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Author Topic: Power walls /battery banks  (Read 4841 times)


  • Joined Jun 2013
  • South Wales .Carmarthenshire. SA18
Power walls /battery banks
« on: August 14, 2018, 07:51:12 pm »
Has any one done any research /looking into the rechargeable battery banks /power walls  that are /can be connected to their solar PV panels?

 If so do you have any rough costs .. for say a 13 kw hr wall hanging or floor standing bank ?

 I've found ""  promoting them, does anyone have any other sources to look into ?
Strong belief , triggers the mind to find the way ... Dyslexia just makes it that bit more amusing & interesting


  • Joined Jun 2013
  • South Wales .Carmarthenshire. SA18
Re: Power walls /battery banks
« Reply #1 on: August 18, 2018, 06:37:41 pm »

 Had a guy come and visit us this morning to talk about the viability of us purchasing a Tesla Powerwall rechargeable battery .

 On doing a simple historic using a compound interest type calculation,  using the high & low electric  meter readings and the FIT income.  It looks like we've earn't almost 1080 more than we paid for the solar PV system five years ago.
We paid by bank transfer the afternoon it was fitted & working no loans or credit etc. why pay 86 %  or so more if you don't need to ?

 The guy couldn't work out why we had an actual 18.3%  increase of solar PV FIT when compared by the average  . Neither could I at the time But I have sussed it after a few minutes of thinking.

 One of the first things he did was to check the orientation of our bungalow , declaring, "Oh your panels should be on the east side of the roof .
 He'd used a snazzy digital compass on his laptop that could align to the N th degree .
 I said to him check to see if you are using true north or magnetic north it will make several degrees difference to the reality of the sun . 
 He'd not realised there was a difference called magnetic variation , nor did he work out that as the days are longer in summer means the amount of sun light must be available for more hours .  This  also caused him to miscalculate where the sun rises and sets . I said it rose in slightly east of north east & set slightly north of north west  from about the end of May to the end of July & couild give 15 plus hous of useable enegy eah day in that period .

He redid his calculations and still found we were way ahead of the estimated generation .

 I then showed him next doors bungalow roof, which is five feet above our bungalow & their long light coloured bungalow side wall  . Told him that they became sun energy reflectors & that their two large side windows that face our bungalow were as good as mirrors from 09.00 till about 14 .00hrs reflecting even more energy on to our panels when the heat of the day sun took over till it was almost sunset ..

 Armed with his recalculations it looks like a power wall installation costing 7.5 K  should pay for itself in eight or so years then be in profit for about the next 12 to 20 years.

 Sounds a lot better ROI than you can normally get from a bank / building society  and nearly as good as the ROI from a proper investment vehicle till you get to the 35 /40 year compound interest point .
 Our next new car will like as not be an all electric one with a 300 mile range,  such is the tremendous range being aimed for . It is an ideal candidate to be charged up if you have a power wall .

Currently it costs us about 70 p to whack a 31 mile charge into the PHEV using off peak electricity or for free in the daytime if it is a really good sunny day.
Whereas a gallon of petrol is approx =  5 x 1.38 round here so about 6.69 a gallon & gives up about 35 mile

 Good value,  especially when you consider that the government of the day will take any money off you that they can when you're in your older years . .

« Last Edit: August 18, 2018, 11:14:09 pm by cloddopper »
Strong belief , triggers the mind to find the way ... Dyslexia just makes it that bit more amusing & interesting


  • Joined Jul 2011
Re: Power walls /battery banks
« Reply #2 on: September 10, 2018, 08:09:53 pm »
Sounds cool.I don't know what technology they use in pwerwall. The Tesla cars use multiple cells aligned inot bricks of cells in a thermal fluid bath (warmed/cooled as needed). Individual cells are linked by thin wires to act as fuses should an individual cell fail the bulk keeps working. One assumes there is a degredation over time with the batteries in the motors (which obviously get hammered more) being waranted for 8yrs and powerwall for 10yrs. So worst case scenario you get your money back with some profit.
I contacted two+ folk over having solar panels fitted and none ever turned up to actually do the job- a general problem in my part of Wales. I'm not quite so sure about the economics now that FIT has reduced. At least I got my car with free supercharging for life although it will be mostly charged at home.


  • Joined Jun 2012
  • Devon
Re: Power walls /battery banks
« Reply #3 on: September 14, 2018, 11:55:45 am »
If you're interested in power walls, I'd highly recommending heading over to where this has been discussed in depth by folks who have a great deal of real world experience in grid tied and off grid systems. For most people who are on the grid, you'll probably never recoup the cost of a battery based system given how cheap grid generated electricity is.


  • Joined Jun 2013
  • South Wales .Carmarthenshire. SA18
Re: Power walls /battery banks
« Reply #4 on: September 17, 2018, 02:43:27 am »
Just seen what the next years contracted electricity charges rates are Eeek!

A power wall might now be a much more viable option,  especially as we look like having two or maybe even three electric cars within the next year or so .
Strong belief , triggers the mind to find the way ... Dyslexia just makes it that bit more amusing & interesting


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