Steve-
It’s not clear to me what you are suggesting with the solar panels, but it sounds like you are suggesting that you would take your no. 144v solar array and apply it directly to your 12v house battery bank without reconfiguring the panels to be connected in parallel instead of series.
If that is the case, then your 144v panel array will only deliver 1/12th the rated power to the 12v battery bank compared to its being connected to the 144v bank. The panels deliver current (not power) proportional to the solar energy captured by them. The lower you clamp the voltage, the less power captured and delivered. Connecting the panels in parallel and direct connecting to the 12v bank would be better. Shading one panel would not affect the others. In series, a single panel or fraction thereof can take down the entire string’s output. But say you go with parallel panels and their Vmpp is 17v. At 12-13v battery voltage, you’d only be capturing some 65% or so of the solar energy. Incorporating a MPP tracker could boost that up above 90%, but then the cost may not justify it.
-Myles
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of Steve D
Sent: Thursday, December 29, 2011 7:54 AM
To: electricboats@yahoogroups.com
Subject: [Electric Boats] Re: Ok solar experts
Hi Damon,
A good point and one I'm questioning as far as running solar through the Propulsion bank. Yes I also have a house bank, 3 agm's at 12v 540AH.
The existing system is set up to take everything through the Propulsion (144v) bank. All charging (regen, Genset, shore) and distribution starts there. The house bank gets it's charging from a 144v to 12v (DC to DC) converter. Since this is the starting point my first thoughts would be to take the solar to that point since any excess solar power would then be sent to the House bank. The question then is with shading will the 144v bank still charge or just shut down the solar since it can't meet the 144 voltage? If this is the case it would be better to have the panels going to the 12V House bank. Another question is can I find an UP inverter from 12V to 144V. If I can than this would be much simpler. Then you also have a charger down (144v to 12v) and up (12v to 144v). I wonder what that would do to everything? It's getting to the point of I can't have it both ways it seems. The good news is if I just do solar to the House bank then a substantial load would be taken of the Propulsion bank. It's just that I think I would still have excess solar that could be added to the Propulsion bank instead of just "throwing it away".
Does any of this make sense?
Thanks,
Steve in Solomons MD
Lagoon 410 SE
> Connecting solar panels in series to get 144v will work, but shading on any
> of the panels will degrade the output of the whole series string. I have a
> friend who built a systems that charges at 12v and drives the boat at 48v.
> Afterwards, he's not convinced it's better than a DC/DC converter, but the
> idea was for charging in parallel and propulsion in series for higher
> efficiency during both.
>
> Didn't the original post mention a big 12v bank that was electrically
> connected to the traction bank? I'm not familiar with DC/DC converters, but
> if you charged the 12v, would the converter charge the traction bank?
>
> Damon
>
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