@hydros Yes, I'd like to buy the batteries for a project I'm doing under the guidance of @Transparent who lives a few miles from me.

We've known each other for a number of years and have already worked together on energy projects.

I happened to call him today to see if I could pop round for a chat and he told me about you wanting to sell batteries.

What a coincidence!

Hopefully, he has independently emailed you my contact details.

Looking forward to hearing from you.

@evermore and I met during the Ofgem-funded OpenLV project in which 80 local substations were fitted with monitoring equipment by EA Technology.

I'm still hoping that the discussion on how he implements the LiFePO4 battery build will appear here. What he learns is just as useful for others to read about, even if I do live within 10 miles of him.

Posted by: @transparent

It's the manufacturer you need to be specifying.

Yes I've been requesting EVE LF280K cells (Grade A, brand new, welded studs) from all the suppliers I've been talking to (Basen, Xuba, Qishou, and tried to contact Luyuan this morning).

In all, there has been very patchy interaction with the sales-people; the communication could be better (e.g. requesting welded studs, being sent pictures of grub screw versions, querying that and then being told "Yes they are welded studs type").

@transparent any thoughts on battery chargers/inverters. I want to add a second as my second batteries can't be used with the pylontechs. But it's pretty scant out there for chargers at the moment. Any recommendations?

I have lots of thoughts on inverters @batalto !

Most people assume that an inverter will be able to charge a battery from the Grid and then operate in reverse to supply 240v AC back to the Grid (& home). To achieve this the inverter uses the 50Hz grid frequency to synchronise.

Such inverters must

• have G98 certification
• be installed by an approved MCS electrician
• and have the connection approved by the DNO

G98 dictates a number of basic requirements, amongst which is the crucial one that the inverter must cease export within 20mS of a grid failure. Ie your battery cannot work as a backup device.

If you have two or more devices which can export back to the grid (and/or home) then you require G99 approval from your DNO. The default position is that any inbuild current limitation won't work, and that both devices will export simultaneously. I've written a comprehensive overview of these G-standards and permissions here on the OVO Forum.

The sort of inverter I've been investigating over the past year is the type which does not (and cannot) export back to the Grid.

This design has its own internal 50Hz generator, thus making its 240v AC output unsynchronised.

There are far fewer of these inverters, and a great number of manufacturers/suppliers who claim that their particular model works like this. Most also have grid-export capabilities.

I have a Growatt SPF5000ES here, operating as a totally off-grid inverter. It currently supplies a 14kWh battery from either the Grid or solar.

However, this model is extremely hard to buy. I've had more on order from different Far-East suppliers since 4th Feb 2022, and I'll be fortunate to have any arrive by the end of July.

Off-grid inverters fall outside of the requirements for DNO permission and MCS-accredited installers.

There is also no safety-guide beyond the need to have the 240v connections made by a qualified electrician. So there are plenty of ways to make mistakes and damage batteries, inverters and yourself!

@transparent cheers for that. Any recommendations on what might be in stock and reasonably priced. I'm kicking myself for not buying a used Sofar for £300 last year. Live and learn

You'll need to better define what sort of inverter you're looking to buy, @batalto  where the battery connects and what devices you're intending to supply.

Would you feel up to creating a rough schematic of your intended layout and posting it here?

I'm hoping for a pencil sketch with some labels if possible. Please don't try to emulate the colour diagrams I've been posting. We really need something of the level where others will say "I could post something like that too!" Just sketch it, take a photo with a mobile phone and upload it 😎 

@transparent I'm currently drinking gin out and about. I'll see what I can knock up later... 

Posted by: @transparent

Such inverters must

• have G98 certification
• be installed by an approved MCS electrician
• and have the connection approved by the DNO

Can I quickly clarify just what needs to be installed by the MCS electrician; is it just the grid side of the inverter (current clamps, circuit breakers and AC wiring), or does this apply to the BMS, batteries fuses/circuit breakers, batteries and certain inverter settings? Put another way, for a battery storage system what level of self-build is acceptable?

Good question @chickenbig

The MCS installation certificate is required by the agency who arranges for you to obtain SEG (Smart Export Guarantee) payments. In my case the approved agency was my Energy Supplier (OVO). Unless they can tick all the boxes for your site, then no payment can be made for electricity sent back to the grid.

That pretty well scuppers any DIY input to the process.

An MCS approved contractor has to recoup the expense of the training courses and annual fees for the business. So they're going to be pretty strict in having everything specified and done by themselves... right down to the screws used to fix PV mounting rails to your roof.

Whatever they install for you must be equipment that has been tested, approved and listed on the MCS database. If any component part isn't MCS-approved, then the contractor can lose their licence.

That means the only battery storage systems available to you are the mainstream commercial units. To obtain their MCS accreditation, those batteries will have been required to have inbuilt BMS, fuses etc.

If you want to use DIY knowledge and skills, then you're restricted to energy storage systems that do not export to the grid.

For similar reasons you're not allowed to install your own Heat Pump or EV charge-point. Both of these devices are categorised as Low Carbon Technology, requiring approval from your DNO. The process includes identifying the approved contractor.

@transparent Thanks for the info. I now know what (Australian) Andy from Youtube channel Off Grid Garage feels like; his power company prevented him extending his home's solar panel setup so he took his garage (and EV charger) off grid.

It seems as if the MCS has the PV/energy storage/heat pump market stitched up! I can understand the safety reasons for this, but I can't help but feel it may somewhat slow down adoption given the limited pool of MSC approved installers.

In my case, I am part of a group-buy scheme but the winning installer wants to install LiFePO4 batteries (Fox ESS) in the loft. Aside from the increased weight on the ceiling, storing charged LiFePO4 batteries in a hot loft will cause them to degrade very rapidly. Hence my desire to install an inverter and self-built batteries (to save some money) elsewhere.

Trying to find a way to work with the "If you want to use DIY knowledge and skills, then you're restricted to energy storage systems that do not export to the grid" statement, is it possible for a DIY-er to install (or manage the installation of) some G100 approved battery storage inverter (connected to self-built batteries) and keep export to grid set to 0W (or some small positive value) to prevent exporting self-generated solar power? Not being able to export energy at peak times takes away some of the economic motivation for installing an energy storage system (peaking using Octopus Agile), but there is some justification to maximise solar self consumption.

Posted by: @chickenbig

the winning installer wants to install LiFePO4 batteries (Fox ESS) in the loft

And how will their system protect the batteries against damage from charging below freezing? See this reference.

Posted by: @chickenbig

is it possible for a DIY-er to install [...] some G100 approved battery storage inverter (connected to self-built batteries) and keep export to grid set to 0W [...] to prevent exporting self-generated solar power?

Technically, yes.

Legally, no!

The mechanism by which grid-export is kept to zero is itself subject to DNO approval. In effect, if the combination of component parts you wish to use is not already on the ENA approved list, then you won't get the G99 certification from your DNO.

I have a PowerVault 8kWh storage battery with inbuilt export limitation controlled by software and a current clamp (ie G100 certified). However, when seeking G99 approval to add a Growatt string-inverter, the DNO required that to be of no greater throughput than 3.6kWh. Ie because that combination wasn't on the ENA list, the current-limiting system within the existing (G98-installed) PowerVault battery was no longer 'trusted'.

The DNOs are not trying to make life awkward. There are very good technical reasons why they will not allow such possibilities of grid-export, particularly from single-phase sites.

I've benefited by being part of the OpenLV Project, working with monitored substations, and talking with network engineers. I was astonished at the losses being incurred on the distribution grid, and I'm fully supportive of Ofgem requiring DNOs to reduce these under the new RIIO-ED2 licence arrangements.