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Old 03-23-2020, 03:58 PM
MotWat MotWat is offline
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Default Motor and controller wiring check-up

Hello everyone!

I'm working on an electric go-kart project and have just finished a mock-up/prototype of the wiring for the motor (Golden Motor HPM3000B) and controller (Kelly KBS72151E). For now everything's flimsy and quickly put together; I did it to get a general idea of how all the components will be wired together later on. Before connecting the batteries, I will connect everything properly - with adequate wires and terminals. Then I'd simply attach the positive terminal of my battery pack to the contactor and the negative to the black wire from the controller.

Before I do that, however, I'd like to ask you for advice. Can you spot anything missing from my setup (apart from the batteries, of course)? I've made several pictures, see attachments. I base my circuit on Kelly's manual (https://kellycontroller.com/wp-conte...UserManual.pdf).

I've already double-checked the white connectors. Also, I'm planning to add a fuse (with a resistor in parallel) on the B+ line for additional safety.
Attached Thumbnails
signal-attachment-2020-03-23-195527_002.jpeg   signal-attachment-2020-03-23-195527_003.jpeg  

signal-attachment-2020-03-23-195527_006.jpeg   signal-attachment-2020-03-23-195527_011.jpeg  

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Old 03-23-2020, 07:43 PM
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itsid itsid is offline
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I strongly suggest to use a bolt terminal block for all bolted connections
(battery and motor phase wires)
something like this:
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just to make sure it's serviceable at all times and insulated properly.

else you'd have to take short enough bolts and high amp shrinkwrap for insulation.
and to service a connection you'd always have to cut and reshrink (which is a PITA[fternoon])

A resistor in parallel with a Fuse is pointless..
if the fuse blows the resistor still has contact..
fuses are meant to DISCONNECT so never parallel them
(other than with a second identical fuse to double the amperage)

'sid
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Old 03-25-2020, 01:06 PM
MotWat MotWat is offline
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I had no idea those existed. I'll try to get my hands on one of them.

As for the fuse: I understand what you're saying and at first I wasn't planning to put a resistor in parallel. But then I read this in the Kelly manual: "All contactors or circuit breakers in the B+ line must have precharge resistors across their contacts. Lack of even one of these precharge resistors may severely damage the controller at switch-on." Therefore, considering that fuses act as a form of a circuit breaker, I thought that maybe I should put a resistor in parallel to the fuse on B+. Same for the emergency contactor I'm planning to add later on (https://kellycontroller.com/shop/kem...ncy-contactor/). Of course, the resistor can let current through, but at 72 V and 1 kOhm, that would mean only 0.072 A could pass through, instead of the usual 50 A or so.

Does this make sense?
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Old 03-25-2020, 07:50 PM
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itsid itsid is offline
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You misunderstood the concept of the precharge resistor...

true it's needed on a contactor..
but the contactor and fuse have to be in series,
the precharge resistor and contactor need to be in parallel.
And the two are not "doing the same"

the problem is NOT the "cutting the power"
the proble arises when a voltage is engaged (and an inrush spike occurs)
and that's what the precharge resistor prevents.. it keeps a minor voltage so the inrush spike is minimized.

cutting the power down (popping a fuse or disengaging the contactor) is harmless
well popping the fuse is..
the contactor will have a collapsing coil charge..
hence you need a flyback diode to stop that voltage from hitting the controller too.

So still.. never put a resistor in parallel with a fuse!

'sid
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Old 03-26-2020, 07:21 AM
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Quote:
Originally Posted by itsid View Post
You misunderstood the concept of the precharge resistor...

true it's needed on a contactor..
but the contactor and fuse have to be in series,
the precharge resistor and contactor need to be in parallel.
And the two are not "doing the same"

the problem is NOT the "cutting the power"
the proble arises when a voltage is engaged (and an inrush spike occurs)
and that's what the precharge resistor prevents.. it keeps a minor voltage so the inrush spike is minimized.

cutting the power down (popping a fuse or disengaging the contactor) is harmless
well popping the fuse is..
the contactor will have a collapsing coil charge..
hence you need a flyback diode to stop that voltage from hitting the controller too.

So still.. never put a resistor in parallel with a fuse!

'sid

Hey pal, if ya got a minute could ya, maybe, unleash some of your artsy-ness & draw us a pic

Um...I mean diagram
...just so all of this "in parallel, in series & what's doin what & where" stuff, on a contactor, is "super clear"
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Old 03-26-2020, 12:23 PM
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I think you're missing something over the diode.
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Old 03-27-2020, 09:43 AM
MotWat MotWat is offline
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What do you mean? I have double checked and haven't found anything to be missing.

Thanks, Sid; I've now done additional research on the topic and it all makes a lot more sense. I won't be putting the resistor in parallel to the fuse For anyone interested, here's a forum thread that describes this topic in more detail: https://www.diyelectriccar.com/forum...-do-25419.html

Anyhow, I have now added the fuse (for now its just 25 A, I've got bigger ones for when things get more serious) and battery connections to the circuit (see attachment). These are XT90 connectors through which I will connect my four LiPo's. Apart from the shoddy connections and lack of insulation, I'd say it's ready for a test. What's you guys' opinion?
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signal-attachment-2020-03-27-120217_003.jpg  
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Old 03-27-2020, 11:06 AM
Bmr4Karts Bmr4Karts is offline
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That looks better. You didn't have the black wire connected to right side of the contactor in the first post.
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Old 03-27-2020, 12:15 PM
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Quote:
Originally Posted by MotWat View Post
What do you mean? I have double checked and haven't found anything to be missing.

Thanks, Sid; I've now done additional research on the topic and it all makes a lot more sense. I won't be putting the resistor in parallel to the fuse For anyone interested, here's a forum thread that describes this topic in more detail: https://www.diyelectriccar.com/forum...-do-25419.html

Anyhow, I have now added the fuse (for now its just 25 A, I've got bigger ones for when things get more serious) and battery connections to the circuit (see attachment). These are XT90 connectors through which I will connect my four LiPo's. Apart from the shoddy connections and lack of insulation, I'd say it's ready for a test. What's you guys' opinion?
The connections look correct
...but, I notice a couple of issues, I'd like to mention

The fuse should be between the batt & anything you want to protect
...on/off circuit fuse is in correct spot
...but,

IMO it's a good practice to only use red wires for positive (+) circuits
…& only black wires for negative (-) ones
…& use other colors for everything else

Like for the on/off switch, "fused" red (power in) looks good
…& maybe use an orange wire from the switch to contactor

All of those wires get confusing, especially at the "other" end
...so, this makes it kinda "idiot proof"

* If ya havta use black (like for batt cables) at least, use some red heat shrink on the ends
...this will indicate that it is a power/positive (+) wire/cable
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