@simonstengineer I could spend a whole evening in the pub discussing these points with you, and I'm sure we'd each benefit!

The enforcement of MCS rules for properties receiving FIT payments is almost non-existent. How would anyone even know if half your panels suddenly didn't supply power any more, for example?

For many households the value of the FIT payment is unrelated to how much electricity (if any) is actually exported to the grid. And the amount you receive per kWh of export is miniscule, especially now that energy costs have increased so much.

You could move half your existing panels to a more suitable carport roof location where they could be better deployed supplying an off-grid battery. Off-grid resources are not covered by MCS accreditation anyway. What regulation do you think you'd be breaking by doing so?

My roof currently has four separate PV arrays, and one solar-thermal panel.

The one PV array which was installed by an accredited installer was to supply a grid-tied battery with export of surplus. That currently costs me almost £300 per year to buy back (import) the electricity required to keep its cooling fans and internet connection live on the days when there is insufficient solar generation to store any of it. 😱 

It is being externally monitored because it's part of a funded trial. But I can assure you that the MCS installed PV array will be swiftly re-assigned to more efficient purposes on the very day that the trial ceases!

@transparent

So the batteries may not survive afterall? 🙄 

Posted by: @toodles

I wrote to my MP about the very restrictive nature of the siting of garden mounted PV panels

Erm... I think that's the 'wrong' level of Government. An MP would only be involved if the point you're making required a change of legislation (in this case the National Planning Policy Framework) or there was a contravention of government policy. Neither is so in this case.

You can construct an outbuilding in your back-garden under PDR (permitted development rights) provided it does not exceed 2.4m high within 2m of the boundary. If it's further than 2m from the boundary then the 'ridge height' can be up to 4m. There is no separate rule about whether you make the roof from EPDM (rubber membrane), slate or a row of solar panels.  😉 

This is a matter for the LPA (Local Planning Authority), which is usually the District/Borough Council, unless you live in a Unitary Authority area. The Planning Officers have a duty to advise if an application is required. Most Councils have the guidance already on their website because it saves time answering the same questions over and over again.

@transparent

To receive FIT payments one has to provide readings of generation to the designated electricity supplier (which may not be the one from which you now get your supply), and also confirm that you still own the system, that it has not been modified in any way and that it is still functioning correctly.

I don't know if they actually check present generation against previous records, but I suspect moving panels to a more beneficial location may cause questions to be asked.

Since the original FIT payment scheme was quite generous, and lasts for up to 25 years, it would be foolish to risk loosing such payments.

If I was in the same situation I would contact both the local council and OFGEM to see if the panels can be relocated without loss of the FIT payments. Maybe time to play the 'saving the planet' and 'saving the country's energy system' card.

Thanks @derek-m  I haven't researched all the rules that covered FIT payments over the years since 2010. But I have been asked for comment/advice by several individuals who were receiving income from it.

I wasn't aware that the home-owner had to repeatedly affirm that

• the installed system was still functional
• the installation has not been modified

If those criteria apply to the FIT claims being made by @simonstengineer then my suggestion would obviously be different.

But... I'm aware of one early adopter who is receiving 53p/kWh despite never having exported anything to the grid. Although they now have a Smart Meter, their Energy Supplier still requires them to report the export figures manually because they only read the consumption/usage when they receive the meter data each night. Why?! 🤨 

I'm also aware of another FIT recipient who has had alterations to their installation, but never suggested that they were required to report this.  There were faults picked up by an electrician whilst on-site to install a new connection from the consumer unit to the kitchen. The two inverters in the attic were not installed as per the manufacturer's instructions, and one had a broken component inside it. The 'monitoring' appeared to have never operated. As the original MCS installer had long-since ceased trading and the inverters were no longer manufactured, appropriate modifications were made to

• bring both inverters back into operation (adapting internal electronics)
• rewire the connection as it originally should've been done
• ensure the PV system passed current IEEE regulations

Common sense prevailed, thanks to a good local electrician. MCS declined the request to be involved as the installation 'wasn't new'. Eh?!

So my understanding of MCS criteria and its limits of responsibility are based on personal experience.

