[County Dangler]

I wonder if anyone has any experience of off grid statics and in particular weather or not to go down the 12v route or get an inverter?

It's only going to be used for the occasional weekend plus daily use of macerating toilet and fridge.

Power requirements will be fridge ( yet to buy so 12v/gas or 230v?) macerating toilet (12v or 230v) waterpump (yet to buy) minimal lighting and charging phones/tablets.

The plan is to wire leisure batteries in parallel and top them up using an adequate solar array (I'm happy to work out my requirements when need be) but I just cant decide weather to buy and inverter to use the current 230v lighting and power circuits with an efficient 230v fridge or to go down the 12v/gas fridge route and put in a few new 12v sockets and a 12v lighting system.

I know inverters are inefficient but it seems the easiest thing to do and if the energy is free anyway, does it matter if it's inefficient?

Does anyone have any thoughts or experience of this?

[goosepimple]

No I don't but we're about to connect up our water wheel to produce power for our mill which is a holiday let and has the same spec as you're listing and so your triganomatry above will all become clear to me in the next month or so.


If my electrician (who's a total ace on all these things) comes tomorrow or monday I'll show him your post and tell you what he says. 


Will watch this post with interest.

[County Dangler]

I'm beginning to answer my own questions actually. The main use for the inverter would be the fridge. Say i buy an efficient fridge for £150, a 1000w inverter for the same money, an extra 100ahr battery to make sure ive got enough storage capacity and also take into account the extra solar panels to charge them then I'm looking at well over £600 but with no on going costs. Where as i can buy a used 3way fridge that i can run off gas for say £50 that will use approx 300g/24hr. Based on a 19kg propane refill costing £35 locally then that should last around 2 months and cost about £4 a week to run. A bit of a no brainer now i have thought about it.

Now onto the lighting......watch this space......good old google.

[chrismahon]

The current requirements for a 12V DC system are much higher (20 times), so cabling costs and voltage drop become major factors. I would invert as close as possible to the batteries and run your lighting system at 230V ac. So that changes the picture somewhat. You also have the option of other appliances you haven't yet thought about. There is the theft factor though. Will someone nick your equipment?


We are considering an off-grid barn conversion at the moment.

[County Dangler]

Thanks for your input. Again though, i think i have talked myself into a simple solution for the lighting without needing an inverter. I think I'm just going to buy a half dozen led push lights that run from AA batteries-the batteries last for ever, they will be plenty bright enough for occasional use and they are cheap (<£20 for the lot)

My next issue is that the macerator fitted does need 230v which looks like it's going to mean stripping it out and fitting a 12v one. the model fitted though costs around £300 new so I'm hoping i might get a few quid back from eBay which should pay for a 12v one.

I take your point about other appliances and i think things would be different if we planned to live in it but as we don't I'd rather keep costs down as much as possible. But yet again your making me think. I would litterally be able to plug the mains feed for the whole unit straight into the inverter and have lights working, macerator working and all the plugs working if the need arises plus the fact that there would be the fuses etc in place (on that note i have not actually looked how it does connect to the mains? any idea's?) maybe i should do it after all? And maybe still go down the gas fridge route which would still mean major savings in battery capacity, solar input and the size of inverter needed.....and i thought i had made my mind up.

[goosepimple]

sorry our brilliant knowitall electrician won't be back until next week - it may be worth your while sourcing an equally brilliant one in your area CA and just paying them for an hour or so of their time for an on site conversation, save you money in the end and a shortcut to what you need. 


There will be other websites than TAS where you can contact other's who have done this sort of thing and save yourself time and money, I know there's ones for waterwheels and they are very helpful.


When you do come to a solution it would be worthwhile putting on here with pics, we'll be doing the same thing with our water wheel.


Good luck, tell us how you go.

[mab]

well it sounds like you've got a plan anyway but here are my thoughts:

fridge:- gas fridges are inefficent but work for a good while off the same bottle as the cooker (if you run them off 12v they are quite a heavy load. You can get 12v compressor fridges (and freezers) that are very efficient (circa 3A draw when running) but the last time I checked prices they were circa £300 - popular in yachts.

lighting: you can get 12v led's designed to work with standard MR16 fittings (normally need a transformer when run off 230v); these are bright, very efficient and in my experience don't mind the variable battery voltage as they are generally internally regulated - I run some off my 24v off grid system even though at 28v it's more than 2* rated voltage). As they're low wattage you can probably use the standard wiring in the static (though use an appropriate fuse of course).

