Wall charger installation

WallChargerThe wall charger has just been installed. The installation took about 1.5 hours, excluding the paper work. It was quick because I had already laid the cable from the distribution panel to the bike shed where the wall charger would be installed. That was much more work than the actual installation of the wall charger itself. But hey, I’m just an amateur!

Most of the time was taken up by all the wiring in the distribution panel. To begin with it is three phase, so that means twice as many wires to connect (four wires instead of two). Of course the wall charger needs a separate circuit breaker. An ordinary one would not be good enough for the Zoe, she needs a very expensive one with a so-called ‘K characteristic’, the installer told me.  The wall charger requires a separate earth leakage protector. Finally, because this is a company car, an extra energy meter was installed to separately measure the consumption of just the Zoe. The leasing company will reimburse me for these costs that I will pay through my normal electricity bill from my power company, Greenchoice.

ymvkas4x6The necessary cable is of type 4×6 YMVKas, which means it is a cable suitable for installation in the ground, has 4 conductors of 6 mm² and a woven armour that serves as the earth conductor. The picture on the right shows an example of such a cable. Talking to the installer I found out that 6 mm² is mandatory for the Zoe, she seems to be quite picky when it comes to how her food is served. It is starting to look like she is a real prima donna!

Another reason why I wanted 6 mm² (instead of cheaper 4 mm², which would be allowed according to the Dutch NEN-1010 safety guidelines) are cable losses. Because the cable length is 30 m, ohmic losses would be a factor. The current has to travel the distance twice, and the losses at 16A charging are not negligible. I did a cost/benefit calculation for the different cable cross sectional areas. The calculation is based on 5000 kWh per year and a kWh price of 22 eurocents. The final column shows how many years it would take to recoup the extra cost of the thicker cable, compared to the previous smaller size. I added the 2.5 mm² as a baseline, not because anyone in his right mind would use that for hooking up a car charger. These are the results:

cross section (mm²) resistance @2×30 m (Ω) losses @16A cost/year (€) cable/30 m (€) payback (years)
2.5 0.40 2.8% 31 98
4 0.25 1.7% 19 145 4
6 0.17 1.2% 13 210 11
10 0.10 0.7% 8 332 24

From this table it is clear that the 6 mm² is worth the investment, but the 10 mm² has a very long payback time. So I chose the 6 mm². If you have a Tesla Model S and want to charge at 3x32A, 10 mm² might be worth the higher investment.

graafwerk 3 Last weekend I dug the cable in beneath my garden at the prescribed depth of 70 cm. I wasn’t helped by the horrible weather: a scorching sun and temperatures well above 25º C. To make matters worse, the builders had left all kinds of rubble in the ground when the house was built 40 years ago. That seems to be common practice amongst construction workers: to not clean up your mess, but bury it beneath the garden ^*$@#%)~!.

The cable runs from the front of the house, 10 m through the crawlspace and then 10 more meters through the garden to the bike shed. Stilt houses are very common in The Netherlands, because of the soft soil that characterizes our river delta. My house is no exception and so I could quite easily dig underneath the foundation to route the cable from the crawlspace to the garden. This is not a problem because the house rests on the piles.

The conductors in the cable are solid, which makes it quite rigid. You can not make sharp bends. That posed some problems here and there, but for the most part it was the digging that made me sweat.

Everything is ready now for my Zoe. I hope she feels welcome at her new home and likes my homebrew solar electricity!

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