Warning "Low battery voltage" at high load

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sascha-brinkmann asked May 19, '22

Warning "Low battery voltage" at high load

I'm operating a 4,8kW Peak PV System with a Huawai Inverter. Recently I've added MultiPlus-II 48/3000/35-32 GX with a 175ah Battery. A Victron Energy Meter ET340 measures the residual load and provides the information to the victron.

I'm operating the MP 2 with ESS to charge the surplus of the PV system into my battery or to level my grid demand to zero to the extend it is possible. When I'm charging my electric vehicle with 6 kW, I'm utilizing the PV system and MP 2 at the maximum possible power supply.

At this load level the MP 2 is quite unreliable. For a short period it works as expected until the voltage and current drops until discharging starts again (see Video)

Charging is not effected and works as expected at the same rate.

This warning is shown in the notifications

Multiplus-II ESS

bildschirmvideo-aufnehmen-2022-05-19-um-125238.mp4 (183.3 KiB)

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Alexandra answered · May 19, 2022 at 12:14 PM

What nominal or continuous current rating is the bms?

It is the bms shutting the system down not the other way around.

40A setting is a lot close to the 37A you are drawing out (discharge current limit on bms)

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2 |3000

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sascha-brinkmann commented · May 19, 2022 at 12:58 PM

This seems to solve the issue. I've just increased the discharge current on the BMS and now it seems to discharge quite stable. Thanks for the crosscheck. I've overseen this setting!

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Alexandra ♦ sascha-brinkmann commented · May 19, 2022 at 05:26 PM

@Sascha Brinkmann

Glad to be of assistance.

The 3000VA will see discharges of 62.5A at max load. And does need to be able to 93.75A (peak) in the case of an overload to be able to shut itself down as a protection. Although it may be best to give it a few more amps headroom for the nominal rating.

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Modifications Space

Node Red Space

Answer 1 · 2022-05-19T11:18:34Z

klim8skeptic answered · May 19, 2022 at 11:18 AM

You are still operating your grid tied inverter on a different phase as to your multiplus is operating.

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sascha-brinkmann commented · May 19, 2022 at 11:40 AM

This is just the drawing. In the meantime, I switched to the same phase. For charging the surplus from the PV system it is helpful to be on the same phase. For utilizing PV and battery at the same point of time to charge for example you electric vehicle you're running into the issue that you're breaking the regulatory for phase dysbalance. In Germany you have to take measures that your dysbalance is not exeeding 20A or 4,6 kW. When you're MP 2 and your PV system are operating at their maximum power at the same phase you're exeeding this value. Operating them on different phases prevents violating this regulatory.

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Answer 2 · 2022-05-19T11:42:37Z

sascha-brinkmann answered · May 19, 2022 at 11:42 AM

Settings from my Dali BMS

screenshot-2022-05-19-13-18-04-442-cominukerblueto.jpg (132.1 KiB)

screenshot-2022-05-19-13-18-11-334-cominukerblueto.jpg (128.5 KiB)

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

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