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Eran Rundstein avatar image
Eran Rundstein asked

Multiplus 3000/24 buzzing when charging, even at low current

My brand new Multiplus (not a Multiplus-II) is making a very annoying buzzing sound, even when charging at 5A or less (on the 110v side) - I recorded it here https://www.youtube.com/watch?v=ooxr1Kx_jAk


I have not experienced this with other chargers, and the noise does get louder as the current increases so I suspect at higher currents it will be unbearable.


Some googling and asking around indicates that some MultiPluses do this, but some don't...

MultiPlus Quattro Inverter Charger
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hjohnson avatar image
hjohnson answered ·

There was a firmware update released recently for the multiplus inverters which will probably resolve this. I don’t recall the thread off hand, but it was within the past month or so.

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Eran Rundstein avatar image Eran Rundstein commented ·
I believe I am on the latest firmware - updated it through the VRM portal today.
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Eran Rundstein answered ·

Four people have told me so far their Multipluses are silent when charging at low currents :(

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Eran Rundstein answered ·

Took some measurements over the weekend using my phone placed right next to the fan.

Ambient noise was 29dB. Charging at 3A was 35dB and went all the way up to 45dB at 15A. Fan was measured at 63dB.

Discharging was similar.

Its not excessively loud but I have had a bunch of inverters that were completely silent until the fan kicked in so this is still a big disappointment.

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pmikep avatar image pmikep commented ·
I have two Multipluses, both with the latest firmware (which fixes the hum for the Multiplus II). As I have posted elsewhere here, the hum didn't change during charging on my units. I suspect that the resonant frequency of the different toroids used in the different units is different.


In fact, ironically, my Multiplus went completely silent today while charging when a 125 W load came on!

I am thinking there should be two different firmwares for the Multiplus and the Multiplus II.

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