Forgive my limited knowledge about circuits but here goes...
I need to apply 48 volts at 3 amps to a load. As I understand
I = V/R
so
3 = 48/16
...meaning a 16 ohm resistor/rheostat
This is probably overly simplistic - there will likely be other sources of resistance like the wires themselves and I'm going to add a switch also. There may even be some resistance in the power source...don't know yet.
But I think wattage is also a challenge. As I understand:
P = I*I*R or P = V*R
so
144 = 3*3*16 or 144 = 3*48
...meaning at least a 150 watt resistor/rheostat? Seems like a lot. Is my reasoning correct?
Assuming some of the above is correct - should I go with a rheostat over a resistor? I'm thinking there's going to be enough variability in the circuit to need the rheostat to regulate the current to 3 amps.
The problem I'm having is finding some of these parts based on my assumptions above.
150 watt/16 ohms resistor assuming all else works out perfectly or
150 watt/16 ohm rheostat?
48 volts. I'm thinking I'm going to use 4 12 volt car batteries in serial to achieve the 48 volts. There's also some 48 volt/3 amp battery chargers with AC input which would be a lot easier, BUT, I think the problem is that these devices actually try to be smarter about charging - like varying voltage, etc, based on the state of the battery they are charging and I'm not sure how the charger would react to the load. But I'd sure like to be able to use something like this so that I don't keep draining and then having to recharge the car batteries - and it would be cheaper than 4 car batteries. I'm sure I'd have to cut open some output wires so I have my leads for my load, but I'd be OK with doing that.
I think this is it, thanks for any suggestions that come my way.
I need to apply 48 volts at 3 amps to a load. As I understand
I = V/R
so
3 = 48/16
...meaning a 16 ohm resistor/rheostat
This is probably overly simplistic - there will likely be other sources of resistance like the wires themselves and I'm going to add a switch also. There may even be some resistance in the power source...don't know yet.
But I think wattage is also a challenge. As I understand:
P = I*I*R or P = V*R
so
144 = 3*3*16 or 144 = 3*48
...meaning at least a 150 watt resistor/rheostat? Seems like a lot. Is my reasoning correct?
Assuming some of the above is correct - should I go with a rheostat over a resistor? I'm thinking there's going to be enough variability in the circuit to need the rheostat to regulate the current to 3 amps.
The problem I'm having is finding some of these parts based on my assumptions above.
150 watt/16 ohms resistor assuming all else works out perfectly or
150 watt/16 ohm rheostat?
48 volts. I'm thinking I'm going to use 4 12 volt car batteries in serial to achieve the 48 volts. There's also some 48 volt/3 amp battery chargers with AC input which would be a lot easier, BUT, I think the problem is that these devices actually try to be smarter about charging - like varying voltage, etc, based on the state of the battery they are charging and I'm not sure how the charger would react to the load. But I'd sure like to be able to use something like this so that I don't keep draining and then having to recharge the car batteries - and it would be cheaper than 4 car batteries. I'm sure I'd have to cut open some output wires so I have my leads for my load, but I'd be OK with doing that.
I think this is it, thanks for any suggestions that come my way.