# Moving car on 12V with jumper cables



## Lucas POD (Feb 3, 2010)

My conversion is still in the very early stages, but I'd like to make the car move under electric power as a sort of milestone / psychological reward for mounting the motor. 

I thought maybe I could just hook up a 12V battery and back it out of the garage.

Then I read NetGain's information sheet about bench testing motors:
http://www.go-ev.com/end-users/005_007_Motor_Bench_Test.pdf

Pardon the dumb questions as to "why" but... I figure better to ask than to find out the hard way.

What's with all the warnings about sparks and batteries? 20' of cables and batteries outside of the building?

Past dealings with jumper cables or other misc car repairs sometimes resulted in an errant spark... but I wasn't worried about blowing something up. Is this a case of liability fears resulting in lots of warnings and cautions? Or am I just ignorant of the real dangers?


Second question has to do with the sequence of cable connections for connection and disconnection.

I assume the last connection to be made is at the Motor A1 terminal (as opposed to the battery) in order to avoid sparks near the battery. 
Is this correct?

And then the prescribed way to disconnect things is to start at the cable between A2 and S2.
What's the reason for that?


As stated previously - I know I'm pretty ignorant, but what harm would I have done if I had enlisted a partner in crime to sit next to me in the car wtih jumper cables and a 12V battery?


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## Ziggythewiz (May 16, 2010)

Lucas POD said:


> I thought maybe I could just hook up a 12V battery and back it out of the garage.
> 
> I assume the last connection to be made is at the Motor A1 terminal (as opposed to the battery) in order to avoid sparks near the battery.
> Is this correct?
> ...


So is the plan is to have your friend sit next to you with a battery in his lap and connect/disconnect the jumper cables? Or will he be riding on the motor?











Also, why do you want to test by reversing out of the garage? I would suggest first removing the car from the garage, and depending on your street, maybe testing it there, going forward first.


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## frodus (Apr 12, 2008)

you'll be pulling hundreds of amps, it won't be a small spark. There's nothing to limit current and the motor is going to be pulling more current than anything you did while using jumper cables or misc car repairs.


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## Lucas POD (Feb 3, 2010)

Ziggythewiz said:


> So is the plan is to have your friend sit next to you with a battery in his lap and connect/disconnect the jumper cables? Or will he be riding on the motor?
> 
> 
> 
> ...


Good one (the Strangelove reference)

As far as reverse and the garage...What's the difference?
What benefits are there to going forward vs backwards?

For what is is worth, after backing out, I'm sure I'd put it in a forward gear and move back and forth in the driveway. However, I don't plan on putting it on ANY street in its current configuration. That's a really bad idea IMO.
(maybe you live in a much more isolated area than I do)


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## Yabert (Feb 7, 2010)

Lucas POD said:


> Pardon the dumb questions as to "why" but... I figure better to ask than to find out the hard way.
> 
> What's with all the warnings about sparks and batteries? 20' of cables and batteries outside of the building?


It's because spark and battery gas can be dangerous.



> you'll be pulling hundreds of amps, it won't be a small spark


Yes, big spark and hundreds amps, but for fraction on sec.
I moved my car with 2 headway 10Ah (6v) easely with 14 Ga wires.
Some spark and uncontrolable acceleration... up to 3 mph...


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## Ziggythewiz (May 16, 2010)

Lucas POD said:


> Good one (the Strangelove reference)
> 
> As far as reverse and the garage...What's the difference?
> What benefits are there to going forward vs backwards?
> ...


I'd test in forward first, just because that's the typical operation, not that it matters much. I would not test in a garage because there is no room for safety. You have it in reverse, but what if you wired the motor wrong and you go forward?

For the street, yes, my street is low/no through traffic, that's why I said depending on the street. 

First you should stop and ask what you are trying to test. If you want to see the motor turn, that's what a bench setup is for. If you want to verify that the motor is coupled you can put it in gear and push it back and forth.

With it on the car, you should wait until you have your controller and contactor wired up before testing further. Holding a battery and hooking a jumper to it is not safe, even if your friend is expendable. Another option would raising the drive wheels on jack stands and testing in the air.


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## skooler (Mar 26, 2011)

Hi lucas,

My maiden voyage was quite similar to what you described.

Jump leads from motor, through passenger window, to passenger with old starter battery.

Power is managed by shouting At the passenger who then connects or disconnects the jump lead from the battery terminal in his footwell

It does spark a lot but it's quite controllable, that was with a fully charged 80a started... just don't touch it!

There's a video in my build thread that you might find interesting , i would post it here but using a new tablet and can't work out how to copy!

Click my name and look at threads started by me, it's in the last couple of posts in ' a good motor'

Hope this helps.

Cheers,

Mike


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## Lucas POD (Feb 3, 2010)

frodus said:


> you'll be pulling hundreds of amps, it won't be a small spark. There's nothing to limit current and the motor is going to be pulling more current than anything you did while using jumper cables or misc car repairs.



You underestimate my ineptitude. I've had a 1/2" drive socket handle bridge the battery terminals before. That's probably pretty close to as much current as you can get out of that battery.


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## Lucas POD (Feb 3, 2010)

Yabert said:


> It's because spark and battery gas can be dangerous.



So by battery gas, do you mean the hydrogen gas that can be produced when charging a lead acid battery?

Can it also be produced when discharging a battery?

I don't mean to sound obstinate, but its a standard 12V car battery that would be recharged slowly on workbench and then carried over to a car and put on the passenger floorboard before attaching the jumper cables.

In this scenario - is there really much risk of their being a fog of flammable hydrogen gas around the battery terminals that may be ignited with some sparks?

Being that the battery is in an open environment, wouldn't the hydrogen dissipate? Or is more going to be generated when the battery is discharging after the jumper cables are hooked up? (and could be ignited when disconnecting them)


On a separate note, for what it is worth, I'm now on board with not having the car in the garage the first time I make it move on electrons only. I'll roll it out in the driveway first. (Whether I go forwards or backwards first will be my secret)


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## Ziggythewiz (May 16, 2010)

Lucas POD said:


> I don't mean to sound obstinate, but its a standard 12V car battery that would be recharged slowly on workbench and then carried over to a car and put on the passenger floorboard before attaching the jumper cables.


That sounds like a much better plan than having it sit in your buddy's lap.


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## locoo (May 6, 2010)

been there done that

Dont forget the transmison oil


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## mora (Nov 11, 2009)

You could use one more jumper cable and connect two cables together on the passenger seat instead of finishing the loop to a battery terminal. At least there won't be sparking near the battery. You can place your 12V battery anywhere you want that way. Two jumper leads clamped together might not make a good contact but it should be enough to move your car. Reversing should be easiest on motor regarding amps anyway. First gear right after that.


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## caffinefiend (Dec 14, 2009)

Some good points above. Your intention to slow charge the battery is good, and if you let it rest for a little while after charging you shouldn't have a gas problem. 
You might put the ICE negative battery cable on the battery instead of a second set of battery cables, It'll give you the distance and protect the bat terminal from arc pits, as well as one less cable to complicate things.


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