Slightly OT, but seeking the advice of those who have Solar PV AND a battery

[emmrecs]

As per the title, this is slightly OT but I thought the combined experience of users who have Solar PV and at least one battery might be able to advise me!

We currently have the panels and the required invertor and everything works well, I'm very pleased with the investment.

Unfortunately, at the time of buying the panels I couldn't afford to include a battery. However, now my local authority has a scheme to encourage greater adoption of Solar PV Technology and so has arranged a "group buy" and installation. I expressed interest in the scheme, though making clear my only "need" was to add a battery.

I now have the quotation for the latter (seems to be a pretty reasonable price as compared with the quotation given, which initially included a battery, when I had the panels installed).

But, and this is the reason for this post, the quote for the battery includes an invertor. Since I already have one (clearly) and its software indicates it has the ability to also have a battery connected to it, do I need a second invertor?

All thoughts and advice very gratefully received!

 

[Gadget Geek]

I have an inverter for the solar and an in-built inverter in the battery which work well. Something to consider is that if one inverter fails, the other one will still give you some energy independence until you can get it replaced.

 

[Jomarkh]

With a house battery you have a hybrid invertor your invertor may not work with a battery

 

[emmrecs]

Thanks @Gadget Geek and @Jomarkh.

I need to investigate further but the point about having a second invertor to "take over" is certainly food for thought. In the situation of the original (Solar PV) invertor failing, would the other one take over all its work, i.e., allow the panels to continue to feed the house and/or grid?

Our invertor is a SolaX X1 (web page) if that is of any help?

 

[Ferretusmaximus]

Does the documentation in the quote specify the purpose of the inverter. The house batteries are DC so need an inverter to supply your house grid. So, is the inverter part of the battery system or a separate one for the PV panels?

 

[emmrecs]

So, is the inverter part of the battery system or a separate one for the PV panels?

My understanding (which is very limited) is that it is for the battery only. The quote states This inverter is used to convert the DC current from your battery storage into AC current to use on your property.

I realise the above is wholly correct, a DC>AC conversion for the house is required. But does it need a separate invertor?

Having now found the contact details for the potential supplier I'm going to email them to ask!

Thanks again for all the advice given!

 

[decrep]

I've just had a battery installed and it plugs straight into the existing inverter, no extra inverter.
However they are both of the same make and designed to "talk to each other.

Sounds like your quote, is for a situations that doesn't already include an inverter.

And the 2 systems would run separately.
I think you need to do some research and make sure panels and battery work together as one system. You don't want the battery charging from the grid, if you have plenty of solar.

 

[Gadget Geek]

My Powervault battery uses CT clamps on the grid connection and the solar to control the charge and discharge.

With two inverters, if the battery inverter stops, you can still get solar; if the solar inverter stops, you can still get electricity from the battery. With a combined inverter, if it stops, you get everything from the grid.

 

[Anon70]

Might also be a difference in the power ratings which will impact how fast the batteries can charge and discharge

 

[GaryMG4]

Our LA promoted a similar scheme last year, at the time I wanted to add a battery and Zappi to my existing solar. When the tailored quote came through it was £1200 for the Zappi (£150 more than Octopus) and the battery was a tiny 4.8 kWh and hybrid inverter. Next step was to pay £150 for a survey, where I suspect the battery quote would have changed as I wanted an AC coupled battery to preserve my FiT payments. In the end I declined the quote and went to Octopus for the Zappi.

 

[Willie]

I agree with gadget Geek. with separate inverters if one fails you still have the other one to supply power. I have a Fox-ess solar only inverter coupled with a Growatt battery inverter including two Growatt 6.5kw batteries. Both systems are fitted with ct clamps connected to my Zappi charger.

 

[emmrecs]

@Willie, @Gadget Geek, @decrep, @Anon70, @Jomarkh, @Ferretusmaximus (hope I've not missed anyone who's replied!)

Thanks to all of you.

It seems my present invertor is a "String Invertor", whatever that means, and its manufacturer has advised that it cannot work with a third-party battery, so an additional invertor is needed.

Now, as someone who long ago retired, I have to decide whether I can actually afford to, or perhaps afford not to, make the investment!

 

[JohnV6]

I have 2 inverters as like you I put in PV first.
That means the battery losses are higher as you convert AC back to DC. But as stated it gives you cover for one system if the other fails.

You might want to see if you can get one new inverter to do both jobs.
With the EV as Octopus charge me 7p / kWh at cheap rate I always charge the batteries off peak.
If the sun shines I therefore export at 15 p/ kWh. Since June my dual fuel utility bill has given me an income. In Aug this will be around £12 in credit to me.

The payback on the batteries (4.2 kWh) which cost £3.3 k in Nov 2022 is running at 8.2 years. I beleive batteries are now cheaper. If you consider the income would be taxed if it came from another finanical instrument then as this is untaxed it falls further.