Originally Posted by Dame.n.Jess
We are currently fitting our boat out to live aboard. My question is around power creation and realistic timelines for usage. We have fitted two 100w panels over the stern and I am in the process of buying
and mounting 8 trojan 6v deep cycle batteries. Essentailly I want plenty of reserve power, I will fit led lights
thru-out and we are only powering two laptops and two cell phones + the normal nav lights sounder gps
etc. No fridge, No autopilot.
Any thoughts on actual performance based off similar systems.
Power usage always seem to exceed the power generation, at least in my experience.
With no fridge and autopilot you've eliminated two high usage items. However I'd suggest the following:
1. Find out the exact usage of the items you have onboard (power draw, time used). That'll give you a good idea of the power requirements. Don't forget to leave some room for future additions (fans, fresh water
pump, more lights, etc). Low discharge levels will actually give you longer power time compared to a heavy drain. If you use an inverter
for the cell phones or computer, make sure you account for the inefficiency of the power conversion.
2. You probably want a 4x capacity to load. That way, you've got reserve capacity for those short/wet/cloudy days when the solar panels
aren't working as well.
3. Two 100W solar panels
will give you about 150W/day total. There is a 20% efficiency conversion loss when charging
4. You also want to be aware that the deeper the discharge cycle of your batteries and the longer you keep batteries at a low charge, the shorter the life.
5. I like the Trojan batteries (mine were 105AH ones) so assuming 100A/battery/bank you'd have 400AH of capacity.
6. If you keep the total load on the batteries to about 100AH/day (150AHx0.8=120AH) you should be fine. This way, you could supply more than you use; great when you drew a bit too much power the day before. It might be good to invest in some kind of smart battery
monitoring system so you have a good idea of the condition of your battery
7. You can gain some more charge power by keeping the panels clean, giving them a clear look at the sky, and rotate them with the sun.
8. Be serious about turning off what you're not using. You'd be surprised at the power you can waste by leaving the laptop
plugged in, the anchor
light on, or that fan running.
9. Check the fluid levels in the batteries weekly. If the level falls too low, you can warp the plates and reduce the load capacity of the battery.
I still find it magical to leave the boat in the morning with a negative charge load on the monitoring system only to return to find the discharge in the single
negative digit, or much nicer, 0 on the display. It wasn't free but it was clean and quiet.