Category: EV driving and charging

In this post we will describe our solution for charging Electric Vehicles from your home across the public pavement when using our super thin EV cable mat with rubber slabs.

Due to the rapidly growing ownership of electric cars, and the fact that roughly 60% of the Dutch population can not charge their car from within their own property, charging across public pavements has become an issue.

25% of Dutch City Councils is involved in pilot projects about all sorts of solutions to get the private energy-infrastructure used for charging ones own EV.  But- there is no general regulation for this.

And- you really don’t want to get all sorts of different solutions for putting charging cables in the way of pedestrians, especially not when these solutions leave something in the way after it has been used. Certainly you don’t want to put anything in the way of people with baby walkers, playing children, people with disabilities, elderly or people that use mobility walkers.

Numerous solutions have been tested and there is not one solution that fits all.

Most promising appears to be the solution of a pavement gutter in which the charging cable can be pushed in, during charging.  But- it has also proved to be difficult in practice since this only works well if no-one interferes with its usage.  If the cable is pulled out, it will be in the way of everyone that needs to step over it.

In my mind, a simpler solution will be required by thinking unconventionally,  typically out of the non-electric box

The problem is that we want to charge the car’s battery from our existing solar panels, we then want to make use of the EV’s battery for our home aplliances through the Vehicle to Load feature during the period that there is not enough sun to use the solar panels.  Then, we can really close the energy circle without additional investments in home batteries and so on.  That is what this is all intended for.  Multi-use of the EV’s battery and of the available solar power.

BUT- this can only work with the EV’s battery connected to your home.

And the public pavement needs to be crossed.

One of the possibilities to do this could be by constructing a charging/Vehicle To Load cable that is flat enough to behave as a doormat on the pavement.  This mat must be flat enough to not cause any interfecerence for pedestrians, walkers and so on BUT it must be tough enough to keep its form and electrical characteristics during its use.

In my view, the flat cable mat should have flat start- and ending docking cables,  reshape to normal round cables and EV charging connectors, connecting to the EV’s charging port and the other end to the charging point at the home.

EV charging from A/C has a maximum power of 11kW, 3 phase 400 Volts.

The current will be 16 Ampères x3 lines and per line at least 2.5 mm2 is required.

Some insulation in between the wiring is regulatory required.

For the 2 management wires we will also use round wires.

We will need 5×2.5mm2 and 2 control wires, a total of 7.

Standard flat elevator cable will be used of 7×2.5 mm2, see the below picture, the lowest one.

And- the mat will need to be wider than this, since we can use this to bring the height (thickness) back to 2-3 mm at the end of the mat’s side.  That gives the look and usage experience that the EV cable mat is hardly in the way of the walking/rolling path.

 

Our ‘patent pending’ design of the  Jantec.nl  EV charging pavement cable mat:

Total width of the EV pavement cable mat is around 40 cm

The slab has the behaviour of a normal doormat. We will pour our rubberized mat around the center EV-cables part.  The rubber will protect the cables and will also keep the EV cable mat flat on the pavement.

Cable center part is only  1,5-2 cm wide and  only 5 mm high (thick)

The EV cable mat will become available in lengths of 1, 1.5 and 2 meters.

At both ends the copper wires are bound into a regular round cable with 2.5 meters of cable, including regular Mennekes a male and a female charging connector.

 

NB: The product is under evaluation 2022-10-29.

Pricing is yet unknown, but will be above Eur 300 per set.

For the  time being,  I will use my old rubber mat that has a cut-out already, although the cable is clearly visible through  he mat.  But it does work!:

 

EV-battery types and their basic differences:

NMC532, NMC811, NCA, solid state and LFP

Due to growing demand of raw materials, required to produce large capacity batteries for electric vehicles, prices are rising and the development of batteries that require less expensive materials is growing.

Lithium-Ion is almost always the  basic component  for existing EV-batteries.

The way that the current is brought to the Lithium is via a cathode and an anode.  The used materials for these cathode and anode differs, and this has great impact on stability, life span, kw/gram thus maximum current and deterioration behaviour of the batteries.

LFP batteries

Recently a new type of battery has been developed, using another type of materials for the anode and cathode than NMC batteries:

The lithium iron phosphate battery (LiFePO4 battery) or LFP battery (lithium ferrophosphate) is a type of lithium-ion battery using lithium iron phosphate (LiFePO4) as the cathode material, and a graphitic carbon electrode with a metallic backing as the anode.

LFP can be cycle-charged to 100% at least 2000x.

But LFP batteries (and -by the way- NMC532 as well) are less compact than NMC811 and NCA batteries. That is because LFP batteries have less electrical capacity per volumetric unit than NMC811 and NCA batteries.

The result is that smaller to medium sized cars will not be able to carry more than an 50-55 kWh LFP  battery pack.

It is expected that LFP batteries will become cheaper than NMC type of batteries in the long run because iron phosphate can be made without  material availability restrictions, while the required raw materials for NMC and NCA batteries will become even more expensive over time.

 

NMC (or NCM) and NCA batteries

The mainstream of Li-ion batteries, however, is currently NMC (and Tesla’s NCA long range and LFP standard range),  with different types of battery composition.

Tesla’s NCA development of batteries for the Tesla3 long range and new Tesla model S long range types has its own kind of composition for the batteries as is also shown in the below raw materials overview:

 

NMC811 batteries

The latest development within the NMC type of batteries is NMC811, which has more power in a smaller pack but requires a very strict producing method and a very tight Battery Managment System.

