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Does any know or can direct me to a site that provides the number of sunlight hours here in Ajijic? I have found Guadalajara but I think they get more cloud than we do. I am a DIY er and that info would help me determine the number of panels I need to charge my battery, the house backup battery that is ...

I only want to provide backup for essential utilities when the power goes out. Mainly the garage door opener and the water pump which only run occasionally and maybe squeeze in the refridgerator. I am going to set up another fuse box from the main panel with only the circuits that I could use when the power goes out, probably around 6. Power outage rarely exceeds 12 hours so I have to factor that into the equation for what I want to do.

I have considered a generator but in the final analysis I dont want to disturb my neighbour’s peace nor my own, although it is a lot simpler and cheaper.

I am now the proud owner of a 115ah deep cycle battery and a 150 solar panel which I tested as putting out 21 volts in the sun so I’m happy. Its giving me 10ah so knowing how much sun we get would help me decide if I should hook up another panel. 

This is a beginning of a fun project.

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The daily UV curve chart is also really useful as a proxy for solar radiation / power; the bottom right of the 6 charts on the page:

You should use a charge controller with the setup mentioned.....did not see that in the OP's post:

vws752.jpg

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2 hours ago, Go Solar said:

The daily UV curve chart is also really useful as a proxy for solar radiation / power; the bottom right of the 6 charts on the page:

You should use a charge controller with the setup mentioned.....did not see that in the OP's post:

vws752.jpg

Of course, I didnt want to complicate the post with all the other components I need including the most expensive item, an inverter with full sine wave output because I want to run motors. The one i am looking at cost 8000 pesos and i havent bit the bullet yet ...laugh.

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Color me curious, but..... how do you define "sunlight hours"?  If a day is partly sunny or partly cloudy do all the hours count?  Also, what kind of solar panel do you have.... some are better at producing usable current in 'cloudy' conditions than others. 

Now color me skeptical.... I doubt very seriously one is going to be able to 'predict' just how much sun is going to strike your panel at your location on any given day/week so as to help you make a decision as to how many panels you will need. Your configuration will absolutely keep your battery topped off and waiting to be drained. One 115 Ah battery, fully charged, will surely give you enough energy to run some lights and maybe the frig, if you run it in economy mode,  but you mentioned motors with an "s" and IMO one 115aH battery won't get you through 12 hours running multiple motors and lights and maybe a computer or TV or ?

To me the question is not 'how much sun will I get' but rather do you have enough battery to run what you want for up to 12 hours. AND, will that one panel recharge your battery from 'drained' to 'fully charged' in time for the next outage. The first part of that equation can easily be tested. The second part will depend on 'how much sun' you are lucky enough to get right after a depletion.

 

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A good "rule of thumb" used for grid-tied systems at lakeside, is a daily average solar kWh production of 4.5 to 5 times the system size in kW.

So a 1 kW system (4 x 250 watt or 3 x 330 watt panels, or equivalent) with an appropriately sized inverter(s), can give an average daily yield of 4.5 to 5 kWh.

YMMV, and yes, we know there are far more than this # of sun hours in a day; this method takes into account both typical system losses and weather factors on a year-round average basis - and is well proven.

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On 10/2/2019 at 2:59 PM, RetiredTraveller said:

Does any know or can direct me to a site that provides the number of sunlight hours here in Ajijic? I have found Guadalajara but I think they get more cloud than we do. I am a DIY er and that info would help me determine the number of panels I need to charge my battery, the house backup battery that is ...

I only want to provide backup for essential utilities when the power goes out. Mainly the garage door opener and the water pump which only run occasionally and maybe squeeze in the refridgerator. I am going to set up another fuse box from the main panel with only the circuits that I could use when the power goes out, probably around 6. Power outage rarely exceeds 12 hours so I have to factor that into the equation for what I want to do.

I have considered a generator but in the final analysis I dont want to disturb my neighbour’s peace nor my own, although it is a lot simpler and cheaper.

I am now the proud owner of a 115ah deep cycle battery and a 150 solar panel which I tested as putting out 21 volts in the sun so I’m happy. Its giving me 10ah so knowing how much sun we get would help me decide if I should hook up another panel. 

This is a beginning of a fun project.

