circuit wiring: sla

Showing posts with label sla. Show all posts

Friday, September 27, 2013

Low Voltage Cutout For 12V SLA Batteries

This simple circuit protects an SLA battery from over-discharge by disconnecting the load when the terminal voltage drops below a preset level. In operation, a sample of the battery voltage is derived from the 22kΩ resistor and 20kΩ trimpot divider. This is applied to the non-inverting input (pin 3) of IC1, where it is compared with a reference voltage on the inverting input (pin 2). When the sampled battery voltage falls below the reference voltage, IC1’s output (pin 1) swings towards ground, switching Mosfet Q2 off and disconnecting the load from the battery. The reference voltage is derived from a 4.7V zener diode (ZD1), which is connected to ground via the collector-emitter circuit of Q1 (ie, when Q1 is on).

However, when the op amp’s output is driven low, Q1 is switched off, causing the non-inverting input to rise towards the full battery voltage. This greatly reinforces the switching action, latching the circuit in the "off" state until the battery is recharged and the reset switch (S1) pressed. The Mosfet used for Q2 should be selected to suit the intended application. The circuit could also drive a relay simply by connecting the coil across the "load" terminals. As is usual practice, a diode should be connected across the relay coil to limit back-EMF spikes.

Saturday, April 13, 2013

Solar Powered SLA Battery Maintenance

This circuit used to be designed to ‘baby-sit’ SLA (sealed lead-acid or ‘gel’) batteries the use of freely available solar energy. SLA batteries suffer from quite high interior vitality loss which shouldn't be normally a problem except you go on vacations and disconnect them from their trickle current charger. In some instances, the absence of trickle charging present may cause SLA batteries to move utterly flat within a few weeks. The circuit proven here is intended to stop this from happening. Two 3-volt solar panels, every shunted via a diode to viapass them when no electrical energy is generated, energy a MAX762 step-up voltage converter IC.

Circuit diagram:

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Solar Powered SLA Battery Maintenance Circuit Diagram

The ‘762 is the 15-volt-out model of the most likely extra familiar MAX761 (12 V out) and is used right here to lift 6 V to 15 V.C1 and C2 are decoupling capacitors that suppress high and low frequency spurious parts produced by way of the switch-mode regulator IC. Using Schottky diode D3, power is saved in inductor L1 in the form of a magnetic container. When pin 7 of IC1 is open-circuited through the interior switching signal, the saved vitality is diverted to the 15-volt output of the circuit. The V+ (sense) enter of the MAX762, pin 8, is used to deal with the output voltage at 15 V. C4 and C5 serve to maintain the ripple on the output voltage as small as that which you could imagine. R1, LED D4 and pushbutton S1 will let you check the presence of the 15-V output voltage.

D5 and D6 scale back the 15-volts to about thirteen.6 V which is a regularly quoted nominal standby trickle charging voltage for SLA batteries. This corresponds neatly with the IC’s maximum, interiorly restricted, output current of about one hundred twenty mA. The worth of inductor L1 is not crucial — 22 µH or 47 µH will also work superb. The coil needs to be rated at 1 A although in view of the height current thru it. The switching frequency is ready 300 kHz. A advice for a pragmatic coil is sort M from the WEPD sequence equipped through Würth (www.we-online.com). Remarkably, Würth provide one-off inductors to particular person consumers. At the time of writing, it was once imaginable, under sure stipulations, to acquire patterns, or order small portions, of the MAX762 IC during the Maxim website online at www.maxim-ic.com.

Author : Myo Min