Help for Newbie

[justmegt]

I am setting up a 12v system in an exhibition trailer in the UK. I have been paying £500 a year for the use of electricity and for various reasons I want to stop using it. So I thought a 12v battery system charged up with solar panels would be the answer.

I have bought 2 x Banner Energy Bull 130Ah batteries, 2 x 5M led tape (I thought this gives the biggest bangs for your bucks) and various connectors plus a voltage display meter.

I have been looking at solar panels and controllers and my head is spinning.

My first idea was to fit the panels to the trailer but now I think the best way is to fit these to my flat roofed garage and disconnect them when the trailer goes out 3 times a week. The trailer is stored under cover, so the panels would only be in the sun for 3 x 8 hours a week. The batteries would get a lot more charge from roof mounted panels.

The problem I have is: which panels and controller to choose. There is so much choice. I can't get my head around the Wattages and Amp hours needed.

I would like to use an MPPT controller, they are more expensive but, over time, will be more cost effective as they are more efficient. I found some PWM controllers that have 2 separate battery connections but I cannot find an MPPT controller that controls 2 batteries. The Morning Star ones seem to be good quality.

I will be powering:

1 x Desktop Computer
2 x Laptops
1 x Till
some LED tape lighting

I've already spent nearly £500, which was my budget for the whole system. I expect to spend another £500, which means it'll take 2 years instead of 1 to get my money back.

I still haven't bought an inverter yet. I have a 150w one, which runs the till OK but won't power the desktop. The LED tape runs directly from the batteries and I have small car inverters for the laptops.

Please can someone advise which solar panels and controller I need and how to calculate the Amp hours and Wattages.

[daz]

This is in the wrong catagory? Should be in the off-grid section?

I have been paying £500 a year for the use of electricity and for various reasons I want to stop using it.

Solar is going to cost you more than grid supplied electricity. So as long as one of the reasons you want to use solar is not to save money, then you are ok. However, if you are trying to save money on your electrical bill, solar is going to cost you more!

I have bought 2 x Banner Energy Bull 130Ah batteries,

You shouldn't have bought anything until you have had a look at what you want to power, and how much power you need!!
For instance, your two 130AH batteries can only give you a recommended maximum combined total power of 1,560WH.......is 1,560WH enough for everything that you want to power?

Assuming a solar insolation of 3 for your area, you would need a solar array of approx 800W if using MPPT...and a solar array approx 1,100W if using PWM (assuming you needed to use the 1,560WH everyday).

So you can see it is always better to first see what you want to run, and how much power you need first before buying anything, as you may buy stuff that you can't use!


So, first things first...what is your total power requirements per day?

[Mike90250]

have you considered a small, quiet, inverter generator, like a honda eu1000 or eu2000 ?
Solar PV on a cloudy day, will leave you short of power.

[t5800512]

As Das explained, you first need to define your requirements. Do you understand how to do that?

There should be an electric label on each electric appliance. Find the watts, and multiply that by the number of hours you will be using it. Then add up all of the Watt Hours to find out how many Watt Hours you will need per day. Now you can go about calculating the battery and size array you will need.

[Sunking]

I have bought 2 x Banner Energy Bull 130Ah batteries, 2 x 5M led tape (I thought this gives the biggest bangs for your bucks) and various connectors plus a voltage display meter.

I have been looking at solar panels and controllers and my head is spinning.

My first idea was to fit the panels to the trailer but now I think the best way is to fit these to my flat roofed garage and disconnect them when the trailer goes out 3 times a week.

You have already answered your own question. You have no need for solar, just a good battery charger at home. Battery chargers work 24 x 365 no sun required. They cost 1/10th of solar and work when the sun is not shinning.

[justmegt]

Desktop Computer = 450W PSU which has ‘input 10 Amps’ printed on the label. I find it hard to believe that the computer is going to use 10 x 240V = 2400W + LCD monitor. That’s got to be wrong. I would rather buy another laptop than use all that power up.

The LED tape uses 9.6W/ Metre x 10 Metres = 96W

The 2 laptops are 19V x 3.16A = 120.08W

The till is 240V x .3 Amp (guess) = 72W

Based on 3 laptops instead of desktop, total power = 348.12 Watts

I would prefer to run more lighting if there is enough spare capacity. I currently have 10 x 5ft 240V 10KHz daylight fluorescent tubes. I realize the LEDs are never going to be as bright as the fluorescents but would like to have the brightest lighting system possible.

