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2002sheds

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Posts: 12
Reply with quote  #1 
Hi All,

Total newbie here. I apologize if these questions have been covered -- I just couldn't find it in the search...

My setup is to be used primarily in the event of power outage or for camping. So far, I have:

* 2 Interstate Deep Cycle Extreme golf cart batteries rated at 225ah and connected to create 12 volts.

* 100 watts, 18 volt solar panels (Harbor Freight). Based on their exposure, I am averaging 2.25 amps/hour.

* PWM charge controller from Amazon.

* 5,000 watt inverter (non pure sine wave).

Despite no load beyond the charge controller, the most I have been able to charge the "battery" over the last 5 sunny days using just the solar panels is to 72%. This drops off overnight to the mid 60% range. The inverter has been turned off, but the charge controller has remained connected.  Is some of the loss of voltage overnight due to the controller being connected? How much (of that loss)?

I plan on replacing the panels with one 435 watt (85.6 VOC, 5.97 amp) panel from SunPower (I am getting the panel for free from a friend). I will be buying a MPPT charge controller that will be rated for up to 100 volts.

Will these changes help get the battery charged to full ? 

And a more basic question:  If the charge controller is reading that the battery is at 70% capacity, what is it relating to in terms of how many amps are in storage? is it 70% of 225? Or ???










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May All Your Days be Sunny,
David

stmbtwle

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Reply with quote  #2 
IN MY OPINION (others may disagree)

Solar for power outages isn't a good idea.  Your batteries will hold less than 2 Kwh of power in an emergency.  That won't get you much.  At full load your inverter MIGHT run for half an hour.  Running a few LED lights and a fridge, maybe overnight.   Yes you can install more batteries and more solar panels but this runs into a lot of money, just for the occasional power outage.  A small gas generator will give you a lot more power for a lot less money.  Two years ago we used a Honda 1000 during Hurricane Irma... it would run for hours on a gallon of gas.  We ran the fridge with it for a good two days.  I've since "upgraded" to the 2200, but it's a lot heavier (and noisier).

For camping... have you looked at the dimensions of that 435w panel?  My guess it's too big and too heavy for "camping" unless you're talking about bolting it to the top of an RV.  Even then, unless you park in the sun (I like shady spots) it's useless.   I would consider buying a couple more of those harbor freight panels and connecting them to what you already have.  They'll fold up nicely, and should keep your batteries charged without that expensive MPPT controller.  Make a portable mount for them and a LOOONG power cord so you can set the panels in the sun and move them about as necessary.  Or simply use the generator mentioned above.

It's my guess that your controller is working as intended.  If properly connected they will not discharge your batteries. However it can take a LONG time to charge a couple golf batteries if they are low.  

Good luck and keep us posted.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
2002sheds

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Posts: 12
Reply with quote  #3 
Hi Willie,

Thanks for responding -- I appreciate it !!   I am definitely new to all of this, and I fear that I have not done a very good job of explaining what I am trying to accomplish.

For me, the generator is really loud -- especially while camping. I also don't understand how a 1,000 watt generator  (I have one as well) would provide enough power -- which is probably more ignorance on my part...    and I didn't mention that we have two houses on our property , so all loads are doubled (and actually more, since the Mother in Law unit has a chest freezer)... As I compared the price of a larger generator, I kept coming back to the idea that this setup will be mostly used for camping -- in a pop up camper for now and eventually an old Airstream with a medium sized multi-fuel fridge. Probably more than a little wishful thinking :-)

I totally agree about the 435 watt panel size. It is WAY too huge for anything but stationary use, in my opinion. I think you are spot on about the portable panels, but that kind of leads me back to my original question(s):

I know how to calculate basic things like how many amps (or watts) the different devices will use, but I am quite clueless as to how to read the rate at which the battery is charging/discharging -- especially throughout the day, without any load on it (our power is back on -- I am planning ahead). If I go by my PWM controller, I am adding around 2.5 amps per hour of sunlight (about 6). Today the controller read that the battery was as much as 92% charged (maybe I am reading this wrong?) at mid-day, and around 70% at around 4 p.m. I am too inexperienced to understand why the battery would lose that much charge...

