|
Off Grid Obs
I live on the edge of a small village on the Darling Downs and when I moved here about 5 years ago, decided to remain off grid rather than pay $27K to have power run 200 metres from the nearby lines. All works well.
I have just finished my roll off obs and it also is off grid, totally separate to the house, although only about 40 metres apart.
I have a mix of 12 x 2V 1000Ah sealed lead acids feeding the main house inverter plus 16 x 3.2V 100Ah LiFePO4 prismatic cells with BMS, feeding the backup inverter used for pumps, etc,
Based on my 12 month experience with the Lithium Phosphates, I decided to go that route (2 x 13.4V 100Ah packs with BMS) with the Obs, and they work well. I use two 200W used solar panels with a Renogy Rover 30A MPPT charger. Highly recommended, only cost about $90 on Amazon Oz and will do Lead acids and Lithiums, and has remote monitoring capability, which I installed but rarely bother with.
You will be using your 12V 200Ah lead acids, and you should be able to find used 250W panels for about $50 each. All my 19 panels are at least 8-10 years old and don't seem to noticeably degrade.
I would suggest you consider 4 x 250W panels to ensure decent charging during cloudy days, and to put them in a 2s x 2p array so that the input voltage to the solar charger is nice and high (~60V) even on cloudy days. Yes, theory says you'll lose half the current capability, but experience shows that is more than compensated for by the higher (and therefore longer) charging time availability during low solar intensity times such as dawn, dusk and cloudy periods.
Based on my five years house lead acid battery experience, I would also recommend you set the initial charge absorption voltage to 14.4 for about 4 hours and the float to 13.8. I had mine set to the lower recommended voltages as shown on the cell casing, but the batteries didn't get fully charged. I suspect the reason is that daily solar charging voltage is so variable, plus there's none at night, whereas charging via the grid allows a stable 24/7 voltage. As an example, my monitoring system shows that the lowest voltage my lead acids produce is 24.4V at around 5am.
I would also suggest you consider running your obs directly from 12V and don't bother with the expense of an inverter. This is the reverse of what I would do with a house, but for an Obs is more power-efficient and also easy to do.
Lucky last comment, I would use either a laptop or NUC-style computer in the obs, with an ethernet cable back to the house if practicable. Reduces the need for routers and wifi hassles. I just changed mine from wifi (range extenders, etc) to one Cat 5 cable, it just works so much better.
I've got lots of pics etc if you want to see some examples. Good luck
|