I may be building an electric go-kart

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dapuma
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I may be building an electric go-kart

Post by dapuma » Dec 18, 2017 7:32 pm

So I have a plan to build myself an electric go kart, but this is a very new concept for me making something bigger than the items I already have made. I have made an electric kick scooter with motors from an automatic toilet flusher, and also some little electric kitchen tools so I do not have to do as much work, but never something very large(and expensive) like this. I have read some other posts and I have learned some things about how to build it.

Body:
Voodoo VR1 go kart
Motor:
72V 550A motor drive kit
http://www.electricmotorsport.com/karti ... ystem.html
(I did not want to do the 84 because The batteries would end up weighing too much and I do not have a high voltage dc power source)
It puts out about 40kW of power, and has a 10 second boost of 660A.
Batteries:
http://www.electricmotorsport.com/ev-pa ... arger.html
It consists of 6 12.8V 40Ah batteries. I can also charge it with the AC charger included. It peaks 76.8V 240Ah total. Each battery pack weighs about 14 lbs. 14*6=84lbs total battery weights.

I have a $10,000 maximum budget.

I was wondering how long it would take to charge with the GBS 72V 20A Charger (110VAC in).
What gear ratio I would need (I want a good top speed and adrenaline-inducing acceleration)
And where to get the gear items.

Thanks.

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Gregory
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Re: I may be building an electric go-kart

Post by Gregory » Dec 18, 2017 8:15 pm

Love the idea of a go kart. I can't speak to gear ratios.

Those prismatic batteries are only good for 3 or 4C continuous discharge. So maybe 150A tops continuous. Which may be OK for your plans. I think they would get hammered on a race track. Any higher and you could be replacing them every season or two.

The charger is 72v X 20A = 1500W.
Battery is 72v X 40 Ah = 2800 Wh.
So around (2800/1500 =2) 2 hours to charge from dead empty.


1) x5305 Hub Motor in a 24" Sun rim with 10G spokes, Kelly 72601 controller, 74V 10Ah Turnigy LiPo 20C Battery and CycleAnalyst
2) Mac 10T rear hub in a 700C "comfort bike" 15S 5Ah LiPo, stock 28A Xie Cheng controller
3) 38" Longboard, Turnigy 6374, CC Mamba XL2 ESC

dapuma
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Re: I may be building an electric go-kart

Post by dapuma » Dec 18, 2017 8:44 pm

Gregory wrote:
Dec 18, 2017 8:15 pm
Love the idea of a go kart. I can't speak to gear ratios.

Those prismatic batteries are only good for 3 or 4C continuous discharge. So maybe 150A tops continuous. Which may be OK for your plans. I think they would get hammered on a race track. Any higher and you could be replacing them every season or two.

The charger is 72v X 20A = 1500W.
Battery is 72v X 40 Ah = 2800 Wh.
So around (2800/1500 =2) 2 hours to charge from dead empty.
Thanks. Do you have a recommendation for a battery that would be able to sustain such a current and be able to be charged with an ac outlet? On the website, the batteries can discharge with 10Cs pulsed. And would they be able to sustain short bursts of >500 amps, or would that be too damaging to the battery? I probably will not be driving it at over 30mph most of the time, unless I am on a racetrack.

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Re: I may be building an electric go-kart

Post by amberwolf » Dec 19, 2017 3:46 am

Lots of sellers claim high rates for batteries/etc they sell, but the voltage will usually sag quite a lot when used at those rates, so the watts you can actually get at the controller/motor from them won't be nearly as high as if the batteries were better.

They also heat up more, which wears them out faster.


You can parallel multiple sets of batteries, so they take less load each. (total load divided by number of parallel cells).


There's a lot of better batteries out there (they're just not all as easy to hook up into packs as those GBS/etc box cells). I use EIG NMC cells, which at 2p (40Ah) can sustain 200A, and 400A for 10 second bursts. (I don't use them at those rates, but that's what they're designed for). At 3P you could do 600A for 10 seconds, and 300A continous. 4P...400A / 800A. Etc.

