Discuss 12v lighting for my house powered by my van in the UK Electrical Forum area at ElectriciansForums.net

Insanity at new levels, I agree that it seems daft but if the OP has legit and honest intentions then surely we should offer advice.

And you'll be wanting a voltage drop relay, try Finder or Schneider for help on this one.

The cost of this setup is likely to reap little for you, it would be cheaper to buy solar torches/lamps and bring them in of an evening.
 
Remember car batteries are not intended to be deep discharged, so as PJ says above you will need some sort of voltage monitor to cut off before the battery voltage gets too low.
 
Just use company fuel to power generator the set up you are suggesting is just insane and potentially kill someone by electrocution or fire
To calculate power usage it should simply be amps per hour 10 bulbs using 1 amp each would use ten amps per hour a simple calculation of ohms law will work fine to work out amps used per lamp
There are loads of channels on YouTube about power walls made from reclaimed batteries maybe that would be a better place to have your questions answered
 
Let's be clear about the economics here.

The average cost per kWh in the UK at the moment is around £0.14.
A 110Ah 12V battery stores (very approximately) 110x12/1000 = 1.3kWh or £1.85 worth of electricity. It's not exactly that figure because the voltage is not 12V over the full discharge, and the 110Ah is quoted at the 20-hour rate but will be less if discharged in less than a day. Let's assume a reasonably optimistic 80Ah representing 100% depth-of-discharge to 10.8V over a full life of about 400 cycles. We can't really push it any harder because of the fairly aggressive charging rate required quite apart from the discharge.

The OP must supply his own battery, even if he's stealing the fuel used to generate the power. To get the performance mentioned he will need a good quality battery. 110Ah non-traction AGMs range from say £120-200. If he spends £175 he will get a good brand that will hold up to this kind of use. A traction battery rated for discharge at C/5 will do better at correspondingly higher cost.

Each daily cycle saves him 80 x 11.5 x 0.14 = £ 1.29 in electricity but costs 175/400 = £0.43 in battery wear and tear. So the maximum possible saving on this scheme is around 86p per day. I would be surprised if, in real-world changing conditions, you would achieve half that.

To quote the wise words of Dave OCD's post:
Why even bother. :rolleyes:

FWIW, you can use a pair of diodes to allow a backup mains-driven PSU to take over seamlessly when the battery gets low. You set the voltage of the PSU equal to the minimum voltage to which you want to discharge the battery. Whichever is higher does the work. Use big, low voltage Schottkys to avoid undue losses.

As mentioned above, heavy cables will also be needed to avoid yet more undue losses. For those unfamiliar with transmitting power at 12V, the power loss is 367 times greater than at 230V for a given power and cable size (230/12)². E.g. the headlamp feeds on my boat are 10mm² (tunnel lights) and 16mm² (spot lights). 24V makes a 75% saving in copper over 12V.
 
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Let's be clear about the economics here.

The average cost per kWh in the UK at the moment is around £0.14.
A 110Ah 12V battery stores (very approximately) 110x12/1000 = 1.3kWh or £1.85 worth of electricity. .....

Logic is spot on, you probably looked at your calculator in disbelief and unconsciously moved the decimal point. It's 18.2 pence for 1.3kWh.

If everything is 100% efficient and the batteries never degrade it takes about 5 years to break even, in real life, break even is approximately never.
 
Yes, well spotted! Made a crucial slip there, I accidentally switched from visualising what the OP's single 110Ah battery holds, to what the battery complement on a recent project holds (just over 1100Ah) and subconsciously changed the numbers as I typed so that they made sense. As I've often used as an example, the average person cannot lift £1 of electricity stored in lead-acids.

So yes, the battery saves less than 20p of electricity per cycle but costs more than that in depreciation, hence the scheme makes a net loss.
 

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