What looms even larger is my lack of understanding about how much power my battery has, fully charged. I get that a 225ah battery can provide 1 amp of power for up to 225 hours, but is there a measure that is easy to relate to in total?  For example, a 225ah battery charged to 75% has X amount of energy available, at 50% the number is Y, etc...  and the same goes for the amount of time/amperage needed to recharge that battery, so I can understand what size of panel array is needed to recharge the battery durning the day. And why is the state of charge (sorry if I am using the wrong term here) is expressed in the number of volts (for example, 12.8 volts or 12.5 volts). How does that relate to how full/depleted the battery is?

I know that some of these numbers are moving targets, but I am so new at this that I am hoping that someone can really dumb this down to my level :-)


Thanks,
David
 

 

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David
stmbtwle

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Reply with quote  #4 
A solar/battery system that will carry two homes for extended periods will cost you MANY THOUSANDS of dollars.  For short periods you can skip the solar system and just use batteries, charging them from the grid when it comes back on.  Still, batteries are expensive and may require maintenance.

For power outages about the only thing that makes sense is a generator.  If your only choice is spoiled food or a generator, you'll learn to live with the noise, trust me.  And there ARE quiet generators out there.  Even a small 1000 honda will run a fridge, the 2000 watt will run two, and a few lights.   They're both pretty quiet (little more than a hum) and can be had for under $1000.  Also bear in mind that the BIGGER the generator is, the more noise it will make.  How SPOILED are you?  During Irma we would run the fridge for a couple hours, then unplug it and run the TV and satellite dish for two hours.  All on a tiny 1k Honda.  For lights we used oil lamps and candles.   For cooking we had a 1-burner camp stove.  

"Camping" is a whole 'nother ball game.  For some it's a tent, a lantern and a camp stove.  You don't even need electricity.  For others it's a 40' RV with all the comforts of home.  Which are you?


The easy way to calculate how much  power you need to run a certain device on 120v is a "kill-a-watt" from the home store or online.  You plug it into the wall, and then plug the device into it.  It will tell you how many watts your gizmo requires.  If left on for several hours (as with a fridge) it will tell you how much you need over time.  (some devices will surprise you).  Then add up everything and start figuring what you can live without.
https://www.amazon.com/P3-International-P4460-Electricity-Monitor/dp/B000RGF29Q/ref=asc_df_B000RGF29Q/?tag=bingshoppinga-20&linkCode=df0&hvadid={creative}&hvpos={adposition}&hvnetw=o&hvrand={random}&hvpone=&hvptwo=&hvqmt=e&hvdev=c&hvdvcmdl={devicemodel}&hvlocint=&hvlocphy=&hvtargid=pla-4583795260952595&psc=1


The best way to keep track of your batteries and DC consumption is with a "battery monitor" but they can get pretty expensive.  On the low-budget side I'd consider this:
https://www.ebay.com/itm/Voltmeter-Ammeter-DC-120V-500A-Voltage-Current-Gauge-RV-Boat-Motor-Camper-CAR/142562930896?_trkparms=aid%3D333200%26algo%3DCOMP.MBE%26ao%3D1%26asc%3D59957%26meid%3Ddbf9860ec67549dc8020fad9dc398761%26pid%3D100008%26rk%3D3%26rkt%3D12%26sd%3D252609495578%26itm%3D142562930896%26pmt%3D1%26noa%3D0%26pg%3D2047675&_trksid=p2047675.c100008.m2219

Bear in mind you need a meter that can monitor charge AND discharge (or two separate meters), and that your inverter can pull up to 400 amps.

Re your battery voltage.  When you are charging your battery, the voltage will be higher.  After it sits for a while the voltage will drop some, even with no discharge at all.  This is normal, and may be what you are observing with your charge controller.

