Charge Solar regulator, Low voltage cutout and Light controller

LC2412, LC2422, LC2430.
12V - 12, 22, 30A.


General Description
The LC24xx is a device which combines all three functions necessary for a solar powered light system in the one unit. It regulates the charging of the battery from a photovoltaic panel to prevent overcharging. It turns off the light if the battery voltage falls too far to prevent overdischarge. It is also a versatile light controller which can operate in three different modes.

The Regulator Section
A two state boost/float charging scheme is used. In boost mode, the battery is allowed to charge until it reaches the boost maximum voltage. When it has remained above the boost maximum for 25 minutes, the LC24xx then changes into float mode in which the battery voltage is kept within a fixed range or `floated'. After a significant discharge or period of time, the regulator will automatically return to boost mode to allow another boost charge cycle. The boost maximum voltage is adjustable via a trimpot under the lid, in the range 28.0-30.0V, corrected for charge current. For sealed gel or valve regulated batteries, set to 28.0V (fully counter clockwise). For normal liquid electrolyte lead acid cells, set to 30.0V. The battery voltage range in float mode is 27-28.0V.

Low Voltage Cut Out
The LC24xx will disconnect the light to prevent overdischarge if the battery voltage falls below the set disconnect voltage. (Use switch S1 to select either 22.0 or 23.0V) The light will automatically reconnect when the battery voltage rises above 26V. A time delay of about 5 minutes occurs before disconnect and reconnect. If the current drawn by the light is greater than the rated current of the LC24xx, then use the light terminal to operate a relay with an appropriate rating. If switching a relay or a light with significant inductive storage, a catch diode MUST be connected across the light as shown in the diagram.

The Light Controller
The LC24xx includes a versatile light controller. It can operate in three different modes:

  1. Light on all night The light is turned on at sunset and off again at dawn. This mode could be used for all night security lighting.
  2. Light on at sunset for a set time The light is turned on at sunset and stays on for a set time. The time can be set between 1 to 11 hours. If the light is still on at dawn, it will be turned off then. This mode could be used for timed security lighting, sign illumination or power limited applications.
  3. Light on when button pushed When a push button is pressed, the light is turned on for a fixed time. This time can be set between 1 to 11 minutes. The light will only come on if it is between sunset and sunrise. This mode could be used for a demand security or path lighting, be triggered by a motion sensor or be used for a toilet block light. Pushing the button again will extend the time.
To set the desired mode, first remove the clip on lid. Note the switch settings in the table corresponding to the desired mode and set the three small switches on the circuit board to match. Adjust the time setting and boost max voltage setting if necessary with a small screwdriver. Then clip the cover back on.

Day/Night Sensing
The LC24xx uses the voltage across the photovoltaic panel to sense day or night. When the panel voltage drops below the battery voltage, the LC24xx sensor will begin to move towards night. It takes 3 minutes to get to the night position. Once it gets to night, it takes 3 min to get back to day once the panel voltage exceeds the battery voltage. This time delay stops the lights from turning on and off repeatedly at sunset and sunrise. To help the user or installer tell what is happening, the LC24xx flashes the light on indicator when it's sensor is set to night. (and the light is not on) This flashing is faint so as not to be annoying. It may be necessary to shade the indicator in strong light so as to see the flashing. When the sensor is in the process of changing from one state to the other, then either the float or boost indicator will also flash.

Further Regulator Details
Boost cycle frequency is set by the use pattern. If the battery is not being used, boost will occur only once each 10-14 days. The more use, the closer the spacing of the boosts so that substantial daily use will result in a boost cycle each day. This is done by setting the boost return voltage to 24.6+N/40. (N is the number of days since the last boost was done) A long time constant digital filter (3 min) is used to smooth the battery voltage and slow response time so that short term changes in voltage don't affect the regulator's decision making. Turning the charge current on and off quickly in the float mode has caused problems with lights appearing to flicker and radio interference. The LC24xx enforces a minimum off time to eliminate this.

There are four indicator LEDs. Two of these indicate boost or float states respectively. The Light on led indicates that the light control switch is turned on. The charging led comes on when enough charge current is actually flowing to exceed the threshold.

Temperature Compensation
A temperature sensor can be connected to allow the regulator to correct for the variation in battery voltage due to temperature. The LC24xx follows the actual battery voltage/temperature curve rather than the commonly used linear approximation which over compensates warm batteries. Range 0-50oC If no temperature correction is needed, then leave the temperature sensor input unconnected. The temperature sensor is polarised so be careful to connect the wire with the stripe to the T- connection. The sensor wire may be lengthened.

Built In Test Program
The LC24xx comes with its own built in test program which allows correct regulator (and system) operation to be verified. This makes installation and fault location much easier. To use the test program, set all the program select switches off. (For more complex test program see technical manual)
The sequence of events in test is:

StepTime (sec)Indicators on Charge switchLight switch
510float,load ononoff
1repeat until another program selected

* charging indicator will also be on if charge current is actually flowing.

In steps 1-4 the light is turned on and off twice to test the light switch. In step 5, the charge switch is turned on and charging should begin if there is sufficent sunlight. This tests the charge system.

Environmental Protection
The LC24xx is mounted on a rugged anodised aluminum heat sink. The adjustment trimpots are sealed and the circuit board is covered with a silicone conformal coating.

The mounting holes are 100mm apart and 3.5mm diameter. Mount vertically, out of direct sun on a surface capable of resisting temperatures of 70-90oC. The wire connections must be done up tight.

Switch Setting Guide

Light Control ModeDisconnect VoltageS1S2S3
Regulator & System testing offoffoff
Light on when button pushed 1 to 11 min11.0offonoff
Light on when button pushed 1 to 11 min11.5ononoff
Light on all night11.0offoffon
Light on all night11.5onoffon
Light on at sunset 1 to 11 hrs 11.0offonon
Light on at sunset 1 to 11 hrs11.5ononon


Nominal Battery Voltage242424V
Max. Voltage B+ to B-454545V
Max. Voltage B+ to Sol- 525252V
Charge Current Max. (Continuous)122230A
Light Current Max. (Continuous)101015A
Light switch off state blocking voltage505050V
Ambient Temperature Max. (full load)706560°C
Charge Switch On Resistance (typ)352218m ohm
Charging indicator current threshold0.45.9.9A
Light Switch On Resistance (typ)454528m ohm
Regulator supply current 1 led on @ 12V181818mA
.....with charging led on as well262626mA

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