Questions About New Small Setup

[DAVEPETERS239]

I have been trying to learn what I can about solar and thought I would post my questions here and hopefully get some advice on what I need.

So far I have four Renogy 100 watt Monocrystaline 12V panels and wanted to ask what the best charge controller and inverter would be for those panels.

This is just something I want to piece together and learn from doing.

Thanks

[SunEagle]

Hello DAVEPETERS239 and welcome to Solar Panel Talk

With 400 watts of panels and I presume a 12volt battery system I would suggest a quality 30Amp MPPT CC.

As for the inverter, depending on what your loads are a Pure Sine Wave type (while costs more) will be a better fit if your loads include any small motors (like a refrigerator) or electronics.

The last bit of info would be me asking you what battery system you plan on using? With 30amps of charging your 12v system should be rated between 240Ah & 360Ah. Based on that sized you should look into getting 2 x 6v 300Ah rated batteries and wire them in series.

Final question. Have you calculated your daily watt hour usage? Based on a 300Ah 12v battery you can safely generate about 900watt hours ( 300AH x 12V / 4 = 900wh) a day. If you need more then you run the risk of killing off your batteries why quicker then if you limit your usage to a maximum of 25% DOD each day.

[DAVEPETERS239]

I am unsure what I am really going to use it for, Will probably just plug in small fan and lights and maybe charge small electronic stuff to see what it can do. Living in Florida we have been pretty lucky in my area with no major storms or power outages but I would like to be prepared with a small system to at least power a fan and stuff should I need it.

I have watched a lot of youtube videos and have read quite a few posts and articles but the best way for me to understand is by actually doing it.

This is kinda where I get really confused also and am trying to learn about watts and volts and amps. What would be the difference between like a battery with 200ah and 300ah?

Would a large AGM Lifeline 12V 200ah battery work? There is a used battery someone has in my area and I was wondering if that would be good to start with for awhile? I think buying a used battery is risky but if the price is right and there is some sort of guarantee would that be ok? They are asking $99 for it.

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[Sunking]

Concorde is the best AGM battery made period and commands a high price when new. However ft used, price is the same as any battery, its salvage value in weight of around 15 to 20-cents per pound. That battery weighs around 120 pounds or about 18 to $20 worth.

The Lifeline series are excellent Marine batteries. 200 AH is about the right size with 400 watts of panels with a 30 to 40 amp MPPT controller. little small, but being AGM will handle the high charge rates. So if you can get it for $20, you do not loose much and can sell it for scrap to recover most of your losses.

Do you know how to Load Test a Battery? If it will pass a Load Test, the battery has some life left in it. Look at the Date Code, if it is over 4 years old, forget about it. 90 is out of the question. A good beginner battery for your setup will cost you $300 to $400 for 12 volts @ 300 AH. That 12 volt 200 AH LifeLine battery cost $600. Also note you get to replace batteries every few years.

Right now if you do not know yet, you need to cough up $200 to $400 for a good 30 to 40 amp charge controller on top of battery cost. Just keep in mind all those panels and the controller is not worth a dime to you if you do not have a good battery.

As for buying the battery, If it can pass a Load Test, and pay no more than $30, OK. $90 is insane. $200 more and you have a new 3 year battery. you will not get one year out of that used battery.

[SunEagle]

Well a 200Ah 12v deep cycle battery system can safely generate about 600 watt hours a day and a 300Ah 12v deep cycle can generate about 900 watt hours daily.

The problem with 12volt batteries bigger than 150Ah is that they get real heavy and expensive. We suggest you build your system using lower voltage batteries (like a 6V) rated at the Ah needed for your system and wire them in series to build a 12v system.

Based on cost an AGM is more expensive then a FLA type and should actually last longer. While the AGM can be charged and discharged faster then an FLA the cost and shorter life does not always make sense.

Now used batteries may work for a short time but will die a lot quicker then new ones. If your system can handle a non working battery for days then I would say you can experiment with one but if you really need power and the battery is dead you have to decide which is worse.

I also live in Florida and while I have 2 small solar / battery systems. I wish I had just spent the money on a good inverter type generator like the Honda EU2000 or Yamaha EF2000. Either of those would have been less then half of what I spent on my solar/battery systems and provide 3 times the wattage..

[PNjunction]

Heh, used batteries are the WORST choice for someone trying to learn the ropes. Since you don't know the history of the used battery, (frequently abused or worn out), you may falsely assume problems with your gear when the battery is entirely at fault.

A voltage shown on the terminals means *nothing* as far as battery health is concerned. Unless I personally know all the details about the battery (and if I actually trust that person), it is better to pass on it.