Posted by: @derek-m

Maybe time to play the 'saving the planet' and 'saving the country's energy system' card.

Well quite!

In an energy crisis, shouldn't we all be using more common sense?

If the UK fails to achieve Nett Zero by 2050, do we expect our representative to that year's COP to say "Yes, but we're British, so we prioritised obeying the regulations" 😖

As a qualified electrician, how would @simonstengineer act if he was called to the second site I've just mentioned?

@transparent

Under the original FIT scheme one gets paid for ALL units generated, not just exported, and a further much smaller payment for half the units generated, which are deemed to have been exported. It is therefore quite permissible to not export any units and still receive full payment.

When our system was installed some 10 years ago, it also included the FIT electricity meter, which had to be registered, I think with OFGEM, by the installer. It is not connected in any 'Smart' way, which is why we have to provide a reading every 3 months. Part of the FIT requirement is that the owner is required to keep records, though I have never been asked to produce such records.

We are registered with EDF for FIT payments, though our present supplier is now Octopus. So every 3 months I receive an e-mail from EDF requesting the meter reading, which I duly take and send. This reading is then 'checked' by EDF, and shortly after the payment is made. Whether EDF actually compare readings over time to ensure I am not 'cooking the books' I don't know, since I have never tried to do so. I don't know if other companies have slightly different arrangements.

@transparent

Balancing cell voltages isn't the most critical feature, although it is often cited. I feel that the safety features are somewhat more important.

It is unfortunate that most sellers still offer BMS units by referring to their ability to 'protect the battery'.

If you want longevity of your investment the balancing is very important, if you think about it the maximum power from the battery is only when healthy and fully charged unless your system allows overcharge. The only protection for ancillaries  from the BMS is overvoltage, something batteries cannot deliver but overcharging due to lack of BMS protection, faulty or unregulated charger can. This is the only protection for your devices the BMS can offer by disconnecting the charger before overvoltage. I would say most tool or laptop batteries are discarded not because the have lost actual capacity but capacity is reduced due to imbalance or one or more cells has reversed due to bad imbalance. Most reversed cells are instantly destroyed. I would say the main and sometimes only purpose of the BMS is to protect the battery 

Interesting comments once more @simonstengineer

If we were discussing only BMS units used in power-tool battery packs, smart-phones and laptops, then I'd be happy to agree with you. Those cells are LiMNC in most cases, and exhibit thermal runaway when incorrectly charged or unbalanced.

There are very few people who would contemplate building a DIY storage battery based on LiMNC chemistry. I do have a storage battery here using LiMNC, but it's a commercially built unit within BMS units from Taiwan integral to the design.

The vast majority of people who need to choose and evaluate a BMS will be using LiFePO4 cells. My comments were aimed at that scenario.

I realise that most DIY-builders do indeed choose BMS units which they select according to the characteristics of the balancing system they offer, amongst other features.

But I wonder if they ever bother to check if the advertised balancing mechanism is really functional?

Have you seen the YouTube videos from Off-Grid Garage in Australia? In particular I'm thinking of the one where he builds his first Seplos Mason box, and concludes halfway through that the balancing system isn't operational!

How many other enthusiast had already acquired a Seplos BMS, whether within a Mason kit or not, and were blissfully unaware whether it was doing any balancing?

And that video is not a one-off. I've seen and read other reports of BMS balancing being tested using external metering, which revealed that it wasn't working or didn't come into operation within the normal charge/discharge cycling of that battery.

Few BMS units undertake balancing continuously. There are two triggers which commonly cause the balancing operation to start

• the cells must be under charge, not discharge
• the cells must be almost full - say above 90%

And yet most LiFePO4 users don't actually cycle their batteries to 90% or above.

Most particularly, those who attempt to derive most of the charge from solar will often be happy if they attain 80% charge on a fine sunny day.

I doubt if the vast majority of those have any idea whether their cells are being balanced by the BMS or not. They've never thought to check, even if they have the equipment to do so.

Since I'm currently surrounded by a large pile of LiFePO4 cells which have yet to be built into batteries, I've had the opportunity to do some actual testing.

