Battery storage yes or no?

[ric.noble_home]

I am currently getting quotes for a 4kw pv solar system, one of my contractors has told me that battery storage is not worth it as the batteries don't like partial charging during the winter months.
Is this correct?
Also is it feasible to charge batteries during the winter from off peak electricity?

 

[johnb2713]

Change your contractors, that's ********.
You can charge the batteries from off peak energy as well as from the Solar PV. I've run in this way for the last year and use very little peak energy, all of the energy I use is either off peak or free. The off peak rate is 7.5p so a really good saving. Just be sure whatever system you get has an inverter that is capable of supplying your loads, many contractors offer a 3kW inverter which wont cope with a toaster and a kettle for example. I would suggest at least 6kW for the inverter and battery storage to match your daily use..

 

[novelsmike]

Definitely get batteries. You use cheaper electricity at night (Octopus GO or Agile Octopus for example or if you have Economy 7) to charge up the batteries (usually to about 80% in the summer to allow some space for panel generation). You charge them too during the day through the panels. My problem is that once the batteries are full during the day when the sun is out, I feed the grid for nothing though I am investigating going to Outgoing Octopus to get something back. However you need an MCS certificate and DNO letter (from your installer) to sign up for this.

 

[binky]

I am currently getting quotes for a 4kw pv solar system, one of my contractors has told me that battery storage is not worth it as the batteries don't like partial charging during the winter months.

Drivel! Batteries often get partial charging during the summer as well, unless you have a very large solar array .

 

[monkey5]

Definitely get batteries. You use cheaper electricity at night (Octopus GO or Agile Octopus for example or if you have Economy 7) to charge up the batteries (usually to about 80% in the summer to allow some space for panel generation). You charge them too during the day through the panels. My problem is that once the batteries are full during the day when the sun is out, I feed the grid for nothing though I am investigating going to Outgoing Octopus to get something back. However you need an MCS certificate and DNO letter (from your installer) to sign up for this.

I'm with octopus for cheap rate and just going though the process to sign up for export with BG. Not alot payback but for the little "have to" send back when everything else full, but it's better than nothing.

 

[novelsmike]

I'm with octopus for cheap rate and just going though the process to sign up for export with BG. Not alot payback but for the little "have to" send back when everything else full, but it's better than nothing.

Outgoing Octopus pays 15p per KwH

 

[johnb2713]

Outgoing Octopus pays 15p per KwH

Not if youre on GO or Intelligent.

 

[novelsmike]

Correct. You have to on Agile Octopus

 

[johnb2713]

Correct. You have to on Agile Octopus

Looking at my usage, it's not worth it. Intelligent prices are down at 7.5p and I can get 4.5p for export, I always consider I've failed if I export, I aim to store or use all what I generate.

 

[monkey5]

I thought agile moves uo and down on export as well as import rather than a set amount of 15p. I to feel I've failed if I send anything back

 

[johnb2713]

I thought agile moves uo and down on export as well as import rather than a set amount of 15p. I to feel I've failed if I send anything back

I'm sure youre right, monitoring it all and then dumping batteries and solar into the grid seems like a load of grief for few pence kWh, not worth it IMHO.

 

[Andy1733]

I fitted a 5kwh battery to my 4kw system last may and another 5kwh battery last November. So far to date the battery's have discharged 1.677mwh. cost of battery's Inc fittings just under £3900

 

[dooda]

Myenergi eddi is great device to divert any excess generated power into an immersion heater for hot water instead of back to the grid

 

[Joules]

Myenergi eddi is great device to divert any excess generated power into an immersion heater for hot water instead of back to the grid

The OP has received some good practical advice but what caught my eye was partial charging. The contractor is right in one respect, the battery BMS will not operate until the battery is nearly full so cells are likely to be unevenly charged which can degrade it. I agree about pushing excess power into hot water as I have previously done exactly the same thing. One downside was that the gas boiler sensed a partial rise in water temperature which forced it into an anti-legionnaires burn which heated the water by gas to 65C which was self defeating in a way.

At the moment I'm looking at zero export micro solar installs that use an Immersun, these predate the Eddi, to divert power not into a heater but a battery charger. This will involve close loop control that increases or modulates charging power which reduces the amount of export power available. In this way all of the solar power is utilised as either self consumption or stored in the battery for later use.