solar newbee

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Old 06-20-20, 12:07 PM
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solar newbee

I'm living/working at a remote site with only solar for electric. I know little about solar power or electricity.

I don't know what the specs of the panels are, but there is a bank of 3 smallish panels each one about 18" x 24 or 36" (don't feel like crawling on the roof to measure). There are two batteries, each says AJC D100S(T6) 12V 1200ah 10 Hour.

There is a Renogy Rover 40a mppt Charge Controller and a Renogy 500w Pure-Sine Wave Inverter. I have an app that I don't fully grok but it appears to show that the panels are generally running at 40% to 60% capacity during daylight hours, which are usually partly cloudy.

I would like to figure out what I can and can't run off of this pooch. It hasn't had any trouble running my 90w laptop charger during the day. In particular I'd like to know whether I'll be able to run a decent box fan off of it at night, and all night, when batteries are not charging, since its going to get quite warm here. I don't need to charge my laptop at the same time, but it woul be nice to know if I could without overdischarging or something else bad happening.

 
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Old 06-20-20, 12:13 PM
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Welcome to the forums.

Right off the bat you know your limit is 500 watts as that is the size of the inverter.
That inverter looks to be fairly good based on it's write-ups.

Do you have a voltmeter connected to the batteries ?
That would be a help in determining battery status.
 
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Old 06-20-20, 12:45 PM
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I have a multimeter and the controller app. The controller will sound an alarm if the batteries overdischarge.

But I need to avoid that. There is a 2-way radio I need to run during the day that MUST have available power. I can't find the model or specs on it, but I can't imagine it draws much except when transmitting and I won't even have it on at night when I want to run a fan. But I cannot overdischarge at night and then not have radio power in the morning. That is what I MUST avoid.


 
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Old 06-20-20, 01:19 PM
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I'm guessing from looking at similar models the radio is only 50w.
 
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Old 06-20-20, 02:50 PM
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You need to know two things; how much power the solar panels are putting into the batteries each day and how much you are drawing out of the batteries. The consumption is easy to figure by adding up each devices draw multiplied by how long it is used. How much gets put into the batteries can be estimated if you can measure the panels size to guess at their output. Then online there are solar estimators that can help calculate the output based on your location. Obviously panels on the equator will generate more than the same panels installed in Yukon.
 
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Old 06-20-20, 04:52 PM
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A 50w two-way radio would use approx 1/2 to 3/4 of an amp while sitting there in monitor mode.
When you transmit it will use approx 5-6 amps.
 
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Old 06-20-20, 05:57 PM
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So help me out here, since I'm not electrically inclined. What information do you need that I haven't already provided? I've given a pretty accurate guess at the size of the panels, the inverter rating, the specs of my radio, laptop charger and estimated wattage of a box fan. I"m not going to buy one unless I know it will work, so I can't provide anything more specific. It'll just be your run of the mill Walmart floor/box fan.

 
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Old 06-21-20, 08:12 AM
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https://www.youtube.com/watch?v=6CSYFf7wAv0

This guy powers a box fan with only 1 panel (I think my panels are the same size, so probably 300 watts total). Of course the sun is shining, and I want to run my fan off the 2 batteries at night so it doesn't quite answer my question.
 
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Old 06-21-20, 07:13 PM
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so your looking at around 6 amps being consumed from the batteries witch are both 100 ah and probably hooked up in parallel so you have a 200ah 12 volt bank witch I am assuming is fully charged, should be able to run about 26 hours on the batteries before they are discharged completely or around 13 hours to 50 percent do not really see any reason you could not run a fan assuming your solar panels do put out enough to recharge them back up during the day.
would probably suggest doing voltage checks on your batteries after sun has went down to get an idea on there lvl of charge and do this over a week and just see if the solar is keeping up.
 
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Old 06-21-20, 11:02 PM
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I have the app that monitors the system, but what am I looking for? Just voltage or battery capacity or both? The batteries get fully charged if its a sunny afternoon. I left at noon as clouds were clearing and came back at 8 pm and they were fully charged, voltage was showing 13.1.

The sun set an hour ago and I've been running/charging my laptop for maybe half an hour. The app says the batteries are at 83% capacity and voltage is 12.7. Usually I just charge it during the day and use the battery at night, but forgot to charge it today.
 
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Old 06-22-20, 12:44 AM
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your app is probably working fine would just use it, voltage can give you a rough idea of state of charge but there is some slight differences between battery types like flooded lead acid and agm and gel and usually the voltage is checked in an open state so there is nothing hooked to it other than a meter if your app is calculating it while its been used state of charge may not be to accurate as the voltage will be pulled down more.

 
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Old 06-22-20, 08:17 AM
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The problem is the app doesn't do me much good while I'm sleeping, and that's the main thing I'm worried about is overdischarge at night with fan on and waking up to find the radio won't work. The overdischarge alarm will probably wake me up but by that time its probably too late.
 
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Old 06-22-20, 10:01 AM
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You just need to do the math. Get the wattage for everything you want to run. Multiply the item's wattage by how many hours a day you will run it. Once you've done that for everything you'll know how many watt hours you consume in a day.

Then look online for a solar estimator for your panels. This will vary depending on your panels and your location. This will give you a rough idea of how much power your panels can generate in a day. You can get even more accurate by figuring in the efficiency loss through the charge controller into the batteries and then the loss from the batteries through the inverter.

The batteries are sort of unimportant because if your consumption is greater than what the panels can put in the batteries you will discharge them eventually no matter their size. The batteries are important though because they get you through the night and hopefully are large enough if you get a few days of storms and your solar generation takes a big drop.
 
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Old 06-22-20, 11:59 AM
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could probably just set you alarm on your phone to go check on it state of discharge is what you really want to worry about cause you still want to be able to run the radio shouldnt have any issue at 30 to 50 percent discharge still have power left to use the radio you do typically see shorter battery life the more you discharge the batteries and recharge them meaning batteries only discharged to 30 percent should last a lot longer than batteries discharged to 50 percent or more.
 
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Old 06-22-20, 06:41 PM
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According to this site https://www.wholesalesolar.com/solar...rid-calculator

I can run a 100w box fan for 9 hours a day with 3 100 watt solar panels. If I run it 10 hours I need another 100 watt panel.

I doubt the box fan will actually use 100 watts. The one I bought yesterday seems to be a .5 amp fan.

Plus that site uses yearly average daylight hours and my site was just over 5 hours, but my location should get a lot more than 5 hours a day on the summer days that might require me to use a fan at night.

So it looks like I should be good unless I get hot or humid cloudy days where I also want to run it during the day. Then I might be in trouble.

But I think I'll do a test some night where I don't really need it, to see how much it runs the batteries down after a few hours.
 
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Old 06-29-20, 07:38 AM
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TTesting the usage of electricity stored in the batteries will help you determine how much electrcity is consumed by the fan. However, i think the fan will not take much of the energy, These type of fans consume less energy.
 
  #17  
Old 06-29-20, 08:20 AM
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I ran it at low speed one night and it hardly drew the batteries down at all. Think it will be fine
 
 

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