Best Low Drop Solar Charger Circuits Explained

The first Low Dropout Voltage (LDO) solar charger controller circuit using transistors makes use of a basic differential amplifier along with series P channel MOSFET linear regulator -their compatible use seems as if a relationship created by great beyond. Voltage output is variable. It will be primarily designed for charging 12V lead-acid batteries.

Solar Charger Controller Specs

Solar panel evaluation: 50W (4A, 12V minimal) (open circuit voltage: 18 to 20V)
Output voltage range: 7 to 14V (adjustable) (not advisable for 6V applications)
Maximum power dissipation: 16W (encompasses power dissipation of D3)
Standard dropout voltage: 1.25V @ 4A
Optimum current: 4A (current restricting offered by solar panel aspects)
Voltage regulation: 10mV (little or no load to optimal load)
Battery discharge: 1mA (Chinese controls discharge at usually 5mA)
LED indicators:
RED: Solar panel active
GREEN: Series regulator limiting current (fully charged or topping off)
Reverse battery protection: Control shuts down whenever battery is unintentionally attached in reverse
Schematic of 12V Solar Charge Controller Circuit

Dropout Voltage

The input voltage is more than the input voltage by 1.25V in case charging at the highest rate -the lesser, the more desirable. Low Dropout Voltage (LDO) is the pick up expression for nearly anything under close to 2V. This may possibly be decreased to under 1V by helping to make D3 a schottky rectifier.

Current Limiting

Current limiting is made available from the solar panel it is not a universally recognized truth that the solar panel happens to be a constant current equipment. Because of this, a solar panel will probably tolerate a short circuit. For that reason, the control will not require current controlling.

Float Charge of Lead-Acid Batteries

This management charges the battery with a constant voltage as well as regulates a charged battery (float charge). The float charge voltage requirements is a touch under a the charge voltage, therefore to allow for the two voltages, a negotiate is achieved through bringing down the voltage a bit that is precisely how Most automobile techniques work with. In order to get hold of optimum charge in a 12V battery, fix the regulation to 14 to 14.6V. Automobile designs additionally bring down voltage to 13 to 13.5V with the intention to meet scorching heat functioning as the battery is commonly situated in the hot engine slot -battery includes a negative thermal coefficient of voltage.

Voltage Adjustment

To be able to fix the voltage, remove the battery and hook up a 1K dummy load resistor to the output. The resistor is essential to shunt potential MOSFET seepage current in addition to the green LED current.

LDO Solar Charger controller Circuit Functionality using transistors

R4 and D1 structure a 6V shunt zener voltage reference. Q1 & Q2 constitute the traditional differential amplifier that amplifies the distinction between the reference voltage and the feedback voltage through the center tag of potentiometer R6. The output is taken out via the collector of Q1 and triggers the gate of P-Channel MOSFET Q3. Differential voltage gain might be approximately 100 to 200. For most desirable accomplishment, I decided on Q1 & Q2 for equivalent hFE. As the feedback voltage boosts at the slider of R6, Q2 triggers on stronger and rips off a part of the emitter current off from Q1. The collector current of Q1 pursues the emitter current and restricts substantially less voltage across R1 consequently eliminating Vgs of Q3 and switching it off. C2 offers frequency reimbursement to avert the amplifier through frequency.

Q3 is inactive unless of course the battery is plugged in reverse -should this materialize, Q3 conducts on and helps prevent the reference voltage input to zero as a result switching Q1 & Q3 and discouraging hazardous battery current.

D3 inhibits the battery voltage from emerging across an dormant solar panel.

Thermal Management

This really is a linear series regulator that will desolve considerable power each time the pass transistor is together executing current and reducing voltage at the same time during optimum charge rate while the voltage restriction is minimal, the heatsink works warm when the battery is completely charged and you have affordable charge current, the heatsink is cool but in case the battery sets forth to peak off at optimum voltage, the heatsink functions sizzling hot such is the characteristics of a linear regulator. During 4A, Q3 lowers 3.3V (considering solar panel voltage is 18V)(the residual 0.7V is the D3 voltage decline. P = 4A * 3.3V = 13.2W. The heatsink is graded at 3.9°C/W, therefore heatsink temperature surge = 13.2W * 3.9°C/W = 51.5°C. Incorporating the 25°C ambient temperature leads to a heatsink temperature of 76.5°C. Even if this may look like scorching hot to the finger, it happens to be gentle to the transistor which is evaluated for a junction temperature of 175°C.