LiFePO4 cells have a measurable ability for self-balancing 🙂

If you charge them up in parallel (top-balancing), then immediately build them into a battery in series, they already start to exhibit differing voltages. The natural imperfections which occurred during manufacture are now showing themselves.

(If I'd allowed the cells to 'rest' overnight after completing top-balancing, the effect is nowhere near as pronounced).

If I then exercise my newly-built battery by discharging about 20% of its 'full capacity' and then recharge to 3.55v/cell, I start to see the imbalance appear on the BMS display or App. But switch off the charger, disconnect the BMS balance leads (ie stop balancing from occurring) and watch what happens. The cells which had been displaying the higher voltages will fall further overnight. A large proportion of their 'high voltage' wasn't due to the true SOC (state of charge), but rather was caused by the cell's reaction to the charge current.

Left to their own devices, cells in LiFePO4 batteries do appear to be being balanced. This remains the case even if the balancing feature of the BMS never actually kicked in. 😲 

My present conclusion is that LiFePO4 users are too inclined to attribute their cells' balance to the action of the BMS. It doesn't actually seem to be as crucial as others would have us believe.

@transparent My take on this; whilst you are correct about most of the balancing being done right at the top end of the charge cycle this applies to cheap much less effective BMS systems. I have looked over a seplos system and I would categorise it as a mid to poor BMS system for balance. The cream of balancers are capacitor based and current shift between cells, they work at balancing throughout the voltage range until balanced to around 0.1v. Most poor balancers are just resistors burning off excess energy on the high voltage cells (read very wasteful and crude). If I were building a storage battery for my solar I would have both a standard BMS just for the charger control and under-voltage disconnect and a capacitor active balancer wired in parallel, this gives the best of both worlds as I wouldn't want to cycle LIFEPO4 batteries over 3.55v apart from first charge so the standard BMS would be redundant when it comes to balancing, the professional BMS systems that do the same are very expensive. So in this crazy world it is cheaper to have two BMS systems than one that does the same!

@transparent in a few words I would say "I am not surprised" i refuse to comment any further as I am receiving FIT payments and don't want to have that end!

Ah... so we now appear to be very much in agreement about BMS units @simonstengineer 😊 

That concept of combining a 'standard' BMS with an additional Active Balancer is indeed what the Off-Grid Garage you-tube channel did to resolve his gripes with the Seplos Mason box. And I've seen a similar approach being undertaken by others online.

As the group of development engineers with whom I work are actually creating a new Smart storage controller, we are in the fortunate position of being able to incorporate features which might be useful, even though we don't require them for our own purposes. One such feature could be an output signal which could be used to tell a BMS or Active Balancer that it should initiate a cell-balancing operation.

I haven't yet found a BMS which could receive such a command, but it would cost naff-all to have such a software/hardware signal available in case such a BMS comes along.

We're contemplating buying in a couple of very high-end BMS units at the moment. Yes, they'll cost £000s but it would be interesting to compare with the lower end of the market. There's no harm with us being able to support as many BMS strategies as possible.

There aren't actually that many different BMS systems available in the world. Unsurprisingly the vast majority are manufactured in China, even if designed and sold by an outlet in the Western world. Overkill Solar (USA) is just such a case. They enhance and modify the JaiBaida (JBD) BMS, made in Guangdong.

Some promising BMS designs seem to lapse before they really get started. The Cosun Active BMS was designed in Germany, then manufactured and sold from China. But there's no response from either end of the operation any more.

The growing energy-crisis and concerns about global warming look set to expand the requirement for domestic storage batteries.

It would be extremely useful if this spurred on some newly-fledged university graduates to design & manufacture a mid-range BMS unit here in the UK.

I contacted my MP on this matter because it was soon after the Glasgow COP, and at the time, much noise was being made about encouraging homeowners to put up some panels and start on their renewable energy projects. I was researching my own possibilities and options at the time and it struck me that local government and national government were very much at odds. I attempted to discuss with my own council (Unitary Authority area in my case) but I was politely deflected and requested to pay a fee before anyone could possibly advise or even comment! (I had read all the guidance on the website first but wanted further details.)

Regards, Toodles.