How we power Bilby

We often get asked about how we run our fridge and TV and charge our phones. Bilby is run purely by the sun. We didn't know anything about solar charging before we started and it took us the best part of the first month of our travels to get it all working properly. We got very confused the more people we talked to. The more things went wrong, the harder it got to understand why things weren't working.

Before we started the local RV shop quoted us about $1200 for a full solar installation. We had looked online and had seen solar panels for about $160 and thought it was as easy as ordering one online. We were very wrong. After purchasing one solar panel and clamping it to our existing bus batteries and folding it out facing the sun every time we pulled over we realised the panel needed to be mounted to the roof so that we could be gaining sun power at all times. This wasn't enough to run the fridge and TV and was causing our batteries to die and not be able to start the bus.

Thats when we bought a brand new Century Deep Cycle 100ah battery ($220) that we kept seperate from the bus. The solar panel was then clamped straight to the battery and the inverter clamped straight to it as well. This would run for about 24 hours with our 160watt solar panel and then die. So it clearly wasn't working. We then thought maybe we needed another solar panel. So we purchased another 160watt panel and Sikiflexed it straight to the roof as well.

Week 2 of our trip things weren't working, and we were getting frustrated as we didn't understand why. With the second panel we were lasting maybe a day and a half and wasting money staying at caravan parks for power. We went to Jaycar to have a chat with them and they suggested we needed something called a solar controller. This device monitors how much sun is coming in and stops it when the batteries are too full to avoid over charging and shuts off drawing power when the batteries are too low too avoid draining them too much. It also gives you an LCD screen to tell you what the battery levels are at and how much sun you've had in for the day. They also recommended we needed another battery.

So we decided to buy another deep cycle battery exactly the same ($220). By this stage we had spent $940 on our solar set up and things were starting to look a bit better, until the front solar panel flew off on the highway and landed on the back panel smashing it and then flying on the road. (Luckily no-one was injured). We had lost both panels now and had to order a new one from eBay. This was a nightmare trying to get it ordered to a caravan park because we were a little remote at the time and the delivery company handed it off to another one and things were delivered and rejected by the office and in the end we spent over $200 on caravan park fees to receive the panel. The new panel we ordered was $250 but was 250watt. This meant we only needed one panel rather than two. However our total expenditure on our power was now about $1400.

Once it finally arrived we made sure to screw it in to the roof and then use the Sikiflex to water seal it. After a month things still weren't working perfectly we were getting 5 days or so and it would be dead. This meant another trip back to Jaycar to talk to them. They said the cables could be average and suggested we try changing them to some of their good quality cables. We did this for about $80 and noticed a big change in our battery life. We now get about 3 weeks out of our batteries running a 12v fridge, TV & dvd, laptop charging (you will need to order a new 40amp charger from Kogan for MAC's), phone & bluetooth speaker charging and more recently a wifi modem so we can run Netflix on our TV. After about 3 weeks we notice the battery levels dropping and we plug in somewhere with normal power and charge our batteries with a battery charger.

Here's what we've learned about electricity. Keep in mind we are no experts and have never been trained in this. Feel free to correct us where we are wrong. We have found it hard to get a grasp on the difference between volts, watts and Amps. It seems that Amps= Watts / volts. Amp hours are how many amps are drawn in an hour. We have found it easiest to revert everything back to amps. So our 250 watt solar panel is 12v, which means at its absolute best sunniest moments it can put 20amps per hours into our batteries. Keep in mind that the most we ever get is 13amps because it is rarely perfectly sunny and the sun is rarely shining straight down on the flat mounted panel. Our batteries are 100ah each. So we have a total capacity of 200ah. This means we can draw 200 amps worth of power for 1 hour or 1 amp worth of power for 200 hours. Our fridge says on the back of it 60watts, so 60/12 gave us 5 amps. However the fridge doesn't run all the time, it only turns itself on when its not at the optimal temperature. We estimate it runs for about 8 hours a day. (5amp fridge =5*8=40amps per day). Our TV draws very similar power to the fridge, except we only use it for maximum 2 hours a day. So 5*2 = 10amps. Then a phone charge is very minimal. Around 2amps per hour. We maybe charge for an hour each a day. So lets say between 4-6 amps a day. On a nice sunny day we are putting about 50 amps back in the batteries every day.

This is our understanding of the maths behind it.

Amps in the batteries= 200

Less fridge (40)

Less TV (10)

Less Phone (5)

Less Other (5)

Plus Sun 50

Equals 190 amps left after one day.

So we lose about 10 amps everyday. 200/ 10 = 20 days. So approximately every 3 weeks we need to recharge our batteries through our battery charger.

One thing we didn't know when we started, that can be a bit confusing is the battery level. We were looking at our battery level and it would say 11volts and we thought that was really good. It turns out thats not good and that a 12v system, when full is actually 14.3v. Keep this mind.

Unfortunately everyday is different, so this is just the basic maths behind it, but seems to work for us. Some days are more overcast than others and you get less sun in and other days you don't draw as much.

We bought a cheap Fridge from eBay and run a normal TV through our inverter. If we had more money we would like to have bought a more efficient fridge and a more efficient 12v TV and may be able to live off grid permanently.

Here is a diagram of our set up.