Snailspace - Power Systems Overview

‘snailspace’ compact 4WD motorhome

Electrical systems and associated key design considerations

1. High Solar Panel Voltage (PV)

Some popular DC to DC /& Solar Combo controller's (Eg Redarc, Enerdrive and Intervolt) suffer from limited Panel Voltage (PV) because they mix solar with vehicle charging. Solar controllers from Victron or Morningstar operate at 98% efficiency and accept high Panel Voltage up to 450V.  Safiery Pty Ltd. aims for a Panel Voltage approaching 100V up to a maximum of 150V.  This means ‘early start/late finish’ capabilities because of the higher PV - solar yield is higher early in morning when panels are cool. Likewise in late afternoon when you want that final boost to topping up the batteries. The cable from the solar panels has 75% less of the current compared to low voltage solar panels. This lower current translates into less losses, meaning that longer cables can be run with portable solar arrays without any significant loss of generated power.

2. Mixed solar panel sizes to maximise panel coverage of motorhome roof area.

To achieve a High PV requires the solar panels to be connected in series. When the solar panels are natively connected in series, shading of one panel in a series string dramatically affects the whole string.  RV roof areas can be a hotch-potch of different sized spaces and with obstructions caused by AC units, TV/Sat aerials, vents, etc. Mixing different panel sizes and even technologies can often be fraught with performance problems.  Safiery Pty Ltd. have solved both of these problems with a proprietary DC to DC solar string that supports individual panels. The DC to DC string ("1/4 brick" high frequency planar transformer that passes the current of each attached panel through a looped circuit to the solar MPPT controller) support panels of mixed sizes from 80W up to 400W and will support panels of mixed technologies (Eg Copperflex and Mono Glass) on the same string and have been specifically designed by Safiery Pty Ltd. to not 'fight' the solar MPPT controllers, such as Victron.

3. Copperflex flexible solar panel and portable solar panel advantages.

Copperflex flexible solar panels are remarkably thin (@<2mm) and lightweight and can make a significant difference to how much weight is carried up high on RVs and motorhomes. I estimate that I have reduced the weight on the roof by @50kg when compared to the factory-fitted 3 x 125W 12V Mono Glass panels, and increased the power-generating capacity by @75% (with 640W of high PV solar panels).

High Heat Dissipation

The backplate is a whole sheet of copper foil. Better strength but, just as important, it has better heat dissipation properties.

Designed specifically for RVs and Marine

Built-in bypass diode, suitable for scenes where the RVs and boats move and change. It can still generate power in a shady environment at reasonable efficiency.

High efficiency

MWT back contact battery module, no busbar, higher module efficiency, size per 100W is only 520-1070mm.

German TUV certification

One of the few TUV-certified flexible solar panels designed for the RV and Marine industries.

Environmentally Friendly

Copperflex solar panels have passed the strict environmental testing multiple times, demonstrating excellent attenuation characteristics. Lead free materials only used. Supports the green photovoltaic design concept, resulting in a lead-free module process and materials.

Warranty

Industry leading 5 year warranty.

Copperflex 60-370W panels:

	60W	70W	100W	140W	370W
Dimensions	1220x290x1.7 mm	1080x369x1.7 mm	1070x520x1.7 mm	1423x540x1.7 mm	1840x1040x2.5mm
Weight	0.9KG	1.0KG	1.4KG	2.2KG	5.7KG
Max System Voltage	1500VDC	1500VDC	1500VDC	1500VDC	1500VDC
Max Series Fuse Rating	9A Copperflex Solar Datasheet		9A	18A
Application Class	Class A	Class A	Class A	Class A	Class A
Pmax	60W	70W	100W	140W	370W
Vmp	12V	13.87V	20.12V	27.73V	35.1V
Imp	5.01A	5.05A	5.01A	5.05A	10.54A
Voc	14.2V	16.38V	24.45V	42.76V	42.6V
Isc	5.31A	5.39A	5.31A	5.39A	11.16A
Voc Tolerance	+-3%	+-3%	+-3%	+-3%	+-3%
Isc Tolerance	+-5%	+-5%	+-5%	+-5%	+-5%
Pmax Tolerance	O-+3%W	0-+3%W	O-+3%W	O-+3%W	O-+5%W
Operating Temperature	-40-+85C	-40-+85C	-40-+85C	-40-+85C	-40-+85C
Temperature Coefficient Pmax	-0.36%/C	-0.36%/C	-0.36%/C	-0.36%/C	-0.36%/C
Module Efficiency	21.6%	21.6%	21.6%	21.6%	21.6%
Nominal Module Operating Temperature	43+-2C	43+-2C	43+-2C	43+-2C	43+-2C

Sunpower is No 1 and Copperflex is No 2 in performance specifications (No.1 in Green. No.2 in Yellow)

	Sunpower 400W Glass	Copperflex 100W	Victron 115W Glass	Enerdrive 180W Glass	Sunman eArc 100W Solar4RVs
Size	400	100	175	180	100
Cell Efficiency Voc/wafer cell	0.726	0.679	0.670	0.669	0.638
Temperature Co-efficient for P Max	-0.29%/C	-0.36%/C	-0.45%/C	-0.371C	Not Quoted
Watts/m2	226.3	183.2	179.2	178.3	144.2
Weight	19.0	1.4	11.0	11.5	2.1
Watts/kg	21.1	71.4	15.9	15.7	47.6

When considering solar options for 'snailspace', however, the critical factors were not just the Watts per m2, but the weight of the panels and wiring, particularly as they are mounted on the roof.

4. Portable solar is a great way to extend replenishment energy when free-camping for longer periods. In 'snailspace', I have 4 x 175W of portable copperflex solar panels configured as two sets of two panels connected in series to independent Victron Smart MPPT controllers.

