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Modern Solar System - Practical Information from a Newbie
There is a lot of information regarding solar usage and I thought I would put in my experiences as a newbie to solar.
Current System:
520 watt MPPT solar system installed - Can bring in up to 40A
4 X 100AH Group 27 Batteries Lead Acid
All systems in the motor-home are 12V (including TV's and USB Charging Stations) except for the AC, Microwave, 110 Plugs, Fridge on AC Mode)
The solar system and the batteries were installed a week ago. I have a decent monitor that tracks most of the useful data.
This has been my experience so far.
The Controller:
Assuming there is enough power coming in the solar controller tries to do 3 things:
1. Keep your batteries charged using similar algorithms to your standard 3 stage charger. (less volts when they are full, more volts when they need to be rapidly recharged)
2. Provide additional amps to meet the current usage to offset the batteries being drained.
3. Boast your charge when the sun is going down to have enough power to get through the night.
Low Light Efficiency:
A common misconception is that solar panels work with sunlight while they in fact work in daylight.
I live in Canada, its winter, the sun is generally low on the horizon. The temperature has been around -7C to Plus 7C. Mix between sunshine and clouds.
Under ideal conditions the System would provide up to 40A (as needed), but in reality nobody camps in ideal conditions.
Solar Power under the worst conditions:
At dusk when the sun is low on the horizon (close to being lower then the panels) there is still power being create.
There is no condition that I have found (shade level / sun height) where the system doesn't work at around 5% - 10% of the 40Amps. Meaning that if there is 8 - 10 hours of daylight I can expect in ANY conditions to at least get
16AH - 40AH in a day.
I believe that in everyday usage it would be unusual to have a 3 day average of less than 100AH per day (I have not been able to test this yet as my batteries have remained charged and not required more than 20AH in a day).
Power Usage:
If we are boon-docking and are attempting to conserve power:
- LED lights as needed
- 24 Hours Propane Fridge (Still has dc power draw)
- 24 Hours of Parasitic draw (CO Detector and other small things)
- .5 Hours of Water Pump
- No furnace / fantastic fans at all
- No TV
- USB charging as needed
The above usage is about 33 - 50 AH per day. In almost any light conditions the solar panels are able to meet the demand and the batteries can supplement as required.
Under realistic conditions we use around 80 - 150 AH per day. Realistically I think we will average around 60 - 130 AH provided by the solar panels per day (based on this last week with less than ideal conditions).
I designed this system to last 2.5 - 3 days in realistic light condition with realistic usage. The reason why I picked 2 - 3 days is:
1. We don't have a toad and will likely have to drive the motorhome to go someplace which will start the batteries charging.
2. Our grey and black tanks are 28 Gallons and will probably need to be dumped causing us to have to drive the motorhome.
3. Its unlikely that 3 days will go by without the wife wanting to run the genny for the microwave or the AC.
Other things I took into consideration:
1. 12 Volt Appliances are superior to AC Appliances using an inverter. Some inverters waste up to 1 Amp meaning that in 24 hours it will use up half the usable AH of a standard deep cycle battery. The AC appliance also uses more power then its DC counterpart. This is especially true of TV's. This board is full of people using inverters to run their TV. You are better off buying a 12Volt TV with a car adapter and plugging it right into your 12 volt system.
2. Using an inverter to run your AC fridge is just not practical for most setups. AC fridges (small ones not residential sizes) use around 40AH at 12volts. In our system with 4 batteries we have a 200 usable AH, this means that at night when we don't have solar power the batteries would be drained in 5 hours. To make this practical you need at least 2000AH (or 1000 usable AH) - Thats 20 Deep cycle batteries, to last you for a day (maybe 1.5 days with solar power) - Who has room or the CCC for that.
3. You can't run your AC off your batteries (see point 2) If you have unlimited money check out lithium ion batteries it might work.
4. Most of your power usage is at night when their is no solar power. Make sure you have enough capacity to make it through. A battery upgrade is probably the most important part of a solar upgrade. A battery upgrade is also the most cost effective way to extend you stay without a genny or solar.
5. No matter how much solar power you have your batteries can only charge so fast.
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2016 Sunseeker 2650
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Linear Mode
