Hey,
I can't believe I'm the only person wanting to do this but I either don't know the right language or it's maybe technically not possible?
I want my inverter to use the battery to power the house (only .30-.45kW average load) and allow the entirety of the solar output to be fed back to the grid. Currently, if the solar array is generating 5kW, the inverter will power the house (e.g .40kW) and send the rest (4.6kW) to the grid whilst my battery sits at 98% because the sun hits our panels at 5.30am.
It seems like a waste and, over the last month, my battery hasn't discharged below 65% in the evening because we're left with so much surplus whilst I'm losing export value.
Am I missing something?
You can’t use the battery to run the house whilst you are generating solar, house load is always prioritised first.
What you can do is to set the work mode to feed-in first which changes the priority to house load, export, (battery only if export limit exceeded) - if you set a schedule to change the work mode at (say between 10am and 7pm) to feed in first then the battery would get a bit of charge to start, then after that all the solar (less house load) will go to export.
What you can do is to set the work mode to feed-in first which changes the priority to house load, export, (battery only if export limit exceeded) - if you set a schedule to change the work mode at (say between 10am and 7pm) to feed in first then the battery would get a bit of charge to start, then after that all the solar (less house load) will go to export.
Thanks. I already have the work mode set to feed-in 100% of the time. Just a shame that I have 10kWh sitting there doing nothing whilst I'm unable to utilise it. Could totally understand if it was pulling a load larger than the rated output but we very rarely if ever are during the non off-peak hours.Dave Foster wrote: ↑Thu Jun 20, 2024 10:05 pm What you can do is to set the work mode to feed-in first which changes the priority to house load, export, (battery only if export limit exceeded) - if you set a schedule to change the work mode at (say between 10am and 7pm) to feed in first then the battery would get a bit of charge to start, then after that all the solar (less house load) will go to export.
Would it make sense maybe to schedule a forced discharge towards the end of the evening to at least generate more return on stored energy? I'm on Octopus Intelligent Go so 7.5p import (11.30pm-5.30am) and 15p export 24/7.
Yep agree, it’s the age old problem of having batteries in summer when they spend a lot of time full, compared to winter when they spend most of their time empty.
At 15p export it’s probably not worth exporting the battery (a rough rule of thumb is the battery costs approx 8p/kWh to purchase and install) so buying at 7.5p and with 10% losses would actually be costing you (nett) 1.5p.
But the other way of looking at it, is your batteries are bought and paid for and so everything you get over 7.5p is a bonus, only you can make that call
I know quite a few people that export batteries with the Flux tariff between 4 & 7pm, some actually switch from Go to Flux in summer, and then back again in winter - like you i’m on IOG and don’t (normally) dump my batteries.
Thanks. I'll try an evening forced discharge to see what difference it makes.
This still the best way of achieving this?
I was a bit disappointed to learn after install that I couldn’t just export everything I generate and run off overnight charged batteries.
Would be great to remove house load from the feed in priority.
I was a bit disappointed to learn after install that I couldn’t just export everything I generate and run off overnight charged batteries.
Would be great to remove house load from the feed in priority.
Sadly it is not possible to remove house load, basic laws of physics it has to be overcome before the direction of flow is reversed to export the remainder.
Re: the battery figures for when it becomes worth charging from grid at night and exporting to grid in the evening.
I calculate it, using nice round figures, with 0% loss
(a) Cost of 2x EP11 inc labour VAT = 0% lets say £5000 (a)
(b) Effective capacity = 20kWh * 90% = 18kWh (b)
(c) Loss of battery capacity after 4000 (c) cycles = 20% (d)
therefore
Loss in value of battery = d * a
= £1000 (e)
Cost per cycle = (e) / (c)
= £0.25 (f)
Cost per kWh = (f) / (b)
approx 1p
So my figure for the added overhead when charging/discharging is around 1p. If you buy at 15p at 2am and sell at 25p at 6pm you make 10p on the deal and lose 1p on the depreciation = 9p. To me that makes sense.
I calculate it, using nice round figures, with 0% loss
(a) Cost of 2x EP11 inc labour VAT = 0% lets say £5000 (a)
(b) Effective capacity = 20kWh * 90% = 18kWh (b)
(c) Loss of battery capacity after 4000 (c) cycles = 20% (d)
therefore
Loss in value of battery = d * a
= £1000 (e)
Cost per cycle = (e) / (c)
= £0.25 (f)
Cost per kWh = (f) / (b)
approx 1p
So my figure for the added overhead when charging/discharging is around 1p. If you buy at 15p at 2am and sell at 25p at 6pm you make 10p on the deal and lose 1p on the depreciation = 9p. To me that makes sense.
There are many ways to calculate this, and the EP11’s represent the most efficient and cheapest LFP batteries to date from Fox - as you say you have not taken losses in to account, nor the 10% of the batteries you cannot use (but have paid for) perhaps more importantly is at what point would you change the packs - i.e. would you really keep using them if the cycle depth was only 40% ?, not to mention cycle ageing would be much faster as the batteries age (superlinear).