Safiery Pty Ltd. has mastered portable solar design to achieve this with:

• High Panel Voltage of 42V per portable panel.

• Two of these portable panels wired in series will produce 84V Open Circuit Voltage (Voc) which will charge 48V systems.

• Optional DC-DC for Solar allows combining this portable with the rooftop solar on 'snailspace' to provide a whopping combined 1.34kW of solar power generation.

• High quality lightweight flexible panels in manageable sizes.

5. Use of Victron Smart MPPT Solar Controllers.

Victron Smart Solar controllers operate at 98% efficiency. In addition to this very high efficiency is the gain from "ultra fast MPPT control". Victron Smart Solar may yield 120-130% more energy per day than DC/DC Combo systems.

Victron Smart Solar Controller can:

• Recover a flat battery. Victron use the solar PV to power the microprocessor. This can't be done with other brands like Redarc and Enerdrive with spiking the battery capacitor.

• Safiery Pty Ltd. use "Expert Mode" that can shift the Solar controller back into bulk charge mode in the afternoon.

6.  All-electric high efficiency HW system for kitchen sink/bathroom handbasin and internal/external showers.

The Hot Water (HW) tank in Kitchen (260mmx240mmx315mm / 4kg / 8 litres) continuous reheat 40-70C 1000W at 48V DC, combined with Instant hot shower water (350mmx235mmx60mm / 2kg) enables endless HW 40-55C using 3000-6000W at 240V AC.  This means: 1) No limit on showers (except overall FW tank limit!); 2) Kitchen HW can be run simultaneously with shower operating; 3) Kitchen HW can be reheating while driving; and 4) Only one cold water supply source (with two check valves) required.  The 48V Kitchen HW system can also be managed independently via Victron bluetooth app from your phone.

7.  Internal heating.

One of the compromises I had to make during the build phase was the motorhome company's unwillingness to rebate the marine ply wooden floor under the vinyl flooring in the main living area of the motorhome to accept two 2mm-thick 48V underfloor heating panels (as it would unnecessarily delay their production line process). This would have enabled the delivery of a more moderate heat (but still up to 40C!) to be generated silently. By comparison, the diesel air heater fitted to 'snailspace', while very effective, is very noisy in getting up to temperature and certainly not something I could sleep through!

I also have the option of operating the reverse cycle air conditioning in heating mode, however, while using about 800W-1000W when running, it is generally best operated when connected to 240V 'shore' power. The aircon can be run in cooling mode via the inverter when free camping, so long as you have nice sunny days to replenish via solar or are planning on driving for a couple of hours the following day!

8. 250A Alternator.

To significantly improve DC-DC charging of the motorhome batteries while driving, Safiery also replaced the standard 80A alternator that comes with the Toyota Hilux model with a specifically-designed and locally built 250A alternator. This delivers approximately 2200W to 2300W of power (the specific amount of power being controlled by the Scotty AI to match engine revolutions and alternator temperatures), meaning that topping up the batteris from 50% to 95% State of Charge (SOC) can take as little as 1.5hours of driving. It also means that I do not need to carry a petrol-powered generator for those days where the sun doesn't shine, saving significant weight and space, and negating having to carry another fuel type.

9. Scotty AI DC-DC (Bi-directional 48V-12V).

Benefits of Scotty Al on 12V or 24V Alternators (over 48V Alternators with External regulators)

• Load dump is impossible:

  Should the target lithium battery being charged opens its relay, any contained energy is reversed to starter battery as Scotty Ai is bi-directional.

• Redundancy and Safer Operation if 48V battery system fails:

  Vehicle system can operate critical electrical systems on 12V power from matching alternator.

• Built-in DC-DC from target lithium battery on high side to low side: Eliminates cost of 48-12 or 48-24 DC-DC converter. Scotty Al is 96% efficient.

• Built-in Smart Battery Protect for high side target lithium battery:

  Eliminates need for additional 48V battery SOC protection to 12-24V.

• Higher idle output with Scotty Al 3000W (compared to 48V / 5000W):

  48V alternators need higher RPM to kick in. 24V 200A or 12V 250A alternators with Scotty Al generally give higher output at idle by 20-30% for solar backup. For 'snailspace', the replacement of the standard 80A alternator with a 250A one, translates to the delivery via Scotty AI DC-DC of up to 2.3kW to the motorhome batteries - better than many compact stand-alone petrol-powered generators).

  
  

10. Recovery Winch.

'snailspace' is fitted with a RUNVA 11,000lb (just under 5,000Kg) winch for self recovery. Winches require a significant amount of Amps to operate (@348A). Instead of relying on under-bonnet starter battery/batteries and 'standard' alternator (@80A for Hilux) - which would rapidly deplete the battery - the upgraded 250A alternator fitted to 'snailspace' would deliver @ 230A at idle and up to a further 250A could be directed from the motorhome batteries via Scotty AI DC-DC.

11. Cooking.

I have removed all LPG/gas from inside the motorhome. This removes the requirement for specialist gas certification and the need for a permanent low-down vent (usually the door footwell) from the inside of the motorhome to the outside. Given the frequency of both gas-related fires/explosions and Carbon Monoxide poisoning events in RVs, this makes 'snailspace' a much safer space!

While I still carry a couple of 4kg gas bottles externally (one on the rack on the rear of motorhome and a 'spare' on trailer), these are exclusively for the slide-out BBQ and an emergency cooking facility should I suffer a total power system failure. Cooking inside the motorhome is via a double induction (1500W/2000W) cooktop, with a small 1100W 240V Air Fryer/Oven/toaster under. I have dispensed with fitting a microwave. I also carry a portable 2000W induction cooktop for use on the drop-down table outside to deal with the cooking of more pungent comestibles, such as bacon or curries and to avoid any associated lingering odours inside the moho!