question

ralf-ct avatar image
ralf-ct asked

LARGE Draw While on Battery

This morning, while checking the night's VRM graphs, I noticed a substantial power and amperage draw at 07h26 while we were running on battery between 06h00 and 08h00 (simple system: 48V 3000 MultiPlus II, Cerbo GX and Pylontech US3000C). Only the PCs and fridge were running at the time. What would cause this, it looks like it may be the fridge switching on (103W motor)? Should I be worried?ralf-vrm-portal-2023-05-29-084446.pngralf-vrm-portal-2023-05-29-084356.pngralf-vrm-portal-2023-05-29-085557.png

Multiplus-IIcerbo gxPylontech
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4 Answers
mvas avatar image
mvas answered ·

Do you have a 1,500 watt appliance?

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ralf-ct avatar image
ralf-ct answered ·

When getting up in the morning we usually switch on a 2,400W kettle (the high peaks above the line), but NOT when running on battery. We also have a 650W 'loadshedding' kettle for when we run on battery, but this wasn't switched on to cause the dip above.

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klim8skeptic avatar image
klim8skeptic answered ·

@Ralf_CT looks like fridge start current spike.

You can see the cyclic current drawn by the fridge. However VRM has only captured 1 start spike. Perhaps..

My fridge will spike at 1000w startup / 55w run, however the spike is rarely captured due to the sampling rate.

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ralf-ct avatar image ralf-ct commented ·
Yes, that makes sense. Sampling is set at 1 minute, so it was pure luck to capture the starting spike, but 35A for a 103W motor, is that normal?
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kevgermany avatar image kevgermany ♦♦ ralf-ct commented ·
Can be up to ten times the normal current.
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ralf-ct avatar image ralf-ct kevgermany ♦♦ commented ·
At 230V the 103W fridge motor would draw 0.45A. 10 x would be 4.5A. The 35A draw when starting while running on battery is concerning. The fridge was on its own surge protector plug (still is) before the inverter was installed (now also with a surge protector on its DB). It operates fine, no problems.
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rvicev avatar image
rvicev answered ·

No, 35A start-up is definitely not normal for a fridge (even at 10x normal current you would only be at 4A or so - assuming you´re at 230 vac).

Most ´normal´ fridges (i.e. not double door american style fridges) these days according to manufaturer´s spec require a breaker of 10A; older ones may have a slightly higher consumption and may require a breaker of 16A).

Edit :

My bad : looking at your graphs, you probably meant 35A withdraw from battery (@48V - almost 1750W), and not 35A @ 230 vac ....

Still, if it is your fridge causing this, that´s a very signficant peak with a 103W motor - that would worry me.

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ralf-ct avatar image ralf-ct commented ·

It seems to be at the start of a fridge cycle, while running on battery. Somewhat concerning.

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