebike guys are using them! That power/weight is just nutty

[NickRummy]

I have no experience in the EV world yet but I have a LOT of experience in the RC world. I've run A123 cells and lithium cells with brushed and brushless motors. I've used the following site many times and have zero complaints. My only concern might be shipping costs. I've had numerous high voltage/current packs from them without any problems.

If you want a beefier pack here is a 6S (22.2V nominal / 25.2V peak) 5000mah 30C pack for $100 with a 40C for 10 second burst. It weighs 789g.

It can be charged at 2C also (10a)

3 of those $100 packs in series would peak charge to 75.6V and capable of 100A cont. and 200A burst for 10 seconds. If you take that set of 3 and parallel 3 sets to make it 3S3P you would be up to a pack that would peak charge to 75.6V and capable of 300A con. and 600A burst for 10 seconds. IT would weight about 7,101g (15.7lbs) and would cost $900 plus shipping.

If you want to up the voltage and capacity a bit you could go to a 4S4P setup which would be 88.8V nominal and peak to 100.8V, would be 20AH and be able to deliver 400A continuous and 800A burst for 10 seconds. It would cost $1600 and weigh 12,624g (27.83lbs)

I ran the older version of the pack above that was 20C in an RC truck I built. I bought this pack to replace a 6S A123 pack I was using. The new lipo pack had so much more current available it was unreal....



The motor that lasted for months on the 6S A123 didn't last but a run or two on the 6S lipo....