Exactly… the Morningstar MPPT controller that Al installed is designed to optimally load the panels at the MPP up until the point where the battery is detected as being at its charged voltage. At that point, the MPPT controller reduces the current drawn from the panels. The controller does have diversion load capabilities built-in that allow the controller to continue to draw maximum power from the panels, but putting the power into a DC resistive “diversion load”.
Further, that controller uses 4-stage charging, so if its brains determine that the CI/CV stage is done, it could well shift to FLOAT and deliver minimal amounts of electricity. Not sure how it decides that it’s time to go into equalization mode.
http://www.morningstarcorp.com/en/support/library/TriStar%20Datasheet%20English.pdf
Ideally, it’d be nice if the MPPT controller could be the master and “control” the output of your alternator to only deliver what the panels cannot.
Short of that, on nice days while underway, if your panels can deliver the power you need, maybe you can switch the alternator output off.
Al- I get a similar “interaction” in running my electric boat (you know my boat J) with the EU2000i delivering power to the system. If the motor isn’t drawing enough power from the pack, the power from the genset and chargers will cause the pack voltage to rise. As my Lester charger detects the voltage at the CV charge point, it backs off the current it draws, so that one could think that the genset power output is continuing at 1.6kw or so, but due to the charger’s controller backing off, the output is less. In running with that genset on, I always make sure that the motor’s drawing at least as much power as the genset is delivering so that the pack voltage is stable or dropping.
In case this helps-
-Myles
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of stmbtwle
Sent: Sunday, June 24, 2012 8:20 AM
To: electricboats@yahoogroups.com
Subject: [Electric Boats] Re: Measured Solar Panel production after 29 days from two 240w panels in the PNW
My guess your system is capable of putting out more than that, but once the batteries are charged the system reduces output to prevent damage to the batteries.
--- In electricboats@yahoogroups.com, "Al Thomason" <thomason.al@...> wrote:
>
> I thought this might be of interesting to the group: A month ago we
> installed solar panels on our powerboat Viking Star. These are used to
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