NMC811 batteries  will deteriorate quickly if they are repeatedly charged at their max power capacity and it is recommended to charge the battery pack as little as possible above 80% of its maximum capacity.

And- it is recommended to only charge to maximum capacity when the charge will be used immediately after charged.  For instance when a large trip is made, before heading off and in between the trip.

NMC811 has a maximum full charge cycle of 200-300x, when performed according to the recommendations.  This might be the main problem with these type of batteries, but in practice it might mean a lifespan of over 8 years.  Provided that you only charge to 100% for the holiday trips.

NMC811 makes it possible to equip a small/medium sized EV(SUV) like the MG ZS EV (2022 version) long range with a 74 kWh NMC811 battery pack.

 

Solid state batteries

Solid state batteries are also becoming available, and these batteries provide the best performance in a similar – or possibly even smaller build volume than NMC811 batteries.

But Solid state batteries are still quite expensive and are not commonly available.

Toyota is one of the main developers of solid state batteries and will equip their hybrid cars with these batteries.

It will be interesting to find out wether solid state batteries will outperform the older//existing type of batteries in the long run, since hybrid cars make maximum use of the charge/recharge cycles.

 

Summary

For small EV’s, LFP will be the best choice. (less range required, usually city cars. USP of LFP: 2000+ times possible to chargecycle @ 100% full capacity.

For the mid-to higher segment, NMC811 and/or NCA will be the best fit. USP of NMC811: more capacity makes longer range possible, with requirement of a very good BMS. Due to less usage of expensive materials in NMC811 (less cobalt&manganese) the price for NMC811 is within affordable range.

For the highest segment EV’s, solid state will be the best option. Solid state is more expensive, smaller, more capacity, recycling to full power is no problem.

For Hybrid EV’s either LFP or solid state can be applied, but not NMC811.

In the Netherlands, City councils usually forbid to put charging cables for electric vehicles on public pavements.

And- to charge your electric car, of course you want to use your solar panels and connect your EV directly to your own domestic power grid.

But what do you do when your municipality forbids you to lay the charging cable across the sidewalk to your car?

My municipality has passed a council resolution whereby you can order a charging station through an external party, and so then you can have a public charging station installed nearby.  Provided there isn’t already a charging point within a reasonable distance.  In my neighborhood there are hardly any charging points, and the only one I have been able to find niche about 400 meters away, consisting of 2 AC charging points where two cars are always charging.

In my search for possible solutions to still make it possible to get to the car via the public sidewalk so that I do get to charge the car at home, I have come across several solutions.  Of those solutions, only one is really useful, because all solutions with cable trays or cable protection over the sidewalk can still lead to liability issues if someone trips over the cable or is otherwise inconvenienced by the cable over the sidewalk.

The solution of using a hinged cable tree placed high on your facade to get the cable across the public sidewalk directly to your car is a pretty eye-catching solution.  But- the sidewalk remains free of obstacles and no one is bothered by it.  Except perhaps for the fact that it doesn’t look very pretty.  I wonder how the municipality would want to and can- prevent this solution.  After all, similar things like flags on the public sidewalk at a sufficient height are not enforced either. If that is even possible by law.

In terms of principle, it looks like this:

The lever can be moved upwards after use.  Then the whole tree falls away into the vertical holder.  Very nice, just a pity that the link to the supplier doesn’t seem to work anymore.

For my home situation, I prefer to place the lever on the facade. With a hinge point, the lever can then be moved away nicely against the facade after use, where you can attach the lever.

Below is an example of a company that makes these levers for hanging welding shields in factory halls.  They also exist in extendable versions up to a length of 6 meters.

When you create such a solution, it must of course comply with all the rules and regulations, and the design must be such that it fits in with the surroundings.  The choice of color and material is also a matter of concern, and it must not cause any inconvenience, such as clattering against the facade, etc.  And the structure must be professionally grounded.

I do expect resistance from the local authority because they assume that electric vehicles are still in the minority and that there is therefore no need for a serious solution for home charging in public parking spaces.

The world is changing so fast towards electric personal transport, the sale of new cars already consists for 10% of electric cars.  Of course the subsidy schemes help with this too, but all those cars sold are just going to drive and need charging spots.

Given the fact that people that already installed solar panels at their home are also the first people to drive electric cars, these people also want to use their installed solar panels for their electric transport.   And as long as the net metering regulation for the return of energy is still in force in the Netherlands, the pressure on necessarily wanting to charge the electric car at home will not be very great.  But with the rising energy prices suddenly making public charging much more expensive than charging at home, the pressure on wanting to charge at home using one’s own solar panels could become much greater.

VEHICLE TO LOAD

In addition, the latest development to run your home on your car battery is suddenly serious, because all brands now supply electric cars with a vehicle to load connection, which means that you can also use your charging cable to feed energy back into your home.  This means that during the day you can charge your car from your solar panels and in the evening you can use the energy from your car battery.  An average family consumes 8kWh in the evening and the car usually has about 50-70 kWh available.  Most private solar panel installations start at 8 panels and that is exactly enough to fully recharge the car for the use of 8kWh per day on an average day during the 8 so-called sunny months of the year.  And the months of November through February? You will still have to ‘buy’ electric energy during these 4 months.  Preferably with wind energy from a green supplier, of course.  When you drive your electric car to and from work every day,  recharging your EV from your solar panels for those days is obviously not true.  But when you regularly work at home, the story does apply for those days, as well as the periods during the weekends when you are plugged in at home.