Simple Solar Panel Help Please

Undervalued

Another factor would surely be whether you want some kind of backup in the event of power cuts? If you do then you may well be prepared to pay for that and any saving you get from routine electric use would reduce the cost?

As I mentioned earlier I have the batteries for another use, although that is probably half a dozen times a year. I have to keep them charged and I have from time to time wondered about panels. However I concluded it was cheaper to charge them from the mains unless the panels would last far more years than I expect.

I would however like to have a backup electric supply to power the electrics for my gas boiler (c. 150 Watts) plus a few lights in the event of power cuts. So I suppose 15 amps at 12 volts.

Probably I should start a separate thread but any thoughts?

Ectophile

The lifetime of the panels is probably the least of your worries.  If you buy good quality ones, they should last 20 to 25 years.  The output will gradually drop over the years, as the ultraviolet in the sunlight gets to them.  But they should come with a guarantee that says how much the power may drop over their rated lifetime.

Does your chosen inverter include a charge controller function?  If not, you need a charge controller, or you will boil the batteries on a sunny day.

Undervalued

Ectophile said:

The lifetime of the panels is probably the least of your worries.  If you buy good quality ones, they should last 20 to 25 years.  The output will gradually drop over the years, as the ultraviolet in the sunlight gets to them.  But they should come with a guarantee that says how much the power may drop over their rated lifetime.

Does your chosen inverter include a charge controller function?  If not, you need a charge controller, or you will boil the batteries on a sunny day.

I've not chosen one yet. I have a number of elaborate chargers for charging Pb batteries (and other types) from the mains or from a 12 Volt DC source but I have not bought any panels, inverters or associated equipment yet.

To be honest I had just wondered about getting a 300 W full sine wave inverter and making sure my boiler connected to the mains via a plug and socket rather than hard wired. All I would need to do is bring in one of my 180 AHr batteries, connect the inverter and plug the boiler in. When the pump is running the total load would be around 120 Watts. So 10 Amps if the invert was 100% efficient (obviously not but what should I expect)? Should certainly allow the boiler to run for a cold winter's evening.

joefizz

Undervalued said:

I've not chosen one yet. I have a number of elaborate chargers for charging Pb batteries (and other types) from the mains or from a 12 Volt DC source but I have not bought any panels, inverters or associated equipment yet.

To be honest I had just wondered about getting a 300 W full sine wave inverter and making sure my boiler connected to the mains via a plug and socket rather than hard wired. All I would need to do is bring in one of my 180 AHr batteries, connect the inverter and plug the boiler in. When the pump is running the total load would be around 120 Watts. So 10 Amps if the invert was 100% efficient (obviously not but what should I expect)? Should certainly allow the boiler to run for a cold winter's evening.

Sounds like a plan.
You would need to work out your own system but thats a good start point. What I would say though is to up your inverter as much as you can initially (within reason) so if a 600w pure sine wave inverter is not that much more then go for that as it gives you a bit of headroom. When I say that I mean for temporarily running things.
If you are thinking about constant in a power out situation then remember that it doesnt necessarily have to be used all the time. So Say you put your boiler on for half an hour to heat up the house, then switch to your fridge for half an hour, all the while keeping some led lighting going etc etc. Ive various heat sources including a caravan 600w kettle so a 1000w inverter will run everything I need.
Things like freezers only really need to be run for a fraction of the time to remain effective (duty cycle) so if you dont mind switching equipment around etc.

Easiest way to do it is disconnect your kitchen ring main from the main fuse box/circuit breaker (isolate it) and then connect your inverter output to one of the kitchen sockets and use that (provided your boiler is on the kitchen ring main of course) to switch things on and off, just make sure everything  is off first.

As far as solar panels go, it depends on what your load is, the size of your batteries etc but the great thing is you can start off with say a 100w flexible panel (just bought one off ebay from china for about 35 quid last week - well I say bought, I;ll see if it gets here). Flexible so that you can use anywhere and store easily when not charging the batteries from the mains. As mentioned above you will need a charge controller and again you can get one initially which takes two panels (for expansion) and more than one battery, or just have separate controllers if required. As with the switching above, if you dont mind manual intervention you can have the batteries either in a parallel bank (although dud one will drag the others down) or have them all connected up with manual cut off terminals and so just charge one at a time etc.
The more manual intervention, the cheaper it is and then if you use it you can add to stuff as you go along.
As for bringing the batteries in etc, I have a couple of outside garden sockets, one of which is attached to my kitchen circuit, so I stick the generator at the bottom of the garden and run a mains lead from it to the garden socket. You will lose 12v with distance but can be a bit more generous with distance at mains voltages so if you have your batteries and inverter in the shed then just run the mains lead to the house. YMMV so will depend on your setup etc but its all very doable with minimal equipment if you already have the batteries which is the expensive bit.

markin

Just to be clear you don't back feed a socket ring main from a generator or an 240v inverter without disconnecting both wires from the Grid, you will kill someone.

I placed an order thats coming from china on 10th March, Expected by 9th Apr, Still waiting. Got plenty of things from Germany in the mean time.

Undervalued

markin said:

Just to be clear you don't back feed a socket ring main from a generator or an 240v inverter without disconnecting both wires from the Grid, you will kill someone.

Quite!!!

Although years ago somebody turned up at a club I was involved with, "helpfully" bringing a home made generator etc which, almost unbelievably, was wired up like that! Earthing was an alien concept to him too. Somehow he had lived to reach his late 70s! 

joefizz

Undervalued said:

markin said:

Just to be clear you don't back feed a socket ring main from a generator or an 240v inverter without disconnecting both wires from the Grid, you will kill someone.

Quite!!!

Although years ago somebody turned up at a club I was involved with, "helpfully" bringing a home made generator etc which, almost unbelievably, was wired up like that! Earthing was an alien concept to him too. Somehow he had lived to reach his late 70s! 

When I was about 10 I got an electric meccano set. The wee dc motor was 6v IIRC and wouldnt drive any of the models.

(dont try this at home kids) I thought if it was 6v imagine the power it would have with 240v. Wired it up to a plug and yet did have some 'sense' to sit well back and switch the socket on with a wooden brush handle. Nothing happened for a second...

I still remember a certain lecture during 2nd year at uni. It was on a monday night about 8pm. We got shown the aftermath of what happens when people try to fix thing themselves with various stages of electricity, from licking pp3 batteries right up to large electric motors (think trains) going bang. Whenever the electrical regs change you can probably be sure its because someone has went bang somewhere and it isnt pleasant.