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Last Post by Transparent 3 months ago
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 JohnR
(@johnr)
Estimable Member Member
Joined: 5 months ago
Posts: 106
03/01/2025 4:53 pm  

One detail that you may want to consider is the warranty on the battery. I recall that the warranty (minimum 70% storage capacity aftre 10 years) for the Powerwall 2 was conditional on the the total energy throughput which worked out to be one full charge / discharge cycle per day. However, if your anticipated 2.5 charge/discharge cycles per day is the worst case then this may average out to nearer unity over a year.


   
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Transparent
 Transparent
(@transparent)
Illustrious Member Moderator
Joined: 3 years ago
Posts: 2365
04/01/2025 4:03 pm  

Well I'm pleased to see you doing the background research first @broadsman !

I can assist with the technical issues, but none of us can adequately predict the future tariffs on which you are building your viability assessment.

I have a fair idea of how future tariffs should work over the next 5-years as the electricity grid is decarbonised.
But both DESNZ and Ofgem have been demonstrating a propensity to manipulate the electricity supply system by 'regulations' rather than the laws of physics.

Yes, there will still be frequent cheap-rate periods, but they will be less regular.
The overnight cheap-rate can't survive because it's based on Combined Cycle Gas Turbine (CCGT) generation, for example.

 

Turning briefly to the matter of a Tesla PowerWall-3:

These Powerwalls vary considerably from the 1st generation which used the same LiMNC chemistry as Tesla cars.

The Lithium Ferrous Phosphate (LiFePO4) chemistry is inherently more stable and can be recharged more often for a given 'loss of capacity'.

However, it's very difficult to assess this because each LiFePO4 cell manufacturer uses a different standard.
Typically they will state something like "10,000 charge/discharge cycles over its lifetime".
But the 'lifetime' might be to 70% of the original stated capacity (in Amp-hours)
or 80% of the actual capacity when first supplied.

These are two different concepts.

All cell manufacturers sell products with a higher actual capacity than that which is advertised.
A cell labelled 280Ah, might actually have 298Ah.
The 280Ah refers to the minimum capacity, in order to satisfy its A-grade rating and trading standards legislation.

 

Equally, households with battery storage aren't very likely to put those cells through complete charge/discharge cycles.

Most of the time we'll be using only the central portion of the available capacity, whilst leaving enough in reserve to ride-out a power-cut.
So our cells won't 'age' as fast.

StorageUse

 

Have you seen the YouTube clip in this post about the new battery/inverter products to be released by Givenergy this year?

It's not the approach which I'm taking, but it's certainly one which might appeal to you.

Save energy... recycle electrons!


   
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