How to run a house off the car battery

Posted on 27 May 2015 by Scottish-Sceptic

With yet more news from Bishop Hill of another coal powered station closing down, the likelihood of power cuts grows.
So, I’ve started thinking about how to deal with power cuts in a more robust way than a few candles and torches.

WARNING!
THE IDEAS IN THIS ARTICLE ARE ONLY FOR DISCUSSION.
DO NOT TRY ANY OF THIS YOURSELF AND IF YOU DO DON’T BLAME ME IF IT GOES WRONG
IF YOU DON’T UNDERSTAND WHAT YOU ARE DOING TRYING THIS IS INSANE!!

Note in the UK the electricians lied to parliament about the dangers of mains wiring (including the much larger number of fires from portable appliance in order to suggest that wiring was an issue when it is not). So there’s some kind of unenforceable rule that only members of the union can do union jobs — unless it’s your own house — when they still try to enforce the non-scab labour rules.
The reality is that if you have an RCD protected fuse box and are reasonably careful you are as safe as you can be from all but the petty bureaucrats.
The problem areas

Lights are the first indication most people have of a power cut (they usually occur on winter nights). And power-cut dark is not just dark as we normally experience it (with external street lights) but pitch dark. Not a huge load – but permanently wired so difficult to power without permanent wiring.
Fridge-freezer. Not the biggest load in the house (We have had 240-516W if I remember right), but still big relative to most appliances and worse an inductive load needing a fairly beefy supply and can ruin cheap inverters.
Central heating. If you live in Scotland – you’ll already know that you need mains to run central heating. So you know that both heating and hot water (instantaneous) goes – even if you have gas central heating. Difficult because it is usually permanently wired and it’s an inductive load which can kill some cheap inverters.
Phone, internet, comms equip. We’ve all grown so used to instantaneous communication, that we e.g. do not use a phone directory but instead search the internet. We have mains powered landlines. Even mobiles need charging. Individually they are not a problem – but when they all go down together it is a nightmare.
Kettle – at 3.5kw kettles are amongst the biggest loads in the house. Even travelling kettles are 1100W and it is far cheaper to buy a camping gas stove and kettle than massively up the spec of your generator to suit this one appliance.
Dishwasher & Washing machine – both contain kettle sized heating elements and inductive motors. Those living off-grid tend to buy their washing machines to suit their generators and wash by hand. So unless the power is off for weeks – just let the washing pile up.
Electric showers – need insane amounts of power.

Car battery mains inverter

For as little as £30, you can buy a plug in adapter for the car with around 60Watts output. Realistically this will just about power a big laptop OR a small TV OR a few LED lights. It won’t power a fridge (or central heating). Unless you have a garage and start living in it you will also need several extension leads.
Equipment

Mains adapter for car. 60W gives around 8hrs, a 240W main drain battery in under 2hours
Long extension lead from car to house
More long extension leads to get power to other rooms
A plug in LED light for each room

Separate mains generator

Generator (diesel/petrol/gas)
There are relatively cheap diesel or petrol mains generators, but if these are anything like the cheap chain saw I bought, they never work when you need them and they are noisy.
But fuel is easy to store (but outside not in a house) and more is easy to come by and (if you can find a petrol station with a pump not affected by the power cut) fuel is available to run almost indefinitely.
Being an inductive generator, they will happily power inductive loads like fridges. So the main concern is whether it has the rated output.
Battery + inverter (NO inductive/motor loads)

(remember lead-acid batteries can generate hydrogen gas – so they must be vented to outside)
Likewise, I’ve had separate lead acid batteries and generators. The problem is that they will run out eventually and surprisingly quickly if you use more than just lights. The biggest problem is their initial cost, finding somewhere to keep them and ensuring they are topped up with charge for the years between power cuts is a problem.
To power non-motor loads like some lights & TV (not kettle) you’ll need a good camping battery and a big inverter. I have a 240W inverter that powers a lot of odd equipment, but check the equipment and make sure your peak load is well within the peak output. The bigger – the less likely to trip it – but the faster it will go through the batteries. And check efficiency, because a big inefficient inverter may quickly drain a battery even without any load.
Battery + inverter (WITH inductive/motor loads)
Inductive loads such as fridges, central heating pumps, and motors (anything with big/fast moving parts) and inverters don’t like each other. Not only do they have a massive inrush current that means they use perhaps 3x their average load at start, but they try to push all that power back into the inverter which if it’s not designed to cope will go up in smoke. So, an inverter has to be purchased to suit the loads – and it will not be cheap – perhaps £200+.
Equipment

