what AWG cable to use for cordless drill + car battery

[mikgol]

Hey there,

I'm making an automatic gate opener powered by a cordless drill and 12v car battery.

What AWG cable should I use for this? I'm thinking 8 AWG?

 

[Tha fios agaibh]

Depends on current and voltage drop consideration

 

[Colin Mitchell]

Use the thickest wire possible as you cannot afford to have any voltage drop. Keep the run as short as possible.

 

[Minder]

Ampacity of 8awg is 50amps at 75°C, shouldn't even come close to this with a Cordless drill.
I would be inclined to use 14g or 12g tops.
M.

 

[Colin Mitchell]

A cordless drill can easily take 20 to 30 amps under load.
Depending on the run, you cannot even afford to have a resistance of 1 ohm when you have such high currents.

 

[Minder]

..Hmmm You must have some much really Larger drills than my Craftsman and DeWalt.
The batteries in each are 19.2v @ 3Ah and 18v @ 2Ah.
I don't see these passing anywhere near 20 or 30Amps? And I would be nervous of having it in my hand if the batteries were passing this much current.
Some also are fitted with current limiting.
M.

 

[Martaine2005]

Sorry to butt in here but the op is going to use a car battery not a drill battery.
Just a FYI.

Martin

 

[Minder]

Obviously the right path to take is do an empirical test of the motor using the Auto battery, I would be very surprised if it were to draw more current than in the hand tool!
M.

 

[Martaine2005]

Obviously the right path to take is do an empirical test of the motor using the Auto battery, I would be very surprised if it were to draw more current than in the hand tool!
M.

Totally agree. I was just bringing it back on track.
If the motor seized or a short across the car battery, things could get very lively indeed.
Martin

 

[Tha fios agaibh]

I saw a youtube video showing the current draw of a DeWalt drill motor near 40a, So, #8 would be good provided it's not too far away.

That said, the idea of using a drill motor and car battery is not feasible. The cost of the cable alone would cost too much.

 

[Tha fios agaibh]

If the motor seized or a short across the car battery, things could get very lively indeed.
Martin

Natural a fuse would be used to limit current, but I could also see the motor being overloaded by exceeding its horsepower rating.

 

[Martaine2005]

Hi Tha fios agaibh. I was searching the net to translate that. So many possibilities.
I also suppose it would depend where the fuse was located too.
Anyway, this thread is like 'think outside of the box'.
A brain twister.. A brain teaser? Can't think of the name.

I'm making an automatic gate opener powered by a cordless drill and 12v car battery.

What kind of gate? Weight? Length? Dry? Wet?
What cordless drill motor? 12v, 14.4v, 18v, 28v, 36v?
Where is the motor located?
Where is the battery located?
What is the distance between all of these?
Is it just to release a latch?
Is it to pull open a rolling gate?
Too many factors to even answer the op.

Martin

 

[Minder]

I will do a test on mine and see what it draws in fact when stalled, I would not be surprised if most hand drills do not have some kind of current limit, as per most specs.
In theory the maximum current of a DC motor is full voltage and stalled by load.
M.

 

[Martaine2005]

Mr M. It sounds like you enjoy Dewalt too.
I am sad and have every tool by Dewalt. Did I mention sad too?
I can hand hold every single 'cordless drill' still!
My diamond cutters and cores, no way!!!
Even cutting a 4" flu can put me off balance, but the clutch saves me.
The stall limit of a cordless drill emphasizes my point.
A leaf in the track can stall it.
Just too many factors to guess!!
Not having a pop at you, but the op's question is too open to speculate.

Martin

 

[Arouse1973]

John and Colin is correct. I found this Video and posted it for another thread. It can draw 30 Amps and it was a Dewalt Drill he was using I think.

Adam

 

[Martaine2005]

Hi Adam, thank you for the video. I saw that ages ago and didn't believe it.
It might give an initial high amperage, but cannot sustain it for more than a few seconds.
Those few seconds wont open a 'ghost' gate.
Why did he have a 3300mah battery powering the the meter?
If the meter was in series to measure amps, no extra power is needed.
Or have I just made myself look even stupider???

Martin

 

[Arouse1973]

I guess the circuit needs power to operate and he is running the drill from this battery I think. I might have this wrong!
Adam

 

[Martaine2005]

I doubt that .In any case. Wasn't a Dewalt battery so

 

[Tha fios agaibh]

I agree, the meter needs a separate power source for it's display.

I also agree, the peak current would probably only be for a few seconds to get the gate rolling. So a smaller gauge could be used.

Although its fun to imagine the possibilities, I can't fathom this drill motor/car battery idea as a feasible one as a gate opener. At best, I'd say it's doomed to failure.

 

[Martaine2005]

I agree, the meter needs a separate power source for it's display.

I also agree, the peak current would probably only be for a few seconds to get the gate rolling. So a smaller gauge could be used.

Although its fun to imagine the possibilities, I can't fathom this drill motor/car battery idea as a feasible one as a gate opener. At best, I'd say it's doomed to failure.

Yes, I watched it several times to try and see what model drill it was and missed the 'drills' battery had been replaced with a blank.
I tried mine this morning (18v 4mah lio) and it did indeed draw 36 amps for a second before the circuitry shut down.
I also tried my older 18v nimh's and in stall mode, it went on and on until it started smoking..So it seems the battery has the overload circuitry.

Martin