Saving economy 7 electric with batteries.

gord115

I've been pondering this for a while.

Supposing I connected say, ten 12 volt leisure batteries and charged them overnight on cheap rate economy 7 electric.

Then I used an inverter to convert it back to AC for use in the daytime,
surely this could save me money.

Or am I overlooking something?

jayme1

I doubt it thoes led acid batteries are only arround 50%-70% (so it takes double the amount of electricity to charge it to the amount of electricity stores when full) efficient and you would also loose efficiency when using power from it onto your electrical stuff.

you would have to do a lot of calculations to work out if it is actually cheaper.

aarrgghh

I think you are overlooking the cost of 20 lead acid batteries, an AC/DC/AC converter, cable, connectors and the very real risk of death by fire or electrocution. Not to mention, as jayme1 says, the energy loss in conversion.

stevemcol

Agree with the others. The losses in storage & conversion would outwiegh the savings.
E7 can be used sensibly in other ways. When I was on E7 (I'm not anymore since I moved) I connected the kitchen ring to the E7 switch so the washing machine and dryer ran at night on cheap rate.

infomonkey

As jayme1 says its really really inefficient, too many stages to be worthwhile I think. + the cost of quality charging equipment a decent "sine wave" inverter and not to mention the batteries and cabling.

Now it has got me being geeky and wanting to work out how many batteries you would need to power a house for a day.

Family with two children - 5,480 kWh electricity

So here goes daily usage = 5470 / 365 = 15.01 Lets call it 15 going forward.

15kWh = 1 Day Consumption.
15000/240 = 62.5A @ 240v
15000/12 = 1250A @ 12v

The reason that the Current goes right up to 1250A is because the Power used is still 15000 watts over the course of a day but the voltage is much lower therefore the system has to "push" harder to get the same work done.

An average lead acid car battery can hold about 60Ah of charge and we will assume a 50% duty cycle.
1250/60*2 (the 2 is to indicate the half charge)
= 41.6 batteries

Therefore to do this you would need 42 batteries!

This does not include any circuit losses and is a back of a beermat calculation.

diable

How much does it cost you to boil your kettle?

moonrakerz

gord115 wrote: »

am I overlooking something?

Yes................... if this did work don't you think someone would be selling "ready-to-install" kits by now ??

Actually, having seen some of the crackpot energy saving things that people pay good money for I am amazed that no one is :rotfl:

nottseagull

diable wrote: »

How much does it cost you to boil your kettle?

This would depend on:
1 The tariff at the time of use
2 The temperature of the cold water
3 The volume of the water
4 The rating of the kettle in Kw

but if your post is intended to belittle an (obviously) non-technical person to save money, then I don't think it is very helpful.

If batteries didn't wear out, then the OP's theory may indeed have saved money (eventually). It reminds me of when I bought an electric pedal cycle a few years ago, lured by the prospect of 1p a mile running costs. It ran on the same lead-acid batteries that the OP proposed, but it soon transpired that taking into account the cost of their replacement, the figure rocketed to 6p a mile - not much less than the cost of petrol for a small car at the time. No wonder battery cars cannot be made for an economical selling price.

moonrakerz

nottseagull wrote: »

but if your post is intended to belittle an (obviously) non-technical person to save money, then I don't think it is very helpful.

If batteries didn't wear out, then the OP's theory may indeed have saved money (eventually).

we can only assume that you are "non-techical" as well.............:D

stevemcol

moonrakerz wrote: »

we can only assume that you are "non-techical" as well.............:D

You take the pi$$ because you are obviously cleverer than normal people. Fact is, there are lots of counter intuitive principles at work such as electrical generating authorities using 'E7' to pump water up hill and store for release during the day at peak times. Not energy efficient granted but the OP was only looking at a variation on a theme and deserved a polite explanation rather than a put down.

basill

So far we have not had a water meter imposed on us, could the experts above work out how much electricity we could generate if we used cold water piped through a hose out through the upstairs bathroom window to turn a water wheel or turbine generator?

Perhaps this small but constant source of energy could be used to charge batteries to cope with bursts in demand like boiling a kettle etc...

Yours hopefully


B