The plan is to charge the batteries while the trailer is parked up. Run the 12V system (discharge batteries) for 3 x 8 hours a week, Mondays, Wednesdays and Saturdays. They would be re-charged in between each 8 hour usage.

I didn’t want to bore everyone with all the details but the main reason for setting this up is: on Mondays I will be losing my current electrical setup and will have to run an 80 Metre cable to the next nearest supply through rubber trunking. This seems like a lot of hard work to me. I looked at the cost of my electricity, £3.50 a day x 3 x 52 = £546 a year and decided to be independent and have my own system. I have generators but do not want the noise from that.

I didn’t post in the ‘off-grid’ forum because I am also considering a grid-tie system. That was going to be another one of my questions.

What is the best angle to mount the solar panels on a flat roof?

I don’t know how to work out the charging Wattage, controller type and Solar panel Wattage/ type number etc. Another unknown is how much charge will there be on a cloudy winter’s day in the UK?

[Sunking]

Desktop Computer = 450W PSU which has ‘input 10 Amps’ printed on the label. I find it hard to believe that the computer is going to use 10 x 240V = 2400W + LCD monitor. That’s got to be wrong. I would rather buy another laptop than use all that power up.

The LED tape uses 9.6W/ Metre x 10 Metres = 96W

The 2 laptops are 19V x 3.16A = 120.08W

The till is 240V x .3 Amp (guess) = 72W

Based on 3 laptops instead of desktop, total power = 348.12 Watts

I would prefer to run more lighting if there is enough spare capacity. I currently have 10 x 5ft 240V 10KHz daylight fluorescent tubes. I realize the LEDs are never going to be as bright as the fluorescents but would like to have the brightest lighting system possible.

The plan is to charge the batteries while the trailer is parked up. Run the 12V system (discharge batteries) for 3 x 8 hours a week, Mondays, Wednesdays and Saturdays. They would be re-charged in between each 8 hour usage.

I didn’t want to bore everyone with all the details but the main reason for setting this up is: on Mondays I will be losing my current electrical setup and will have to run an 80 Metre cable to the next nearest supply through rubber trunking. This seems like a lot of hard work to me. I looked at the cost of my electricity, £3.50 a day x 3 x 52 = £546 a year and decided to be independent and have my own system. I have generators but do not want the noise from that.

I didn’t post in the ‘off-grid’ forum because I am also considering a grid-tie system. That was going to be another one of my questions.

What is the best angle to mount the solar panels on a flat roof?

I don’t know how to work out the charging Wattage, controller type and Solar panel Wattage/ type number etc. Another unknown is how much charge will there be on a cloudy winter’s day in the UK?

No one can answer you as you have not provided how many watt hours per day you will need. From the sounds of it it will be much larger than you think. Here are two kickers you had better be ready for.

1. Any off grid system requires a generator or commercial AC power in the event you have a cloudy day. Last time I was in UK for 2 weeks I never seen the sun.
2. It is going to cost a whole lot more than your were paying. You wil paying about 10 times more for electricity that will not always be available unless you follow rule 1 of having a generator or commercial power available to recharge.

[justmegt]

348.12W x 8 hours = 2784.96 Watt hours per day

The batteries can then be re-charged after each day's use, from solar panels or the mains supply, as necessary.

[Sunking]

348.12W x 8 hours = 2784.96 Watt hours per day.

Do you have any idea of what you just asked for?

To pull 2.8 Kwh per day requires a 800 pound battery costing some $3000 and in UK another 2000 watt of solar panels costing another $4000 which your trailer does not have enough room for to mount all of them. Those 800 pound batteries will need replaced every 3 to 5 years at even higher cost.

Did you consider any of that? That $500/year you are paying is a deal of the century for you.

[Mike90250]

Desktop Computer = 450W PSU which has ‘input 10 Amps’ printed on the label. I find it hard to believe that the computer is going to use 10 x 240V = 2400W + LCD monitor. That’s got to be wrong. I would rather buy another laptop than use all that power up.

///////


Another unknown is how much charge will there be on a cloudy winter’s day in the UK?

desktop/tower computers have at least 2 fans in them for cooling, and at the very least, a stripped down computer will burn 200W. If it came with a 450W supply, it will likely be idling with 250W. Time to look for a laptop, or maybe an android tablet for internet.

PV array in clouds. Power output is about 10% of nameplate, if it's bright clouds. On a real gloomy rain day, I get 200W from the 3KW array.