I HAVE OWNED two solar blankets over the years. One so long ago it would be considered near useless by today’s standards; the second is a little beauty (one of the first amorphous blankets to hit the market in Australia) and I remember raving about it to anyone who cared to listen.
As with all things in life, time and technology has moved on massively and the latest solar blankets from Redarc are not only class-leading but there is a range of four blankets to choose from, featuring two different types of solar cell. These include one amorphous blanket rated at 112W and three SunPower blankets rated from 115W to 190W. Prices range from $1230 to $2026 for the monocrystalline blankets, while the amorphous blanket hits the wallet for $2354.
The SunPower blankets are monocrystalline, so they’re more ridged and heavier than an amorphous blanket of similar output. However, rated watt-for-watt, monocrystalline blankets are much cheaper than amorphous blankets, to the tune of a thousand bucks or so. And while a monocrystalline blanket mightn’t be able to withstand a gunshot (as the amorphous blankets were designed for the military to do), the unique design of the SunPower cell reduces failure from corrosion and breakage.
These blankets feature a solid copper backing with thick connectors for higher efficiency, while the face has an anti-reflective, scratch-resistant ETFE coating that has a high melting temperature, is non-stick, self-cleaning, and UV and chemical resistant.
These blankets may be a little heavier than the equivalent amorphous blankets, but they still weigh less when compared to a glass/aluminium crystalline panel which produce around 10 watts of power for every kilogram you have to carry.
4x4 gear: Solar panel comparison
A monocrystalline blanket produces approximately 25 watts per kilogram. However, with price being a big factor for this black duck, and the weight difference compared to the more expensive unit being deemed insignificant, we opted for the super grunty 190W unit.
Redarc recommends this panel be used in conjunction with – at a minimum – a 20amp solar charger. This will ensure the correct charge is supplied to the batteries safely and efficiently, and it will protect the batteries from overcharging.
A standard ‘Anderson’ SB-50 connector on the blanket allows you to connect the blanket, via a similarly setup cable, to your vehicle via a regulator. We opted for a Redarc five-metre cable, but in hindsight would have preferred a 10-metre cable. Still, these Redarc cables are as good as you can get, with good weatherproof cable connections into the plugs.
Before we get into measuring current and the like from the panel we had on test, I’d like to clear up something which has always puzzled me… up until now. A panel will be claimed to put out so many watts at a certain voltage, but I’ve always found in our testing that a panel will never reach that stated wattage or current in practice.
Then I discovered the maximum current capability of a panel is measured under short-circuit conditions (whilst disconnected from any form of regulator or charger), something you don’t want to see in any practical situation.
However, Redarc does make the distinction between short-circuit amps and max-power amps, the difference being only slight in this case. Other manufacturers aren’t so forthcoming.
SEMA 2018: Redarc Manager30
The type of regulator you use will also affect the outcome. To get the most power from the panel over any given time period, an MPPT-type solar regulator is recommended. These include the Redarc BCDC1225D, BCDC1240D, BMS1230S2 and similar Redarc regulators, as well as the ones we often see in dual-battery systems.
To see a peak current reading (which doesn’t necessarily mean the most power over a given period of time) a PWM Regulator connected to a relatively flat battery will generally show the highest reading. The Redarc products suitable for the 190W blanket and using this technology are the SRPA0240 and SRPA0360 regulators.
Of course, added to those variables is how much sunlight is available and the varying angle of the sun, both of which will affect the amount of current produced. It’s no wonder I’ve had so much trouble getting a reasonably accurate reading that equates to the manufacturer’s specs.
How flat the battery is will also depend on the power output of a panel. We tested the output under mid-summer (Melbourne), midday sun (11am to 1pm), feeding into a partially flat battery which was running two fridges – an Engel and an ARB unit – both set to minimal temperature; i.e. maximum current demand. Current, voltage and watts were measured by an in-line electronic gauge.
This Redarc blanket is rated at a maximum of 16.5 volts and 11.6 amps, which works out at a tad over 190 watts. As you can see by the readings, during our test our panel had an output of over 13.9 volts and 8.96 amps, giving 124.8 watts of power.
As previously indicated, that difference has more to do with the state of the battery, the regulator in use and the power demand of the fridges. Under the right conditions I reckon I could get this panel to deliver what is stated on the spec sheet.
I’ve been very impressed with this Redarc solar blanket; its toughness, ease of use and electrical output.