Quattro 15kVA Loud Oscillating Noise when Charging Batteries

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colin-cannon asked Dec 14, '23

Quattro 15kVA Loud Oscillating Noise when Charging Batteries

We have installed 2 x Quattro 15kVA units in parallel on a grid tied site with 2 x 15.4kWh BYD batteries and 2 x fronius 6 primos.

All is well with the system except when it begins charging the batteries from the grid.

A loud oscillating humming noise comes from the Quattros and the amps start to fluctuate with the noise. The amps recorded on a DC clamp meter jump from 90Amps to 125Amps, then back down, then back up.

This happens when charging from the grid only. When the grid is feeding straight through it is fine. When the batteries are discharging, also fine.

Any ideas as to what is causing this problem or any other similar examples anywhere?

Quite urgent to resolve this before Christmas as there are usually power cuts in the area where the system is installed.

https://www.youtube.com/shorts/4FViEa14HNo

battery charging quattro 10kva

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Answer 1 · 2023-12-14T12:08:13Z

Alexandra answered · Dec 14, 2023 at 12:08 PM

@Colin Cannon

If expecting power cuts the batteries should be sized for off-grid. That is BYDs official response to another thread somewhere on the forum.

That being said, why not just turn down the charging amps from grid?

I have heard the oscillating sound like that when the AC wiring is not quite right. Not just referring to the parallel, but on 15kvas in general got something to do with either the resistance from grid connection (like actual grid) or internal innthe wiring to the inverters.

Does it happen with no loads connected?

Second scenario - in charger only mode?

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Answer 2 · 2023-12-14T16:24:41Z

colin-cannon answered · Dec 14, 2023 at 04:24 PM

Understood on the batteries, this is something we have considered. Thank you.

We have turned the amps down. The cutout is 100Amps, we have limited the battery charge current to 125Amps per 15.4kWh BYD. Even when charging at a lower rate, the oscillating is there, albeit not as loud. So the noise is relative to the charge current for sure.

When you say the AC wiring wasn't quite right on the other occasion you had heard this, what is it that was not quite right about it? We will be heading back down to the site next week to give it everything we have, so any ideas to try whilst we are there would be much appreciated - very remote.

Yes, this does happen when loads are connected and when all the loads are individually turned off (apart from the light bulb in the room we were working on). We have not however, tried it with just the charger at this point - so will put that on the list for next week. I appreciate the inverter and charger are separate.

Thank you very much for answering my question @Alexandra and offering some advice. Very grateful.

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