Hello and underpowered kids go-kart

R

rcotteleer

100 µW
Joined
Apr 28, 2011
Messages
8
Hello, I have been reading ES for the last month or so, soaking up the knowledge here. 

As my first foray into EVs, I repurposed an older ICE go-Kart for my daughter ( she started complain that her power wheels was too slow for her).  Originally it was a manco silver streak with a 50cc gas engine.

I built it with 24V 20ah of SLA, an 800 watt, brushed mobility scooter transaxle http://tncscooters.com/product.php?sku=106124 and a yi-yun yk48-2 controller  http://tncscooters.com/product.php?sku=101185

It is plenty fast on the flat, 10-11 mph, but it suffers climbing small hills,it will do it, but really slowly. My thought is that the controller is undersized ( rated at 30 amps) but I'd be interested in what people here thought and what possible solutions might be.

Thanks, Randy

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The 24V motor will probably be fine with 36V, but the brushes may not last long if you try 48V. The controller may not be able to use 36V, but brushed controllers are cheap from TNC.

http://tncscooters.com/partsdb.php?type=ES

More volts will help a little, but simply throwing motre amps at it will result in a hot motor and a hot controller. I don't know if you can change the gearing in that, but a lower gear ratio would help on the hills, however, it will hurt the top-speed on the flats.

Kudos on the roll-bar and the helmet, start them off right and live by example...
 
That was my first thought as well, go to 36 volts, but I was worried that it would give it additional speed which I don't want for her at the moment. If the controller is rated at 30 amps, will it not supply more than that? If that is the case it is not using even it rated wattage, that's why it thought a higher amperage controller might help.It has a 40 amp breaker inline and it isn't popping that. The transaxle is geared 20-1 and the motor is rated for 5200 rpm. I don't think re- gearing is an option, based on what if researched

Randy
 
According to the page on the transaxle it'll take 45.6amps...though they don't say for how long. Maybe a few minutes at a time.

Cool little kart anyway. 8)
 
REdiculous,

That gets to the crux of my question, if the controller, link above is rated at 30 amps max, does that mean it will only supply 30 amps? If so, it would mean that I could feed the transaxle 50% more power and still be within spec. I'm not opposed to buying a new controller, or modding the one I have. The question is, is that controller limiting output to 30 amps and will more amps increase power? Our lot is mostly flat so uphill time is pretty gentle and minimal.

Thanks for everybodys help

Randy
 
The question is, is that controller limiting output to 30 amps and will more amps increase power?
Click to expand...

Yes (if it's hitting the current limit) and yes...but...

The transaxle is rated for 800w..
24v*30a=720w
..so you can't feed it that much more than the controller is capable of putting out. 45amps would be more than 1000w.

Are you using just a pair of 20ah SLAs? I'm running about the same and I'm not seeing mine deliver 700w - I think I'm getting more like 450w or so. Maybe that could be the problem.
 
Gears/trannys don't have power limits, they have torque limits.

36v 50amp controller would do the trick. Put a little resistor or pot in the throttle line to dial it down to where ever you think its safe, then as she becomes a better driver, you can gradually turn up the limit for her.
 
Any recommendations on a controller? If I can buy from an active forum member, I'd like to. Currently the kart is set up with a hall throttle. it seems like the bigger controllers aren't setup with internal reverse so I'd have to add a reverse contactor, which isn't a big deal.
 
Gears/trannys don't have power limits, they have torque limits. 36v 50amp controller would do the trick.
Click to expand...

Except the motor on the tranny is rated for 800w, not 1800w. :|
 
Hi Randy,
That is one cool kart. Do you have a watt meter or some sort of current meter? It can be really handy in troubleshooting a situation like this.

Like others have said, it is possible the SLA batteries can't put out the power needed to climb hills. My first thought was the gearing though. I imagine those mobility scooters are intended for level pavement, not climbing grass slopes.

Throw an amp or watt meter on that thing and have your daughter do a few test runs.
Colin
 
I bet it'd even do 48 or 60v without overheating with that weight driver. Weight makes a big difference.

There are not many options for low power brushed controllers. Looks like there is a 36v "40a" from ecrazy on ebay. All the 40+ amp controllers from TNC are above 36v. You might do just as well to solder up your shunt and run 36v on your stock controller. Worth a try.
 
I'll order up a watt meter and see what we find out. any suggestions on which on to buy?
 
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