Solar panel for garden log cabin

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Can anyone recommend the correct size and power for a roof mounted solar panel for our log cabin please and Where's best to buy from?

We have a southwest facing garden and get a lot of the sun in the afternoon, we'd be running a 2.5kw electric radiator in the winter, lights, laptops for office and also my guitar and amp setup...

The cabin is currently connected to the mains electricity so we have power there for inclement weather as a backup

Thanks
 
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You may need to manage your expectations :)
I'm not an expert and others will provide far better answers, but in winter the solar output may be 20% of the summer output, and your panels may already be non-optimally positioned if they are southwest facing.
A cost/benefit analysis may give you a definitive answer!
 
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A solar panel to charge a battery so you have lights, OK, but 2.5 kW an inverter cheapest is around £150 mark, the battery would need around 240 Ah at 12 volt so another £150 and the MPPT controller another £50 so looking at least £400 without any grid tie and not added cost of panels, which quick look around £2500.

The batteries if lead acid will going by narrow boats, last around 2 years, theory says 10 years, but bitter experience says 2 years.

So if looking at £3000 how long before it pays back? The only reason narrow boats use solar panels is there is no option to use a hook up. And in the main they use oil heaters to keep warm, the 12 volt only runs the pump and fans, heat comes from oil.

I would go onto a narrow boat forum as ask, they use them all the time, plus wind chargers, so they are the people to ask.
 
The batteries if lead acid will going by narrow boats, last around 2 years, theory says 10 years, but bitter experience says 2 years.



I would go onto a narrow boat forum as ask, they use them all the time, plus wind chargers, so they are the people to ask.
Only 2yrs, sorry but there must of been a problem. As a boat owner I hear wind turbines offer very little compared to the cost of buying and ask on boat forums but stay away from boat chandlers as they Bung On Another Thousand! :ROFLMAO:
 
The problem with lead acid, is the plates sulfate. And it hardens over time. So they need charging up fully at least once a month.

But it also takes time to charge, and all cells are never identical so don't want a constant voltage, the normal is charge until 14.4 volt then stop until 12.8 volt, but can't do that when being used while being charged.

In the main a stage charger monitors current near the end of a stage and drops the voltage once the current dips under a set level, but if being used at the same time, then can over charge.

I can continue, but main problem is to ensure battery neither under or over charged, and one would need more control than a MPPT charger is likely to give.

The other option is diffrent battery, nickle iron for example, but with lithium batteries again arranging charge rates is critical.

What is often done is a capacitor is charged then this charges battery, but this is rather complex.
 
The problem with lead acid, is the plates sulfate. And it hardens over time. So they need charging up fully at least once a month.

But it also takes time to charge, and all cells are never identical so don't want a constant voltage, the normal is charge until 14.4 volt then stop until 12.8 volt, but can't do that when being used while being charged.

In the main a stage charger monitors current near the end of a stage and drops the voltage once the current dips under a set level, but if being used at the same time, then can over charge.

I can continue, but main problem is to ensure battery neither under or over charged, and one would need more control than a MPPT charger is likely to give.

The other option is diffrent battery, nickle iron for example, but with lithium batteries again arranging charge rates is critical.

What is often done is a capacitor is charged then this charges battery, but this is rather complex.
I think you have hit the nail right on the head here.

One thing I have noticed is mobile phone base stations the jel cells last about 3-4years but they sort of don't bother replacing them. In one I have access to, the 4x 200AH 12V (48V) batteries the sulfate has expanded so much the plastic cases have split open and they have been like that for a number of years.
 
When my dad was alive, stair lift batteries lasted around 4 years, when he died around 2 years, basic problem was over charging and drying them out. Stenner who made the lift seemed to expect it to be used 4 times a day, and at that it would keep batteries about right.

Using a Smart battery charger I can fully charge and maintain a lead acid battery not in use, it has four charge rates 3.8, 3, 0.8, 0.1 amp and off, the 3.8 and 3 amp rates are only used once for each charge, as soon as it moves to next rate it will not return, this means should a cell go short circuit it will not bake the battery once it has passed the first two stages.

The next two rates it alternates, 12.8 to 14.4 volt, in real terms it gives a quick pulse of charge, as once charged it returns to 14.4 very rapid. So 98% of the time the battery sits at 12.9 volt. And cared for like that a lead acid battery will likely last 10 years.

In a car either there is a computer controlling battery charge rates, as with stop/start technology, or the battery is used for 2 minutes to start car, then held at between 13.8 and 14.2 volt, the float voltage should be 13.4, but there is a limited time to recharge, so depending on the vehicle, we use a slightly higher charge voltage, using the smart charger talked about in last paragraph it can take days to recharge the battery, and the vehicle does not run long enough.

Narrow boats use in the main stage charging when on shore supply, so 14.8 volt until the amps drop to around 4 amp, then drops to 13.8 volt for last 15% of the charge. The alternators use pulse charge and capacitors to store energy between pulses, and the amount of charge is worked out by the decay time of voltage between the pulses, this is for the domestic batteries, the engine start batteries just have 13.8 volt to them shore or engine. It is common to have two 70 amp alternators linked together with a charge controller, which is an inverter which kids the standard alternator to produce more power. 1659340449705.pngThese are expensive bits of kit, even the 80 amp version costs around £350.

The wind and solar MPPT chargers are similar, 1659340662949.pngthe terminals
1659340709674.png
separate load from battery so it can monitor the load, the one shown is £76 with a maximum battery current of 10 amp, for a 2.5 kW heater looking at over 200 amp at 12 volt.

So not really looking at lead acid, and looking at a much larger battery, some thing live the Tesla Power Wall, now your looking as serious money, around £8,600 to £10,500, I am sure they work well, but think some thing like this 1659341415686.png is a better option.
 
The single biggest problem on boats in my mind is that there are only so many times a battery likes a deep discharge and recovery and people on holiday boats abuse the batteries hence boat owners need to fit more.

Holiday person booking a boat "Does it have sky TV?"

Boat owner "Open the sunroof and look up!"
:ROFLMAO: :ROFLMAO: :ROFLMAO:
 
The single biggest problem on boats in my mind is that there are only so many times a battery likes a deep discharge and recovery and people on holiday boats abuse the batteries hence boat owners need to fit more.

Holiday person booking a boat "Does it have sky TV?"

Boat owner "Open the sunroof and look up!"
:ROFLMAO: :ROFLMAO: :ROFLMAO:
Maybe they are fitting the wrong batteries then.
A lot of years ago, C1980, I purchased a pair of 110AH traction batteries which were rated at 1000 discharges to zero volts.
 
If every so often the narrow boat goes into a marina and the batteries are charged for a few days then not so bad, but the hire people seem to think the batteries will fully recharge with the engine, and the engine does not run for long enough.
 

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