How long does a self-heating 12V lithium battery take to warm up, and what does it cost in energy?

Direct answer: We cannot give a reliable warm-up time or energy figure, because Redway does not publish heater power, trigger temperature or warm-up data for these models, and the result depends heavily on the starting temperature, insulation and charge source. What is published is the reason heating exists: these batteries list charging from 0°C, so without heat they cannot charge below freezing. Ask Redway for the heater figures in writing and plan with a margin.

What the pages list. The 12V 100Ah (self-heating, OEM) lists self-heating as a feature, with charge 0°C to 60°C, discharge -20°C to 65°C and storage -10°C to 50°C. The 12V 200Ah and 12V 75Ah list self-heating as an optional upgrade with the same charge and discharge ranges.

How it usually works. In most designs the BMS turns on a heater when a charge source is connected and the cells are below a set temperature, holds off charging until the cells are warm enough, then switches the heater off and starts charging. Whether a specific model can also heat from its own stored energy is a design choice; ask.

What decides warm-up time. Starting temperature, heater power, how well the battery is insulated from cold air and surfaces, and how much charge power is available. A battery in an insulated compartment warms faster and stays warm longer than one on a cold floor or exposed frame.

Energy cost. Heater energy is heater power multiplied by heating time. If heating runs from solar or a DC-DC charger, it uses part of the morning’s charge before the battery begins storing energy. On short winter days that can mean less net charge. Ask for heater power so you can estimate it.

Planning. Mount the battery inside the heated living space where possible, insulate the compartment if not, and make sure chargers have a lithium profile with temperature-aware settings if available. For cold charging in general, see charging a 12V 200Ah in cold weather and charging from the alternator.

Check it works. On the first cold morning, watch the charger and battery monitor: charging should start after a delay rather than not at all. Note how long the delay was; that is your own warm-up figure for your installation.