Battery Rating vs Capacity Monitoring

BFL13 wrote:
Thanks. almost got it that time! :) so when the monitor is doing amps as the read-out, it says 5 amps no matter what the battery voltage is, 12.5 or 12.1 it still says 5 amps if that is the draw.

So is 5 amps at 12.5 the same draw as 5 amps at 12.1 ? the discharge graphs for decline in SOC are quite linear. (not so with charging graphs--not linear)

I know a light bulb gets lower in amps draw as voltage goes down and the lamp dims. to maintain a 5 amp load with lights you have to keep raising the voltage. (if that has anything to do with whether 5 amps is 5 amps or that is just because lamps do that)

5 Amps is 5 Amps regardless of the voltage, just as with a water pump 5 gpm is 5 gpm regardless of the water pressure. Whether it's the same draw or not hinges on what exactly you mean by "draw": it's the same current, but not the same amount of power. It causes the same rate of change of charge, but not the same rate of change of stored energy.

For the light bulb, and indeed any load, current and voltage are not independent variables: altering one will of necessity alter the other through some defined relationship. For (purely) resistive loads, that relationship is Ohm's law and the two are related linearly. Light bulbs are not quite purely resistive, in that the voltage/current curve is curved, particularly near the lower end of things; but for small changes in voltage, particularly around their nominal operating point, it's a close enough approximation. In any case, to maintain the same brightness from a light bulb, you need to keep the voltage constant (and thus the current will remain constant)--or, alternately, regulate the current so that it's constant (and the voltage will also follow).