Re: 12 volt 7amp/h versus10amp/h ??


>The resistance of filament lamps is current dependent. I think you'd
have a better comparison test if used used a fixed value resistor.

Although it is true the resistance of a lamp changes with applied voltage, it is not an issue since the current flowing through a fixed resistor will change as the voltage decreases. As the voltage decreases, current decreases. As a matter of fact, as the voltage on the lamp decreases, the temperature of the filament will decrease, which will decrease the resistance, which will increase the current drawn. Thus, the lamp should result in more constant current flow and improve the accuracy of a constant current graph.

If you start at a certain voltage and discharge to a defined ending voltage, it should not matter whether your resistance is slightly variableor fixed. In neither case will you have a constant discharge, which is often what the hypothetical battery discharge graph imagines.

I have used lamps successfully for years to check out batteries. The secret is to select a lamp with the same current draw as the equipment you are using. You can glance over at the lamp and see that all is well.

Colin

I also reversed the lamp to make sure I was getting the same results.
Udo

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