How would you build an AATV,(amphibious 6 wheeler)?

I think I'm going with an Alltrax AXE 4845, used for $300. No need to spend more for voltage I don't need right now, and if I really feel the need to go higher in the future I'm sure can sell the 4845 for close to what I paid. Plus I don't need to spend an extra 100 for a DC/DC as I would with the Kelly.
 
You're probably right about the resale value. I can't seem to find one for cheap no matter how busted up it looks.

You wouldn't need to spend $100 on a DC/DC. It's just for powering the electronics in the controller. It doesn't need to be very powerful. You could probably get away with a linear voltage regulator (like $2 max).
 
You may very well be correct but Kelly doesn't mention that option, they just sell a $100 DC/DC, and since this is my first EV I don't feel like experimenting too much, the whole thing is and experiment to me :mrgreen: Also I wonder what shipping from China might add to the cost of the Kelly :shock: I'll let others test out that situation and report back.
 
The Kelly website and manuals are not all accurately translated. I'm pretty sure their controller does not need the dc-dc coverter to operate, but you need it for the main contactor relay coil. You'll have the same issue with an Alltrax.

I think if you snoop around enough you can find contactors that have 48v coils.

The Alltrax is a great controller, with nearly the same features as the Kelly, and they have a proven track record.

You might want some kind of dc-dc converter anyway to run your lights and accessories. Figure out what you want to run first, then figure out if you need a converter.
 
They say that their 24-72 volt controllers require the 18-40volt power supply. Initially I took that to mean all their controllers in the 24 to 72 volt range, but it probably just means their 24-72 volt controller specifically. It's at the bottom of the first two tables on this page:
http://www.kellycontroller.com/mot/Brushed-Motor-Speed_Controller.html
I have no need for a DC/DC since there are no accessories on this machine, besides headlights, which I don't see me needing.
There are 48 volt contactors available.
 
This is one person's thoughts, (I think he builds his own conrollers), on the subject from the EVDL which seem to match what some of you have been saying:
They likely require only a small amount of current at 18-40 volts. For example, my controllers require 18-30 volt supply for logic section and up to 72V for the power section. For the logic section they require less than 100mA at 24V. You can have a simple 24V zener followed by a transistor (with heat sink) and capacitor for a low current 24V supply - only costs a few bucks to build. For 72V from the batteries and assuming 100mA current you would have (72-24) * 0.1 = 5W on the transistor. You can easily heat sink 5W.
Click to expand...
 
Yup. That's just an amplified Zener voltage regulator. When the voltage is high enough to reverse-bias the Zener, the transistor starts to conduct and shunt power away to drop the voltage to whatever the Zener is rated for. If the Zener is big enough, you can skip the transistor completely and use the Zener to shunt away the extra voltage.

Honestly, I don't know why all controllers don't have this sort of thing alreadly built-in. It's an extremely cheap piece of cicuitry (probably cents if in sufficient bulk), and very simple to integrate into the controller.
 
A lot easier to do and zero cost is tap into the 2nd battery to get 24 volts out of it, if using SLA. the power consumption is so low 100 MA that I really doubt it would unbalance your batteries much.
 
Probably not, but he'd have to make sure he left the charger on for a while.

Incidentally, what are you going to charge this with? I don't really think you could get away with the chargers most of us use :p.
 
drewjet said:
A lot easier to do and zero cost is tap into the 2nd battery to get 24 volts out of it, if using SLA. the power consumption is so low 100 MA that I really doubt it would unbalance your batteries much.
Click to expand...
Actually one person has commented that over time you would unbalance your batteries. I suppose you could switch to the other 2 every once in a while to even things out.
Another method some people use is to run the controller
from a tap in their pack.
That causes unbalance in their pack, in the case of 100mA
into the controller, you are un-balancing your pack with
2.4 Ah each day. It will take only a few weeks to get a
dangerously out-of-balance pack, where the choice is to
always over-charge and end its life too soon or to have
it die from unbalance and reversed batteries....
Click to expand...
 
