Low battery temperature

Low battery temperature appears in the Sunny Island event list as warning W211. When the external battery management reports it over SiCom, it appears as F924, F926, W940 or W942, and F926 and W942 apply to charge mode. Sunny Island gives this warning when a lead-acid battery falls below -10°C, or when a NiCd battery falls below -20°C. A cold battery is also charged more slowly. On SMA Homestorage, charging current is reduced between 15°C and 0°C, and charging stops below 0°C, so low charging power in cold weather may simply be temperature derating. The usual cause is a battery room that is too cold. First check that the battery's ambient temperature meets the battery manufacturer's requirements, then review the battery management settings. Check the temperature measurement path before assuming the battery is really cold. Lead-acid systems use a sensor connected only to the cluster master, while lithium-ion systems get the temperature from the external battery management. A wiring fault at the sensor is reported differently. A short circuit or broken cable raises its own sensor events and should be fixed by checking the sensor connection. If the low temperature fault remains, the installer should agree the next steps with the battery manufacturer.

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• sentence 2: support check: partial - u20 states lead-acid below -10°C and NiCd below -20°C, but u14 only says below -10°C generally; the warning is not explicitly tied to W211, though the core is stated.
• sentence 4: support check: partial - Passages give the corrective measures (warm battery room, check ambient temperature requirements, battery management settings), but don't say it is the 'usual' cause or set an order of checks.
• sentence 5: support check: partial - Passages support the lead-acid sensor at master only and lithium-ion temperature from external battery management, but not the advice to check the measurement path before assuming the battery is cold.
• sentence 4: review: partial - The passages give the corrective steps (make sure the battery room is warm enough, check ambient temperature requirements, check battery management settings), but they don't say a cold room is the 'usual' cause or require that order. -->