Directly driving 36v golf cart with 12v genny

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Directly driving 36v golf cart with 12v genny

Post by TheScout » Sun Jul 19, 2015 9:22 am

I'm new to MVing and to electrical stuff, but I ended up with an old ('76) electric golf cart so that's what I built on. I want to drive the motor (36V, 55A, 2hp) with a honda eu2000i and this speed controller[http://www.ebay.com/itm/10-50V-60A-DC-M ... 1247561012] . I'm not married to that speed controller, and I'd certainly be happy to step up the voltage to 36, but I can't find a 12v to 36v converter for anything approaching a reasonable price, and I'd still have to put a few in parallel. I do want to use the generator though since I have access to that one.

http://i.imgur.com/dqXyWYW.png [https://i.imgur.com/dqXyWYW.png]

I'm trying to keep this super simple, and was hoping that someone might be able to offer a few words of advice.

This is the "big wheel" http://i.imgur.com/nRpNvDP.jpg

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Re: Directly driving 36v golf cart with 12v genny

Post by The CO » Sun Jul 19, 2015 9:32 am

Driving a 36v motor at 12v is a surefire way to burn it out. Probably when you least want it.


36v carts (especially a 1976) have like 4 parts. They are aesy to work on. My work cart (duece Anna half) is a 1996 36v, and it took 3 days total to rebuild from non functional. Most of that was waiting for new batteries.
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Re: Directly driving 36v golf cart with 12v genny

Post by Captain Goddammit » Sun Jul 19, 2015 9:52 am

Are you thinking of running off the Honda EU2000's 12 volt battery charging output?
That won't work, it's only 8 amps max. About 100 watts. Not enough to even budge your cart.
The 1600 watts (2000 surge) from the generator is only at the 120 VAC outputs.
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Re: Directly driving 36v golf cart with 12v genny

Post by FIGJAM » Sun Jul 19, 2015 10:11 am

(36V, 55A, 2hp)

I saw this and my first thought was the EU2000 can't push out 55amps no matter what you do.

I could be wrong. :?
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Re: Directly driving 36v golf cart with 12v genny

Post by Captain Goddammit » Sun Jul 19, 2015 10:22 am

You're wrong. If you use a big transformer to drop the 120VC down to 12VDC, you'd get well over 100 amps.
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Re: Directly driving 36v golf cart with 12v genny

Post by Token » Sun Jul 19, 2015 10:24 am

It is not very realistic to direct drive a cart like that.

If you must go this route, no other way than getting a legit 36V charger, say in the 20A range, spend the $200 or so and continuously charge the batteries from the Honda 120V AC line.

Might have to figure some kind of isolation circuit, or get an older charger without all the fancy detection circuits and whatnot.

Also check out marine chargers. 36V is common in that world.

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Re: Directly driving 36v golf cart with 12v genny

Post by TheScout » Sun Jul 19, 2015 11:50 am

So given that I'm running up against deadlines, and assuming that I have no emotional attachment to anything (I'd be happy to chop the frame and weld it to something else) and also assuming that if the expected result is a MV that I can drive around all night every night (having to stop to charge is OK) my budget is around 2K. What do you think that the best plan would be?

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Re: Directly driving 36v golf cart with 12v genny

Post by The CO » Sun Jul 19, 2015 12:09 pm

What's wrong with using batteries? Either 6@6v or 3@12v, depending on weight needs.

6@6v is pretty standard, should cost $650-800 brand new.
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Re: Directly driving 36v golf cart with 12v genny

Post by TheScout » Sun Jul 19, 2015 3:18 pm

Mostly that if I'm going to be putting $1000 into it (I need to replace the speed controller too) I want to make sure that I'm not going down the wrong path.

