Diving in w/o any knowledge or skill...

[Molloy]

I've been intrigued by EVs for a long time and figured this would be a great way to learn, wo spending obscene amounts of money. Also used this as a way to teach my son how to fabricate, while I (try) to learn the electrical fundamentals.

So the karts runs pretty good, but has some issues too, as would be expected. I'll fill in more details below when I have time.

 

[Bansil]

kool,
specs? How fast is it and how long can you ride?

 

[Molloy]

Probably the main issue right now is that the main contactor gets really hot when the unit is powered on, just sitting there. The high amp wires can be carrying no current, but the contactor just gets hot. Wonder if the solenoid is wired backwards (by me) or something else?

 

[Molloy]

kool,
specs? How fast is it and how long can you ride?

Based on tire diameter and the motor going to 5000 RPM, it could theoretically hit about 50 mph. I did a few long pulls and it felt like the top end was limitless, and I ran out of testosterone. Don't know how long it will run. Still need to get he charging/BMS set-up.

 

[ezcome-ezgo]

We can ship you some testosterone. We really want to know.

 

[Functional Artist]

Howdy &

Nice lookin' kart

What motor & controller?

What voltage are you running?

Is it the contactor's coil specified for use with that voltage?

 

[Molloy]

We can ship you some testosterone. We really want to know.

Well, let me finish welding the upper parts (some of that is just tack welded) and gets some 5-point harnesses first. Front shocks are trash too, lol. Battery pack needs to come out to set up and validate the Emus BMS, and I have a steep learning curve for that. I'll finish up the fabbing/mechanics while the pack is out.

 

[Molloy]

Howdy &

Nice lookin' kart

What motor & controller?

What voltage are you running?

Is it the contactor's coil specified for use with that voltage?

ME1114 and Sevcon Gen4. 48 V GBS LiPo (4 12V Modules).
Coil says 12/24V on the side. It's a Gigavac GV200PAC-1. I thought the same thing last night...12/24V is not 48V. But maybe the Sevcon steps it down?

 

[Molloy]

Any recommendations for front shocks that aren't super light duty The Grandaddy design called for cheap 9-3/4 shocks from BMI, but these are a not up to the task.

 

[EpsilonZero]

Here's that motor running in my kart if you want an idea of performance (ME1904/ME1114 is the same). It can run harder than my setup pushes it, too.

 

[EpsilonZero]

Based on tire diameter and the motor going to 5000 RPM, it could theoretically hit about 50 mph. I did a few long pulls and it felt like the top end was limitless, and I ran out of testosterone. Don't know how long it will run. Still need to get he charging/BMS set-up.

Keep in mind that an ME1114 motor won't spin 5000rpm @ 48v without incredible field weakening. Do you know how the controller is configured? Without field weakening, it will be closer to the low 3k range loaded and running low 30s MPH based on your speed estimates for 5k RPM.

The contactor doesn't need to be rated for the full voltage of your pack with the precharge resistor. The contactor isn't experiencing any voltage difference upon activation, so there is no chance that it will arc. I am using a 12V 400A contactor with 80V+ currently. If the contactor is getting hot without even engaging the controller/motor, there is current flow to somewhere. It could be as simple as a ground fault. Check your wiring.

 

[Functional Artist]

Keep in mind that an ME1114 motor won't spin 5000rpm @ 48v without incredible field weakening. Do you know how the controller is configured? Without field weakening, it will be closer to the low 3k range loaded and running low 30s MPH based on your speed estimates for 5k RPM.

The contactor doesn't need to be rated for the full voltage of your pack with the precharge resistor. The contactor isn't experiencing any voltage difference upon activation, so there is no chance that it will arc. I am using a 12V 400A contactor with 80V+ currently. If the contactor is getting hot without even engaging the controller/motor, there is current flow to somewhere. It could be as simple as a ground fault. Check your wiring.

Hey EZ,

Does your controller step down the voltage to 12V
...to activate & supply power to the 12V contactors coil?
or
Are you powering that 12V contactors coil, with 80+V?

