Hi.

I am working with electromagnet which has a resistance of about 100ohms. I want to put about 4amps through it.

Could this be done with 4x 12v SLA 1.2ah battery’s? Or 6v 4.5ah sla battery’s?

And if so how do I draw 1amp from each battery ?

Cheers

 

To draw 4 amps with a 100 ohm load requires 400 volts. See Ohm's Law.

 

If you want to put 4 A through a resistance of 100 Ω, you are going to need 400 V to do it.

To do that from a lower voltage battery pack, you would need a suitable DC-DC converter. To go from a 48 V battery pack you would need to increase the voltage by a factor of 8.3. and would need to draw 33.33 A. Allowing for about an 85% efficiency and you will actually need to pull closer to 40 A.

 

Driving 4A into 100 ohms requires 400V, so no.

 

Not to mention the 1.6 kW of energy, that's one hell of a heater.

 

Not very many batteries are going to last very long, either. Those 1.2 Ah batteries will last less than two minutes.

 

You could use one battery and a DC-DC inverter to charge a capacitor up to 400V or more, then discharge it through the resistor: but your 4A pulse would last only a few milliseconds at most, unless you can afford a lorry load of large capacitors.

 

I just want to know where the OP got a 100 ohm electromagnet. Maybe 10 ohms but 100 ohms,WTH
SG

 

Using Ohm's Law, I=V/R. V is constant, battery voltage. The only way to adjust current I is to adjust resistor R. Resistor R in this case is a load attached to the battery. Therefore to have large current I you will need resistance R to be small.

 

These are the types of posts that make me wonder how there aren't just constantly stories on the news of kids/people just killing/electrocuting themselves, blowing up their houses,etc...
Also wonder why people think electronics/electrical projects are just so simple/harmless that they can just jump right in without any basic knowledge what so ever...

"Hey guys... watch this".... BOOM...

 

These are the types of posts that make me wonder how there aren't just constantly stories on the news of kids/people just killing/electrocuting themselves, blowing up their houses,etc...
Also wonder why people think electronics/electrical projects are just so simple/harmless that they can just jump right in without any basic knowledge what so ever...

"Hey guys... watch this".... BOOM...

How many of us played around with electricity when we were kids? How many of us really had any idea what we were doing? How many of us got zapped now and then or let the magic smoke out of something from time to time?

I remember winding bare wire around a big nail to make an electromagnet and connecting it to some big-ass dry cell batteries that my dad brought home from work (they were the used batteries from their burglar alarm system) and wondering why things got hot but almost nothing got picked up. I was perhaps eight at the time. That night my dad introduced me to the notion of "electrical insulation".

 

How many of us played around with electricity when we were kids? How many of us really had any idea what we were doing? How many of us got zapped now and then or let the magic smoke out of something from time to time?

I remember winding bare wire around a big nail to make an electromagnet and connecting it to some big-ass dry cell batteries that my dad brought home from work (they were the used batteries from their burglar alarm system) and wondering why things got hot but almost nothing got picked up. I was perhaps eight at the time. That night my dad introduced me to the notion of "electrical insulation".

I just did some searching and I'm pretty sure those batteries were No 6.

 

I just did some searching and I'm pretty sure those batteries were No 6.

Put out as much current as a modern AAA alkaline.

 

Put out as much current as a modern AAA alkaline.

I don't know what the peak current is, but the capacity of 40,000 mAh is a wee bit more than a modern AAA alkaline.

 

If you read/study darwinawards.com u will find a few experimenters whom paid dearly for being uniformed, or just stupid.

 

If you read/study darwinawards.com u will find a few experimenters whom paid dearly for being uniformed, or just stupid.

+1 for Darwin Awards, great website. Have you seen the movie? some of them are true stories.

 

If you read/study darwinawards.com u will find a few experimenters whom paid dearly for being uniformed, or just stupid.

Yep. And most of us could easily have been among them at several times in our lives. Then again, I doubt that there's a single person that's ever lived (that made it to the age of five or so) that wasn't a Darwin wannabe at least once.