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Re: Directly driving 36v golf cart with 12v genny

Post by sparr » Sun Jul 19, 2015 3:31 pm

TheScout wrote:So given that I'm running up against deadlines, and assuming that I have no emotional attachment to anything (I'd be happy to chop the frame and weld it to something else) and also assuming that if the expected result is a MV that I can drive around all night every night (having to stop to charge is OK) my budget is around 2K. What do you think that the best plan would be?
$2k budget? Buy another whole working golf cart. Or 2-3 of them.
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Re: Directly driving 36v golf cart with 12v genny

Post by Popeye » Sun Jul 19, 2015 4:29 pm

I think new batterys are the way to go along with a factory speed controller. Based on comments made in other threads speed on these are controlled by varying field current. Most DC drives control speed by Pulse Width Modulation or by varying voltage using thyristors or SCR's. You would probably have to rewire the motors to make this work.
Many DC drives can only control one motor. Check that yours can control 2- one in each wheel. This is probably your setup.
If there is a high frequency output from your drive, judging by the age of the motor you could have problem with arcing to the motor windings. Not real common and newer motors have been designed to prevent this but..
You probably want an isolation transformer between the generator and the drive to protect the generator.

You could find/build a DC power supply and connect to your generator but I don't think the cost and noise would be worth it. YMMV
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Re: Directly driving 36v golf cart with 12v genny

Post by MikeGyver » Sun Jul 19, 2015 4:48 pm

With a 2k price range just get a go kart engine and make it gas powered. Probably cost you less than a charging system anyways.
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Re: Directly driving 36v golf cart with 12v genny

Post by Captain Goddammit » Sun Jul 19, 2015 4:59 pm

If you can make it happen, I'd recommend the go buy a gas cart option. Battery power sucks for MVs. You're usually running on gas anyway, whether you charge at camp or run an onboard generator. Electric carts have long recharge times and no way to generate power for your lights, which every MV should have an impressive amount of.
Get a gas cart and add an alternator or two. Then you will be able to drive all night every night running lots of lights.
Sorry electric fans, but gas wins on playa-bound MVs.
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Re: Directly driving 36v golf cart with 12v genny

Post by EspressoDude » Mon Jul 20, 2015 7:23 am

comment:

DC motors run on lower voltage than nameplate all the time. The key is to watch the amps. The horsepower is a lot less. A 36 volt motor at 55amps creates 2 horsepower ( according to the original post ) At 12 volts, 55 amps it will turn 1/3 the rpm, create the same torque, and 1/3 the horsepower.

better off with gas if you are starting a 'fresh' build.
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Re: Directly driving 36v golf cart with 12v genny

Post by TheScout » Mon Jul 20, 2015 7:46 am

Thank you!

Gas sounds like the way to go. Now I just need to get my hand on one.
Should I be looking for go cart or golf cart or both?
Same HP as what I have in there now?
I assume that 4 stroke is preferable but harder to find, but 2 strokes are acceptable. That sound right?
and the obligatory if anyone knows someone that's selling something that would work in the colorado area...

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Re: Directly driving 36v golf cart with 12v genny

Post by Captain Goddammit » Mon Jul 20, 2015 8:31 am

I'm going to suggest trying to find a golf cart if that's what your original vehicle was, primarily so your final product more closely matches the plan you submitted to DMV.
If you don't find one and you do find a good deal on something else that will work, try to keep the overal execution as close to the plan as you can, don't let it start looking like a buggy or whatever.
An on-playa denial would suck!!!
Changing from electric to gas won't be an issue in itself, as long as the whole thing still looks like it was gonna look.
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Re: Directly driving 36v golf cart with 12v genny

Post by TheScout » Mon Jul 20, 2015 8:56 am

Craiglslisting like mad as we speak.

Thanks!

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Re: Directly driving 36v golf cart with 12v genny

Post by FIGJAM » Mon Jul 20, 2015 9:54 am

CL here usually has several at around $1400 ready to roll.
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Re: Directly driving 36v golf cart with 12v genny

Post by TheScout » Mon Jul 20, 2015 1:41 pm

It looks like I can go with something older (mid eighties two stroke) for around $1700. This one already sold, but it's a good example (http://denver.craigslist.org/snw/5111769343.html). I assume because it's short notice I'd end up paying a bit more.

