SLA charger from Car socket

Discussion in 'General Electronics Chat' started by Johnr86, Sep 24, 2016.

  1. Johnr86

    Thread Starter New Member

    Sep 24, 2016
    1
    0
    Hi Everyone,

    I'm trying to put together a circuit to charge a 7Ah SLA battery from a car lighter socket.

    I am part of a neighborhood watch group in my country (South Africa). As part of this group we all use flashing lights on our scheduled "patrols". This is a simple strobe type LED light that plugs in the car lighter socket. What I would like to do is use an SLA battery with the light so that when I turn off the engine, the flashing light stays on even with the lighter socket off. I do not want to run off the car battery when the ignition is off.

    Points I would like to achieve:
    • Have the light running when ignition is off
    • Not use the car battery when ignition off
    • Use an SLA battery (7Ah)
    • Charge the SLA battery whilst ignition is on
    • Have the light on whilst charging the SLA battery.
    • Protect the SLA battery to extend its life.
    I have done some searching around and so far I have decided on the simple circuit supplied in the datasheet for the PB137(link) regulator (ST). I am concerned that this simple circuit will not provide necessary protection for the SLA battery to prevent premature "battery death".

    I would appreciate your advice!

    My background:
    Trade Electrician
    Diploma Mechatronic Engineering
    8 years Work experience in Maintenance Department of Factories ranging from Heavy metals to Food processing
    Not much experience on circuits < 220v but I have dabbled.

    Thank you!
     
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