BFL13 wrote:
"If the output voltage is higher, then the power is of course greater...and conversely if the system voltage is lower, the output power is lower, assuming the current remains constant."
I am not clear on the "system voltage". The charger's voltage is set at 14.6v and stays there solid the whole time. 75 is constant the whole time during these two situations.
In "power supply", the battery bank is being drawn down by the inverter pulling 127 amps (MW) and so battery voltage is low. The charger then supplies 75 amps and now the battery draw is 52 amps but its voltage is still low, just not as low.
In "battery charging" the battery voltage is in the 13s at first then climbs. So the charger is facing higher resistance than when doing "supply", but it is still doing its 75 amps.
I have seen it before where a converter will do full amps doing "supply" but not when battery charging. Eg a 7355 in the 5er did 56 amps but only 35 amps battery charging--and on the same wires to the battery.
So I think the charger doing 75 on battery charging could need more input than when doing 75 amps as supply. No?
Brings up an old question I never got clear on--is charger "output watts" using the charger's voltage setting, or is it using the battery voltage in the watts?
I'm assuming your converter/charger/supply is connected directly to the 12V distribution system, as is the battery; if that's not true, then there's a good bit more going on than was obvious to me from your posts and I apologize for giving any misleading or confusing info.
Assuming they are wired together, though, the (actual) output voltage of the converter/charger/supply and the battery voltage are always the same voltage, save for any wiring voltage drops which I can only assume you have minimized. If the battery voltage is 13V, the output voltage of the supply is actually 13V, even if its regulator is set to output 14.x volts; you're running into current or power limits and its output voltage is drooping. Likewise, when the inverter is running and consuming a lot of current, the battery (and converter output) voltage might be perhaps 12V and the converter is supplying it's full 75A; it's solidly in the current limiting part of operation.
If, somehow, the converter or charger or whatever is connected to the battery and maintaining an actual 14.6V while the battery voltage is 13V, you must have a 1.6V drop in the wiring!