 

[EpsilonZero]

Hey EZ,

Does your controller step down the voltage to 12V
...to activate & supply power to the 12V contactors coil?
or
Are you powering that 12V contactors coil, with 80+V?

Good point. No, the KLS72701-8080N/NPS controller logic uses an isolated 12v I generate from a buck converter that I also control the contactor with. I run higher rated contactors on lower-end non-isolated controllers. I assumed the Sevcons were isolated, which they are apparently not!

 

[Molloy]

Keep in mind that an ME1114 motor won't spin 5000rpm @ 48v without incredible field weakening. Do you know how the controller is configured? Without field weakening, it will be closer to the low 3k range loaded and running low 30s MPH based on your speed estimates for 5k RPM.

The contactor doesn't need to be rated for the full voltage of your pack with the precharge resistor. The contactor isn't experiencing any voltage difference upon activation, so there is no chance that it will arc. I am using a 12V 400A contactor with 80V+ currently. If the contactor is getting hot without even engaging the controller/motor, there is current flow to somewhere. It could be as simple as a ground fault. Check your wiring.

This makes me feel better. This kart has no business going more than ~30 mph, but it does seem "fast"... Also, FWIW I'm running a 4:1 ratio (15T-60T) with 18" tall tires. 420 chain.

I wish there was an easy way to check the voltage at the solenoid that holds the contactor closed. The wires from the Sevcon to the contactor are sealed and I'd rather not open them, but...

 

[EpsilonZero]

This makes me feel better. This kart has no business going more than ~30 mph, but it does seem "fast"... Also, FWIW I'm running a 4:1 ratio (15T-60T) with 18" tall tires. 420 chain.

I wish there was an easy way to check the voltage at the solenoid that holds the contactor closed. The wires from the Sevcon to the contactor are sealed and I'd rather not open them, but...

That ratio and voltage will get you into the 40s. How much does the kart and rider(s) weigh together?

About the contactor... I skimmed some of the Sevcon manual. It seems like the controller can use PWM to reduce the effective voltage to the contactor to allow lower-rated contactors to be used. If the controller isn't configured properly, though, you may be getting full voltage. I think the relevant setting is "contactor chopping": "On" (not "24v"), but I am just skimming the manual like I said.

Main contactor rating:
The controller can drive any contactor with coil voltages from 12 V to Vb. It is worth considering the
use of 24 V contactors with the contactor drive output set to voltage-control mode. This allows you to
use one type of contactor for any battery voltage (24 V to 80 V). Pull-in voltage, pull-in time and hold-in
voltage values are all configurable

Inductive drive outputs:
Voltage-controlled (PWM) mode allows contactors with a
rating less than Vnom to be used (range 24 V to Vnom).​

 

[Molloy]

Whelp, I broke it. I was playing with the contactor state in settings. I heard the solenoid click off and then it went into "Pre-Operational" state. I guess this is pretty much a disabled state for making adjustments to the Sevcon (which I was doing). I don't seem to have the access to take it out of the pre-operational state, which really sucks. So I'm dead in the water now, lol.

 

[EpsilonZero]

Whelp, I broke it. I was playing with the contactor state in settings. I heard the solenoid click off and then it went into "Pre-Operational" state. I guess this is pretty much a disabled state for making adjustments to the Sevcon (which I was doing). I don't seem to have the access to take it out of the pre-operational state, which really sucks. So I'm dead in the water now, lol.

You have to have a license to use the software to make adjustments. What, do they let you use it just enough to break it?

 

[Molloy]

You have to have a license to use the software to make adjustments. What, do they let you use it just enough to break it?

I just went in through the Sevcon display under the configuration menu. Guess I wasn't supposed to...

 

[Molloy]

I shot an email to Electric Motorsport, but I suspect they won't respond until the 5th. Too bad as my son is in town and he wanted to check it out.

 

[EpsilonZero]

I shot an email to Electric Motorsport, but I suspect they won't respond until the 5th. Too bad as my son is in town and he wanted to check it out.

The first result I got when searching that message was "You need an IXXAT branded USB to CAN adapter and a copy of Sevcon's DVT software to get it out of preop".

That is some mega-dumb interface design to let you lock yourself out like that.