Solar + battery project thoughts


I want to go solar, if not for economical reasons, at least to try and preserve our environment. I now have the proper authorisations from the local authorities for a 20m² solar array (about 3kWp). I have been putting a lot of thinking in that project so I am going to share some here.

Standard system without batteries

First of all, this is a bit daft. Yes I know batteries are expensive, but how much my almost 4MWh (1300 x 3kWp) system will I actually use without storage? Also, if I get some cheap 2.88kWh batteries from eBay at 923€, then I am not so bad off.

Simple inverter or MPPT charger with AC-coupled batteries

AC-coupled batteries system are not cheap  Whether you go for Tesla Powerwall 2 (7000€+), a Sunny Boy Storage (around 1100€) with a high voltage (> 100V) battery or a Sunny Island 3.0M (starts at 2000€) inverter with 48V batteries. The cheapest seems to use a Victron Multiplus charger/inverter (around 1500€ + 330€ for the power meter), but still: buying a storage-ready “hybrid” inverter always comes cheaper (not taking into account the product life time).

Grid-tie hybrid inverter

There are quite a few grid-tie hybrid inverters these days. The cheapest I found here in France is the SolaX X-Hybrid SK-SU3000, which suits my needs at 1750€ and supports 48V batteries. This will of course not provide much backup in case of power failure: only 2kVA via the specific EPS output, but that’s not bad, especially as it uses both battery and solar. A good point is that its MPPT solar charger accepts up to 530V, so only one string of solar panels is needed in my case which means a maximum current of 9A (under 360V) and thus 4mm² cables.

Off-grid hybrid inverter

Why go off-grid when you are in France with a reliable grid? So you can have big backup and grid independence. There is cheap inverter out there that can do just that. Call it Voltronic Power Axpert MKS 5kVA, WKS, MPP Solar PIP-MS, or some other brand (I found it under like 5 or 6 brands, usually in grey but also in red or green), this inverter is cheap (less than 900€) and can deliver 4kVA directly to your home (or more if you buy several and put them in parallel), switching back to grid when necessary (more power needed for example!).

Note that this is not a grid-tie inverter: it either inverts the DC from the solar array and/or batteries or connects the grid directly to the loads. It can charge the batteries from the grid though, if that is required.

One issue I have with it is that, unlike the SolaX, its solar MPPT input is only 115V, so the solar panels need to be arranged in 4 strings of 3 panels, and the current will be high (up to 36A under 90V) so the cables needed will be quite big (minimum 10mm²). I saw some guys on Youtube add an external MidNite Classic MPPT along it but they did not say why.

I should add that, as this inverter is off-grid and not grid-tie, you don’t need any authorisation from your local grid provider, as you are not injecting any current into their system. On the other hand, it really needs to be installed very close to your grid supply…

Edit: there seems to be a new “Heavy Duty” (WKS 5kVA 48V HD, 990€) version of this which cannot be put in parallel, but supports a panel array voltage of 120 to 450V. On top of this, it claims to run the loads from a mix of solar/battery and grid, which would be great, but does it do without injecting? Needs more research…


It’s hard to draw a clear conclusion as there is no clear winner. I also have some issues with space as these inverters are big and require proper ventilation, so having the choice of where to put the inverter is a plus. I shall write again when I have chosen my solution…

Becoming a plumber!

After having tried and failed to find a decent plumber to execute my project, I have decided to take it into my own hands to do the job.

I first started with a simple water heater installation so we can wash dishes downstairs in winter too:

I then removed the last piece of lead pipe in my system and separated my circuits:

Lastly, I started replacing the temporary connections by permanent ones:

Next step is to replace the ready-to-explode steel pipe, but I am failing so far to find the ideal solution to go through my concrete walls!

Still, tiring but rewarding experience, especially as the budget is less than 1k€ including tooling instead of 2.5k€ for the cheapest quote I could get…

Integrating my Daikin A/C into HNet and openHAB

Took me some time to find out that RealTime provide devices to interact with Daikin SkyAir indoor units such as mine. This RTD-10 device talks ModBus over RS-485 links, so I also bought a USB to RS-485 adapter that works.

Thankfully, the RTD-10 comes with two cables: one that connects to the indoor unit 16V power supply (X35A undocumented connector), and one to connect the P1P2 network.

Once all was connected, I plugged the USB to my closest Raspberry Pi, [ab]used the unit test client from libmodbus, and quickly got the on/off, setpoint, fan speed and mode information, and could update it too. I can also read the Daikin remote control temperature reading.

HNet was not really ready for ‘system’ integration, but after a few hours I could read and change all settings from my openHAB application (HNet generates the whole configuration for openHAB 1.x). Of course it is now possible to set some integer to text mapping as “mode 1” does not help much, so we have mode heat (or chaud in the French openHAB sitemap).

Some news

No news, good news!

I did not post in a long time because things are going rather smoothly. Héloïse is still on the path to full recovery and is doing wonderfully at school. She still likes to dress and can change clothes several times a day, to her mother’s despair.

Her brothers are OK too. Pierre has had some support with writing and Ana Paula and I are now jealous of his wonderful handwriting. He can draw as well, which I never could, so I am stunned every time by his skill and creativity.

Antoine is as funny as ever, and as naughty too. We had to put locks on doors that we did not want him to mess with. He talks a lot and we start understanding a little, but as his brother and sister, he is taking longer than other children because of the multi-lingual environment.

Ana Paula is fine too. The house slowly starts resembling what she wants it to be, and lets me enjoy restful week-ends.

À Léna

Ce soir j’ai croisé
Un jeune homme et une dame agée
Leurs yeux de la même couleur
Ils ont touché mon cœur

J’étais allé voir ma fille
Dans une de ces chambres stériles
Et je devais repartir
Pour manger et dormir

J’étais dans un lieu surprenant
Ou n’entrent pas les enfants
Sauf bien sur ceux qui sont là
Où les fenêtres ne s’ouvrent pas

Malgré tout j’étais presque heureux
Tout n’allait pas pour le mieux
Mais quand même une certaine chance
Nous avait souri vu les circonstances

Puis j’appris et je compris
Pourquoi ces gens m’avaient saisi
Pourquoi mon cœur s’est arrêté
Lorsqu’en silence ils m’ont regardé

Ce soir j’ai croisé
Un jeune homme et une dame agée
Leurs yeux de la même couleur
Rouge, couleur de pleurs

12 mars 2013.

ER6-F ’06-’08 mirror replacement

I could not find much on the net about this so I thought I’d take a few pictures and post them… The operation should take less than an hour, taking your time and cleaning the parts as you go 🙂 These are the tools you’ll need: Phillips screwdriver, 10mm spanner and 5mm Allen key.


First thing is to remove the windscreen (easy), then the fairing side tops as shown here. They lift upwards to free themselves from the central part:


Next, remove the central piece, held by two Phillips screws:


The bike will look like this:


With the 10mm spanner, you should be able to unscrew the two bolts that hold the mirror:


Hope this helps!

One year ago

One year ago, Ana Paula called me home early to bring Héloïse to hospital as she had pain in her foot. She still associates her foot pain to her long stay in hospital and the never ending treatment.

Hopefully, one year from now, the treatment will be finished, her hair will have regrown to more girl-looking size, and we will all take a deep breath. Then one day she will know that it was not just foot pain.