Battery Chargers » Solar

Solar panels switch

eBatteryChargers.com — Tue, 17 Mar 2009 18:29:16 +0000

So a battery is charging during daylight from a solar panel and can discharge through solar panels during night. This problem can be prevented with a diode but this has a disadvantage so we use this switch.
This solar panels switch circuit replaces the diode and connects the panel to the battery through a relay contact. This is powered by the panel. When the supply voltage is low, the relay wont act so the battery is not connected to the solar panel.

When the voltage is high enough to start the relay and the resistor LDR R2 receives enough solar light to open T1, the relay starts and the battery will charge.
With P1 you adjust the level when the relay acts. Because the current consumption is determined by the relay, it is important that it will be a miniature type, with high coil resistance, but strong enough to comute up to 10A (eg: Siemens V23037-A0002-A101)

Solar panel switching circuit schematic

DC to DC converter

eBatteryChargers.com — Fri, 06 Mar 2009 20:09:12 +0000

This dc to dc converter raise a dc voltage at almost a double value and is useful for raising the output voltage of solar batteries up to the required level for charging acid or NiCad batteries. It can deliver up to 3Amps. The measurement values with 2A load are shown in the bottom table.
In this dc converter article we assume that the input voltage is 12V and the output is 22V. IC1a, R2 and C5 build a square wave generator. This signal is available in reversed form at IC1d output. The R2-C6 network delays the IC1a output signal, so at the AND/OR gate of IC1b we find a filling factor > 0.5. The same thing is available for AND/NO IC1c output.

IC1c output is passed through 3 levels: in IC3f, IC3a and the four gates connected in parallel IC3b-IC3e. Then it is used to command t3 FET.
IC1b commands T1 and when this transistor conducts, the common point of R6-R7 will drop at 2V in the absence of D1.
T2 and T3 conducts alternatively. When T2 conducts, C10 charges untill the input signal level through T3 and D3. When T2 is blocked and T3 conducts, C9 is charging in the similar way.
It is essential that D2, D3, T2 and T3 to have a good cooling. For the best, mount them on a common heatsink.

The bold lines represent high currents circuits which must be as short as can be, because it transport up to 6A.
A very well constructed dc to dc converter can have as much as 94% efficiency (at 22.2V and 1.8Amps)

dc converter circuit diagram

Input and output voltages at a 2A load current:

Solar Battery Charger

eBatteryChargers.com — Fri, 06 Mar 2009 19:37:50 +0000

This is a great a simple Solar Battery Charger circuit. The most simple power systems with solar panels are composed of 3 parts: a diode, a solar cells system and a rechargeble battery. The diode prevents the battery discharging through the solar cells in the lack of solar light. Although the diode is often a Schottky type, the direct voltage applied on it can produce a high power leakage.
The featured solar battery charger circuit presented here uses a special diode with reduced direct voltage.

The OA OP60 consumes a very low current: 20mA. Although it can work with a 1.6V voltage, the T1 gate needs at least 3V to switch. To adjust the circuit, replace the solar cell panel with a adjustable power supply with the current limited at a low value, safe for the battery. Adjust the voltage supply at 0.1V higher than the dc voltage of the battery. Then, adjust P1 until IC1 output is “1″. At the end you can chech with an ampermeter is the battery is not discharging when the power supply voltage is under the dc battery voltage.

Solar Powered Battery Charger Circuit Diagram

Solar energy is very cheap so buy solar panels