How to: 12V Off Grid Living
By Leana, KickAss’s all-round gun and marketing expert
2 Minute Read
Life in this beautiful country of ours is amazing, and it’s even more amazing with a little somewhere to call your own. As the environment changes and social awareness of the damage done by fossil fuel dependence informs the conversation about energy, more and more people are realizing how much of their hard earned cash goes towards maintaining “the grid”, or a privately owned energy distribution infrastructure the pricing of which would almost certainly make your skin crawl if you ever really understood it!
This is leading to a healthy discussion about alternative living arrangements such as the tiny houses movement, communal off-grid living communities, and many who have done the research and stacked the numbers may willingly opt for the quick and painless solution of simply disconnecting from it, which in most States bar Queensland is done by paying a small fee to Council and having your domicile disconnected from the supply of council services, whether they be water, gas or in our case in point, electricity.
Off-grid systems are also an interesting solution for people building their homes, as semi-permanent solutions to natural disasters, or simply to power up your weekend retreat on a budget.
The first element we take into consideration when designing an off-grid system is to refer to a chart like this one
We know the average panel outputs 18-21v which will be regulated by either a PWM or MPPT unit to charge and maintain a deep cycle battery bank at a constant 14.8v. So based on the above we can see most locations north of Canberra have at least an average of 7hrs of sunlight exposure generating above 18 Megajoules per square meter, and further factor that solar PV panels work most efficiently at lower temperatures, and come to an average production of 30Ah per day per 100W of panels.
This rounded figure helps us identify how much we’re likely to put back into our battery bank with solar, now we need to garner how much we’re taking out.
Let’s use a 210l upright fridge for our base calculation and deem it a 70Ah/day draw.
For our offgrid system we might have a pump for our water tank, a set of LED lights, a large 2kW inverter and a microwave, and a couple of high efficiency 12v fans - we’ll deem all this to be drawing 90Ah/day on average.
We may in a location though that gets sunshine only a third of the month, and we’re heading into summer in our scenario getaway, so believe us when we say almost always buy a bigger panel!
With a 300W panel we’ll be replenishing 90Ah/day, so a bank of 3 batteries connected in parallel with linking cables to a fourth battery in a battery box with 25A MPPT regulator DCDC charger gives us a respectable bank of power to draw on, and a system of this sort will have us running strong through an MPPT regulator all year round for approximately $5k and no more electricity bills ever while halting our dependance and contribution to the maintenance of an overpriced fossil fuel electricity grid.
If after a few months we find we’re drawing more than we’d like and not replenishing the bank fast enough, the 300W panel is rated at 14.28A thus we can safely add another 200W to our system and the 25A MPPT regulator won’t bat an eyelid while replenishing a further 65Ah/day to our system.