Captive battery

bat1 may only charge from pv1. That single restriction changes the answer in two opposite ways depending on whether pv1 is producing: when it is, the captive sink depletes it before anyone else may share it; when it is not, the sink has nowhere legal to draw from.

What this case shows

• A captive sink is served from its allowed source before flexible sinks share it.
• When every allowed source is idle the restriction is relaxed as a last resort: the sink is booked for what it actually drew.
• The unservable draw is reported as a restriction deficit.

Each snapshot below is one set of readings on this wiring, drawn as a flow chart — how to read it.

Captive depletes first

Captive battery · snapshot 01

pv1 produces exactly what bat1 draws, so bat1 takes all of it.

Reading	W	Of gross	Share	Made of
Gross power	900 W	1		grid 500 W · pv1 400 W
Grid import	500 W	5/9		grid 500 W
Grid export	0 W	0		nothing exported
PV production	400 W	4/9		pv1 400 W
Charging power	400 W	4/9		bat1 400 W
Discharging power	0 W	0		no battery discharging
Standby power	0 W	0		no standby draw
Self-consumption	500 W	5/9		grid 500 W
Metering imbalanceok	0 W	0		readings reconcile exactly
Home base load	300 W	1/3		unmetered remainder of consumption

Ribbon widths are watts in every view. Hover, focus or tap a ribbon to see the sensor behind it.

Source in standby

Captive battery · snapshot 02

pv1 is drawing standby, so it is a sink; bat1's only allowed source is not supplying. bat1's 400 W still came from the grid, so that is where it is booked, and all 400 W are its deficit — a "PV only" battery topping up from the grid. The base load is only what no meter measured.

Reading	W	Of gross	Share	Made of
Gross power	1000 W	1		grid 1000 W
Grid import	1000 W	1		grid 1000 W
Grid export	0 W	0		nothing exported
PV production	0 W	0		no PV system
Charging power	400 W	2/5		bat1 400 W
Discharging power	0 W	0		no battery discharging
Standby power	20 W	1/50		pv1 20 W
Self-consumption	580 W	29/50		grid 580 W
Metering imbalanceok	0 W	0		readings reconcile exactly
Home base load	480 W	12/25		unmetered remainder of consumption

▲ a restriction is relaxed: the readings cannot be met without it.Ribbon widths are watts in every view. Hover, focus or tap a ribbon to see the sensor behind it.

Why this case exists

One restriction, two opposite consequences — which is why both snapshots share a wiring.

When the captive battery's allowed source is producing, the battery depletes it first: it takes all of pv1, and the unrestricted consumer is left with the grid. A naive implementation that shared each source proportionally would hand the battery a slice of grid power it is not allowed to touch, so this snapshot separates the two implementations immediately.

When that same source drops into standby it stops being a source at all. The battery now has nowhere legal to draw from, and rather than dividing by zero the row collapses to zeros and the shortfall is reported as a restriction deficit.