# Wiring Diagram - Extra eyes please!!



## Travdude (May 11, 2009)

Hey illuminateddan, I am no expert, but can you help me understand your diagram a little..

What is SAFETY & SAFETY 1?

What is the METER RELAY?

Can you describe your CHARGE SWITCH?

What BMS are you using?


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## Electric Car-Nut (Jul 5, 2009)

Illuminateddan, The details you have shown seem reasonable to me, Except, the wires from the pack to the voltmeter and from the shunt to the ammeter are only protected by two fuses. There are four wires, four fuses are needed, one for each WIRE, not one for each meter...

You of course are far from complete, so as you determine where additional wiring will be connected I will be happy to check them out for you too.


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## illuminateddan (Dec 19, 2009)

Travdude said:


> Hey illuminateddan, I am no expert, but can you help me understand your diagram a little..
> 
> What is SAFETY & SAFETY 1?
> 
> ...


Hey Travdude,

in answer to your questions to my slightly esoteric naming system....
Safety 1&2 are the little red buttons, one on the dash and one by the controller/motor.

Meter relay is the relay used to switch on the meters (left side of the diagram) and is operated when the keyswitch is turned.

Charge switch is a dpdt microswitch located in the charging socket. The idea is that when the mains is not plugged into the car, contactor 1 & 2 are controlled via the zilla (and all safety switches)

When mains is plugged into the car, the zilla recieves a "plugged in" signal and thus will not run. The contactor circuit then becomes open preventing contactor2 (rear pack) from operating (even though the zilla is doing this too), but, as the pack is split into front and back, the charge switch will also energise contactor1 allowing the charger to charge both front and back packs.
The charge switch state is also watched by the BMS so the charger only fires up when it has a full circuit. I'll be building the BMS myself from a modification of design from peter perkins over at the battery vehicle society in the UK and I'll be recoding the whole thing to run on a faster master bus. I've got an Arduino Mega (Atmega 1280) running the whole show.

The BMS will have indivdually serial numbered slaves (a bit of a pain but worth it IMHO for 40 units) that will squirt back their voltage and temp when called.
This system also lets me have 'non battery modules' that will squirt back multiple temperatures, rpms, speed and other stuff.

The Arduino Mega has 54 digital i/o channels (14pwm) 16 analogue inputs and 4 serial ports, it's a little bit of overkill but I'd eventually like it to connect bluetooth to my iphone when I'm in the car for pack data display and also jump onto the wifi network at home as a http server so I can check its status from the house. Hell, I may even get it to twitter all the battery voltages, temps and charge states!!!


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## illuminateddan (Dec 19, 2009)

Electric Car-Nut said:


> Illuminateddan, The details you have shown seem reasonable to me, Except, the wires from the pack to the voltmeter and from the shunt to the ammeter are only protected by two fuses. There are four wires, four fuses are needed, one for each WIRE, not one for each meter...



Thanks Mr Nut! 
I will get those fuses in there. Will two fuses on the shunt input change the resistance on the shunt signifigantly and thuis change the ammeter accuracy???



Electric Car-Nut said:


> You of course are far from complete, so as you determine where additional wiring will be connected I will be happy to check them out for you too.


Are you talking about the additional BMS wiring, the cars basic wiring (lights horn ect) or have I missed something else? I was thinking the traction pack system was pretty close to done bar a little tweaking??

Thanks for your time!


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## Travdude (May 11, 2009)

Now I understand, great explanation.

Your BMS is very interesting, I would like to follow your progress on that.


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## Electric Car-Nut (Jul 5, 2009)

The wires connecting the ammeter and the shunt together are inputs to the ammeter and outputs from the shunt. The shunt is in series with the pack and all pack or battery current passes thru it. the tiny resistance of the shunt results in a tiny voltage drop and a tiny fraction of total current is routed to the ammeter which indicates by proportion the amperage flowing in the pack battery circuit. The fraction of an ohm of resistance in the two protecting fuses have less than 0,1% affect on the current readings.

