How to connect DC motor to battery pack? Do I need a fuse for safety?

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Kim_G

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Hi. Forgive me if this is in the wrong category but I would love some help with a project I’m working on.
How do I connect my DC motor to a 12v(8 AA batteries) battery pack? The wires are not the same gauge but very similar (pic included)
Most importantly, should I buy a fuse? This project will be attached to my body and I don’t won’t to get sparked or worse, catch on fire. Do I need certain calculations to connect a fuse?
Again forgive me if I sound uninformed about this, I am very new to all this.
any help would be greatly appreciated!!
Thank you!
 

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This is a professional site for electricians but I am going to allow this but would you explain what you are doing with this?

Hook up is easy-- red to red and black to black-- use a butt splice or wirenuts.


Butt Splice

70092501.jpg



Wirenuts
71Iu7HGM69L._SX425_.jpg
 
Kim_G said:
Hi. Forgive me if this is in the wrong category but I would love some help with a project I’m working on.
How do I connect my DC motor to a 12v(8 AA batteries) battery pack? The wires are not the same gauge but very similar (pic included)
Most importantly, should I buy a fuse? This project will be attached to my body and I don’t won’t to get sparked or worse, catch on fire. Do I need certain calculations to connect a fuse?
Again forgive me if I sound uninformed about this, I am very new to all this.
any help would be greatly appreciated!!
Thank you!
Click to expand...
Two points. 12V isn't likely to hurt you.
The current an AA cell can delivery is quite low so a fuse would be ineffective.
 
To Besoeker’s point, AA batteries are good for a constant draw of 50mA (0.05 Amps) each. You have 8 of them, but you have them in series to get to 12V, so the current draw remains the same, 50mA just at a higher voltage. Wires are rated for current. Even if those are 24ga wire, it can safely carry 2A of current without over heating, so 40 times what the batteries will deliver, NORMALLY.

AA batteries are CAPABLE of a peak delivery of up to 2,000mA or 2A, but only for a very brief moment. Still within the capacity of that 24ga wire, but it might feel a bit warm, right before the batteries die. What we don’t know, because you didn’t say and the photo is too blurry, is what that motor will draw, so how long those AA batteries will even last is beyond our help (and not what you asked anyway).
 
That looks like a car window motor/regulator to me.

If that is the case, that motor is designed to run only for a few seconds at a time.

If I were doing the connections for the finished product, I would use solder and shrink tube.

I would also use a fuse.

That's just me, but I have designed and built many 12V projects over the years and I know what works the best.
 
K8MHZ said:
That looks like a car window motor/regulator to me.

If that is the case, that motor is designed to run only for a few seconds at a time.

If I were doing the connections for the finished product, I would use solder and shrink tube.

I would also use a fuse.

That's just me, but I have designed and built many 12V projects over the years and I know what works the best.
Click to expand...
8 AA batteries probably isn't going to power a car window motor. If they do it won't be for very long.
 
K8MHZ said:
Typically, 4 amps no load, 10 amps stalled. If he is just moving sign or something, the load would be close to the no load rating.
Click to expand...
I understand no load helps, but 4 amps? Jraef said AA can deliver 2 amps, but briefly.
 
If a double-A Al Kaline cell can deliver 3 amps for 10 minutes, it can probably deliver 6 or more amps of short-circuit fault current.

I'm never going to say that using a fuse would be a bad idea, but it might be entirely superfluous -- there's just not enough energy in eight double-A cells to do very much damage.

I'm sure everybody here would like to help you succeed -- not merely avoiding spontaneous human combustion but also enabling your project to do what you want it to do -- but we need a little more insight into just what you're trying to do.

Let me also recommend that you get yourself a multimeter. A $10 cheapie from Harbor Freight will suffice for projects like this, and can safely be used on circuits up to 50 volts or so.
 
K8MHZ said:
That's 2 amps at 1.5 volts.

8 AA in a battery set will start at 12 volts will only have an equivalent of 3 amps at 12 volts.
Click to expand...
If they are all in series current is same in every one of them. If max each can deliver is 2 amps how do we ever get to 3?
 
190205-0913 EST

Somebody go measure the short circuit current capability of a AA cell. Ampere-hour information does not tell you what short circuit capability is. Yes a fuse should be used close to the battery.

Note: you can get a severe skin burn by putting a 9 V battery in a pocket of coins. I believe this was mentioned somewhere on this forum.

Many years ago I used a series of 6 V car batteries to produce a high current thru a circuit breaker. If I remember correctly this was above 5000 amperes.

.
 
gar said:
190205-0913 EST

Somebody go measure the short circuit current capability of a AA cell. Ampere-hour information does not tell you what short circuit capability is. Yes a fuse should be used close to the battery.

Note: you can get a severe skin burn by putting a 9 V battery in a pocket of coins. I believe this was mentioned somewhere on this forum.

Many years ago I used a series of 6 V car batteries to produce a high current thru a circuit breaker. If I remember correctly this was above 5000 amperes.

.
Click to expand...
A 6 volt car battery is huge in comparison to a AA cell, or even 4 AA cells used to get 6 volts.

I could see you getting a high available fault current but can they sustain such high current for long at all? Or is any reliable usable current mostly limited to how many amps each individual unit can deliver?
 
190305-1645 EST

kwired:

My car battery example was simply an example of how high battery short circuit current can be in relation to battery anp-hour rating, or a normal battery load current.

None of you responders have measured the short circuit current of a AA cell. My quick measurement on one arbitrary cell, unknown initial state, was 16 A, or about 0.1 ohm internal resistance under the test conditions.

Assuming constant conditions maximum power transfer to a load is 8*8*0.1 = 6.4 W. This can produce a severe skin burn. Go to 8 series cells and maximum power is 8*8*0.8 = 51 W.

A fuse is a good idea.

.
 
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