How do you set a solar charge controller for a LiFePO4 battery?

Direct answer: Select a lithium or user-defined battery type; keep the charge (boost/absorption) voltage at or below the battery’s published maximum, 14.6V for the Redway 12V models and 29.2V for the 24V 200Ah; turn off equalisation and temperature compensation; set the charge current within both the controller and the battery limits; set the load cut-off above the battery’s discharge cut-off; and stop charging below 0 °C unless the battery has self-heating. Then check the result with a meter.

Page values to work from: the 12V 100Ah lists 14.6V maximum charge, 10V discharge cut-off, 0–60 °C charge temperature and maximum continuous charge of 50A or 100A by version. The 12V 200Ah lists 14.6V, 10V and 100A, 150A or 200A by version. The 24V 200Ah lists 29.2V maximum charge and 20V cut-off. These are limits, not targets.

Battery type. Many controllers have a LiFePO4 preset; check what voltages it uses, because presets differ. A user or custom mode lets you set each value. Avoid lead-acid presets such as flooded, sealed or gel.

Charge and float. Set the boost or absorption voltage at or below the maximum above. Some installers choose a little lower to reduce time spent at full charge; ask Redway for its preferred value for your model. A lithium battery does not need a lead-acid style float; if the controller insists on one, set it below the charge voltage, at a value Redway confirms. Disable equalisation, and set temperature compensation to zero, since lead-acid compensation would raise the voltage in cold weather.

Current. A controller can only deliver its rated output current. Check that this is within the battery’s maximum continuous charge current (for example 50A on the lower 12V 100Ah version). If the array can deliver more than the battery or controller allows, the controller limits it; set a charge-current limit where the menu offers one.

Load output and cold. If loads run from the controller’s load terminals, set the low-voltage disconnect above 10V (12V) or 20V (24V) so the controller switches off loads before the BMS does. For winter, use a controller with a battery temperature sensor that stops charging below 0 °C, or check whether your battery version has self-heating (listed as “Yes” on the 12V 100Ah page). Our posts on mains charger settings for a 12V 100Ah and cold-weather charging cover the related cases.

Verify: on a sunny day, measure the voltage at the battery terminals when the controller reports full. It should not exceed the value you set.