Hey, Dan, your picture needs Illuminated. LOL -))


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## Overlander23 (Jun 15, 2009)

I'm curious, why two fuses in this situation (either the ammeter or voltmeter)?


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## illuminateddan (Dec 19, 2009)

Overlander23 said:


> I'm curious, why two fuses in this situation (either the ammeter or voltmeter)?


I think I understand why.... If the ammeter shorts and blows its fuse, it is still linked to pack via one unfused wire _and_ the voltmeter via the isolated battery, thus and fault could still cause problems via the voltmeter, and vica versa.

Makes sense. Also I'm thinking that when I'm playing with 120v at 270+Amps available in an instant, I'd rather stuff went pop than sizzle sizzle bang!!

I was looking at a dc/dc isolator for the battery but couldn't find any easily (although to be honest I didn't really look!). Anyone know any good ones?


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## illuminateddan (Dec 19, 2009)

Electric Car-Nut said:


> Hey, Dan, your picture needs Illuminated. LOL -))


yeah, I haven't put in the lighting circuits yet.....


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## Electric Car-Nut (Jul 5, 2009)

Not exactly the problem. Ammeters almost never short. however, the wiring from the shunt to the ammeter as well as the wiring to the voltmeter connect directly to the pack which is over 120 v. when charged and usually over 1,000 amperes of current for at least a minute or more when those little wires and their plastic insulation short out somewhere along their route especially as they pass thru a hole in a box or the firewall, and such. That is why there should be a protective fuse next to the pack or shunt terminal where you connect the leads for the voltmeter and the ammeter. the small fuses rated 250vdc or higher and at 1/2 amp. or less current protect the wiring, not the meters. 
I show my students this, a piece of #14 lamp cord wire two feet long, one inch of each end stripped and twisted. and a automobile battery jump cable and a 12 volt auxiliary battery, lay piece of wire on cement floor, clip jump cable to wire red on one end black on the other,clip other end of jump cable red to 12 volt battery positive. have everyone step back 10 feet. touch black clip to battery negative, wire on ground twists, smokes, flames, glows red then white and breaks remove jump cable from battery, careful wire is still hot for a minute. then un-clip jump cable from burned wire and pass it around saying "This is what a fuse protects you from!"


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## Overlander23 (Jun 15, 2009)

OK, but in your example you don't have any fuses in the system. 

Don't get me wrong, I'm all for advocating safety and am not trying to start an argument, but if at least one fuse is in the circuit, won't it do the same thing? 

Technically, shorting the HV line to the chassis should have no effect considering the HV circuit should not be grounded to the chassis in any case to begin with. I'm just trying to clarify the use of two fuses in one circuit in this situation.

I've heard the same argument of having multiple fuses in the HV section if the battery boxes are split apart (front and rear, for example.) I know it's safer to be sorry, and if that's the only reason to do it, fine. But I also would like to know where the theory is.


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## Electric Car-Nut (Jul 5, 2009)

My example was only a demonstration for the advantages to using fuses. 
Your question is reasonable, one fuse is enough to protect one wire. But, what protects the other wire? You have four wires! Two go to pack (-) and one to pack(+) and one to shunt (+) The two to pack (-) are not fused, in your diagram. If in the hole leading thru the firewall one pack(-) wire shorts to the car metal, nothing may happen, BUT, now if a wrench is dropped near the controller and pack(+) is shorted momentarily to the car metal, the wiring under the dash on the other side of the firewall ignites, and you wouldn't notice it until a lot of the under dash wiring is damaged! The extra two fuses are there for "Unforeseeable Circumstances."


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## Overlander23 (Jun 15, 2009)

In that situation, I agree that having the extra fuses will help.


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## illuminateddan (Dec 19, 2009)

Sounds like the moral of the story is.... if it aint fused, fuse it!!

But seriously, I agree that any lv equipment connected to the isolated pack should carry multiple safety fuses. I'll be adding some in....

It's good as I'm rewiring the entire car from scratch anyway so 2 extra fuses ain;t gonna blow the budget!


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## Jan (Oct 5, 2009)

illuminateddan said:


> The BMS will have indivdually serial numbered slaves (a bit of a pain but worth it IMHO for 40 units) that will squirt back their voltage and temp when called.


