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The WRND WDB1220LSM is a dual battery charger and maximum power point tracking (MPPT) solar controller in one unit (the unit). The purpose of the unit is to charge a secondary auxiliary (aux) battery installed in a vehicle. It will charge the aux battery automatically from either the vehicle or a solar panel. It also isolated the vehicle starter battery from the aux battery. The unit was designed with off-road vehicles in mind and every care taken to ensure it withstands the vibrations, heat and moisture associated with these harsh environments.

The unit fully charges the aux battery. If sufficient input power is supplied the unit will start charging the aux battery at 20A while below 14.4V.The unit will charge both Lead Acid (LA) and Lithium (LiFePO4) batteries. After careful consideration and examination of the charge specifications for Flooded, Gel, AGM, Lead Crystal and LiFePO4 chemistry's and the temperatures involved it was concluded that boost charging to 14.4V for up to 2 hours and then float charging the battery at 13.7V is the best fit for all. If the battery voltage drops below 13.5V the unit will revert to boost charging. A comprehensive source of information regarding batteries may be viewed at batteryuniversity.com/learn

The unit isolates the vehicle battery from the aux battery by discontinuing charging after the engine is turned off. In essence, the unit takes power from the alternator and leaves the vehicle battery charged. This is done by not loading the vehicle battery below 12.8V for more than 5 minutes. After 5 minutes if the vehicle battery is below 12.7V the unit will enter sleep mode with all LEDs off. This allows the unit to remain permanently connected without draining the vehicle battery. The unit resumes charging once power is supplied from the alternator.

Vehicles fitted with regenerative braking (smart) alternators only charge during braking or when it senses a voltage drop across the vehicle battery. To ensure continuous charging the unit creates a voltage drop to signal the alternator to supply power while the engine is running.

A 30W to 300W solar panel (PV) may be connected to the unit when camping or as part of a permanent installation. With the panel exposed to direct sunlight, the unit will charge the aux battery using the MPPT function. Note that the open-circuit voltage (Voc) of the panel may not exceed 40V. If the solar input exceeds 45V the unit might be permanently damaged. At night the unit will power down and only power up once the solar input exceeds 13.6V.

If power is available from both the alternator and solar panel the unit will automatically select what source to charge from. The blue LED indicates charging from the vehicle and the green LED charging from the solar panel. The unit will also operate from only one source without the other being present. All the above-mentioned functions are performed automatically and thus no need for manual intervention by the user.

The unit can perform a chargeback function. If the vehicle battery was drained by the headlights, winching, excessive starting, the audio system, a cabin light or other means the unit can be used to charge the vehicle battery from the aux battery or solar panel. This is a manual process and needs to be planned for during installation. By having the same type of Anderson or Brad Harrison connectors on the unit for both the vehicle and aux batteries these connections may be swapped around. Unplug the solar panel, aux battery and vehicle battery from the unit. Plug the vehicle into the aux connection. Then plug the aux battery into the vehicle connection with the solar panel disconnected. If the aux battery has sufficient charge the unit will now charge the vehicle battery from the aux battery. The chargeback will stop after 5 minutes and can be repeated by unplugging the aux battery from the vehicle connection then reconnecting after 30 seconds. This will initiate a new 5-minute chargeback cycle. If the solar panel is connected then power will only be taken from the solar panel and not the aux battery. Solar charging will continue as long as the solar panel supplies power or until the battery is fully charged. Remember to switch the connections back to the original configuration when done.

Parameters:
Vehicle (CAR) input voltage range: 12.8V to 14.7V
Solar panel (PV) input voltage range: 13.6V to 40V
Maximum solar panel open-circuit voltage (Voc): 40V
Maximum charging current: 20A
Recommended solar panel power: 30W to 300W
Electronic protection: Short circuit, Overload and Over temperature
Self current draw (LED on): 0.09A
Current draw in sleep mode (all LEDs off): 0.01A
Internal temperature at which current will be reduced: 60degC
Dimensions in mm (W x L x H): 130 x 105 x 40

Download the user manual: WDB1220LSM User Manual