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Topic Title: Off grid questions
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Created On: 09 June 2018 12:53 PM
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 10 June 2018 04:21 PM
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Zoomup

Posts: 4156
Joined: 20 February 2014

All of this extra expense, complication and vehicle weight to cool just what exactly? A few cans of beer or pints of milk perhaps? I'd just buy a cold beer in the local shop or pub, and use long life milk for a few days travelling. You can save a fortune by not buying all of this unnecessary stuff. Just keep to basics I recommend. Save money, lighten your vehicle and have more vehicle space as well. Keep it simple.

Z.
 10 June 2018 04:30 PM
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Zoomup

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Joined: 20 February 2014

"Also am thinking in the highlands you don't get many shops if you venture out - you defiantly have to plan fuel etc., Water from freshwater lochs via Osmosis filter, and catchy some fishy"

I have rough camped in the highlands, both off road and nearer to civilisation, both with a vehicle and just a tent. You can cool stuff in lochs or burns. It is best to take dried food, long life milk and tins of food if you are going into the wilds for a long time rather than try to keep eggs and milk etc cool in a fridge. Shops are everywhere if you travel around by road. You will be near to a shop if you are driving about and none is normally farther away than a half day drive. Only drink water from fast running streams or clean lochs and always filter and boil it first before drinking it.

Z.
 10 June 2018 09:09 PM
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jonny705

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Joined: 26 September 2015

Thanks to all, think I have my head round this at last -

I have 2x 70 ah batts wired in parallel with diagonal connection for balance =140A.

Recommended C/12 charge current = 140A/12 hours =11.6 A

12v x11.6 A= 139.2 watts panel or more required.

Max charge current going in not to exceed C /4 =140A /4 =35A else will overheat cells.
So 25A plug in charger for top will be ok from geny.

If using MPPT controller better to use higher wattage house type panel typically 30v and not 17volt type and likely cheaper.
So a single one at around 250-300watt will be fine, and can add another at later date and decent batteries obviously.

Cannot believe when you work it out my 800w Cotek Inverter with 20% say loss = 1000w will pull 83A!
More mind bending and likely dangerous are 5kw Ebay Inverters @£42 =6000watts will pull 500A!
I bet they don't supply the cables!

Zoom I totally appreciate what you are saying but, will have to have a few luxuries as my Mum is 80 this year but is eager to come along (not in middle of no-where though!).

Hence super Van insulation likely Webasto, Fridge etc, I will be in tent outside with a pot noodle and mutt to keep me warm
 10 June 2018 09:46 PM
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Fm

Posts: 1827
Joined: 24 August 2011

I use a split charge controller, 12 volt leisure battery approx 100Ah and a peltier fridge.
It's all about keeping the weight down in my camper
 10 June 2018 10:11 PM
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jonny705

Posts: 202
Joined: 26 September 2015

Fm, my van is also my work van , so am building modular units which i can remove to turn it into a van again .

X1 sink/x1 cooker/x1 PSu unit with batts and other electrical bits- solar pane will be removable.

If i get really into it , will save up and likely get a Sprinter 4x4 from Germany and convert that permanently as such.
 10 June 2018 10:22 PM
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Fm

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Joined: 24 August 2011

Good Luck!
 13 June 2018 09:18 AM
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broadgage

Posts: 2749
Joined: 07 August 2007

Originally posted by: jonny705

Thanks to all, think I have my head round this at last -
I have 2x 70 ah batts wired in parallel with diagonal connection for balance =140A.
Recommended C/12 charge current = 140A/12 hours =11.6 A
12v x11.6 A= 139.2 watts panel or more required.
Max charge current going in not to exceed C /4 =140A /4 =35A else will overheat cells.
So 25A plug in charger for top will be ok from geny.
If using MPPT controller better to use higher wattage house type panel typically 30v and not 17volt type and likely cheaper.
So a single one at around 250-300watt will be fine, and can add another at later date and decent batteries]


I largely agree, with the exception of the charge rate and PV module size.
I would consider C/10 charging for leisure batteries to be fine, so about 14 amps rather than 11.6 amps.
Since some current will be used whilst the batteries are being charged, I would aim for about 15 amps to 20 amps input current, although this sounds a bit high, remember that it will only be achieved fairly briefly under ideal conditions, the average will be less.
With a MPPT a module size of about 300 watts should be fine, as implied later in your post, 360 watts might be better.
I do not feel that 140 watts will suffice.

I f you need a single large PV module cheap, ask around if anyone you know is planning a grid tied PV install. The vendors might be willing to supply an extra module cheaply, due to the saving on carriage.
I recently got a single large module for £180 as part of a larger order, it would have been nearer £250 if ordered on its own.
 13 June 2018 09:20 AM
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Fm

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Joined: 24 August 2011

Have a look at Navitron they have a good online shop.
 13 June 2018 10:49 AM
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Zoomup

Posts: 4156
Joined: 20 February 2014

"Zoom I totally appreciate what you are saying but, will have to have a few luxuries as my Mum is 80 this year but is eager to come along (not in middle of no-where though!)."

I hope that you have a good trip Jonny, and that you have sufficient tea making stuff for your mum! Take a midge hat or two for protection, they are active this time of year and live around water in the shade of trees and bushes. Their bit is ferocious. You may like to invest in a U.V. insect killer or two as well. If you stop at a cafe or pub, a meal of haggis, neeps and tatties is very good.

Bye,

Z.
IET » Wiring and the regulations » Off grid questions

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