Hi Dan,

How are you going to do that? Is ther a component you can buy, or are you bluiding those thing by yourself?


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## illuminateddan (Dec 19, 2009)

Hi Jan,

I will be using a picAXE 08M processor chip, which is basically a tiny microprocessor in a 8pin dip package. This has serial input and output, pwm channels and ADC channels (jargon buster - DIP - Dual Inline Package - your standard microchip with the two rows of pins, PWM - pulse width modulation (if you didn't already know!) and ADC - Analogue to digital convertor)
I'm playing with each chip having a software serial number which it responds to when called. this is proving tricky as the 'serial listen' function prevents other code functions from running and so the circuit isn't monitoring the voltage until it gets a serial command. I'm currently working on this but there is much head scratching going on!!


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## Jan (Oct 5, 2009)

illuminateddan said:


> Hi Jan,
> 
> I'm playing with each chip having a software serial number which it responds to when called. this is proving tricky as the 'serial listen' function prevents other code functions from running and so the circuit isn't monitoring the voltage until it gets a serial command. I'm currently working on this but there is much head scratching going on!!


Hi Dan. 

Why do you think it's a problem they only measure when asked? 

And is it possible to connect those chips in series on the serial ports? So you write to the first, that gives its measured values on to the second and so on?

And how are you going to measure the voltage and temp exactly? What components do you need more?


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## Jan (Oct 5, 2009)

Jan said:


> Hi Dan.
> And is it possible to connect those chips in series on the serial ports? So you write to the first, that gives its measured values on to the second and so on?


Off course not. It's a little more complicated than that.

Here's a design for a two wire network and power supply for a PICAXE network:

http://www.kranenborg.org/ee/picaxe/SerialPower/V3.0/PicaxeSerialPowerNetwork_V3.0.pdf

Seems doable. But the price per cell isn't clear to me yet.


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## illuminateddan (Dec 19, 2009)

Jan said:


> Hi Dan.
> 
> Why do you think it's a problem they only measure when asked?
> 
> ...


Hi Jan,

The system i'm basing off is this: http://www.batteryvehiclesociety.org.uk/forums/viewtopic.php?t=1245 
I'll need to constantly monitor the voltages so I can trigger alarms when the lifepo cells go to high or low. if the unit is waiting for a 'serial send' command and there is a break in the wire/ main unit crash etc, then it cannot protect the cell.

Interesting link though... one of my main problems is the interrupt on the serial which for the 08m is more limited than the bigger chips....


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## Jan (Oct 5, 2009)

illuminateddan said:


> Hi Jan,
> 
> The system i'm basing off is this: http://www.batteryvehiclesociety.org.uk/forums/viewtopic.php?t=1245


Thanks Dan.



> I'll need to constantly monitor the voltages so I can trigger alarms when the lifepo cells go to high or low.


OK. I only want a bms that tells me the voltage and temp per cell when asked. And doesn't do anything smart in the mean time. So, I start to believe I can connect the chips in series.


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## illuminateddan (Dec 19, 2009)

Hey Jan,

I'd highly recommend the PicAXE 08M at a platform as it's cheap and tiny and reprogrammable so you can make changes when ever. Keep us posted on what you do as I'd be interested to see your approach! It's about time to start a new thread over in the BMS area!! Sidetrack?


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## Jan (Oct 5, 2009)

illuminateddan said:


> Hey Jan,
> 
> I'd highly recommend the PicAXE 08M at a platform as it's cheap and tiny and reprogrammable so you can make changes when ever. Keep us posted on what you do as I'd be interested to see your approach! It's about time to start a new thread over in the BMS area!! Sidetrack?


I even think the PicAXE 08 would be good eough for me. But I suck at electronics. My experience is zero, I'm just starting to understand these tiny components. I'm a just a simple programmer, not a hardware designer. I think I know now how to connect them, and measure the temperature with a thermistor. But have no idea yet how to measure the voltage through an opto isolated circuit. If that's even possible.


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