A very useful , but not very simple SEPIC Sealed Lead Acid (SLA) Battery Charger can be constructed using the LT3755 DC – DC controller . The LT3755 is a DC/DC controller designed to operate as a constant-current source and supports a wide input voltage range from 4.5 up to 40 volts and a can provide a maximum output voltage of 70 volts .
Also the LT3755 is a DC/DC controller can be used for any other applications where is needed a high efficiency ( like LED drivers ) .
The main features of this Sealed Lead Acid (SLA) Battery Charger circuit are : adjustable frequency 100kHz to 1MHz ,low shutdown current: <1μA , constant-current and constant-voltage regulation .
The Sealed Lead Acid (SLA) Battery Charger based on the LT3755 require an input voltage between 8V to 40V and has VFLOAT = 13.5V and VCHARGE < 14.7V