question

love2learn avatar image
love2learn asked

Understanding idle battery status

I'm trying to understand what the shunt is saying by reporting the battery at "Idle 29w". Wouldn't idle necessitate it being 0 watts since a positive number would mean charging, and a negative number would mean discharging?

screenshot-20221214-142900.png

VRMSmartShuntmonitoring
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love2learn avatar image love2learn commented ·
(Is bumping allowed here?)
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shaneyake avatar image
shaneyake answered ·

There is just some hysteresis on what is considered idle.
I am not sure on the exact number but probably around +50W / -50W or some percentage of battery capacity.

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love2learn avatar image love2learn commented ·
Ok, so would hysteresis also account for the "missing" watts Im seeing? The battery shows -102w, 37 watts on AC, 37w on DC. 28w arent accounted for... Shouldnt DC loads + AC loads = total battery discharge amount?
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JohnC avatar image JohnC ♦ love2learn commented ·
@Love2Learn

Think efficiency and standby losses on the inverter. That's not reported, but it can be approximated and shown if you enable the DC Power tile. This might jump around a bit because the sample times of each component don't exactly coincide. There's a Widget for it in VRM Advanced, and you can get a good idea of the 'average' missing watts from that.

This assumes a shunt giving an absolute value to and from battery. For systems without the shunt, anything below like ~50W becomes neither-here-nor-there territory with respect to whether the batt is charging or not, so they've just called it Idle.

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Alexandra avatar image Alexandra ♦ JohnC ♦ commented ·

Idle means it is not exactly charging or discharging.

Either it is is full and PV is covering everything.

Or in your case... PV is barely covering loads (Including equipment) so it is not really charging.

If you dont have a shunt or bms connected the 29w is a calculated value.

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love2learn avatar image love2learn Alexandra ♦ commented ·
That's why I was confused, because I DO have a SmartShunt in there so I didn't think it would need to "guess" at any value. I have the Cerbo GX pointing at the SmartShunt for battery calculation.
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Alexandra avatar image Alexandra ♦ love2learn commented ·
Still, there is not enough current there for charging, so it is idle.

It really is not charging at 26w.

Something is truckling in, true, but in bulk phase which you will be at that percent SOC is not a bulk charge.


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