For the Long term

A 6V model while this regulation could be fine-tuned right down to 7V for charging 6V batteries, the efficiency is minor, and definitely will impact at cut down current. A 6V variant is on the drawing board.

High Current Low Drop Solar Charger Circuit

This low drop solar panel charger circuit is going to be used to accomplish optimum current from a solar panel system whilst charging a conventional lead acid 12 volt battery. It gives you approximately the identical current as though the solar panel was attached straight to the battery. The circuit is a discrete equivalent form of the LM1084 which is basically a 5 amp variable, 3 terminal, low dropout regulator available in the market for around $3. The regulator voltage for the battery is determined to 13.6 that could be in the vicinity of full charge. The voltage could possibly be somewhat over at 14.1 however this would demand temperature stabilization which means that the voltage collapses a tad bit as the temperature goes up. Employing 13.6 with no stabilization need not include a temperature issue.

Procedure:

Transistors Q1, Q2 is wired as a differential couple where Q1 detects the battery voltage and Q2 is positioned at a reference voltage fixed by the white colored LED. Resistors R3, R4 are cinfigured a voltage divider to ensure that the input to Q1 can be the just the same as Q2 while the battery is at 13.6 as well as the regulator is going to turn off to certain nominal current to keep up 13.6 volts on the battery. The white LED voltage is around 2.7 volts.

Resistor R5 (330 ohm) fixes the current for the transistor set (Q1, Q2) to approximately 6 milliamps because the voltage across R5 will likely be the reference 2.7 - 0.6 (e/b drop of ). This offers us I=E/R = (2.7-0.6)/330 = 6.4 milliamps. Whenever the battery is noticeably below 13.6, Q1 is going to be off and 6.4 milliamps is going to move via Q2 and R6 delivering a voltage across R6 (750) of E=IR =.0064 * 750 = 4.8 volts.

Q3 is designed as a barrier for the voltage across R6 as well as guarantees current to the bypass transistors Q4,Q5. The emitter/base junction of Q3 will probably shake off around 0.6 volts as a result the voltage on the emitter will likely be 4.8 - 0.6 = 4.2 as well as the current all through R8 (330) is going to be I=E/R = 4.2 / 330 = 12.7 milliamps. This certainly will be adequate to operate Q4,Q5 at 5 amps or perhaps higher when lowest possible amount gain of at least 20 for Q4 and Q5. Resistor R9 (750) is employed to confirm a little some current needs to switch on Q4. This functions to approximately 1 milliamp. Resistor R10 (750) acts as a pullup to secure the circuit initialization any time a battery is not plugged in. The regulator could be utilized in the form of a 13.6 volt power supply with no the battery hooked up.

Insights:

Drop-out voltage checked 0.82 as soon as the input had been 13.86 and output had been 13.04 and charge current had been 1.92 amps.

The gain (hFE) of Q5 (2N3442) checked roughly 45 at 2 amps with under 1 volt between emitter and collector. This must run at 5 amps with a gain of possibly 20, although I could not check it out. The posted spec is hFE=20 minimum at 3 amps with VCE = 4 volts. The significance of R8 can certainly be lesser or R6 larger to augment the drive current to Q4 in case demanded.

R1 and R2 signify the inner resistance of the battery as well as the solar panel. In case the panel (no load) voltage is nineteen and the charge current is two amps, and the battery voltage is thirteen, along with the drop-out voltage is 0.82, subsequently the panel's internal resistance (R2) could very well be R=E/I = 19 - (13 + 0.82) / 2 = 2.6 ohms.

As soon as the battery is in close proximity to full charge along with the current is suppose 200 milliamps, the panel voltage is going to be around E = 19 - IR = 19 - (0.2 * 2.6) = 18.48 so the drop throughout Q5 is going to be approximately 18.48 - 13.6 = 4.88 volts.

However these datas are rough assumptions given that the panel impedance is not really persistent.

