gokart battery

[howler45723]

Hello ALL,

I am trying to get a gokart to achieve 7.90 1/8 mile @ 600 lb, I would like you suggestions on motor type, controller, Batteries\ configuration. I can use up to 144 volts. I believe the motor needs to spin at least 5500 - 6000 rpm. Batteries will need to be lite,sealed,and around 50 lbs. ( cost needs to be around 1500 - 2000 dollars )

Thank you
Mike
terawattracing.com

[bearing]

To be able to make the budget, I think you'll need to use a used forklift motor, about 1-2kWh of good RC Lipo, and some cheap but yet powerful controller. Not sure which the best controller choice is. Perhaps a Kelly. Or maybe the DIY Open Revolt.


Does it have to be >600lbs? in that case lead acid may be a better battery choice.

[howler45723]

Hey bering

the kart will probably be in the 450-500 range kart 200 driver 125 ( lol not me ) + drive + batt

I know 0 ( ZERO) about controllers, why are they 1000 + dollars, I have seen some for 750 . I need to be able to creep for about 10 feet , stop, apply 45 hp, and be able to adjust the time i hit the gas pedal and voltage is applyed ( delay )

I'm beggining to ramble

Thanks
Mike
terawattracing.com

[howler45723]

bearing

good stuff, i just read this article on RC Lipo

http://www.rchelicopterfun.com/rc-lipo-batteries.html

wow

Thanks

[Arlo1]

The Open revolt (cougar controller) is your best bet. And a 6.7" forklift or golf cart motor will do just fine. Most the brushed electric motors for the forklifts and pumps and golf karts are all very similar. You will find they Can be 6.7" 8" 9" 11" and 13" Dia commonly. The 70,000 watt kart I linked uses a 6.7" motor. Make sure you know what the connection type the motor is before buying a controller. My 6.7" motor is a shunt wound motor meaning the feild coil has to be powered and limited separately so this means I need a certain controller. The Revolt controller is for a series wound motor I believe and this meens the feild coil is connected in series to the brushes and it is very tricky to reverse. Then there is a parallel wound motor which means the feild is connected in parallel to the brushes. Mine is the easiest to have reverse with the controller just switches polarity to the brushes or the field but not both at once for reverse. Just find a motor with the highest HP:Voltage rating you can for as cheep as possible Then run the highest voltage you can to it. If you look at the 70,000 watt kart build they tell you what voltage they tried and blew the motor its pretty hi. Just make sure you do your research first. Electric motors are rated in continuous ratings and you can put more then 10x that rating into them for a few seconds. Use lipo batteries its the only way you will achieve what you want. LEAD is DEAD. Rc Lipo can make the most HP per pound and cost wise Turnigy Nanotechs are going to be what you need.

REMEMBER DO NOT USE LEAD!

[howler45723]

Arlo
thanks so much, i see you can buy the controller yet, but can buy kit ? also the area i have to contain batteries is about 16 x 16 x 16 any thoughts ?

[howler45723]

arlo1

I will also need to recharge in 15 -30 min. or switch out to another battery pack......

Thanks

[Arlo1]

Spend some time on this website http://www.hobbyking.com/hobbyking/stor ... _Pack.html
the batteries I linked are just a quick pick. They can be charged at 8c and discharged at 130c C means fraction of an hour. So 8c is 1/8th hour 130c means 1/130th of and hour its a 5ah 6 cell battery so it will charge to ~4.2v a cell 6s means 6 cells so 6 x 4.2v = 26.4v per pack the nominal voltage is rated at 3.7 per cell so the pack holds 3.7 x 6 x 5ah = 111wh or energy and because it can release it in 1/130th of an hour it will produce 14430 watts for 27.7 seconds. You can parallel as many as you need and run them in series as you need to get the total voltage and KW/h you need.

[Arlo1]

Arlo
thanks so much, i see you can buy the controller yet, but can buy kit ? also the area i have to contain batteries is about 16 x 16 x 16 any thoughts ?

The couger controller is a DIY it is a DIY to help people like us save money and learn what we can. If you want something alread finished then you will pay a lot more money.

