Originally when it was just going to be me in the truck I planned to just have a laptop charger and lights, which would hardly use any power. So I just thought I’d get a secondary battery that looks big and a solar panel that also looks big and that’d do.
But the girlfriend gets cold all the time and also says we need a fridge for cheese.. so I decided I better calculate all this stuff, otherwise we’re going to be sitting in the dark having to play cards or talk whilst trying to make a fire and eat mouldy cheese.
According to my 100% accurate calculations the expected power usage per day will be: 82 amp hours.
| Power (watts) | Usage per day (hours) | Amp hours per day | |
| Laptop charger | 48 | 8 | 32.00 |
| Lights | 2 | 4 | 0.67 |
| Diesel heater | 14 | 8 | 9.33 |
| Fridge | 40 | 12 | 40.00 |
| Total | 82 |
When the truck engine is running it can charge our battery, but I’d like to be able to not have to drive everyday just to charge the battery, so we’d need solar panels. Or a wind turbine, which would be much sexier but unfortunately I couldn’t find a good sized one online.
When calculating how many and what size solar panels to get I came up with a simple formula which I’ve named Jeremy’s Law of Solar Panels: get as many and as big as will fit on your roof. So according to the roof size I’m getting 4 x 120 watt panels.
With 4 x 120 watt panels at 100% efficiency we get 480 watts, or 40 Amps. However we’d never get that in reality if there is some shade or the panels aren’t angled directly at the sun, so as an estimate let’s say we get 8 hours at 50% efficiency, that’s 160 Amp hours per day, which is slightly less than double our expected daily use.. great – the rest can be used to charge the battery 🙂
When calculating what size of battery to get I couldn’t be bothered anymore and just looked on the internet for a decently priced lithium ion deep cycle battery. Ended up finding a 200 Amp hour one, which would allow us to have power for slightly under 2 and a half days with no driving and no sunlight. (our battery capacity 200 / our daily use 82 = 2.44)
I bought a a bunch of stuff from the internet but unfortunately with this pesky Corona virus it’s all going to be delayed:
4 x 120w solar panels + mounts: + $615
200Ah lithium battery: + $1,181
DC Battery charger + MPPT solar regulator: + $630
12V laptop charger: + $99
12V diesel heater: + $211
LED lights: + $36
Total: $8,924