Parts List for the low drop solar panel charger circuit:
Q1, Q2 = 2N3906 or the majority of small signal PNP.
Q3 = 2N3904 or the majority of small signal NPN.
Q4 = 2N2905A or comparable medium power (500mA) PNP
Q5 = 2N3442 or 2N3055, high power NPN
One White LED (2.7 volt)
D1 = 1N4148 or just about any small silicon diode

R1, R2 = N/A (see text)
R3 = Approximately 560 ohms. Fine-tune this resistor to get the preferred battery voltage.
R5, R8 = 330 ohms
R6, R9, R10 = 750 ohms
R4, R7 = 2.2K

Zero Drop Solar Battery Charger Circuit

The post talks about a basic zero drop LDO or low drop solar charger controller circuit which is often altered in lots of alternative ways according to user choice. The circuit would not rely on microcontroller and can be developed even by a layman.

A zero drop solar charger is a device which guarantees tat the voltage from the solar panel reaches the battery without undergoing any kind of drop either due to resistance or semiconductor interference for example diodes etc in line.

The circuit here makes use of a mosfet as a switch for being sure minimum drop of voltage received from the attached solar panel. Moreover the circuit has a distinct advantage over other forms of zero drop charger designs, it does not pointlessly shunt the panel ensuring the panel is permitted to work at its largest effectiveness zone.

Let's know how all of these features could possibly be accomplished during this novel circuit idea created by me. Talking about the offered zero drop voltage regulator charger circuit diagram we observe a rather simple configuration comprise of an opamp and a mosfet as the main energetic components.

Right here the opamp is cabled as a comparator in which its non-inverting pin is placed as the voltage sensor via a voltage divider stage created by R3 and R4.

The inverting pin is as normal rigged as the reference input utilizing R2 and the zener diode.

Considering the battery to be imposed is a 12V battery, the junction between R3 and R4 is determined such that it generates 14.4V at a certain optimum input voltage level which can be the open circuit voltage of the associated panel. On making use of the solar voltage at the demonstrated input terminals, the mosfet is linked to with the aid of R1 and permits the whole voltage across its drain lead which lastly actually reaches the R3/R4 junction.

The voltage level is immediately felt here and if in the event it's more than the set 14.4V, switches ON the opamp output to a high potential.

This activity immediately switches OFF the mosfet making certain no more voltage is able to achieve its drain. In spite of this along the way the voltage now has a tendency to decrease below the 14.4V mark across the R3/R4 junction which one more time encourages the opamp output to go low and in turn turn on the mosfet.

The above switching continues repeating quickly which ends up in a continuing 14.4V at the output given to the battery terminals.

The utilization of the mosfet assures a nearly zero drop output from the solar panel. D1/C1 are launched for sustaining and preserving a persisting supply to the IC supply pins.

As opposed to shunt type regulators, right here the excess voltage from the solar panel is managed by switching OFF the panel, which guarantees zero loading of the solar panel and enables it to generates its most effective problems, quite similar to an MPPT circumstance.

The circuit may be very easily improved by attaching an auto cut off, and an over current limit capabilities.

Parts List

R1,R2 = 10K R3,R4 = use an online potential divider calculator for fixing the required junction voltage

D2 = 1N4148 C1 = 10uF/50V C2 = 0.22uF Z1 = ought to be much lower than the chosen battery over charge level IC1 = 741

Mosfet = in accordance with the battery AH and the solar voltage.

Including a current control characteristic to the above zero drop solar charger circuit

The above circuit appears quite an effective design in spite of this lacks a current control feature. The diagram below demonstrates how the above circuit could be enhanced with an existing control feature by simply including a BC547 transistor phase across the inverting input of the opamp. R5 may be any low value resistor for instance a 100 ohm. R6 decides the highest permitted charging current to the battery which might be set by utilizing the formula: R(Ohms) = 0.6/I, where I is the optimal charging rate (amps) of the attached battery.

Note: A P-channel mosfet might not function properly, consequently the mosfet in the above zero drop solar circuits needs to be restored with N-channel mosfets as presented in the folowing diagrams. Viewers are suggested to do the changes according to the following diagrams.

Tips on how to Begin the zero drop solar charger circuit

It really is very simple. You should not hook up any supply at the mosfet side. Upgrade the battery with a adjustable power supply input and adjust it to the charging level of the battery which can be allowed to be charged. Now cautiously change the pin2 preset until the LED just shuts off....flick the preset to and fro and check the LED reply it ought to also blink ON/OFF in the same way, definitely regulate the preset to a point where the LeD just shuts off totally....seal the preset. Your zero drop solar charger is set, and set. It is possible to verify the above by using a higher input voltage at the mosfet side, you'll discover the battery side output generating the entirely controlled voltage level which was earlier set by you.