[howler45723]

arlo1

Thanks, head ready to explode

[howler45723]

arlo1

Is my math right, 6 batteries, 2.5 lbs, $700.00 ish, for the lipo 500ah

[Arlo1]

arlo1

Is my math right, 6 batteries, 2.5 lbs, $700.00 ish, for the lipo 500ah

Post a link and i will work the math for you. 1000 mah = 1ah btw

[Hillhater]

...Is my math right, 6 batteries, 2.5 lbs, $700.00 ish, for the lipo 500ah

Lets have a quick estimate ..
Assuming you have a 45kW motor at 144v....
..and assuming you need that full 45kW power ability for (say) 30 secs max ..
then you will need 313 Amps @ 144v, for 30 secs
..and 375 Whrs of energy ( 45kW/120hrs) .. or 2.6Ahrs @ 144v
so 144v is around 36 cells or 6 x 6s packs
for the 313 A capability you will need the 90-130C Nanotech packs of 5 ahr size
http://www.hobbyking.com/hobbyking/stor ... _Pack.html
At $117 each = $702 + shipping , connectors , charger etc

NOTE; .. at full charge a 36s pack would top out at 151v. (4.2v /cell)!
If that is a problem , you may chose to go with 7 x 5cell packs which would give you 144v when charges to 4.11v per cell
..and cost less !

You could recharge the pack in 30 mins with a 1Kw , 144v charger,
http://www.bmsbattery.com/alloy-shell/2 ... arger.html
... or you may prefer to have a 2nd pack ready to go and a slower(?) cheaper charger.
A 2nd pack would be a good back up in case of problems.

[Kin]

It's a gokart. Why are we talking nanotech? If there's space, grabbing 10ah of 30C turnigy is much better than 5ah of 60C, because you have twice the capacity. Although it looks like to focus of the conversation is other components (which is great), if there's any concern about LiPo, a123 is a decent option as well. Simply making balance leads and treating it like LiPo is a way to get around the BMS issue for a high voltage pack.

Am I mistaken? I assume that gokart has as much, if not a bit more, space as a bike.

[Arlo1]

You are right kin if he wants to race a 20 min race cheep turnigy lipo is the way to go but he is trying to get a 7.9 1/8 mile time so its my understanding he wants to build a drag racing kart which then makes nano tech the best choice.

[Kin]

Ok! Yeah! You are right. I wasn't looking as closely at his parameters, somehow I read "I want to go 7 and 1/8 miles". apologizes.


Humor me for a moment, but: Perhaps there are certain benefits to a brushed system. If it's a drag race, perhaps there would be no need for a controller, and you could simply use some insane mechanical switch to connect the batteries directly to the motor (if it's just a DC motor, as opposed to AC or BLDC. Is that ever done? Kind of absurd, I admit.

[chbaird]

A mechanical switch works great until it welds itself closed and you can't open it when you're going 90+ mph down a very short road..

[999zip999]

Pic's please.

[Kin]

A mechanical switch works great until it welds itself closed and you can't open it when you're going 90+ mph down a very short road..

True! yeah. Freakishly true. Thinking through the consequences of what I suggested, I had a worried laugh. I suppose, though, that it could be designed with a failsafe (second crowbar designed to always be connected, but with the option of disconnecting it).

Still, I don't like the mechanical solution for further reasons in so far as it's so un-useful.

[Arlo1]

A mechanical switch works great until it welds itself closed and you can't open it when you're going 90+ mph down a very short road..

True! yeah. Freakishly true. Thinking through the consequences of what I suggested, I had a worried laugh. I suppose, though, that it could be designed with a failsafe (second crowbar designed to always be connected, but with the option of disconnecting it).

Still, I don't like the mechanical solution for further reasons in so far as it's so un-useful.

Yup working on harleys I have seen lots of start solinoids weld them selfs shut. The the bike wont quit cranking till you pull the battery wire off.

On another note You can not use a mechanical set up on a lot of motors the one I have is shunt wound so you need to limit the amperage going to the field coil seprate from the brushes and you can gain some speed by weakening it at higher rpms. As well you can not just short LIPO batteries to any motor as a rule because either the batteries or motor will fail. Lipo will produce more amps then its rated for causing damage to the battery and the motor is only going to take so many amps before the windings burn as well. Remember the brushed karts with BOOST SWITCHES use Led based batteries and led can take it because it just SAGS the voltage way down saving the motor!

[Kin]

True, Arlo1. There would have to be ways to limit the current. I was hoping the resistance in the brushed motor would be enough to limit the lipo's short so that things wouldn't blow up over 15 seconds, but I might be underestimating how precisely low the resistance of these batteries are. anyway, I think i distracted the post a little; i apologize. Your warning is good to keep so that anyone reading this out of context doesn't go ahead without thinking through that problem.

[Arlo1]

They are taking orders for prebuild Revolt (couger controllers) Here 144v 500 amp $700 pluss 20 shipping in us. 6 month warenty.

[Arlo1]

Pic's please.

Here is a couple of mine Its 234lbs with full rollcage and suspension. No driver or batteries.