Multi-battery management

The integration manages up to 6 batteries as an aggregated system, distributing power intelligently to maximise efficiency.

Efficiency principle

Based on measured Venus efficiency curves, batteries are activated only when total power exceeds the efficiency crossover point — the wattage at which splitting load across two batteries becomes more efficient than running one alone. Running fewer batteries at higher power is more efficient than spreading the same load across all of them.

The crossover points (derived from η external measurements) are:

Direction	Crossover	% of 2500 W physical max
Discharge	1500 W	60 %
Charge	1750 W	70 %

The activation threshold is computed dynamically as crossover_W ÷ configured_max_W, clamped to [50 %, 95 %]. This means users who configure a lower power limit per battery activate additional batteries later (closer to their configured max), which correctly reflects that their operating range stays within the single-battery efficiency peak.

The following measurements show DC power consumption/output, AC power at the meter (internal clamp) and at the wall outlet (external clamp), and the resulting efficiency at each power level:

Charging

% of max	Setpoint (W)	DC internal (W)	AC internal (W)	AC external (W)	η internal	η external
3 %	63	41	58	68	70.7 %	60.3 %
5 %	125	105	123	136	85.4 %	77.2 %
10 %	250	232	247	262	93.9 %	88.5 %
15 %	375	357	372	387	96.0 %	92.2 %
20 %	500	481	497	513	96.8 %	93.8 %
25 %	625	604	621	639	97.3 %	94.5 %
30 %	750	727	743	766	97.8 %	94.9 %
35 %	875	850	871	892	97.6 %	95.3 %
40 %	1000	973	995	1019	97.8 %	95.5 %
45 %	1125	1095	1120	1146	97.8 %	95.5 %
50 %	1250	1245	1271	1274	98.0 %	97.7 %
55 %	1375	1339	1369	1401	97.8 %	95.6 %
60 %	1500	1460	1494	1530	97.7 %	95.4 %
65 %	1625	1581	1618	1658	97.7 %	95.4 %
70 %	1750	1702	1743	1786	97.6 %	95.3 %
75 %	1875	1823	1868	1916	97.6 %	95.1 %
80 %	2000	1942	1992	2044	97.5 %	95.0 %
85 %	2125	2062	2117	2175	97.4 %	94.8 %
90 %	2250	2183	2242	2304	97.4 %	94.7 %
95 %	2375	2304	2366	2436	97.4 %	94.6 %
100 %	2500	2424	2491	2567	97.3 %	94.4 %

Discharging

% of max	Setpoint (W)	DC internal (W)	AC internal (W)	AC external (W)	η internal	η external
3 %	63	80	63	60	78.8 %	75.0 %
5 %	125	160	124	118	77.5 %	73.8 %
10 %	250	284	249	243	87.7 %	85.6 %
15 %	375	416	373	368	89.7 %	88.5 %
20 %	500	550	498	494	90.5 %	89.8 %
25 %	625	685	623	619	90.9 %	90.4 %
30 %	750	820	747	745	91.1 %	90.9 %
35 %	875	956	872	870	91.2 %	91.0 %
40 %	1000	1092	997	996	91.3 %	91.2 %
45 %	1125	1230	1121	1121	91.1 %	91.1 %
50 %	1250	1369	1246	1246	91.0 %	91.0 %
55 %	1375	1507	1370	1372	90.9 %	91.0 %
60 %	1500	1647	1495	1497	90.8 %	90.9 %
65 %	1625	1789	1620	1623	90.6 %	90.7 %
70 %	1750	1931	1745	1748	90.4 %	90.5 %
75 %	1875	2073	1869	1874	90.2 %	90.4 %
80 %	2000	2218	1994	1999	89.9 %	90.1 %
85 %	2125	2362	2118	2124	89.7 %	89.9 %
90 %	2250	2508	2243	2250	89.4 %	89.7 %
95 %	2375	2654	2368	2375	89.2 %	89.5 %
100 %	2500	2801	2492	2501	89.0 %	89.3 %

Selection priorities

Discharge

Highest SOC first: the most charged battery discharges first to balance the state of charge across the system.

Charging

Lowest SOC first: the least charged battery receives energy first.

Hysteresis

To avoid "ping-pong" activation/deactivation, three hysteresis levels are applied:

Hysteresis	Value	Description
SOC	5 %	An active battery stays active until another exceeds it by 5% SOC
Lifetime energy	2.5 kWh	Breaks SOC ties using accumulated lifetime energy with an advantage for the active battery
Power	10 pp	Activation threshold derived from efficiency crossover; deactivation = activation − 10 percentage points

Power distribution

Once active batteries are selected, the total power calculated by the PD controller is distributed among them proportionally, respecting each battery's individual power and SOC limits.

Optional system-wide caps can also be configured in Advanced PD controller after enabling Enable system power limits:

Setting	Effect
System Max Charge Power	Caps the combined charge power across all active batteries
System Max Discharge Power	Caps the combined discharge power across all active batteries

Set either value to 0 W to disable that direction's cap. These limits are applied after per-battery eligibility is determined and before power is distributed, so one battery can still use its full individual limit when it is the only active battery. If several batteries are active, the combined total is throttled to the configured system cap. The corresponding runtime slider entities are only created when the feature is enabled.

Per-battery charge/discharge controls

Each battery exposes two software switches:

Switch	Effect
Allow Charge	When turned off, this battery is excluded from automatic charging. It may still discharge if Allow Discharge is turned on.
Allow Discharge	When turned off, this battery is excluded from automatic discharging. It may still charge if Allow Charge is turned on.

These switches do not write Modbus control registers directly. They only affect the integration's automatic PD controller. If a battery is active in the disabled direction, the integration sends that battery to 0 W and the next control cycle reallocates power to the remaining eligible batteries.

The state is stored per battery as allow_charge and allow_discharge. Missing values default to enabled, so existing installations keep their previous behavior after updating.

Unified blocker registry

Charge and discharge permissions are resolved through a runtime blocker registry. Blockers can be system-wide or scoped to one battery. The controller checks this registry before deadband and stale-sensor early returns, so an active command is stopped as soon as a blocker appears.

Global blockers include solar charge delay, charge/discharge time slots, price-based discharge control, and EV charger no-telemetry pauses. Per-battery blockers include the Allow Charge and Allow Discharge switches, maximum SOC, minimum SOC, and charge hysteresis. Other availability checks such as backup/off-grid exclusion and non-responsive exclusion remain separate from the blocker registry.

The top-level charge_blocked and discharge_blocked attributes report the effective system state: they become true when a global blocker is active or when every known battery is blocked in that direction. Per-battery details remain visible in battery_charge_blockers and battery_discharge_blockers.

The registry is exposed on the Integration Status diagnostic sensor through these attributes:

• charge_blocked
• discharge_blocked
• charge_blockers
• discharge_blockers
• battery_charge_blockers
• battery_discharge_blockers

Non-responsive battery exclusion

When a battery consistently fails to deliver the commanded power — for example due to a Modbus communication glitch or a firmware self-protection response — the integration detects this and temporarily removes it from the active pool.

A battery is flagged as non-responsive when its measured output is below 5% of the commanded setpoint for 3 consecutive control cycles. Once flagged, it enters a 5-minute exclusion window during which it receives no new commands and the remaining batteries absorb its share of the load. After the window expires the fail counter resets and the battery becomes eligible again.

This mechanism prevents a single misbehaving battery from silently degrading system performance without raising alarms or requiring manual intervention.

Compatible modes

Multi-battery distribution applies in all modes: - Normal PD control - Solar charging - Predictive grid charging