Can't really offer an opinion of the macerator toilet as I don't know much about them.

[cloddopper]

County Angler
In B&Q this weekend there were some two pin mini light sockets that  looked suitable for 12 volt two pin LEDs stuff .... . MR6  fittings ?

Even if they are not suitable look on line for 12 volt  boat lighting and you be able to get them or find a scrap ,damaged unrepairable caravan under 7 yrs. old & take the light fittings .
 They are also available in lots of caravan seller show room shops.
 
 I have converted all of our 5 berth caravan to 12 volt two pin  LED lighting , it is brighter than when using the 12 volt incandescent halogen bulbs as I used bright white instead of soft warm LED's  .
Best of all the current drain on the battery is a fraction of what the 12 v halogens lights were on the battery .
 There are zillions of 12 volt ac/dc LED lights & DC only lamps to be had for a fraction of the UK retail prices if you're prepared to wait three to five weeks for it to come from China etc on eBay ( same place as most come from that are in the UK shops )

 re the fridge.. you can get second hand ones in three way energy from caravan breakers for far less than buying a brand new one .
 I have the current caravan club monthly mag if your after some addresses ( drop me a PM with your address )  .
 

[County Dangler]

Did you use the exisiting wiring for the 12v lighting sytem and just change the fittings over to accept the 2 pin bulbs? i hear you can get away with using the same wiring?

[mab]

In my case I've used the standard existing wiring (1.5mm2 T&E) for 12v or 24v. The important thing is to have a fuse or similar between the battery and the wiring - 5-6amp max for 1.0mm; with 1.5mm2 cable you could get away with 10A fuse but with LEDs you shouldn't need to go that high.

[County Dangler]

many thanks

Once I've got this polytunnel up I'll get cracking with the static and let you know how i get on.

Has anyone tried the light fitting converters? The ones that fit into the existing fittings (i think they are screw in ones on the van) and adapt them to the 2 pin mr16 fittings suitable for the 12v led's? Or would it be best to just fully change the fittings?

[pigalicious]

we are completely off grid, we use a battery bank 24v and an inverter 2500w , we manage well  with input from a 100w wind turbine and 8 x 80w solar panels. when buying appliances it is important to look at the wattage. if we turn on all our appliances we use less than 200w. we could have gone with a smaller invertor but being larger means we can also use our mincer etc. we use all LED lighting (1.3w/unit). Definitely reccomend it for two reasons, saving on electric bills and mainly self satisfaction! 

P

[County Dangler]

many thanks for that. I'm sure there will come a time, at some point this year when i have enough time to start work on the caravan. A couple of questions though if i may?

Why did you go 24v as opposed to 12v and what sort of a/hr batteries have you got?

[pigalicious]

We opted for 24v over 12v as the conversion (step up) is supposed to be more efficiently dealt with. the higher the voltage of the storage, the lower the current will be which should equal less loss of power. 48v systems are probably the optimum but the inverters and controllers are very expensive!  The batteries we use are 2v cells, 12 0f at 900ah each (they are the type used in electric forklifts etc) they too are very expensive but well worth the investment. we used six 110ah leisure batteries for six years which worked ok but obviously did not store as much power, they eventually clogged up became very poor at holding a charge. we did clean them out and fill them with fresh electrolyte which worked briefly (6 months or so).  hope this is useful.
Interestingly we purchased our inverter from china. it arrived at heathrow less than 24hrs after we ordered it, but it took 7 days to get from there to the north of Scotland!!!!!
     P

[County Dangler]

Thanks for your help.

I've just been looking at the 2v battery arrays. Hellish! but cost per amp hour is vastly lower so i can see how it would be worth it in the long run. If i were planning on living there i would be happy to make that sort of investment but for the odd weekend and to run a fridge it's a bit excessive.

I think I'm going to go down the 12v route and a 1.5kw ish inverter, with 3x130a/hr ish batteries wired in parallel and 3-400w solar panels. That way i can run 12v appliances staright from the batteries and the rest through the inverter. I'm hoping to bring it all in for around £500 which should be just about do'able with a bit of bargain hunting. I'm also looking at adding a turbine further down the line to keep things topped up over winter and if my batteries last 6 years i'll be over the moon.

Any other tips? I'm struggling to find a wattage for fridges though.....but most have an anuall usage so i guess i can divide that by 365 which gives me it's approx daily use. I guess it will pay to find the most efficient one possible within a sensible budget?