On 08/07/13 00:59, Eric wrote:
> Hi Matthew,
>
> Thanks for posting. Something for people to think about, if your entire season's worth of electricity cost less than $10, how long would it take to recover the cost of a solar panel? Of course if one's boat never sees a dock where electricity is available, the math is different, but for most of our boats, solar electricity can be pretty expensive by comparison.
A solar float charger was on my 'long term' plan, but i've mostly given
up on the idea. The boat is under a cover to stop the sun from
destroying the finish. A solar panel would end up under the cover :-)
Also my house has 2Kw of Grid-Tie solar on it. The solar array has
generated about 1/4 of my household's total consumption. (That's
including the boat :-)
So while my boat was charged mostly at night on cheap off peak power,
thus wasn't using solar excited electrons, the boat's power consumption
was a fraction of the output of my PV system.
>
> That said, solar makes a very convenient battery maintainer and may very well extend the life of one's FLA or AGM batteries. I have found that lithium cells really don't need maintenance charging. The manufacturers state that storing lithium cells at 100% may reduce their lifespan (not much) and that long term storage should done between 70 and 50% charge. But for lead based batteries, an automated maintenance charging system can definitely save you money in the long run.
>
My charger can handle all that on it's own - it turns off after the
'finishing' charge instead of going into 'float'. It then periodically
turns back on to 'maintain' the cells. Only I don't leave it plugged in
as it's idle power is about 30w. Over time it's idle power consumption
would swamp the power consumption of the actual charge cycle.
If the boat was used more (or I was charging an electric car that gets
used a lot), it would be a different thing. The charger is actually
designed to charge electric cars not boats.
My Grid-Tie inverter has a 'programmable relay' output, I have toyed
with the idea of hooking a power socket via that output and programming
the inverter to turn the circuit on when say the output of the array has
been over 1kw for several minutes - thus running the charger only when
there is sufficient solar production to run it. Then I could really say
the boat is solar powered. :-)
--
Matthew Geier,
Systems Administrator, Australian Centre for Field Robotics
+61 2 9351 8149
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