Lead acid battery charger

Posted on Feb 5, 2014

Battery manufacturers recommend charging 12V lead-acid batteries at a charge voltage of 13. 5 - 13. 8V for standby, and 14. 4 v - 15v for cyclic use(charging and discharging) - but if using the latter, which gives a faster charge, you must turn it off when fully charged. I use the 13. 8V option, and leave my battery charging until I need it - although

Lead acid battery charger
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it`s always fully charged after about 12H. The charger uses a LM317 adjustable regulator. This is an adjustable 3 terminal positive voltage regulator capable of supplying in excess of 1. 5 amps over an output range of 1. 25 to 37 volts. The device also has built in current limiting and thermal shutdown which makes it essentially blow-out proof. A 6 - 0 - 6V (or 12V) 6VA transformer feeds a bridge rectifier, and the signal is smoothed with a capacitor of 4700uF at any voltage above 16V. This gives about 17. 5V to the regulator. The output voltage is set to 13. 75V by the two resistors. Only 6 components, it can be built as a birds nest on the transformer, or as I have on a little bit of veroboard. The 1A regulator doesn`t need a heat sink. All parts available from Maplin`s.

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