You are short  information. What type of solar charge controller will you be using to charge your battery? PWM or MMPT   

Assuming your battery is 12V your charge to the battery is a maximum of 120/12 or 10 amps at full sun, (which you indicate),  so you will need about 2 1/2 to 3 1/2 days at like side to charge your battery depending on the solar charge converter type.

Assuming your 110v inverter works at 95% efficiency  you will have appx  1kwh of possible use from your battery. A typical refrigerator is 200-250 watts. Depending on the size of your water pump 150-300 watts.  

 

Also your description of connecting a separate box for those items to your main panel.... you will need an automatic disconnect so that you are not sending power to the grid from your battery when the power goes out.

Think of a lineman working on a "dead " power line when some one is sending a charge through from their house.  Injury could result.  All grid connect inverters will automatically stop producing when they there is no power in the grid. The setup you desire will be producing power when the grid is not.

 

  

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On 10/2/2019 at 6:49 PM, RickS said:

Color me curious, but..... how do you define "sunlight hours"?  If a day is partly sunny or partly cloudy do all the hours count?  Also, what kind of solar panel do you have.... some are better at producing usable current in 'cloudy' conditions than others. 

Now color me skeptical.... I doubt very seriously one is going to be able to 'predict' just how much sun is going to strike your panel at your location on any given day/week so as to help you make a decision as to how many panels you will need. Your configuration will absolutely keep your battery topped off and waiting to be drained. One 115 Ah battery, fully charged, will surely give you enough energy to run some lights and maybe the frig, if you run it in economy mode,  but you mentioned motors with an "s" and IMO one 115aH battery won't get you through 12 hours running multiple motors and lights and maybe a computer or TV or ?

To me the question is not 'how much sun will I get' but rather do you have enough battery to run what you want for up to 12 hours. AND, will that one panel recharge your battery from 'drained' to 'fully charged' in time for the next outage. The first part of that equation can easily be tested. The second part will depend on 'how much sun' you are lucky enough to get right after a depletion.

 

You are spot on with your comments. The garage door opener motor use can be controlled by us, the other motor is the water pump which is also intermittent and we can control how often we flush when the power is out so the 115ah battery will supply for 12 hour outage easily, especially with a little help from the solar panel. I currently have a power meter connected to the fridge and will use that info to estimate the daily draw from that and whether I need to increase the panels or the battery pack to accomodate. 

I am leaning to add another 150w panel (monocristoline) for at least the advantage of reducing the voltage drop. To keep a 2 % limit on voltage  drop, the wire sizes become huge and the controller I bought will handle 24v even if i am charging a 12 volt battery. That means that I can increase the efficiency by connecting another one in series (24v) and getting the most from the 8AWG I have. Especially since I am looking to possibly expand the system that will give me 30 amps where wire size becomes critical to distance. 

I have to consider that the wet cell battery I have doesn't like to be depleted more than half so for the extra $1900 pesos to buy another 150 panel, I will increase the efficiency to a 24 v system, and add another 10ah =20ah total and that should be pretty good.

The question about sunlight hours, and not daylight hours, helps to estimate the output of the panels on average for design of the system. Once I have it set up, I will be able to monitor and make any adjustments, the fewer the better, because components are expensive ...laugh.

Thank you for your input.

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11 hours ago, MarkWebles said:

This site will give you all the information you'll need. There is a bit of a learning curve to it, though.

https://www.timeanddate.com/sun/mexico/ajijic

Thank you for the link but daylight hours and sunlight hours are quite different. If I were to use daylight hours I would overestimate the  amount of power the panels collect and send to me. That is an important consideration when selecting the number of panels needed. 

I am using 8 hours of sunlight as a beginning estimate as opposed to the 11+ hours daylight on the charts. That brings down my total input by about 30-40ah per day for each 150w panel.

Thank you for your comment.

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I had a solar panel electric system installed in 2008 and have added additional panels soon there after because I underestimated how many I needed. In those days the first panels I purchased were rated at only 170 watts per panel. Because in those days CFE was less reliable than today,  I installed 8 deep cell Trojan 6 volt Golf cart batteries. to power my backup system should CFE go down,  And as a result I have never had a total power outage.

I use all three phases at home, but only one of the three phases is connected to the power backup system, and this phase feeds at least one light in every room, the refrigerator, freezer, alarm system etc.  Oh and of course one TV, to include the sat receiver etc.

I have additional solar panels and inverters feeding the other phases too, but these stop providing power, when CFE goes down.

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