Eon offering £100 goodwill for mis selling battery capacity, fair?

sewingqueen

I purchased 12 panels and a 5.2 kwh Givenergy battery from Eon, at the time of the quote I was told that the battery had a usable capacity of 5.2kwh.

I have recently had a email from Eon advising that they made a mistake and the battery only actually has 80% of it usable capacity, which they now quote as 4.2kwh

They are offering to perform a firmware update which will give me the 100% capacity I was sold and £100 as compensation.

Or I can leave the battery as it is and have £100 compensation.

From my own research overriding the capacity to 100% may not be in my interest as the 80% is a form of protection for the particular battery, it has not been designed to be charged to 100%, depth of discharge was mentioned. 

Would you agree I should resist changing the capacity to100% if this is not how the battery has been designed?

If I am not changing the capacity, how would I go about working out that £100 compensation is fair?

I am currently on Octopus flux and charge the battery each night so am losing a kwh a day where I can cheaply store energy and of course I loose out when the solar system is generating too.

They say they are offering a blanket £100 because of the complexities of working out how much each person is loosing out on and I must admit I am a bit flummoxed as to how to work out what loss this represents to me.

Any ideas how I can come up with a reasonable calculation?

Between Jan 2023 and Dec 23 we generated 4209 kwh, 1560kwh went to the house, 1232.07kwh to the battery and 1416 kwh to the grid.

Thanks for your help

Netexporter

If it is an LFP chemistry battery I'd definitely take the capacity boost. If it is NMC you can charge to 100% but it is not good practice to leave it at full charge for long periods. Usually a home battery is cycling every day, so the higher SOC shouldn't increase degradation.

Magnitio

Here's a go at a calculation, though much depends on your evening usage:

The round-trip cost of charging and discharging 1kWh at about 18p/kWh would be about 22p. On the worst days, you would have been able to use that 1kWh at peak times when rates are about 40p. You would therefore have saved 18p. If there are 100 such days in the year (hopefully your solar generation will help for the other 265 days) then that is £18 per annum. There is very little difference between the daytime export rate and overnight charge rate, so charging from solar costs much the same as charging from the grid, especially when you take into account AC to DC conversion.

With LFP battery, I would accept the increase and set a min charge level of maybe 5%.

EricMears

If your BMS is able to set a max & min %SOC (surely most do ?)  then you should choose the increase in capacity but use your local settings to work only between 10% & 90%.  On days when you anticipate needing extra capacity you could change upper limit to 100% and lower to 5%.

Magnitio

EricMears said:

If your BMS is able to set a max & min %SOC (surely most do ?)  then you should choose the increase in capacity but use your local settings to work only between 10% & 90%.  On days when you anticipate needing extra capacity you could change upper limit to 100% and lower to 5%.

LFP should regularly be charged to 100%.

EricMears

Magnitio said:

EricMears said:

If your BMS is able to set a max & min %SOC (surely most do ?)  then you should choose the increase in capacity but use your local settings to work only between 10% & 90%.  On days when you anticipate needing extra capacity you could change upper limit to 100% and lower to 5%.

LFP should regularly be charged to 100%.

Another reason for getting them to scrap the 80% !  But of course charging to 100% once a month should be OK.

sewingqueen

Thanks for the replies, I am unsure what type of battery I have, does it say on this data sheet?

Magnitio

It is LFP, so should be charged to 100%. 

mortgageFTB

100£ and getting an improved outcome? Sounds great!

sewingqueen

Thanks for putting my mind at rest