Mains grid electricity is something many of us can no longer live without. So much so that when venturing beyond the realms of mains power one can often feel vulnerable, constantly worrying about your phone battery dying or not being able to keep food cool.
Throw an off-grid location into the mix and the problems become even more astute – but this is where wind turbines and off-grid solar panels can be a lifesaver. However, it is often unclear as to the size of the system and the bits and pieces that are required. This blog has been written specifically with solar panels in mind – allowing you to get the perfect solar panel system up and running on your tent, caravan or even boat that little bit easier.
The pieces required for the off-grid solar system
Solar panels – leads – charge controller – battery
When camping with solar panels, how many do I need?
For camping with solar panels, first of all you need to work out what size panel, or panels, you need. Off-grid panels are available in all shapes, sizes and structures. From flexi-panels that mold to the roof of your caravan or boat, to rigid panels and even foldable panels that can be erected when you set up camp and folded away again at the end of the day.
The size of the panel depends on what you are aiming to get out of it. For the smaller tasks, such as trickle charging a battery to compensate for self-discharge, a 5W or 10W would be adequate. However, if you use your battery to power energy saving lighting, a radio or small appliance charging such as mobile phones, then you should look at a 50W to 80W panel to replenish the spent energy used up. For TV’s, larger lighting rigs and water pumps for your daily shower, you should aim to reach at least 100W worth of solar panels. For the larger campervans, where you would have all of these appliances plus a 24h fridge, you should have around 150-200W worth of solar panels to ensure enough charge.
What size and type of battery do I need?
Once you have decided on your solar panels, you must then have a look to see what size of battery in AH capacity you require. A way to do this is calculate the average watt-hours per day required and then multiply that by the number of days you may be without generation and then multiply by 2 again. Finally, you divide that number by the Voltage of the system you require. So if you use 500w/day and you would expect to be without proper sunlight for 3 days you would go:
500 x 3 x 2= 4.8. 4.8/12 = 250AH
The type of battery you go for is also fairly important – there are a couple of different types you can get, from lead, to gel and then AGM. They all have their benefits as well as a few negatives. For example, AGM batteries are better for appliances that require more than average power consumption and run most efficiently between +10C to +40C. Gel, on the other hand are more expensive but is the better battery in applications where a constant lower current is required and works best between a temperature range of -10C to +50C. They also tend to store the electricity without needing topping up for longer periods.
How can I prolong the battery life?
The life of a battery depends on how it is used and the duration of discharge and recharge. Generally, the less discharge between recharging means more charge-discharge cycles in the battery’s lifetime. Using this logic, it becomes obviously that a battery that is regularly discharged to 30% remaining will have a shorter lifespan than that which is discharged to 40% remaining. Some batteries, like deep cycle versions, can tolerate this but it is still not advisable. What we would recommend would be to recharge it as soon as possible and not discharge it excessively or leave it discharged for long periods.
What about charge controllers?
Solar charge controls are essential pieces of kit for any off-grid solar panel system. They prevent excess charge from damaging the battery. Another key part they play is that they don’t let charge leak from the battery during periods of none generation. This maintains the battery’s performance, lifespan and charge increasing the efficiency of the system.
There are three main types of solar charge controllers.
Simple 1 or 2 stage controls: The dinosaurs, although still available to buy, they just shut off the solar panel when a certain voltage is reached. They are cheap and reliable, but have sever limitations. We would advise giving them a miss.
Maximum power point tracking: MPPT, the ultimate controllers but sadly prices to match. The efficiency is up in the high 90%’s so they can save masses of money on larger systems since they provide around 20% more power to the battery by shifting the input voltage.
PWM: 3 Stage, the industry standard and the go to charge controller for smaller systems. We advise a PWM controller on caravans and small off-grid systems.
Can you appliances straight from your solar panels?
Due to the intermittency of renewable energy, both solar and wind, it is not possible to power appliances straight from you source of electricity generation. For example, with solar panels you would find that the output fluctuates throughout the day so much that the only way to harness the electricity generated is to feed it into a battery and power your appliances from there.