Limited Space for Panels - Should I Go 24V or 48V?

[eric@psmnv]

We have a tiny cabin surrounded by trees, with only one spot free of significant shade. It has room for 3 panels. We're seriously considering the purchase of 3 x Solarever 370W Half-Cell Mono PERC panels, plus an MPP LV6048 6KW 48V All-in-One Inverter/Controller/Charger, and an EG4 Lifepower 48V 100AH battery. By "seriously considering," I mean I might order everything tomorrow.

Why that inverter? We want to run our 1HP 240V well pump on solar about 30 minutes per week. The MPP LV6048 is a split-phase unit that can do 120 or 240 without paralleling, and 6000W will be enough to handle the well pump and the rest of the cabin at the same time.

Right now the thing that concerns me is the idle draw of the inverter. With only 3 panels, I don't want to consume a big percentage of our generated energy just keeping the inverter running. I'm a fan of Will Prowse's videos and he's a proponent of 48V systems for cabins, but I've also read that 24V systems are better when it comes to idle consumption. (Not to mention safe for newbies to operate.)

Thoughts from the gallery would be welcome and appreciated!

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[organic farmer]

I know many off-grid homesteaders in my area.

The best system I have seen, is a 12dvc system from the 1980s. His house is completely wired for 12vdc. All his appliances, etc, are 12vdc. He uses car batteries that he acquires from a local junkyard for $10 each as 'core-charge' some are bad and some may still have 5 years of life still in them.

In 2015, when we were at the point to leap into solar power, we already had a 240vac wellpump and my wife insisted that she did not want us to replace it with a 12vdc wellpump. At that time the only inverters capable of producing both 120vac and 240vac were inverters that use 48vdc battery banks. So that pushed us into a 48vdc system.

We also know a few homesteaders who have very tiny solar systems, primarily to operate an AM/FM radio and to charge cellphones.

Good luck

[Ampster]

What is the idle draw of the invertter. Will the solar panels give you enough to run the pump once a week and cover the idle draw? Have you accounted for lower winter insolation?

[eric@psmnv]

What is the idle draw of the invertter. Will the solar panels give you enough to run the pump once a week and cover the idle draw? Have you accounted for lower winter insolation?

According the manual, the idle draw is "< 100 watts". I have reached out to the pump vendor to find out the power consumption and am waiting for a call back. I wouldn't imagine that 30 minutes of runtime would be a big deal. In terms of winter insulation, based on the historical data from VisualCrossing, there are about 20 days each year when the temperature gets down to freezing.

Question: Is idle draw only a factor that kicks in when there is truly no load on the inverter? Or is idle draw really more like minimum continuous overhead? For example, suppose the rated idle consumption is 100W. If I have a 20W light-bulb running in the cabin all night, is the inverter using 20W, 80W, 100W, or 120W during those night hours? (That's without considering efficiency yet.)

[Buck Rogers 2000]

Is this roof or ground mount? How many hours will the panels receive on December 21st? I have a 10 panel ground array, actually pretty primitive. My goal is to power a 1,500 watt heater for perhaps a couple of hours past sundown on the Winter Solstice. My limited understanding is that the voltage of the system is more for the surge amperage. 48 volt systems enable operation of air conditioners better than 12 volt systems. I'm just a novice geek though. My storage will be eight 6-volt, 416 ah AGM batteries hooked in series. Winter is the time where batteries go to die. The cold WILL wreak a toll unless you have a plan. My plan is to house my battery array in my garage. I may have to cover them in blankets but the draw I use in my home should keep them safe. Thankfully, my simple ghetto ground mount will be EASY to maintain! By now you probably made your purchase - WHAT YA GOT ?! Good luck!