Rogue MPT-3024 in Remote Cabin

BB.

Re: Rogue MPT-3024 in Remote Cabin

I am not sure what your question about low charge rates...

Assuming a 70 watt, Vmp=17 volt panel, and the standard rule of thumb of 5%-13% charge rate--we would recommend a battery capacity of:

• 70 watts * 1/17 volts * 1/0.05 = 82 AH
• 70 watts * 1/17 volts * 1/0.13 = 32 AH [fix to 0.13--typo]

So, just based on the size of the battery bank, a 70 watt panel would support around 32 to 82 AH capacity of 12 volt battery bank..

Load wise--say you want to run an AC inverter... For most people, their winter sun is around 2-3 hours per of "full sun" per day in winter and around 5-6 hours of sun in summer. A typical solar system is around 52% efficient (panel, charge controller, battery bank, inverter efficiencies):

• 70 watt panel * 2 hours of sun * 1/0.52 eff = 73 Watt*Hours per day
• 70 watt panel * 6 hours of sun * 1/0.52 eff = 218 Watt*Hours per day

So, roughly a 73 watt load would run 1 hour per day in winter and 3 hours per day in summer.

• 73 WH / 73 Watts = 1 hour per day
• 218 WH / 73 Watts = 3 hours per day

Running the battery dead, running it for long periods of time below 75% state of charge, deep cycling often below 50% state of charge all are "hard" on the battery (shorter life)....

Having too much load and too little solar charging is the typical earlier battery killing setup that most people end up with. First battery packs, usually, do not have long life with first time solar users. We always tend to under estimate our loads and over estimate our available charging power.

-Bill