__________________
Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
2002sheds

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Posts: 12
Reply with quote  #5 
Hi Willie,
     
Thanks for the response!  I feel like I am getting somewhere, thanks to your help. To answer your questions (or comments):

I don't hope to fully power 2 houses during the occasional power outage. The only things that we would want to power would be the two fridges (and not 100% of the time), a chest freezer (also not 100% of the time), a few lamps with LED light bulbs, and that is about it. 

Although I feel as if I know the energy consumption of these devices, i will definitely get a Kill-a-Watt to be sure -- great idea!

As far as the generator, I have one -- it is a 1,000 watt model, and I ran it during a previous outage. Like you said, it can power some things, not all. Since I am not a fan of the noise, taking it (or a larger generator) camping -- the main use of the system I am writing about -- is not something I would do. I used to tent camp only, and have moved to an old Coleman tent trailer and someday maybe a 1970 Airstream that we bought a few years ago (if I ever get it fixed up, that is). I hope to use solar/battery for the water pump, refrigerator, a few LED lights and occasional AC (if the setup is powerful enough) Thankfully, our climate is usually cool in the evenings, so I may not need to test that last possibility.

As far as the question of how spoiled I am, I guess the answer is that I am semi-retired and live in Northern California... so plenty :-)

Thanks for the explanation of how the batteries (connected as one 12v battery) can charge and discharge. I have a ton to learn about this  -- for example, how did you arrive at the number of KW the 225ah battery can hold? 225 times 110 is 2.475 kw, but I am sure I am looking at the wrong numbers. Likewise, should I use a Kill-a-Watt device to determine how much amperage the inverter -- mine is 5,000 watts/ 10,000 watts peak -- uses? 

And I am still unclear about the 14.4 volts (fully charged) as a measure versus, for example 13 volts. Can this be expressed as a percentage? Of what -- 225 amps, or ???


Thanks,
David





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May All Your Days be Sunny,
David
stmbtwle

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Reply with quote  #6 
A 6v, 225amp hr holds a MAX of 1350 watt hours (6*225). Two of them, 225*6*2 (2700). I use the easy rule of thumb of 1 kwh per regular-sized battery or 2000 watt hrs for the pair.  In an EMERGENCY you might get this much energy but it could damage the battery.  It's not recommended to regularly go below 50 %, so you wouldn't want to use more than about 675 watt hrs per battery or 1350 for the pair.  Again, I'll use that conservative rule of thumb so you'd get 1kwh (usable) per pair.  This should allow for wiring losses, etc.

The kill a watt doesn't work on 12v so you couldn't use it to check how much your inverter uses.  HOWEVER you CAN use it to check your inverter's 120v OUTPUT and  convert.

Assuming your inverter inputs 12v from the battery and outputs 120v AC, it's a simple factor of 10.  If the Kill a watt measures 10 amps at 120v, that means the inverter is drawing 100 amps.  120v * 10 amps =1200 watts = 12v x 100 amps.  Actually it would be a little more than that due to inefficiencies in the inverter.

So... if you're drawing 10 amps at 120v, that's 1200w.  You're good for about 1 hour for those two batteries (maybe two in a pinch).  If you add up how much each house uses, you're going to need a LOT of batteries ($$$), and a LOT of solar panels to charge them (more $$$).  Now you see why I recommend the generator.

My house is grid-tied.  The PV array (installed) cost me $20,000 after rebates plus another $5000 for the solar water heater.  Since "she" moved in, it covers about 70% of my total electrical usage.  

Now for the camper.  We have an A-liner, not a whole lot different from a pop-up.  I converted ALL the lights to LED and put a 12v "create-a-breeze" fan in the roof.  The stove and fridge run on propane.  I run all the 12v electrical loads on single 12v marine deep cycle battery.  To charge it I have a single 60w PV panel on a long cord, with a PWM controller stuck to the back of the panel.  I set the panel in the sun and prop it up with a couple sticks, and plug the cord into a 12v accessory outlet on the camper.  Turn the panel from time to time as the sun moves.   Works just great.   The battery is probably good for a couple days of bad weather.  

