Well, today I solved the funny ‘interaction’ issue. It was made so simply once I dumped real-time parameters using the connected computer. What had bothered me was this reduced out would occur even when the batteries were down in charge (Vbat at say 14.2-14.4v while under heave recharge) – I expected ALL sources to be in ‘bulk’ mode.
The issue is I have not wired up a remote sense to the Morningstar controller – as that would require a not-so-simple pulling of yet another wire from the front of the boat to the back. And even though I am using mcm373 cable from the Common to the battery, the 195A from the mains alternator results in a almost 0.6v drop. This was reflected back to the Morningstar and it entered ‘float’ mode….
Example – today I measured:
Vbat = 14.30v – per remote sensed Link-10
Valt = 14.85v – Per DMM.
Vmsc = 14.80v - Per Tristar internal reporting.
The Morningstar can only see the voltage at the ‘common’ distribution point, as opposed to the actual battery voltage. (I confirmed these voltages with spot checks using the DMM.) And I do have remote sensing for the mains alternator regulator.
Lesions learned:
1) Even if one uses Fat A__ Wires (mcm-373)- Lots of Amps still can cause a significant voltage drop.
2) Don’t be a lazy bum, pull the remote sensing wire!!!
Oh well, guess will need to set aside a day to pull a cable. Just need to decide how I can get it past the back of the washer without having to pull that out…
-al-
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of Myles Twete
Sent: Sunday, June 24, 2012 11:44 AM
To: electricboats@yahoogroups.com
Subject: RE: [Electric Boats] Re: Measured Solar Panel production after 29 days from two 240w panels in the PNW
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
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