Tag: Skylla-TG

Charging Leisure Batteries at Electric Vehicle Charging Stations

I am not the first and probably not the last, either. With leisure batteries becoming larger and larger, fuel becoming more and more expensive and the EV charging network better and better, I thought it was time to rethink charging leisure batteries in campervans, mobile homes and the like.

For example, in UK the Tesco run EV charging stations currently offer charging at 3700W/16A at 0.288 GBP/kW. This is actually cheaper than the rates I had last year when I rented a flat. And it is still slightly cheaper than the cost of power generation with my JCB generator.

As I restrict the charging of my EVE 280Ah cells to 125A, the maximum power to charge with is either 8* 3.2V * 125A = 3200W for a 8s 24V battery or 16* 3.2V * 125A = 6400W for a 16s 48V battery. But as of now, I only plan for 24V batteries in our vehicles. This means, that even with the lowest single phase Type 2 charger in a EV charging station we get more power (16A * 230V = 3680W) than the battery can be charged with.

With the help from Remo Fleischli of Mobilize I found two adapter cables from Elektroscout:

  1. A single phase Type 2 plug to a Swiss T23 socket, which I ordered with a “loose end” to connect a Neutrik powerCON TRUE1 TOP NAC3FX-W-TOP-L with it;
  2. and a single phase Type 2 socket to a Swiss T23 socket, which they call a “bike adapter” – this comes in handy at charging stations with a 3-phase Type 2 cable.

As a 24/3000 MultiPlus-II (or EasySolar-II) does only support charging of up to 70A (resulting in a nominal charging power of 24V * 70A = 1680W), we would still be 55A “short” of the desired maximum charge current of 125A. With the EasySolar-II GX or the MultiPlus-II GX there is no 24/5000 version and the MultiPlus-II 24/5000 uses considerably more power (18W vs 13W) and is way heavier (30kg vs 26kg [including MPPT charger] vs 20kg). In addition the inverter would be massively oversized as the maximum expected inverter power would be limited to 8* 3.65V * 125A = 3200W (^=4000VA), anyway.

So, I came to the conclusion the least expensive and space/cost-efficient solution would come in the form of a Victron Skylla-TG 24/50A Charger:

  1. Weight: 5.5kg
  2. Price around 500,00 GBP
  3. Dimensions: H 365mm * W 250mm * D 147mm

So, with the combined power of the EasySolar-II and the Skylla-TG (70A + 50A = 120A), I can now theoretically charge at 8 * 3.2V * 120A = 3072W – near the maximum supported power. As the charge current will probably reduce at around 80% SOC, my 24V battery can be charged from 40% to 80% within one hour – at a price of less than 30p per Kilowatt (or 90p the hour)!

Here a comparison with some smaller generators:

  1. a Honda EU10i will deliver 900W with 0.538l
    (around 1671W/l or 0.598l per 1000W)
  2. a Honda EU22i will deliver 1800W with 1.075l
    (around 1675W/l or 0.597l per 1000W)
  3. a Honda EU32i will deliver 2600W with 1.394l
    (around 1865W/l or 0.536l per 1000W)

If one liter of E7 costs roughly 1.50 GBP, the price per 1000W is between 0.80 GBP and 0.90 GBP.

Comparison of different charging options

And with a standard vehicle alternator of 100A the maximum charge current for a battery would not exceed 60A. So, a realistic amount of power to charge the battery with a running engine is around 12V * 60A = 720W. If we expect the vehicle to use 2l per hour running idle, the price for 1000W would sum up to over 4.17 GBP – not cheap.

Only the Honda EU32i comes near to the maximum charging power of 3200W/h. But the initial cost for the inverter and the price per 1000W is far beyond the cost of an additional AC charger, a Type 2 adapter and the energy cost at the EV charging station. And ideally, the energy from the EV charging station is “greener” than the energy from the vehicle or stand-alone generator.

Note: I did not write about solar panels at all. The reason for this is our special “use case” where we are mainly in northern europe where during autumn and winter there are very little hours of sunlight – at a time when we need energy the most. Plus, only two of our vehicles have actually space on the roof for solar panels.

This is my current take on charging larger leisure batteries. What is your opinion on this?