Diesel/Petrol Generator
Fuel
or
Big Battery (12v 100AH)
Inverter specked for equipment (at least 600W)
Charger (ideally one that can be left charging permanently)

A long Power lead to reach each room + multi-way distribution leads to any equipment in each room
Plug in lamps for each room

The ideal solution would be a large lorry battery (24V) with more than 100AH capacity which would give 6 hours standby at average household consumption of 400W. But the inverter needs to be capable of driving large inductive loads like a fridge.
Separate Mains Generator + plug in circuits
So far, all the equipment has been powered directly by plugging each piece of equipment into the extension leads from the portable generator. However the next step is to create plug in circuits power permanently wired from the mains.

“Plug in” Central Heating

Typically a boiler is on its own circuit and its not that uncommon for them to be plugged in rather than hard-wired in. So, all we need do is convert them back.
A boiler doesn’t use a lot of electricity when running (200W?) but its a dog to start. (see above). Typical fuse ratings are 3A which suggests a 750W. A petrol generator with that rating should be fine, but not an inverter. An online forum recommends 1kw and probably a “true sine wave” type.
However, if there is a generator/inverter available with the right power, it can power the central heating meaning you will have heating when others are shivering. This requires a relatively simple change. Usually, the boiler runs from its own power spur and if like ours the final connection is a appliance cable from a wall outlet, this wall outlet merely needs converting to a socket and a plug added to the end of the appliance cable.
Then if there is a power cut, you simply unplug the boiler from the dead mains, and plug it into the live generator.

“Plug in” circuits

The way to do this is disconnect the circuit from the main distribution unit and then to wire it to take power from a plug. Then the circuit from the mains distribution unit is changed to be a power socket circuit with a single plug. Finally, the plug is goes into the socket and power is restored. So, now the circuit – let’s say downstairs lights – works as normal. It is fully protected and quite safely plugged into the mains.
Then if a power cut occurs, that circuit is unplugged and plugged into the separate generator.
Lighting circuits
A normal 13A (UK) plug will work fine for 5amp circuits (like lights). However if you are going to effectively convert the circuit to a spur, you need to upgrade the wire as far as the socket (if the circuit is converted back the socket it may end up being used as a socket so the wiring should be rated for that). The plug will have a fuse – which is now the main protection for the attached appliances. That suggests the fuse should be as small as the lights attached will permit (2 or 3Amp for a lighting circuit), however, that now means that if there is excess current which sometimes happens when filament lights go – instead of the mains fuse going where one normally expects the fuse, the fuse will go in the plug. This is a problem mainly because many people will not think to look at this plug fuse.
Remember all this fault finding could be done in the dark!

One approach is the increase the size of the plug fuse so that the first fuse to blow is in the distribution box.
Another thing that may help is a neon power indicator in the socket
Another approach is so that not all lights are plugged into the one plug. This way only some of the lights will go out. Turning off the circuit – will turn off lights which were on showing it is working. That will quickly indicate that it is a part of the circuit that has blown – thus pointing people toward the plug (which if there’s a neon will turn off and on showing it is part of the lighting circuit).
Another possibility is to use the 5Amp round plugs which are unfused. These were often used for almost the same type of application whereby they powered standing lights around a room which were switched on and off from a central light switch.

I can’t say whether it breaks any codes – my feeling is that it’s more likely to be objected to by people like building standards who might insist it is not permanent light rather than electricians. The round pin plugs are often used to plug in permanent lights – so there shouldn’t be a problem – but common sense doesn’t always prevail (and in Scotland the council behaves as if it owns people’s properties and so they go way beyond what is reasonable).
From an electrical point of view it should be safe (but see grounding below) – and what building standards don’t know about doesn’t concern them. A bigger problem may be trying to sell a house with such “non-standard” wiring. So, a plan to be able to relatively easily bypass the plug-socket to make it into a standard domestic circuit again would be sensible.
Power circuits
As I said, a 13Amp socket will do for many circuits, but not power. But if you want to power something like a fridge you need a power circuit. A single spur would probably be rated 15-20Amp which is too much for a 13A plug. But caravan sockets are rated at 16Amp and intended for just this type of permanent wired application.
However there will be problems with a normal domestic ring main which is rated 30-35Amp. I don’t know of a suitable plug with this rating. There may be something available but with bigger loads it is not sensible to try to connect in a ring main. So, the best strategy would be to select a few essential sockets and run these as separate spurs. These should be well marked because because anyone working on these sockets will expect them to turn off when others in the same room turn off.

