48 volt all in One system....need advice on how much of a solar array - I have budget for 1800-2000 watt solar array - is that to much?

NomadRogue

New Member
Will; I want to get the 48volt all in one system and have 18feet by 8.5 room on cargo trailer. I want to be able to run a/c such as a min split. I am think if I have a solar array of 1800 I would be good to go but can I used 2 batterys versus 4??????I'm really lost....I thought I wasn't when watching your videos but then the DC converter threw me for a loop. I'm just slow on the draw I guess. The other question is installing the system. Once installed where do all the wires go from within the camper conversion to what panel (or do I need a separate electrical box with one wire going into the solar?
 

MichaelK

Photon Sorcerer
The number of panels you use depends on the size of your battery, it's voltage, and the relative positioning of your panels. Different kinds of batteries are charged at different rates, typically 1/8C for lead-acid, 1/5C for AGM, or 1/4C for Li. C is the 20hour amphour capacity of your battery.

The maximal charging amperage usually occurs at about 13V for a 12V battery, 26V for a 24V battery, and 52V for a 48V battery. That's not going to be the maximal voltage the battery will see, but the voltage when the battery is charging at about maximal current.

In addition, you usually put in a fudge factor for system losses. For panels pointed directly at the sun, the FF might be 0.85X. For panels mounted flat, with lower output, the FF might be 0.6X.

So, for example, here is the panels needed for charging eight 6V 225Ah lead-acid batteries wired in series for a 48V bank.

[225Ah X 1/8C (0.125) X 52V charging] / 0.85 = 1462/.85 =1720W of panels

So, your question can't be answered until YOU specify what type and how big the batteries you have are at your system voltage.

The second question you should be asking is whether or not your battery bank is large enough to support the running of this air-conditioner. It will improve things a lot if you can specify how many watts the unit consumes while running.

In general, the wires from the panel strings first enter a combiner box, then the output of the combiner goes to the controller, then the output of the controller goes to the batteries, and the batteries go to the inverter powering the air-con. Wire gauges changes at each step depending on how much current they are carrying.
 

NomadRogue

New Member
Michael,

Thank you for your response but what you said I only understood a little bit. I'm very ignorant of solar use and power. I do know that I'm going to use the 48volt package that Will suggests......which I will be using two 24 volt battle born batteries in parallel I believe with room to grow for another two batteries of same size down the road. My solar array - I'm looking at the 400 watt solar panels as I can fit 5 of them on the roof of the enclosed trailer - does that help? I will be running an economical min split - not sure which kind as of yet. I'm also going with a standard residential fridge/freezer 7.2 cubic feet......the rest of my appliances will be used sparingly such as the micro wave for pop corn or to warm something up. I will have a tv (preferrably 12 volt, 2 water pumps - for grey water and shower/sink. I will be using a composting toilet so need for black tank just a fresh water tank and grey tank. I have an electrician friend that can do all the electrical but we both need guidance on solar. So I am attempting to do as much as I can without driving him nuts in the process and again - I have very limited knowledge. I have figured out from googling I need to keep electrical usage as low as possible but I'm still going to need A/C now and then due to health conditions. generator now and then
 

MichaelK

Photon Sorcerer
Even a little air-con is likely to use at least 500W. Maybe 500W for the first hour or two, and then maybe 250W cycling on and off. A small frig/freezer maybe 200W, consuming maybe 800 Wh over the course of a 24hr period.

Add up the wattage of the appliances, and how many hours you will use them and convert that to Watthours (Wh). A 100W lightbulb on for three hours consumes 300Wh. A 100W lightbulb left on for 10 hours consumes 1kWh.

Assume that your 2000W of panels laying flat on the roof will only output maybe 60% of nameplate wattage, so your 2000W of panels is actually 1200W. In winter, with 3 sunhours of light you are likely to make1200W X 3sh =3600Wh total. In summer with 5 sh then 1200 X 5sh = 6000Wh.

The problem with having 5 panels is that you most likely can only wire them in a 1S5P configuration, so unless the Vmp is >58-60V you can not charge a 48V battery bank. Four panels could be wired in 2S2P. Three could be wired in 3S1P. Five panels in series most likely exceeds the Voc of most charge controllers, so 5S1P is likely not doable.

I'd say the configuration with the highest likely-hood of success is four panels in a 2S2P wiring configuration. It will help a lot if you can first get the nameplate specifications off the back of the panels. Working with the real numbers will be much better.
 
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