Photo voltaic panels for caravans are a difficult topic to get proper. Marty reckons he’s had a eureka second about solar energy and you could possibly be doing it unsuitable.
Arms up in case you’ve had issue along with your RV batteries maintaining along with your energy calls for? Even regardless of having caravan photo voltaic panel set-up. I really feel your ache. Through the years I’ve had a number of completely different 12V installations that included photo voltaic charging. Subsequently, they’ve all let me down in a technique or one other. What was I doing unsuitable?
As we journey round this nation, speaking to different caravanners, all of them share comparable experiences. For no matter purpose, their photo voltaic charging techniques simply can’t sustain with the drain on their batteries. After contemplating this difficulty and experimenting just a little, I reckon I’ve figured it out. We’ve all been making an enormous mistake with our caravan photo voltaic installations.
Firstly, let’s perceive that solar energy technology is just not all that environment friendly. At greatest, trendy photo voltaic panels will convert about 20 per cent of the vitality falling on them into electrical energy. To attain even that low stage of effectivity, the panels have to function in good circumstances with daylight falling straight on them from an angle of 90°.
Are your photo voltaic panels mounted on the caravan roof? Properly…
Most new caravans, motorhomes, and, to some extent, campers have photo voltaic panels mounted on the roof or different flat surfaces. This can be a very handy technique to transport and use photo voltaic panels. Nevertheless, it doesn’t assist them to face straight into the solar always. In Australia, relying on the time of yr, the solar can be at a less-than-ideal angle to the floor of our photo voltaic panels, and we might be fortunate to attain 14 per cent effectivity.
So, you may surprise, how does this translate right into a real-world expertise? Our specific caravan has 450 watts of photo voltaic panels mounted on the roof. In good circumstances, it could possibly theoretically output as much as 30 amps. They by no means do, and right here’s why.
A short time in the past, we upgraded our photo voltaic charger to a Redarc BMS 1230S Battery Supervisor. Now, this unit is not out there, however you will get the newer mannequin, The Redarc Manager30 S3. This intelligent Australian-designed and constructed gadget can inform you numerous about what’s occurring along with your 12V system. This contains what number of watts your photo voltaic panels are literally producing.
In winter, within the southern states, even in full daylight, the 450W photo voltaic panels on our caravan had been fortunate to supply 230 watts. That’s round half of what they’re rated at, and it interprets into simply 15 amps of cost.
What occurs once we use energy concurrently charging?
Now take into account we’re utilizing energy concurrently charging our caravan photo voltaic panels. Equipment just like the fridge, TV, DVD participant and telephone chargers all take energy from the battery even when it’s being charged. Because of this, we could possibly be placing lower than ten amps of cost again into our batteries per hour. Introduce some cloud cowl or shadows falling onto the panels, and we are able to get down as little as simply 5 amps.
5 amps is just not quite a bit when charging 200Ah of AGM batteries. In winter, we would get six hours of daylight, however solely 4 of these hours, between 11 am and a couple of am, would the solar be at an angle that’s near being perfect for producing helpful energy. Conservatively, we would get a complete of 20 amp hours of cost over the whole day.
The ultimate nail within the coffin is that we not often park our caravan in open daylight, which isn’t perfect for roof-mounted photo voltaic panels. Normally, we camp underneath timber or in a valley. Even a slight shadow forged by an air conditioner over a part of the photo voltaic panel can minimize output in half.
The fact is that with all these variables considered, we’d actually be getting solely 10-15 amp hours of internet cost per day, and that is merely not sufficient. Take out the facility we use through the night time, and it’s little surprise our batteries would barely final a complete weekend with out some type of extra charging.
All is just not misplaced …
Happily, all is just not misplaced. There’s one quite simple factor you are able to do that may dramatically enhance your potential to recharge your batteries.
When our van was constructed, we requested the producer to incorporate a separate Anderson plug that was wired into the prevailing photo voltaic panels. This permits us to plug in exterior photo voltaic panels for our caravan. These, after all, will be positioned in direct daylight to enhance the roof-mounted panels. Utilizing the Redarc BMS to watch our photo voltaic watts, we plugged in an exterior 100W panel within the full winter daylight. Instantly, our out there photo voltaic panels jumped by a further 80 watts!
Now, that’s about pretty much as good because it will get with trendy photo voltaic panels for caravans. By constantly repositioning this panel to be in as close to direct daylight as potential over the out there daylight hours, we had been ready so as to add round 20 amp hours to our complete cost for the day.
An analogous impact will be achieved by plugging an exterior photo voltaic panel into the Anderson plug of your trailer that takes cost from the tow car’s alternator. Simply ensure that the panel has an inbuilt regulator if the connection goes on to your battery. When you’ve got a DC-DC charger or comparable, then an unregulated panel will suffice.
I’ll admit that repositioning the panel all day is a little bit of a chore and never all the time potential. Nonetheless, it goes to indicate that including photo voltaic panels exterior to your caravan roof-mounted panels can result in a dramatic enchancment in your potential to recharge your batteries day-after-day.
The important thing to understanding your 12V electrical system
The important thing to understanding your 12V electrical system is to know one quite simple equation:
Watts = Volts x Amps or Amps = Watts / Volts.
That is how we all know what number of amps of cost we are able to count on from any caravan photo voltaic panels. A 100W photo voltaic panel divided by 12 volts equates to eight.3 amps. Nevertheless, an unregulated 12V photo voltaic panel can output as much as 22 volts in full solar. Because of this we want a regulator or photo voltaic charger to cut back these excessive voltages to a stage that our 12V batteries can settle for. This can lead to increased charging amps. Sadly, 12V DC is vulnerable to voltage drops and different inefficiencies within the system and making an attempt to work out the variances within the resultant output is extraordinarily troublesome. To maintain it easy, it’s higher to make use of 15 volts as a baseline when figuring out recharge time from photo voltaic.
It’s necessary to know {that electrical} charging and discharging occurs over time. Because of this batteries are rated in amp hours. It offers us the power to estimate how lengthy a battery will final. If we apply a continuing load of 1 amp to a typical 100Ah battery, that battery can be absolutely discharged in 100 hours. Nevertheless, most 12V RV batteries don’t prefer to be discharged beneath 50 per cent of their state of cost (SOC). With that in thoughts, our 100Ah battery with a continuing load of 1 amp will be run for 50 hours earlier than we begin to injury the battery.
The exception is lithium batteries, which have the power to discharge to very low ranges with out sustaining long-term injury.
See, I informed you getting photo voltaic panels proper for caravans was difficult
Again to our instance, if we discharge our 100 Ah battery to 50 per cent SOC, it’s going to require 50 amp hours to recharge utterly. A 100W panel producing 6.6 amps per hour will theoretically recharge this battery in roughly eight hours. Nevertheless, that is provided that the unique load has been turned off and the panel is in near-perfect situation. In actuality, it’s going to take round 60 per cent longer because of the inefficiencies of most batteries and the way in which most photo voltaic controllers have what is named an “absorption remaining stage” of their recharging profile. That is crucial as a battery’s potential to simply accept charging present will lower because it will get nearer to reaching full cost.
If the photo voltaic panels are mounted on the roof of a caravan and are working through the winter months in southern Australia, it might simply take three days or extra to completely recharge that battery. If a load is related on the similar time, reminiscent of a 12V compressor fridge, it’s going to take even longer.
So along with your caravan photo voltaic, hopefully, you’re not doing it unsuitable – and now you understand how to do it proper!
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