Here's why I think 48 volts will be enough for my project. This is the closest thing I've found to my vehicle:
http://www.gorillavehicles.com/GorillaSpecifications.htm
It weighs 540lbs and will go between 20 and 30 miles with a top speed of 19mph on 36 volts. I'll end up weighing close to that, don't need to go 20 miles on a charge, and with 48 volts I should be able to go faster than that, depending on how I gear it, though top speed is not my main goal. With the gearing in the trans at around 5 or 6:1, plus maybe a 2:1 gearing from the trans to the axle chains, I might be able to set my motor to trans sprockets in a close enough ratio that I could just swap them around if I wanted to gear up or down. I still have to figure out exactly what this thing is currently geared at.
 
On the Alltrax page it lists the following for throttle input choices:
Throttle Input:

* ITS (inductive)
* Resistive 0-5K ohm (+/-10%) (2-wire and 3-Wire)
* Resistive 5K-0 ohm (+/-10%)
* 0-5Volt
* 6-10Volt
Click to expand...

What do I need/want, what are the differences, one better than another? I'd prefer cheaper of course unless there is a good reason to spend more.
 
How do you operate the throttle on one of those things? A gas pedal? Twist grip?

My guess is you could make a pot box that goes to whatever the original throttle cable went to. A pot box would be a 0 to 5k resistor. You could build a pot box with Radio Shack parts or buy one already built.
 
I plan to use the existing cable setup if possible. It's a lever on the right side stick with a cable going back to the carb. How complicated are pot boxes to make? I've seen some for around $100 bucks which seems steep.
 
Yikes! $29 for a pot!? That seems a bit steep. Those usually go for about $2.

Take a look at this setup:
http://endless-sphere.com/forums/viewtopic.php?f=6&t=2522&hilit=+waterproof+throttle

I wouldn't suggest using a linear pot, but the mechanical setup is the right idea.

A "normal" rotary pot has 270deg. of rotation. In a pot box, you would be limited to around 90 deg unless you wind the cable around a pulley or something.

Since the controller can work with a 2 wire setup, you could get a 15k pot from Radio Shack, Mouser, DigiKey, old radio, etc, and mount it so the resistance goes from zero to 5k with a 90 deg. rotation. Then it's just a matter of mounting it inside a box with a return spring and a lever to attach the cable to.
 
What Fechter said. $29 for a pot? WTF? How do they even get away with that? Is that some sort of special pot, and I'm not seeing it?
 
I don't think so. The pot boxes are constructed so that there isn't much torque on the pot. There's no reason to use a super-robust pot.
 
Yeah, that $29 pot looks a lot like this $10 pot from digikey
http://rocky.digikey.com/WebLib/Clarostat/Web%20photos/381%20SERIES.jpg
http://parts.digikey.com/1/parts/737215-pot-25k-ohm-1w-cond-plastic-381n25k.html
It's a 25kohm and would give me my 0-5k in less than 90* rotation, and it looks a little thicker than the Radio Shack versions. The Radio Shack pots scare me a bit since this will have a metal lever arm, throttle cable, and a spring tugging on it, plus it will be bouncing around off road a lot. You're average volume knob doesn't see that kind of stress. At least mine don't :mrgreen:
 
A possible explanation for the expensive $29 pot: It may be a custom pot that really is a 0-5k that works through the short range of motion and that way it will work with controllers that require the 3 wire setup. I have no idea what that means though and have been meaning to ask how to wire one up and what the 3rd wire is for and why an over sized pot wouldn't work in that situation :?:
 
It looks like a typical pot to me. Sized such that 90* gets you the range needed.

Marked-up a tad for finding one that fits the application.

:roll:
 
This is what gave me that idea:
http://www.evdl.org/archive/index.html#nabble-td12462524%7Ca12465221
The Curtis potbox takes the latter approach. They use a custom potentiometer that only needs90 degrees of rotation to go from 0 to 5k ohms of resistance. You can accomplish the same thing by using a regular 20k pot, and not using the parts of the rotation past 5k.
Click to expand...
Reply:
Just be warned if your controller needs to see the other leg of the pot that
the 20K method doesn't work.
Click to expand...
I don't know what that means or why it won't work in a 3 wire setup.
 
You must log in or register to reply here.
Back
Top