There's someone selling used ones in the items-for-sale-used section here on ES; you could see if you can go test them if you're in the area (since you don't say where you are and it's not in your profile). I got mine used and they work for me, but not all used batteries are worth anything, so testing for your application is a good idea.


All batteries can be charged with an AC outlet, but none can be directly connected to AC, they can only connect via a charger--all batteries will need a charger, whether the charger runs from DC (solar, etc) or AC. Some people (like me) use certain types of adjustable constant-current constant-voltage power supplies (PSUs), like the Meanwell HLG series LED PSUs, various lab PSUs (Sorenson, etc), rather than "real" chargers, some use dedicated chargers for the purpose; depends on your needs and budget, and availability.


There's a number of kart threads you may want to read up on before you buy anything, especially teh one by Nuxland.
https://endless-sphere.com/forums/searc ... mit=Search

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Re: I may be building an electric go-kart

Post by MrDude_1 » Dec 19, 2017 12:53 pm

dapuma wrote:
Dec 18, 2017 8:44 pm
Gregory wrote:
Dec 18, 2017 8:15 pm
Love the idea of a go kart. I can't speak to gear ratios.

Those prismatic batteries are only good for 3 or 4C continuous discharge. So maybe 150A tops continuous. Which may be OK for your plans. I think they would get hammered on a race track. Any higher and you could be replacing them every season or two.

The charger is 72v X 20A = 1500W.
Battery is 72v X 40 Ah = 2800 Wh.
So around (2800/1500 =2) 2 hours to charge from dead empty.
Thanks. Do you have a recommendation for a battery that would be able to sustain such a current and be able to be charged with an ac outlet? On the website, the batteries can discharge with 10Cs pulsed. And would they be able to sustain short bursts of >500 amps, or would that be too damaging to the battery? I probably will not be driving it at over 30mph most of the time, unless I am on a racetrack.
for a gokart?
A ton of RC lipo. The 4s Hardcase packs are easy to stack and chain together.
Warning:This post is being read via light, a substance known to the state of California to cause cancer.

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Re: I may be building an electric go-kart

Post by dapuma » Dec 19, 2017 8:12 pm

MrDude_1 wrote:
Dec 19, 2017 12:53 pm
dapuma wrote:
Dec 18, 2017 8:44 pm
Gregory wrote:
Dec 18, 2017 8:15 pm
Love the idea of a go kart. I can't speak to gear ratios.

Those prismatic batteries are only good for 3 or 4C continuous discharge. So maybe 150A tops continuous. Which may be OK for your plans. I think they would get hammered on a race track. Any higher and you could be replacing them every season or two.

The charger is 72v X 20A = 1500W.
Battery is 72v X 40 Ah = 2800 Wh.
So around (2800/1500 =2) 2 hours to charge from dead empty.
Thanks. Do you have a recommendation for a battery that would be able to sustain such a current and be able to be charged with an ac outlet? On the website, the batteries can discharge with 10Cs pulsed. And would they be able to sustain short bursts of >500 amps, or would that be too damaging to the battery? I probably will not be driving it at over 30mph most of the time, unless I am on a racetrack.
for a gokart?
A ton of RC lipo. The 4s Hardcase packs are easy to stack and chain together.
ok then... will that be out of my budget? And I would need a peak detecting charger... Do you have any recommendations which batteries are safe, affordable(as you can get), and has a good charger? I have a bit more knowledge of Lipo batteries because I have a traxxas rc car... But they are quite expensive.

EDIT: I just realized the original ones I had would work because it contains six 40Ah batteries... 3C on 240Ah is continuous max discharge rate of 720 Amps.

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Gregory
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Re: I may be building an electric go-kart

Post by Gregory » Dec 19, 2017 10:28 pm

No you don't add the Ah with the cells in series, only if you parallel 6 batteries would you get a 12v battery of 240 Ah capable of 720 A.