OR

A newer, Yamaha G22 (2004) for $2300, maybe $2200 if I can sell the seats back he said.

Thoughts?

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Re: Directly driving 36v golf cart with 12v genny

Post by rmc50 » Fri Jul 24, 2015 4:02 pm

There is an easier way:

Make your golf cart a "hybrid"

The issue with an electric golf cart is that the batteries go dead, which can be a big problem if you are in the deep playa when that happens. But you have an electric, so what do you do?

Set it up, bone stock as electric. Then strap your ultra quiet Honda generator to the back and use it to charge the battery. So if you don't already have one, you will need to get a 36 volt charger. They are not hard to come by.

Note that you do NOT need a charger that will handle the full current of the motor (55 A). The batteries will handle the surge, you just need a charger that will recharge your batteries. 10 amp would be more than enough, I would think.

For a short trip you don't have to start the generator at all. On a longer trip, you start the generator and let it run. It will run at a fairly constant rate, pumping current (10 amps, if you bought that size charger) into the batteries. All the time you are stopped or driving slow the batteries will increase in charge. Only when you stomp on it will the batteries lose charge. You can let the generator run while you are out and looking at an art piece or in at a theme camp.

IF the generator is a quiet one this will be a great thing. I don't recommend a cheap, noisy generator if you wish to leave it run while your cart is parked outside a theme camp or art project.

R. Mc.

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Re: Directly driving 36v golf cart with 12v genny

Post by Captain Goddammit » Fri Jul 24, 2015 4:14 pm

Way to say exactly what's already been said as if it were a new idea!
It's already established he's got a Honda EU2000.
A 10 amp charger typically MAXES at 10 amps, it doesn't usually pump nearly that much into the batteries. It depends on their state of charge. You can't just buy a "10 amp charger" and calculate that you're gaining 10ah every hour. It doesn't really work like that.
If you don't mind buying batteries and a REAL charger, the hybrid plan will work.
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Re: Directly driving 36v golf cart with 12v genny

Post by Token » Sat Jul 25, 2015 3:54 pm

rmc50 wrote: Note that you do NOT need a charger that will handle the full current of the motor (55 A). The batteries will handle the surge, you just need a charger that will recharge your batteries.

R. Mc.
How much current gets drawn and from where will depend on the impedance of all three devices.

You will probably get lucky with hooking up random pieces and not frying anything right away, but the advice was not very solid.

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Re: Directly driving 36v golf cart with 12v genny

Post by TheScout » Mon Jul 27, 2015 9:32 am

Ended up going with the newer yamaha G22 and it's driving great. Now it just needs some lights.

Thanks all!

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Re: Directly driving 36v golf cart with 12v genny

Post by WileE13 » Thu Mar 10, 2016 9:19 am

There is a cheap, simple solution. Your EU2000 will put out about 20 amps at 110v AC. Get (3) standard 12v battery chargers which put out 6 amps ea, for a total of 18 amps DC. Connect each charger across a 12v series of batteries. I'm guessing that cart has (6) 6v batteries, so you'll bridge two at a time. This is how we charge our old tractor which has (2) 6v batteries in series to make a 12v system.

This system will constantly trickle 18 amps at 12v, or 216 watts. Not much, but your cheapest option. Otherwise, invest in larger chargers. Problem with larger chargers, however, is they can charge too quickly and damage the battery if it isn't made to handle the current. With the method I mentioned, you would have to park the cart every hour or so to trickle charge it before continuing to drive. Not a big deal if you ask me, gives you time to enjoy where you are at.

Otherwise, you could spend the money on a 36v charger at a site like this: http://electricscooterparts.com/36vchargers.html. Problem is, they only go up to 4 amps (for reasons explained in paragraph 2) which is only (4 x 36 = 144 watts) which is less than the method I recommended.

Another charger I found will do 25 Amps (http://www.cartpartsusa.com/battery-cha ... r-charger/) but costs 400 dollars. Still only 7 more amps then the method I recommended, and my method uses 30 dollar chargers, not 400. For the price difference, you could probably get (6) 6v, 6 amp chargers, run one to each battery, and draw 432 watts.