Rewiring the new “distribution box”
It is likely that you have several mains cables going into the fuse board. These need to be rerouted to a new place where they can be brought together and then this needs connected into the mains with a plug lead and plug. Then you need a socket which in turn is connected to the mains.
It should be quite safe, but I have no doubt that some “professional” electricians won’t have a clue about anything unusual and may insist that it’s got to be a permanent wired ciruit for them personally to pass the circuit. So, I would put it together so the plug is relatively easily replaced.
You want people to consider these plugs as part of the mains circuit and not a handy point to plug in a vacuum. So, if possible try to find non-standard plugs that look “electrical” and then have an adapter to a 13A socket to plug into the generator. At the very least – there are orange sockets available and some handy “lightning” symbols will make it all look official. And if possible try to put all these power sockets in a purpose made box so no one is even tempted to use the plugs for other purposes.
Equipment
The generator equipment is as above but will be larger. A bigger system will need bigger equipment and bigger more expensive batteries (if you use an inverter). So you will want a purpose made charger for standby use that keeps the battery properly charged and can remain connected during a power cut.
Simpler setup
Above is a possible schematic perhaps a lighting circuit. A single wire comes out of the mains distribution unit to a plug (5Amp, 13Amp or caravan would do). The fuse should be rated according to the plug – but if not the plug needs to be distinctive with warning signs that it is not fully rated. Try to arrange so that if at any point someone wants to remove the off-grid connection, the plug can be removed + the wire to the mains can just be rerouted to the distribution box
More complex
The above could be used for several circuits, but I expect any electrician will take a very dim view if e.g. the upstairs lights can be connected into the socket going to the downstairs lights (and quite dangerous if anyone works on the lights). So, for a more complex system, I would consider something like the following. Here we have added in another consumer unit (as available for caravans). Now we have a single power lead and in essence we can treat it like a caravan – except …

Grounding
Not quite worked out grounding. In principle grounding works by ensuring all bare metal which is not electrically isolated in some way – is all at the same potential. It doesn’t actually matter if its all at 230V – so long as you can’t then touch something at 0V (relative to the earth outside)
If no RCDs are used in the circuit, then that means to ground everything you can. So, that suggests a permanent connection to ground. If the added fuse has RCD protection, then most should work, but to be safe I suggest grounding the plug side of the fuse box with a great big ground connection (enough to take all the current but something that looks robust will convince most elections so perhaps 10mm²).

Going the whole Hog

The ultimate solution approach is to have a very simple switch that disconnects the whole house from the mains supply and then connects it to an inlet socket.
The big problem is that the switch will go before the consumer on/off switch so you will have to bring in the electric supply company and convince them to install the switch.
But once you have the switch, the great think about this approach, is that the wiring is now all non-mains so you can stick two fingers up to all the electrical union cartel imposed domestic wiring rules as all that now matters is what is safe and sensible. (Although seriously, your house probably comes under rules usually intended for things like caravans and without the same strong arm tactics of the electricians unions these are probably what is sensible rather than what makes works for electricians)
So, one way to use this approach is to have a caravan style power inlet socket. The generator is then connected from outside to the socket and in theory by turning the switch, the WHOLE HOUSE can be off-grid.
But realistically a 16 amp lead cannot power everything in the house, so you would need to go around disconnecting all the big power users like washing machines, kettles, etc.
The problem with this approach is that because we are so used to just turning things on (like kettles) it may prove to be very unreliable as every time there’s a power cut, someone forget that there’s a power cut, turns on the kettle and trips the power.
The other problem is that you’ve no way to know whether your power is back on. In reality, you probably need an additional distribution board powering a few lights.

How to run a house of a car battery

And if you do go the whole hog and if you disconnect all the circuits leaving only the lights. (or remove everything from a power circuit) And if you turn off big fluorescents and leave a few very small LED lights turned on.
Then you can literally run the house from a small inverter fitting into the car.

But if you are insane & lazy & generally have a death wish & you live on your own
and basically don’t!!!