460 watt solar setup: wire sizes?
I want to change out my old 50 watt panel and 10 amp controller with at least one and hopefully two 230 watt 24 volt panels and whatever controller would be best. Right now the roof on my fifth wheel ...
Forum Discussion
Almot wrote:12thgenusa wrote:
I quite often will operate a high demand appliance during the day; MW, coffee maker, hair dryer so voltage will drop well below 13v.
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For the OP at 460 watts a voltage of 14.6 or less will hit the 30-amp max. (460*.96/30=14.56)
I am not sure about this math. 96% is Rogue efficiency at 30A (according to the manual), but then there is also 2% lost in cables, so it's more like 14.4V to hit the 30A limit of Rogue at ideal conditions (70F, optimal aiming of the panel and no dust on the glass).
I'm just reporting what I have seen. I also sized the cables for less than 1% drop. If 411 watts is seen by the controller, that is after any wire losses. What you seem to be missing is that at any voltage BELOW 14.6 or your 14.4 it would be possible to hit the 30-amp limit.
Such ideal conditions won't happen at sea level. It also won't happen for users with less than perfect aiming which is anybody but BFL ;)...
But I'm not after those particular numbers here. One thing I don't understand - what "volts" we are talking about. In the absence of charging current, the battery voltage is less than 13, yes. When it is charging, can it be less than 13V?
In MPPT mode when the batteries are low or if you have a moderate demand in addition to charging, you will definitely see voltages less than 13. In a previous post I was also talking about creating a high demand, beyond what can be supplied by the panels alone. Obviously the batteries are also discharging at this point and the voltage can/will drop below 13.
