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…

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.

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!

Changing jobs

As most of you probably know by now, Texas Instruments (AKA TI), which still is my employer, is going to close down its Villeneuve Loubet development centre. The official notification is expected end of June. Knowing that the decision from TI was taken middle of November, one can understand why Google and Amazon are not keen on investing in France! 7½ months to close down a site is just absurd IMO.

Anyway, I was fortunate enough, like a number of my ex-colleagues, to suspend my work contract with TI and start a new job, at NVIDIA. The job is interesting and the colleagues are very nice, helpful and knowledgeable, so I am quite happy so far!

BTW, TI was not about calculators but processors for phones and tablets and NVIDIA in France is not about graphics card (where they are n°1) but modems and integrated processors for phones and tablets.

On extended warranties…

I did not take the extended warranty for my Bosch dishwasher. The reason is that I bet it won’t fail, or if it does, I will be able to fix it for cheap. A few days ago, after two and a half years, it failed, so I went searching the Internet for clues. It quickly became clear that only two parts where known to fail:

  • the control board can have a solder point melt
  • the flow meter can start faiing

A quick check to the control board (thanks Internet for the unmount instructions) led me to order a new flow meter for the huge amount of 24 €, P&P included. Changing it was rather easy and did the trick! No thanks, I won’t take the extended warranty – just cross my fingers instead!