question

winterstormcrow avatar image
winterstormcrow asked

sharp voltage drop at charge controller

i have been using a 150/60 mppt with mc4 connectors from victron energy happily for about 6 months. recently i had some kind of fault possibly in my wiring that prevented voltage from reaching the controller. i fixed this wiring, and now when i measure the voltage before connecting to the mppt it is a proper 80v or so. however when i connect to the mppt, it drops to between 20v and 30v, usually not enough to charge my 24v system at all, though it occasionally charges at around 2watts. (on a 1200w system that generally gets at least 400watts)


my question is: is this likely the fault of the mppt? did i trip some kind of internal fuse? i suspect not about the fuse since it sometimes charges. or is it likely that my panels are somehow putting out sufficient voltage but not amperage and the mppt is stepping down the voltage coming in? again, ive never had this problem before and im very frustrated.

MPPT Controllers
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1 Answer
klim8skeptic avatar image
klim8skeptic answered ·

Clue, PV voltage dropping to near battery voltage.

Indicates a high resistance joint.

Check array wiring/fuses/breakers/connections.

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winterstormcrow avatar image winterstormcrow commented ·

since i can read 80v at the ends of the wire before i plug it in to the mppt, does that mean the only possible high resistance joint is that final connection? or can it suggest one further back in the chain?


i just checked the array wiring. one of the series (3 series each with 4 panels) had a faulty wire which ive now (since asking the question) replaced, though this has not solved the problem. it does shoot up to 79v for brief seconds here and there.

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klim8skeptic avatar image klim8skeptic ♦ winterstormcrow commented ·
Measure the voltage across each connector.
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