# [EVDL] Ammeter to shunt wiring



## EVDL List (Jul 27, 2007)

All,

Is it necessary/recommended/ a good idea to put a fuse in the wiring 
that goes from a shunt (traction battery and or motor loop) to the 
ammeter guage?

Thanks,

John

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## EVDL List (Jul 27, 2007)

Hello John,

I fuse all my sense wires that go from the shunt to the indicators. The 
fuse type I use is a Bussman Limitron 1 amp 500 volt rating or equal type of 
fuse with the correct voltage. You can either use a terminal strip fuse 
unit place close to the shunt or you can use a spade type fuse that will 
bolt directly to the shunt sense screws.

I do not like the ideal of have 2000 amp potential on a no. 16 wire up 
behind the dash plates on this indicator. If this wire shorted, it will 
normally burn the insulation off and than melt the copper wire.

One thing to remember in tapping off any devices off the main battery lines 
like the DC-DC converters, make sure these tap off are on the load side of 
the battery shunt. If you also use a motor shunt, there should be no tap 
off of accessories between the controller and the motor.

There was one person on the list that could not figure why his main battery 
had discharge so much, while the E-meter only show so much usage. It was 
that he had his accessory DC-DC converter and electric heater tap off on the 
battery side of the shunt.

This will show a error of battery usage and you think you may be only doing 
1 to 2 ah per mile instead of 2 to 3 ah per mile.


----- Original Message ----- 
From: "John in Ma" <[email protected]>
To: "Electric Discussion List Vehicle" <[email protected]>
Sent: Tuesday, April 08, 2008 9:01 PM
Subject: [EVDL] Ammeter to shunt wiring


> All,
>
> Is it necessary/recommended/ a good idea to put a fuse in the wiring
> that goes from a shunt (traction battery and or motor loop) to the
> ammeter guage?
>
> Thanks,
>
> John
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
> 

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## EVDL List (Jul 27, 2007)

It is absolutely a necessity safety-wise to place a fuse in each line!
Even though the voltage drop across the shunt may be just 50 MV or so,
there is always a possiblity in a crash or due to a breakdown in
insulation that the wiring could short to the body or electrical system
- or even worse to the opposite potential of the traction pack. A fire
or major disaster to your 12 volt system is possible if enough things go
wrong. I used 1/2 amp fuses coming off both of my Empro 1000a shunts.
Your wiring harness will melt a long time before your Main fuse (600
amps on my car) will ever blow.

Others here will probably give you about the same advice.

Mark Ward
www.saabrina.blogspot.com





> John in Ma wrote:
> > All,
> >
> > Is it necessary/recommended/ a good idea to put a fuse in the wiring
> ...


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## EVDL List (Jul 27, 2007)

It is also a good idea to put some limiting resistors in the lines to the
gauge. Large enough to reduce the instantaneous current capability of the
these high voltage lines, small enough not to reduce accuracy too much.



<Is it necessary/recommended/ a good idea to put a fuse in the wiring 
that goes from a shunt (traction battery and or motor loop) to the 
ammeter guage?
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View this message in context: http://www.nabble.com/Ammeter-to-shunt-wiring-tp16578463p16585136.html
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

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## EVDL List (Jul 27, 2007)

[No message]


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## EVDL List (Jul 27, 2007)

[No message]


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## EVDL List (Jul 27, 2007)

Alot of shunt's and AH counters don't instruct you to put fuses in the
signal wires, only in the positive wire... but most of them are not
designed to be used on ungrounded systems, so they assume that the
signal wires are, at most, maybe 100mV potential with regard to
ground. With the floating pack in an EV, I would argue that ALL the
signal wires, whether at positive or negative potential, should be
fused, and probably run in shielded cable too.... so if it does start
to get cut, the wire hits the grounded sheath before the metal of the
car, to make sure that it blows the fuse before electrifying the car's
grounded metal frame.

If you are putting a resistor in line with a signal line, make sure
it's a signal line only, and that the meter is not trying to pull any
power from it. The trimetric (not often used in EV's because it only
goes to 48 volts) draws it's positive and negative power from two of
the signal lines, and uses two (or three) others for sensing shunt
voltage.

Z



> Roland Wiench <[email protected]> wrote:
> > Hello Sam,
> >
> > I get these Busmann fuses from a electrical supply house. You can also get
> ...


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## EVDL List (Jul 27, 2007)

> Zeke Yewdall wrote:
> 
> > With the
> > floating pack in an EV, I would argue that ALL the signal
> ...


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## EVDL List (Jul 27, 2007)

Yes, thinking about it more you are right. Unless you had ground
fault detection circuitry on there, it wouldn't help to have the
grounded shield.

The question is what is a safe current level. The ground fault
protection for American PV inverters is a 1 amp fuse (on a grounded
system) so it will protect against fire, but doesn't help people at
all. The European inverters use an ungrounded system more like an EV,
and a much more sophisticated ground fault detection circuit that can
protect down to a few milliamps, and actually protect people. But
that's getting a bit off topic for the original question.

Z



> Roger Stockton <[email protected]> wrote:
> > Zeke Yewdall wrote:
> >
> > > With the
> ...


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## EVDL List (Jul 27, 2007)

Roger,
This is probably an ignorant question, but wouldn't putting a resistor
in a signal line change the signal?
storm


>
> If you have a signal lead, then placing a resistor in series with it will probably provide more effective protection. You can't prevent a connection between the traction pack and chassis or anything else, but you cna limit the available current to a safe level.
>
> Cheers,
>
> Roger.
>
>
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>



-- 
http://www.austinev.org/evalbum/1059
http://stormselectric.blogspot.com/
Storm

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## EVDL List (Jul 27, 2007)

> storm connors <[email protected]> wrote:
> > Roger,
> > This is probably an ignorant question, but wouldn't putting a resistor
> > in a signal line change the signal?
> ...


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## EVDL List (Jul 27, 2007)

> John in Ma wrote:
> > All,
> >
> > Is it necessary/recommended/ a good idea to put a fuse in the wiring
> ...


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## EVDL List (Jul 27, 2007)

> storm connors wrote:
> 
> > This is probably an ignorant question, but wouldn't putting a
> > resistor in a signal line change the signal?
> ...


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## EVDL List (Jul 27, 2007)

Thanks to all that responded. Looks like there are some fuses in my 
future.


> John in Ma wrote:
> 
> > All,
> >
> ...


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## EVDL List (Jul 27, 2007)

>> If you have a signal lead, then placing a resistor in series with 
>> it will probably provide more effective protection. You can't 
>> prevent a connection between the traction pack and chassis or 
>> anything else, but you can limit the available current to a safe
>> level.



> storm connors wrote:
> > wouldn't putting a resistor in a signal line change the signal?
> 
> It depends on the situation. Most ammeters are really 0-50 millivolt
> ...


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