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Building a golf cart. How fast would a golf cart move with 2, 1 hp engines pulling around 250-300 lbs? Answered

Thanks! Also, where can I find a huge battery that has an output of 115v ac and can run at 5 amps for over 2 hours?

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PhatRATTY
PhatRATTY

11 days ago

On the flip side... What about two 4 horsepower engines in terms of speed?

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Orngrimm
Orngrimm

Reply 9 days ago

HP is NOT = speed!
1HP is 745W.
Depending on gearing and efficiencies and weight and drag and friction and Wheelsizes your speed will be different.

More power can mean more torque as well so maybe a bigger gear ratio (faster spinning wheels) or larger wheels (more meter per wheel-revolution) can be added. Depends all on torque.

2x4HP? OK... 28-30 Packs total. 84kg of Lipo packs.
Bordering the C-Rating of LiPo-packs! you will be in the ballpark of 250Amps on the inputside of the 2pcs 3000-3500W inverter. Cannot drive more as the rating of the LiPo packs is 12C --> 240Amps out.
Per Motor:
14 or 15 Packs in parallel ----> DC/AC (3000W+) -----> Motor

As electrical engineer, i would not dare going in this region of power in a DIY...
Cabling is more rod-Bending than cable... 0000 (4/0) AWG or 107mm^s is needed at least if you tolerate Cables heating up to 70°C / 158°F (https://en.wikipedia.org/wiki/American_wire_gauge#Tables_of_AWG_wire_sizes)
This is a HUGE Cable!
https://www.batterycablesusa.com/0000-gauge-batter... has images...About 0.75" diameter of Copper... Close to 9$ per foot. weight: 0.858 lbs per foot. Ouch!

--> Thats more a rod than a cable...





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Orngrimm
Orngrimm

9 days ago

Look, if you dont get a confirming Answer on your first thread (https://www.instructables.com/community/BP4C032K5A... it has no use opening a new thread and basically ask the same again...

It will still be 42kg of LiPo Batteries for around 3000 USD if you go with 120V & 20A.
With 115V & 5A (Thats only about 20% of the power initially requested!) it would scale down to about 8.5kg of LiPo's... Go with the batteries i linked you.
For 115V AC you need an inverter for DC/AC.
600W should be doable with LiPo's.
5Amp @ 115VAC for 2h = 5 x 115 x 2 = 1150Wh.
Your 100Ah are not bad of an estimate.

With the linked batteries in the other thread:
Assuming a 100% conversion-efficiency in the inverter (it is NOT!) it would roughly go with 100Ah @ 12VDC --> 10Ah @ 115VAC (2h @ 5Amps @ 115VAC)
Go with 5 of the linked packs from the initial thread in parallel and thru a Inverter capable of 1000W i would say to have some headroom.

| LiPo-Pack |
| LiPo-Pack |
| LiPo-Pack |---12VDV---[DC/AC]---115VAC---(Mot)
| LiPo-Pack |
| LiPo-Pack |

However, you are talking about 2x1HP motors...
1HP = 745W
5 Amp @ 115VAC = 575W and this is less than 745W so less than 1 HP.
If we go for 1 HP / 745W, that would mean 6.5A per motor or 13A total.
Lets go with one motor and you can just double it if you want to know the total...
6.5A for 2h @ 115VAC = 13Ah @ 115VAC
Again, going with the WRONG 100% efficiency in the inverter, this gives us 130Ah @ 12V
This in turn ends in 6.5 --> 7 LiPos like in linked you int eh other thread in parallel.
| LiPo-Pack |
| LiPo-Pack |
| LiPo-Pack |
| LiPo-Pack |---12VDV---[DC/AC]---115VAC---(Mot)
| LiPo-Pack |
| LiPo-Pack |
| LiPo-Pack |
Per motor...

So 14 packs in total.
Each pack is 2.1kg --> 29.4kg of LiPos for 2x1HP motor for 2h if driven @ 100% efficient converted 12VDC to 115VAC.
The linked packs still are powerfull enough for this application:
Again, going with 100% efficient converting (incorrect!), this would end in about 10x the current from the batteries than to the motor (DC/AC-Inverter has a factor of 10 in that case). This means 6.5A out = 65A in. Well within the 12C of 20Ah per battery (=240A).

No idea about the efficiency of such onverters thous... Lets assume a very high and go with 90%. This would mean, you loose 10% and therefore need 10% more capacity in the batteries than you will have at the motor. 6.5 LiPo packs * 110% = 7.1 Packs --> 8 Packs.

Also, be sure you know how to handle cabling and especially connecting for 65Amps! Thats no childsplay anymore! Different sources on the net tell me, for 65Amps in free air without cable-pack, is 8 AWG or 10mm^2. I would go for 6 AWG or 16mm^2.
https://www.distrelec.ch/de/stranded-wire-radox-125-16mm-tinned-copper-green-yellow-100m-huber-suhner-radox-125-16-mm-yellow-green/p/15541482 lists a price around 7US$ per meter for such cable...



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TheNecromancer13
TheNecromancer13

11 days ago

Batteries by definition produce DC, not AC. Also why do you want to use 2 motors instead of 1? Electric golf carts usually have a 3-5 hp motor, but hp isn't everything. There's also torque output and RPM, both of which depend on both the motor and the gearbox you use. You could use a 1/4 hp motor and gear it way down, and it would move the cart, but not very fast. You could take a 5 hp motor, not gear it down at all, and it might not have enough power to move the cart at all. Also the battery pack you're describing would need to be something like 1000 amp hours, which would cost an obscene amount of money. If you need it to run constantly for 2+ hours (not driving from hole to hole on the golf course every 5 minutes, but actually moving for most of the 2+ hours) you might want to consider a gas powered cart instead. You could get a 13 hp harbor freight engine for less than $400, bypass the governor system so it makes 20 hp and double the rpm (it's really easy), build a chain drive transmission with a centrifugal clutch for another couple hundred, then all you'd need would be some sort of differential for the rear axle.

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PhatRATTY
PhatRATTY

Reply 10 days ago

Actually it would need to be 100 ah sorry. I figured out the math. For my eight horse power engine it would take 4 200 ah lead acid/lithiium ion batteries. Still fairly cheap and much cheaper than buying diesel whenever I want to ride my go kart.