Hint: You can get standard automotive-base LED bulbs on Ebay for about a dollar apiece.  Simply remove the old bulb from the 12v fixture and insert the LED.  Done.  


__________________
Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
2002sheds

Registered:
Posts: 12
Reply with quote  #7 
A 6v, 225amp hr holds a MAX of 1350 watt hours (6*225). Two of them, 225*6*2 (2700). I use the easy rule of thumb of 1 kwh per regular-sized battery or 2000 watt hrs for the pair.  In an EMERGENCY you might get this much energy but it could damage the battery.  It's not recommended to regularly go below 50 %, so you wouldn't want to use more than about 675 watt hrs per battery or 1350 for the pair.  Again, I'll use that conservative rule of thumb so you'd get 1kwh (usable) per pair.  This should allow for wiring losses, etc.

The kill a watt doesn't work on 12v so you couldn't use it to check how much your inverter uses.  HOWEVER you CAN use it to check your inverter's 120v OUTPUT and  convert.

Assuming your inverter inputs 12v from the battery and outputs 120v AC, it's a simple factor of 10.  If the Kill a watt measures 10 amps at 120v, that means the inverter is drawing 100 amps.  120v * 10 amps =1200 watts = 12v x 100 amps.  Actually it would be a little more than that due to inefficiencies in the inverter.

So... if you're drawing 10 amps at 120v, that's 1200w.  You're good for about 1 hour for those two batteries (maybe two in a pinch).  If you add up how much each house uses, you're going to need a LOT of batteries ($$$), and a LOT of solar panels to charge them (more $$$).  Now you see why I recommend the generator.

My house is grid-tied.  The PV array (installed) cost me $20,000 after rebates plus another $5000 for the solar water heater.  Since "she" moved in, it covers about 70% of my total electrical usage.  

Now for the camper.  We have an A-liner, not a whole lot different from a pop-up.  I converted ALL the lights to LED and put a 12v "create-a-breeze" fan in the roof.  The stove and fridge run on propane.  I run all the 12v electrical loads on single 12v marine deep cycle battery.  To charge it I have a single 60w PV panel on a long cord, with a PWM controller stuck to the back of the panel.  I set the panel in the sun and prop it up with a couple sticks, and plug the cord into a 12v accessory outlet on the camper.  Turn the panel from time to time as the sun moves.   Works just great.   The battery is probably good for a couple days of bad weather.  

Hint: You can get standard automotive-base LED bulbs on Ebay for about a dollar apiece.  Simply remove the old bulb from the 12v fixture and insert the LED.  Done.


 Hi Willie,
      Thanks again for the response and patience. I feel as if I am finally starting to get it...

If I am understanding you correctly, I am limited to about 1,350 watts/hour with my existing setup (without any input from the charging side). If I am using nearly 1,000 watts to power those fridges, I will quickly "empty the tank", battery-wise unless those watts are being replenished at the same rate, if not faster. Is this correct so far?

As I mentioned in my earlier response, a friend of mine is giving me two 435 watt SunPower panels. I also have the 4 Harbor Freight panels 
totaling 100 watts, and another 45 watts worth of panels from an older Harbor Freight setup.        

Quick question: The big panels deliver 86 volts, the 100 watt panels come in at 18 and the 3 small panels deliver 45 watts at 12 volts. I was told to not bring different voltages to the controller, so I disconnected the 45 watt setup for now. Can I run the small group of panels through its own controller and then connect to the battery? Same for the larger panels (I realize that I need a larger capacity controller)?

I am starting see what you mean about the generator. Even with 4 times the number of batteries I may not have enough to power those devices -- certainly not all night...


Thanks,
David




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May All Your Days be Sunny,
David
2002sheds

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Posts: 12
Reply with quote  #8 

Hi Willie,
Thanks again for the response and patience. I feel as if I am finally starting to get it...

