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widu avatar image
widu asked

MPPT 75/15 not charging?

Hi All, I am a bit stumped with this one. Since day one my MPPT doesn't seem to have behaved normally. I have around 20.85v coming in from a 21v 160w solar panel and around 13.3v being outputted to the battery, both confirmed by a meter. Fuses, continuity, polarity and gauge is all good, but the app consistently reports zero output. Any ideas?

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smart solar charging behaviour
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6 Answers
widu avatar image
widu answered ·

Final update...unit confirmed by dealer as no output, replacement being sent. Many thanks to those that contributed.

Whilst noted for quality, my internet searches have noted many failed Victron units. Ultimately, they are mass produced electrical items and are subject to dry/insufficient soldering and circuit board issues just like anyone else.

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nickdb avatar image
nickdb answered ·

What have you set the charging voltages at? You need +5V to activate the MPPT so it does look like you need more panels to get to the minimum threshold.

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widu avatar image
widu answered ·

Set to Lifepo. Lifepo charges at max 14.2v, so +5v is 19.2v? I am getting 6+v above the max charging?

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JohnC avatar image
JohnC answered ·

Hi @widu

Your logged battery V max/min figures look unrealistic. Check your wiring to the batts, crimps, fuse, whatever.

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widu avatar image
widu answered ·

I think I have my answer. I have de-wired the unit and replaced the fuse, I don't know whether the fuse was good or not (earlier testing said that it was but it appeared to have been "glued" in place with blue plastic or thread lock type stuff and broke apart on removal!) but with a new fuse I have no output at the terminals. I am going to guess that this unit has never charged since installation some months ago- I have just blindly used it taking the status indicator on faith- sometimes blinking fast and sometimes slow. The unit has to be goosed. Thank you all for your input.


5 comments
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klim8skeptic avatar image klim8skeptic ♦ commented ·
Hmm mppt showed signs of life 3 days ago.

Further testing is warranted.

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JohnC avatar image JohnC ♦ commented ·

@widu

"I have no output at the terminals"

You should have battery Voltage, don't you? Too early to give up yet..

Is it actually set for 12V, not 24V?


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widu avatar image widu JohnC ♦ commented ·
Hi John, I deconstructed all of the wiring, replaced the fuse and connected power (solar) only. With the battery output leads removed, but the connection screws tightened, there is no voltage at the battery out terminals.
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widu avatar image
widu answered ·

Just a quick update. The unit has gone back to the retailer for testing. I have hooked up the solar to an existing CTEK 250SE and it does charge via that, so the cabling is ok.


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