Solar Panels

In our ever increasing bid to be green we are now the proud owners of a 4kW Solar array and a 5.8kWh battery. The panels themselves were installed last week. Steve and Dan from Pure Electrics were here today to wire everything up, install the battery and the inverter and get it all up and running.

Solar Panels

The solar panels took up more of our roof than we were expecting. We had 12 360W panels fitted, which is a total of 4.32kW. We can probably fit another 4 or 5 panels on in the future should the need arise which would allow us to increase our maximum generating capacity to around 5.7-6kW.

You can’t really see them from the road or the garden but I did sneak up the scaffolding to get a couple of photos of them over the weekend.

The roof faces directly south so they should be in the ideal position.

Battery and Inverter

With the panels on the roof the job today was to install the battery and the inverter. The battery is a 5.8KWh affair. The inverter converts the DC output of the panels into AC current that we can use. It also determines where the power is needed and directs it there.

The battery itself looks fairly nice in the office. Certainly no worse than the storage heater that was there before.


It even has some nice flashy lights on it to tell us how much charge it has and whether charge is being added or drained from it.

The inverter isn’t quite so pretty and the isolator switches next to it and the cable ducting around it look a little industrial. Fortunately it is behind the door so is never really seen. I guess if we felt the need we could get a cupboard constructed around it to hide it all away.


Energy Priorities

There are of course various ways these things can be set up. We’ve gone with what is probably a fairly standard set up.

When the solar panels are generating it will first be directed to whatever is using energy within the house. We always have the aquarium on and at least the 24/7 weather station computer. There are plenty of other things that are always on and drawing small amounts of power too. A fridge, a freezer, a fridge-freezer, several things on standby, the router, telephones, the water feature, the chargers for our three robots and such like all contribute to our background consumption. This means even if everything else is off we are constantly using about 0.2kW. Anything from the solar panels will go to that first. If we have more power-hungry appliances on such as the shower, washing machine etc then it’ll go to that as well. Essentially if there is enough power coming from the solar panels then it’ll get used by whatever we are doing first.

If there is more power being generated than we are using then it will next go to charging the battery. That will continue until the battery is fully charged At that point, if we have the car plugged in then any excess from the solar panels will go to the car.

Finally, if we are generating more than we are using, the battery is full and the car is either full or not plugged in then any surplus will then be fed back into the grid – we’re not set up to get paid for this yet though and we’re not sure if we can as we don’t have a smart meter and apparently we can’t have one fitted either.

So, the power from the solar panels will follow this hierarchy

Solar -> House Requirements -> Battery Charging -> Car Charging -> Export to Grid

As far as where our energy will come from this means that if we are using less than we are generating it will of course be coming from 100% self-generated solar power. If we are using more than we are generating then any further requirements will be drawn first from the battery and then from the grid.

So, at the moment a few hours after the installation it is pouring with rain and almost dark. The solar panels are barely generating anything (according to the display on the inverter just 90W). From what I can see, the house is using around 0.5kW, so quite a lot more than we are generating. The battery however has 39% charge so we should in theory be using power from that. I’m not completely convinced we are but I’m also not properly familiar with the various displays on the inverter yet.

It seems to be suggesting that the full 0.5kW is being drawn from the grid rather than the battery which isn’t what we want. But then again, the battery charge level has dropped a little which would suggest that power is being drawn from it as intended. I guess we’ll have to keep an eye on it and get used to the various screens. We’ll need some sunshine at some point too so that we can see if everything is working as we want.

We’ll also connect a wi-fi dongle to it soon so that we can monitor things on a app which might make it easier to understand.

It’s not going to change our world or save us huge amounts of money but every little helps.

13 Responses

  1. Avatar forComment Author Mum x says:

    I’m sure you’ll manage to work it all out and hopefully it will save money in the long run .
    Glad it’s all up and running now

    • Avatar forComment Author Alan Cole says:

      I’m sure we will. I’m also fairly certain that the problem at the moment is that the house isn’t using the power stored in the battery. It’s been dark here for 4 hours now and the battery charge level has only dropped by 1% despite having cooked dinner and had the dishwasher on. According to the console on the inverter and our MyEnergi app all the electricity we’ve been using during that time has been coming from the grid. Really, if there’s charge in the battery it should be coming from the battery.

      Hopefully it’s just a setting that the installers can talk us through on the phone. However I’ve checked the various settings and it seems to be set correctly as far as I can tell. Obviously if it’s wired incorrectly or there’s something else wrong then they’ll come back out to fix it.


  2. Avatar forComment Author john david williams says:

    Hi Alan
    How much you can take out of a battery depends on the battery type. I’m not sure of the exact % but lead acid typically 50% and lithium 70+% the figures are available with a search. The battery controller will limit what you discharge based on the type. Perhaps it says in the manual.
    I’d be interested to know what happens with a power cut? Will the battery unit take over?

    • Avatar forComment Author Alan Cole says:

      Hi John,
      It’s a Li-ion battery and the settings say that it can discharge down to a minimum of 10% – so I would have expected it to discharge to that overnight. Maybe once it receives some charge today then it’ll kick in properly – we’ll see.