If I am understanding you correctly, I am limited to about 1,350 watts/hour with my existing setup (without any input from the charging side). If I am using nearly 1,000 watts to power those fridges, I will quickly "empty the tank", battery-wise unless those watts are being replenished at the same rate, if not faster. Is this correct so far?

As I mentioned in my earlier response, a friend of mine is giving me two 435 watt SunPower panels. I also have the 4 Harbor Freight panels totaling 100 watts, and another 45 watts worth of panels from an older Harbor Freight setup.

Quick question: The big panels deliver 86 volts, the 100 watt panels come in at 18 and the 3 small panels deliver 45 watts at 12 volts. I was told to not bring different voltages to the controller, so I disconnected the 45 watt setup for now. Can I run the small group of panels through its own controller and then connect to the battery? Same for the larger panels (I realize that I need a larger capacity controller)?

I am starting see what you mean about the generator. Even with 4 times the number of batteries I may not have enough to power those devices -- certainly not all night...


Thanks,
David

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May All Your Days be Sunny,
David
stmbtwle

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Reply with quote  #9 
Yes, you pretty much have it figured out.

You could connect both arrays to the batteries BUT you'll need two separate controllers, one for each system.

The two fridges won't use 1000 watts continuously they'll cycle on an off according to load. There IS a possibility that they'll both be on at the same time and you'll have to prepare for that. AVERAGE power will probably be more on the order of 200-300 watts. This is why you need the kill a watt. Plug a fridge into it and let it run normally for 24 hours. Note the STARTING load in watts (you have to be quick), the RUNNING load in watts, and the watt-hours consumed over the day. Dividing the watt hours by the hours will give you the AVERAGE watts. The starting load is the MAXIMUM. Separately add those loads to the corresponding loads from the other fridge and any other devices you will be running. The STARTING TOTAL is the absolute maximum surge load your system might have to deal with when you first throw the switch and everything comes on at once. If your system can't handle it then you will have to start your equipment at different times. The AVERAGE TOTAL helps you estimate consumption. If your average is say 300 watts and you have 1350 watt hours in your battery, then you'll get 1350/300 or 4-1/2 hours (probably less as battery performance is not linear). So for 24 hours you'd need SIX TIMES as many batteries.

Now you have to charge them. What your batteries deliver in a day needs to be replaced in maybe 5 hours of good daylight (this varies). So, if your average load is 300 watts, you're using 7200 watt hours per day (300*24). 7200wh/5h = 1440 watts you will need in solar panels (in theory). The sun is not always directly overhead and sometimes the weather is crappy, so in reality you'll need quite a bit more. Go to https://pvwatts.nrel.gov/pvwatts.php for a better estimate.

Of course, you're dealing with power outages instead, so you have to guess how long the power will be off (your call)

There is a gizmo called an inverter-charger, it will automatically recharge your batteries when the power comes back on. They're not cheap, but are probably cheaper than the solar panels you'll need.

A note  on power failures vs full-time.  If it takes 2,3,5 days to recharge your batteries, no problem as long as the power doesn't go out again (your call)  So you can save some $$$ and undersize your solar array somewhat. You can always add more panels later as long as they're the same type.

And you'll STILL need that noisy generator for backup.


__________________
Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
2002sheds

Registered:
Posts: 12
Reply with quote  #10 
Hi Willie,
     Okay, I finally get it [smile]  Fortunately, the store accepted the 2 golf cart batteries as a return since it was a recent purchase and these had not been installed in a vehicle.

    I have now turned my attention to which generator (or generators)  will be the best solution for the occasional power outage (with the option to bring along while camping).

   I did not know that a difference of 3 decibels is roughly 3 times as loud (or less loud). There are many options that don't fall into the skull rattling category that had turned me off to these machines years ago, so that is shaping up to be a productive search.

     And I still have my original solar panels and deep cycle battery for camping, so none of it was a waste -- especially since I now have a better understanding of how to calculate the system's capabilities, thanks to you !!!


David

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May All Your Days be Sunny,
David
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