# My EV Wiring Plan. Thoughts, Comments?



## KiwiEV (Jul 26, 2007)

Hi Folks,

As many of you know, I'm very close to getting the Tredia on the road at long last. In fact, within a matter of a week or two I'll have the cables connected ready for the car's first (not quite legal) drive up the street and back!

First though, I want your opinions on this wiring plan I whipped up for my 144V system. If you see something that needs modifying please don't hesitate to post a comment: 








Luckily we're still in that flexible "moving things about" stage so I can rearrange the control box set up and even relocate things to other parts of the car if need be. I've excluded the 12v supply at the moment (that would make it even messier). 
Most importantly, are the control box & controller going to be happy together with this set up? 

Thanks folks, and be gentle.


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## Mr. Sharkey (Jul 26, 2007)

Well, you asked for it,,,

First of all, I think you will find that the heater is miswired. The lower of the two wires shown going to the heater needs to be connected to the negative common, not the positive terminal of the controller.

Normally, shunts are placed in the negative end of the battery string, which means that it should be between battery #12's negative terminal and everything else in the circuit. This is done partly to keep the number of high voltage connections that appear in the car to as few as possible. It will work fine being anywhere in series with the loads, but will be much safer in the negative circuit. If you were to install something like the Link 10 digital ampere hour meter, you would find that the shunt ~must~ be placed in the negative circuit.

I think that the fuse shown between the shunt and the contactor is a bit redundant. The fuse in the middle of your battery pack should be capable of protecting the circuits from overload, as should the breaker. Another fuse in series with it all is just one more place for connections to fail.

Other than that, it looks to be fit.


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## KiwiEV (Jul 26, 2007)

Ok thanks for that Mr S, very good! Constructive criticism is just what I need at this stage to save me doing things again later.

I can't find any documentation about my particular ammeter needing the shunt to be in the - side of the circuit so it should be ok. Cheers for the tip about the danger of shunts in the + side of the circuit though. 

You're right about the fuse, I thought it was a little redundant myself having a breaker right there but it should keep the inspector happy. Better to have too many fuses than not enough.

Now, regarding the heater. Do you think it would work ok by connecting it (via the relay) from the + and - on the shunt? Would that complete the circuit?


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## Mr. Sharkey (Jul 26, 2007)

After reflecting about it for a while, I realised that if your traction pack is not earthed to the frame of the vehicle, and your ammeter doesn't care, there probably isn't any advantage to moving the shunt. Just be sure to remember that it's in the positive leg if you ever change over to a different system. There's also no reason you couln't add a second shunt for a digital meter in the future, putting in the negative leg.

Years back I built a very extensive shunt system for a renewable energy system that I was installing. I built and calibrated my own shunts, and placed them in the positive lead of the battery. Problem was, the negative of the battery was grounded, so every wire that lead from the sunts back to the metering had to be fused, least there was a contact between the tiny shunt sense wiring and ground. If I was doing it over, I would have made the shunts in the negative leg and bagged the fuses.

I need to be sure I understand your heater. It's a ceramic or other type of heater that's intended to be powered off of utility mains? If so, then the upper wire going to the heater shown in your diagram is correct. You are supplying the heater with power from the poistive terminal of the battery pack through the breaker, master fuse, shunt, fuse dedicated to the heater, and the heater relay. That's good. In order to complete the circuit and suppy the heater with 144 VDC, you need to return the lower wire of the heater to the battery pack negative terminal, that's the minus on battery #12. Nothing else would be appropreiate, and no other connection will supply your heater with the proper voltage needed.

If I'm not correct about your heater's power requirements, then we need to talk more about this...

Also I don't know what the "KSI Relay" is, so maybe someone esle who does can check that part of the circuit.


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## KiwiEV (Jul 26, 2007)

Hey that's good news. Thanks for that.
To save me taking a new cable all the way down the back to battery 12, do you think it would be ok to put the - of the ceramic heater across the - of the contoller?

(The KSI relay wiring is ok, that part's simple, it simply connects to the pin on the controller).

Cheers!
Gav


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## Mr. Sharkey (Jul 26, 2007)

The negative lead on the controller (the battery lead, not the motor lead) would be fine. The heater can't draw all that much current in comparison with the traction motor.

Out of curiousity, and because I keep harping on the subject here on the forum, what are you using as a relay to control the heater?


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## KiwiEV (Jul 26, 2007)

Ah that's good. I'll re-wire the - of the heater this week.
As for the relay:








It's that expensive little thing. Do you think that should be sufficient to do the job?


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## Mr. Sharkey (Jul 26, 2007)

A solid state relay? Good for you, that should cause no trouble. I was concerned that you might be trying to control the heater with a contact-type relay that wasn't rated for interrupting direct current of the voltage level your system uses.

One tip: You might want to consider mounting that relay to some sort of a heat sink (the metal cabinet of your control box would do) using silicone heat sink compound (grease) between the surfaces. If you look at the back of the SS relay, you'll see it has a large, flat metal surface. This radiates any heat generated by the relay, and it's always good to dissapate heat before it can build up.


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