1) x5305 Hub Motor in a 24" Sun rim with 10G spokes, Kelly 72601 controller, 74V 10Ah Turnigy LiPo 20C Battery and CycleAnalyst
2) Mac 10T rear hub in a 700C "comfort bike" 15S 5Ah LiPo, stock 28A Xie Cheng controller
3) 38" Longboard, Turnigy 6374, CC Mamba XL2 ESC

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Re: I may be building an electric go-kart

Post by amberwolf » Dec 20, 2017 12:41 am

dapuma wrote:
Dec 19, 2017 8:12 pm
EDIT: I just realized the original ones I had would work because it contains six 40Ah batteries... 3C on 240Ah
That only works if you parallel the 40Ah batteries. What voltage is each of the six? If each one is 12v, then that means you now have a 12v 240Ah battery, and you'd need a motor/cotnroller that runs on 12v.

At 12v, teh current demands for the same wattage are six times higher than at 72v, so your problem doesn't change--you now need six times the current that you did before and the cells are still pushed exactly as hard as they were before.

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Re: I may be building an electric go-kart

Post by MrDude_1 » Dec 20, 2017 7:59 am

dapuma wrote:
Dec 19, 2017 8:12 pm
ok then... will that be out of my budget?
That depends on your budget and where you buy them. Most RC lipo is expensive, esp here in the US. Hobbyking lipo is the only cheap lipo I buy... that leads to this:

dapuma wrote:
Dec 19, 2017 8:12 pm
Do you have any recommendations which batteries are safe, affordable(as you can get)?
None. No 18650, no pouch cell, no prismatic cell is safe. They are all dangerous always on power sources that will throw 1000s of amps for a second if shorted. they all burn if overheated. they demand a huge amount of respect, and safe storage throughout their life.
if you can do this, cool. If you cant, then dont build a battery. That said... You can get these for $23each https://hobbyking.com/en_us/turnigy-500 ... -pack.html

dapuma wrote:
Dec 19, 2017 8:12 pm
And I would need a peak detecting charger... and has a good charger? I have a bit more knowledge of Lipo batteries because I have a traxxas rc car...
All lipo packs need a BMS to keep cell balance. If its RC lipo, the BMS may be built into the charger. if its being built for plug and charge use, it needs an onboard BMS and a bulk charger. they both plug in the same way. in a pinch a bulk charger and a cell monitor can be used but that is for building and hobby use by a responsible person. Not for everyone.

In a nutshell... yes you can do it cheap and easy if you learn what you're doing, but its very far from foolproof. adding in the safety features is needed to make it fun and safe to use by anyone besides the builder...
Warning:This post is being read via light, a substance known to the state of California to cause cancer.

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MrDude_1
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Re: I may be building an electric go-kart

Post by MrDude_1 » Dec 20, 2017 8:04 am

on another thought, you could always do what I did on my electric kart...
run nissan leaf battery modules as a giant lipo pack. :lol:

(way overkill and oversized for most karts)
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dapuma
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Re: I may be building an electric go-kart

Post by dapuma » Dec 20, 2017 11:01 am

amberwolf wrote:
Dec 20, 2017 12:41 am
dapuma wrote:
Dec 19, 2017 8:12 pm
EDIT: I just realized the original ones I had would work because it contains six 40Ah batteries... 3C on 240Ah
That only works if you parallel the 40Ah batteries. What voltage is each of the six? If each one is 12v, then that means you now have a 12v 240Ah battery, and you'd need a motor/cotnroller that runs on 12v.

At 12v, teh current demands for the same wattage are six times higher than at 72v, so your problem doesn't change--you now need six times the current that you did before and the cells are still pushed exactly as hard as they were before.
Ohhh. Now I get it. I would have to be able to connect them to be used all at once for maximum performance. Well... and to the other guy, thanks for the lipo information. I understand none are safe, but by “safe” I probably meant “not lead acid”. I should have worded it correctly. Also, with those 4s batteries, it would not end up with as much storage as I would probably need. I will see if I can get a 2s with 10Ah. Thanks though.

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Re: I may be building an electric go-kart

Post by dapuma » Dec 20, 2017 12:14 pm

So I found this 8Ah 2S1P lipo from hobbyking.
https://hobbyking.com/en_us/zippy-fligh ... tore=en_us
I would need 12 of them. They are $34 each, and rated at 30c. The only thing I am wondering is would 2 of them working together be able to put out 500A, or would I need a battery this size with about 75C?

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