Sizing the electrical installation for our König KHC303630 Trailer

On our seemingly never-ending quest to the perfect “mobile home” and its electrical setup.

Once, someone told me the perfect vehicle for a mobile home would be a tri-fold:

  1. a 20m truck when stationary;
  2. a Unimog when off-road;
  3. and a Porsche when on roads.

As it seems hard to get hands on such a vehicle we have tried different combinations over the years – with a few “failed” attempts such as our VW California T6 or the Hymer B-MC I WhiteLine.

So, recently we took a different tac and went for a trailer. A “König KHC303630” to be precise; which is a 2m high, 2m wide, 3.66m long sandwich cabin on a twin-axle trailer (with an overall length of under 5m). The idea was to have something more comfortable and spacious than our Hilux with the roof-top tent. If you want to get an impression of how this looks have a look at one of these videos.

Before we actually made the decision to purchase the trailer, we went to Trochtelfingen to see for ourselves. It was then when we decided to have the main battery system voltage different from the 12V standard.

Originally, I thought to have a 16s 48V system with Eve 3.2V 280Ah cells. However, the resulting weight would be over 80kg – without BMS, case or inverter. So, I thought about installing an 8s 24V system with a resulting nominal power of 7168W. And it seemed that such a system would still satisfy our requirements.

  1. The mximum single load would be 2000W for a duration of up to 35min.
  2. The sum of all 12V loads would not exceed 360W.
  3. The total load would not exceed 2300W.

The Eve cells support 0.5C, meaning I could constantly draw up to 2800W (at 2.5V) and 4088W (at 3.65V) at 140A. However, as my largest DC MCB is only rated for 125A I could only use between 2500W and 2650W. But that would be still more than sufficient. And the Victron EasySolar-II GX 24/3000/70-32, the inverter which I had in mind for this installation, supports sustained loads only up to 2400W anyway.

So first determine, how many 24V connections do we need?

  1. 8s 24V battery, via SmartShunt 500A (in/out)
  2. inverter/charger (in/out, interally fused)
  3. 24V/12V DC-DC converter (out, interally fused)
  4. 12V/24V DC-DC converter charger (in)
  5. 2* 24V USB-C sockets (out, interally fused)

With 125A as the maximum expected current the use of the Victron Lynx Distributor bus bar seemed a bit oversized. So, I decided to use a pair of (way cheaper) 6P 150A Victron Busbars.

For the 12V system, I expect to use a 12 port Plus/Minus distribution:

  1. Refridgerator
  2. Bed
  3. 5* lights
  4. 12V socket for shower
  5. 4* 12V sockets

To convert the battery voltage to 12V, I opted for a Victron isolated Orion-Tr 24/12-30 converter. The whole 24V/12V converter will be able to be by-passed and directly connected to the 12V of the trailer, as well.

For minimum chargin on the road, I plan for a Victron Buck-Boost DC-DC Converter 50A. But as this would take more than 6 hours of driving to fully charge, the idea is to mainly charge via AC. However, the EasySolar can only charge with up to 70A. And in order to get closer to the maximum of 125A, I would add a Skylla-24/50 TG . Why I chose the Skylla-TG over the Skylla-I? I only need it for sporadic AC charging and the TG model is lighter and cheaper.

So, with the EasySolar and the Skylla the total amount of charge current adds up to 70A + 50A = 120A, which totals in a theoretic 3072W (just over 13A at 230V). So, any standard 16A cable would do to charge the battery.

A quick overview of the AC connections/RCDs in the trailer (all sockets will be Neutrik powerCON TRUE1 TOP NAC3FPX-TOP):

  1. Inverter/charger (out)
  2. Bath Immersion Heater
  3. Kitchen Microwave
  4. Kitchen Coffee Machine
  5. Kitchen Kettle
  6. Kitchen Stove/Oven
  7. Kitchen Spare
  8. Entrance AC-DC USB-C Charger
  9. Entrance Spare
  10. Back Left Spare1
  11. Back Left Spare2
  12. Back Right Spare1
  13. Back Right Spare2

For external AC input, I plan for a Neutrik powerCON TRUE1 TOP NAC3PX-TOP input with a pass-through and a separate 16A RCD.

Anything that I forgot? We will find out, once the trailer is delivered and we begin with the installation.