Plug and play versus DIY solar
to everyone's great advice, I'm starting to narrow down our choices for
outage solar backup system. First of all, Joey
and Roland (and the web) helped me figure out what size system I should
be looking for. I added up two hours run time on our laptops,
router, and two lights and came up with 150 watt-hours per day.
Using Joey's math, or just dividing by the 3 peak sun hours our area is
rated to receive in the dead of winter (from the map above), we would
need a 50 watt solar panel to achieve our goal. Since it's bad
business to discharge your batteries more than halfway, we would need
to buy two Duracell Power Packs and two 25 watt panels to reach this
level --- total cost roughly $450.
For comparison's sake, I
followed Daddy's advice and gave Backwoods Solar a call. The salesman
there was happy to walk me through my choices, even though he clearly
wasn't going to make much money off me. Here are the components
and prices he quoted me for a 50 watt system:
- 50 watt solar panel - $275
- charge controller - $33
- 400 watt inverter - $45
- 2 RV or marine batteries (bought locally) - $180
also mentioned buying a tilt mount ($68), which would let us adjust the
panel's orientation seasonally for slightly higher output.
Assuming Mark could make our tilt mount, but that we would have to buy
some connectors not on the list, the total would come to around
$600. On the other hand, I suspect I could shave around $100 off
the cost by hunting down the components elsewhere on the web.
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In other words, the plug
and play version and the real DIY version have a comparable price
tag. But do they have comparable longevity? I asked the
Backwoods Solar salesman what he thought of using a 600 watt Duracell
Power Pack as our battery, controller, and inverter. "That would
probably work," he said (and I paraphrase), "if you're just going to
use it very ocassionally as a backup. However, if you'd like to
take the laptop and lighting loads permanently off the grid and run
your solar system daily, you would be better off with a different
Now, I trust that he knows
what he's talking about, but I don't quite understand why he would be
right. My research shows that AGM batteries have a rated lifespan
of 4 to 7 years while marine batteries have a lifespan of 1 to 6
years. In addition AGM batteries are sealed, which means no need
for us to fuss over them, worry about fumes, or freak out when I
accidentally knock them over. Finally, they can be shipped, so we
can shop around and buy the ones at rock bottom prices on Ebay.
As far as I understand it, the main disadvantage of an AGM battery is
price, but the cost of the Duracell Power Pack seems to be roughly
comparable to a marine battery when you consider that the former
includes a charge controller and inverterter.
So, I'm opening up to
questions and answers again. Can anyone think of a reason that
the Duracell Power Pack would have less longevity than a different
system? Currently, I'm leaning toward trying out one 25 watt plug
and play system, doubling it later if all goes well.