Speccing new PV install for DIY battery

[rikdogguk]

Hi

I’m in the process of speccing a 6kw pv install. The batteries offered by the installers seem poor value. I’d like to have the option to install diy in the future - possibly the Fogstar 48V rack system or similar.

My system will come with a 5kw GivEnergy hybrid inverter and will allow export to the grid. The installation manual for this inverter indicates adding a battery would appear to be relatively straightforward (connecting battery to correct terminals on inverter plus comms cable). Am I missing something and this more complex? I’m aware of need to adequately earth battery and add means of isolation between inverter and battery.

Would I need to notify the dno? Presumably they will already be notified as part of the pv install and the max rate of export into the grid will be the same whether the energy comes from solar or the battery?

Apologies if these are silly or uninformed questions, I am still learning!

RD

 

[SeaGal]

Welcome!

The installation manual for this inverter indicates adding a battery would appear to be relatively straightforward (connecting battery to correct terminals on inverter plus comms cable). Am I missing something and this more complex?

I'm not familiar with GivEnergy, but you would need to check compatibility of battery's BMS to inverter connectivity. Givenergy is not one listed on Fogstars compatibility list. Check with GivEnergy to see what battery protocols they support. If they support generic SMA or Pylontech protocol you _should_ be OK. It could be that they use a proprietary protocol to tie you into their expensive batteries. If so, choose a different inverter.

Would I need to notify the dno? Presumably they will already be notified as part of the pv install and the max rate of export into the grid will be the same whether the energy comes from solar or the battery?

G99 approval will need to be sought for a 5kW grid-tied inverter, but presumably already done or in the process. That covers the inverter whether or not you are using it with batteries.

... I am still learning!

We all are

 

[rikdogguk]

@SeaGal thanks

Reflecting further I am thinking I can realise the majority of my financial savings through a battery only install (no solar) and diverting my energy use to off peak tarrifs. The Fogstar batteries are incredible value and will payback in 3-4 years.

If I use an inverter with no export capability then DNO notification is not required (I believe) which also simplifies things. Still learning….

 

[Hedges]

An inverter which is grid-interactive, synchronizes to grid and blends in power from battery (and possibly PV) lets grid supply what it can't including motor starting surge. It may be permission to connect is required in that case.

These can operate as UPS, feeding only downstream loads. Or they can use current transformer at meter, backfeed to the house but not the grid.

You may want PV later for extended backup or for other reasons, so consider inverters which support optional PV and battery.

In the US, SolArk is popular and supports many modes of operation. Over there, likely Deye or another name is similar but lowrer cost. Also look at the SMA Sunny Island and their high-frequency hybrids (one single phase, one three phase.) The higher priced supported batteries may be a reason you don't go with those, but good to understand what features various brands offer.

 

[SeaGal]

@SeaGal thanks

Reflecting further I am thinking I can realise the majority of my financial savings through a battery only install (no solar) and diverting my energy use to off peak tarrifs. The Fogstar batteries are incredible value and will payback in 3-4 years.

Possibly, but do factor in conversion losses - ballpark 10% loss from 230V AC to 48V DC and same again back to 230V AC. Adding 16 PV panels (around £1500) will likely make you self-sufficient power-wise for 6 months, which is a pretty good payback

If I use an inverter with no export capability then DNO notification is not required (I believe) which also simplifies things. Still learning….

Only if your inverter is not grid-tied. For grid-tie, a type tested / approved inverter for < 3.6kW (G98) then DNO retrospective notification is required. For > 3.6kW G99 prior approval is required. See also my posting here for more details..

Octopus Energy will no longer require MCS certification in the UK

https://gtec.co.uk/clause-5-8-octopus-opens-up-the-solar-pv-market-with-a-paragraph/ I'm not sure how exactly the UK's permitting and approval process works but this sounds like a major win for DIY.

diysolarforum.com

re...

Over there, likely Deye or another name is similar but lowrer cost.

In UK Deye also sold under Sunsynk brand. I have Solis which is also popular in UK.