      As far as power cuts go, then the battery and the inverter do have EPS (Emergency power Supply) capabilities but in the UK we aren’t allowed to use them. Apparently this is a safety issue to protect engineers working on any faults. Usually engineers would of course turn off the power supply from the grid to the area they are working on, but if people are producing their own power then then that could still flow through the grid which might not be ideal for the engineers! So, in the UK we aren’t allowed to use the battery as an emergency back-up in case of a power-cut. There are some special exceptions to this where critical life-support equipment is in place but that requires special permission that I presume the electric companies know about. It’s a shame really as we get plenty of power-cuts here so an automatic back-up power system would be useful. We do have a switch that can turn on the EPS, but I think this just allows the PV panels to charge the battery so that we can still take advantage of the sunlight but won’t allow the battery to discharge or allow any power from the PV to the house / grid.


  3. Avatar forComment Author Anonymous says:

    Great explanation and set up.
    We monitored (and still do) our ground source heating and that helped us change a heat curve setting saving loads. Good luck and great installation!

    • Avatar forComment Author Alan Cole says:

      We did think about ground source or air source heat pumps as well, but as we don’t have central heating it probably won’t be particularly useful for us at the moment. Just our luck really as we never seem to be able to make use of the government grants for such things!


  4. Avatar forComment Author Alan Cole says:

    Just a quick update. It doesn’t seem as though the battery is working.

    Not only were we not using charge from the battery as mentioned in the post, but yesterday while it was sunny we didn’t seem to be charging it either. The solar panels seemed to be working quite well while the sun was out and were generating close to 2kW at times. We were only using around 0.3kW of that so the rest was just getting exported back to the grid. It should have been going to the battery but we don’t think it was.

    What is weird though is that although we don’t think we are charging the battery from the solar panels and we aren’t using charge from the battery when we should be, the charge state of the battery has still be dropping very slowly. It was on 39% it is now down to 19%. If we were actually using it then it should have dropped more than that, but if we aren’t using it then it should have remained at around 39%. So, we’re not sure what is going on.

    One explanation could be that it has been wired up to the economy 7 circuit by mistake. That could explain the behaviour. As far as we know the economy 7 circuit is completely separate and wouldn’t be drawing much power at the moment as there is very little being used on it. It should be just a single storage heater and the hot water tank. This might explain the slow drain of the battery as those appliances might well have used just a small percentage of its charge. It would also explain why nothing else seems to be using the charge from battery. If the battery is on a different circuit to everything else then everything else can’t use it. As far as why it isn’t charging from the solar panels then I’m not sure, but again I guess if the battery is on a different circuit to the solar panels then that would explain this issue as well.

    Pure Electric have been informed and will no doubt have to return to sort things out for us.

    Whilst on the subject of exporting back to the grid, we want to try to avoid this too much of we can as we don;t get paid for it. We can only get paid for it if we have a smart meter and apparently that’s not possible. So, anything we export to the grid gets ‘given’ the the electric companies for free which seems a little unfair.


  5. Avatar forComment Author Ben says:

    Hi @justal. I have had a look at your site, it is really nice. Your Solax installation is also really neat.
    If you would like to get instant readings from your inverter you can get the data by using Modbus. You poll every few seconds and a whold load of data comes back, again I use Node Red to do this and feed to an old Ipad which is now on a stand in the kitchen.
    Are you using your EPS output ?. We don’t have many power cuts but just in case I have wired the EPS output to a changeover switch so in the case of a power cut I can power the house from the battery. (up to 4kW
    Keep up the good work. PS A bit of a coincidence our new Kona comes on 1st March (hopefully)

    • Avatar forComment Author Alan Cole says:

      Hi ben,
      The Modbus / Node Red to ipad sounds interesting – do you have any instruction on how to do this or a link to online guide?

      EPS – We do actually have lots of power cuts here (probably once a month). But no, we were told (incorrectly it now seems) that we couldn’t use the battery as an emergency back-up because the power companies don’t allow it in the UK. We asked a few potential installers the same question as it seemed like a useful feature to use and the fact that the Solax Inverters and battery have the EPS functionality sounded interesting. All companies told us we couldn’t do it so we took their word for it. It would have been particularly useful to keep the PC that powers our online weather station functioning in the even of a powercut, although that wold require the EPS system to kick in automatically and instantaneously in the event of an outage which might not be so easy.

      A manual switch over to EPS mode would be useful in its own right though, but I’m not sure if we can do it.


  6. Avatar forComment Author Anonymous says:

    Hi Alan. I have done a very boring and unprofessional Youtube video on how to use Modbus, you do need some experience with a Pi and Node Red but there are loads of videos on how to setup a Pi and NR.
    or search solax modbus
    EPS I have fitted a changeover switch so if there is a power cut I can power the house from the inverter up to 4kW. Before I operate the c/o switch I ensure that there are no high loads running

  7. Avatar forComment Author MR BENTLEY FLETCHER says:

    Sorry just realized I have repeated myself re changeover switch

  1. Tuesday, November 30th, 2021

    […] couldn’t resist building a Solax WordPress plugin as a project following the installation of our new solar panels and battery. The Solax Inverter has a Wi-Fi dongle that uploads data to Solax Servers where we can see various […]

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Alan Cole

Alan is a Freelance Website Designer, Sports & Exercise Science Lab Technician and full time Dad & husband with far too many hobbies: Triathlete, Swimming, Cycling, Running, MTBing, Surfing, Windsurfing, SUPing, Gardening, Photography.... The list goes on.

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