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Re: Directly driving 36v golf cart with 12v genny

Post by Captain Goddammit » Thu Mar 10, 2016 9:27 am

Where did you get the idea a Honda EU2000 will produce 20 amps at 120VAC? That's almost twice the truth, especially at playa altitude.
Assuming a "6 amp" charger will be actually charging at that rate all the time isn't realistic either, especially when paralleled with others.
If you do this system you're going to want a much larger charger.
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Re: Directly driving 36v golf cart with 12v genny

Post by WileE13 » Sun Mar 13, 2016 12:42 pm

I probably confused people with the 20 amp comment, that is based on AC, which won't be used for DC batteries. Watts are volts times amps, so 2000 watts / 110 v = 18.18 Amps. 20 was just a estimate. Never thought of the elevation thing, probably cause I live at a similar elevation and never notice a difference in how the genny runs.

I mention the 6 amp charger because that is standard equipment. You can pick them up for about 30 dollars each. I've never seen a larger one in common use. I did include references for larger chargers, but the price goes up, and as I mentioned, depending on the battery you use, it may or may not handle the larger amperage charges. Also, a general rule of thumb with batteries, long slow charges store more energy and preserve the life of the battery compared to high amp charges.

Ultimately, if I personally had to decide between multiple small cheap chargers or one large expensive one, I'd got with the multiple small ones.

No matter what you do though, the energy harnessed from the generator will be limited and never enough to power the vehicle constantly. Even with the full 2000 watts you are only getting only 2.68 horsepower (745 watt per hp). Based on my research, you'll need about 5 hp just to move a vehicle that size loaded with people. This means the genny will only be a supplement and require regular charging stops.

Hope some of this is helpful. Just passing on what I learned while looking at electric golf carts. I gave up, now we are working on a gas powered one with an 8 hp Kohler engine.

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Re: Directly driving 36v golf cart with 12v genny

Post by Elliot » Sun Mar 13, 2016 7:14 pm

The EU2000i has a "max" output of 2000 Watts / 16.7 Amp. "Max" means... for a few seconds -- for the start "surge" that electric motors draw when they start.
The "rated" output is 1600 Watts / 13.3 Amp. That the steady output.
The engine is capable of up to 3.5 Horsepower.

The owner manual for my EU1000 states that horsepower will decrease by 3.5% for each 1000 feet elevation. I expect the EU2000 will be similar. BRC is near 4000 feet, so 3.5 x 4 = 14%. That leaves the EU2000 with 3 hp, and 1370 Watts / 11.4 Amp.

(Above 5000 feet, the carburetor must be re-jetted.)

I'm just exercising my calculator on a rainy day -- and maybe helping a tiny bit with these numbers.

I can move a couple thousand pounds up a steep hill with pedal-power, which is maybe 1/4 hp. But I almost need to put a chalk mark on a tire to see that I am moving. This is all about gearing. Since you want to go 5 mph... yeah, it is easy to underestimate the power needed.

Best of luck! :D
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Re: Directly driving 36v golf cart with 12v genny

Post by dustyfux » Mon Mar 14, 2016 5:27 pm

There's a reason why Clubcart doesn't do this and its not because they haven't thought of it.

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Re: Directly driving 36v golf cart with 12v genny

Post by Elliot » Mon Mar 14, 2016 7:54 pm

At the same time... there are vehicles that use the engine>generator>el-motor arrangement, such as these -- called Diesel-Electric locomotives. Why, I don't know, but I might venture to guess at smoothness -- not ripping apart any U-joints or frying a clutch when starting out. Oh... and el-motors deliver max torque right from zero RPMs -- that might be it; with no slipping clutch.

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Re: Directly driving 36v golf cart with 12v genny

Post by Roundabout » Tue Mar 15, 2016 12:13 am

Good point Eliot. I hope someone brings one of those to the Playa.
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