Its been a very long time since I last posted due to a number of things going on in life, however I am finally starting my long anticipated teardrop trailer build in the next couple of weeks. One thing I am a little confused over is what AH Leisure Battery I should be looking at getting and what Watt Solar panel to keep it topped up. If anyone has any experience and can offer advice i would greatly appreciate it.
I will not be using electric hookup so relying solely on solar for trips away. I will have minimal lights which will all be led, no TV heater or anything like that, it will just be my Halfords 40ltr electric cool box I would like to run. The specs say on 12v its 42W & 3.5ah and 240v its 55w & 0.25ah, does this mean i would be better off having a converter and running it on 240v appose to directly off the 12v, or would there be more drain on the battery by using a converter? Also how should i be working out what Watt solar panel i need to keep it charged with this level of usage?
Sorry if this all sounds a bit dumb? But i appreciate any guidance :)
Your going to need a bank of 110ah leisure batteries.
Inverters are not efficient, the watts count. 55w at 240v will still be 55w at 12v so instead of drawing 3.5amps your pulling 4.5 amps instead.
You need enough power stored to run the box overnight (say 9 hours). Approx 31.5 amps. It may sound OK when you think of a 110Ah battery. But the battery wont actually allow you to draw that amount until its a very low power draw like a single led.
Pulling a constant 3/5 amps will most likely kill a 110ah battery, or push its voltage down so low that it will shorten its life if done repeatedly.
There are links to an article done recently where they tested leisure batteries and most were well down on the real capacity.
Then you look at a solar panel, you want something that will put at least the same charge that you took out, so 3.5amps over 9 hours. Less hours in winter or on dull days though.
Some of the holidays we have had you would be lucky to put 1/4 of the rated power out of a solar panel.
Probably 150 watts (ish)
Heating, cooling etc is best done with gas or mains.
You might be better off getting a gas fridge, to run your 12v fridge overnight you'll need a battery as big as a chest freezer and a solar panel as big as our back garden (I might be exaggerating a wee bit)
However with a gas fridge you can get away with a 110ah battery and a 100w roof mounted panel or a 50-60w freestanding panel.
A solar panel produces nothing when dark As it gets light it slowly starts producing a little bit then gradually increases until mid day then decreases to nothing again.
It will produce its peak amount (100watts for a 100 watt panel) only under specific conditions of temperature, sun strength and sun angle.
April to September it produces a reasonable amount. Clouds, shade from a tree etc all reduce the output.
A 100 watt panel is around 8 amps at 12 volt peak but most of the time it will be less.
Your battery will start off charged and a 110AH battery will probably do you for a fortnight as long as you don't use a bog user like the cool box.
Don't forget, power used depends not only on how much an item uses but also on how long it is used for. Domestic fridges, although only using a small amount in theory, use a huge amount overall because they run 24/7. A hair dryer which uses a lot more than a fridge at around 2000 watts, uses a lot less overall than the fridge because it is only used for a few minutes.
The thing to remember when using 12 volt battery power is never use anything with a heating element in it, or any kind of coolbox. The only fridge to use on battery power is a compressor type as these use much less power. However, even those use quite a bit, so for more than a day or two you would need a bank of batteries. I had 2 x 110ah batteries on my boat, and these would run my compressor fridge for a few days, but for any longer I had to run the engines to charge them up. I learnt my lesson on a previous boat. I plugged in a coolbox and it killed my leisure battery completely in a few hours!
Inverters use quite a bit of power in themselves, so are best avoided unless you have huge batteries.