Tuesday, February 1, 2011

12 Volt 20 Amp Solar Charge Controller

SCC3 - 12 Volt 20 Amp Solar Charge Controller

 Introduction

The SCC3 is a solar charge controller, its function is to regulate the power flowing from a photovoltaic panel into a rechargeable battery. It features easy setup with one potentiometer for the float voltage adjustment, an equalize function for periodic overcharging, and automatic temperature compensation for better battery charging over a wide range of temperatures. The SCC3 is able to handle reverse polarity connection of both the battery and photovoltaic panel.
The design goals of this circuit were efficiency, simplicity, reliability and the use of field replaceable parts. A medium power solar system can be built with the SCC3, a 12V (nominal) solar panel that is rated from 100 milliamps to 20 amps, and a lead acid or other rechargeable battery that is rated from 500 milliamp hours to 400 amp hours of capacity.
It is important to match the solar panel's current rating to the battery's amp-hour rating (C). A typical maximum battery charging current is C/20, so a 100 amp hour battery should have a solar panel rating of no greater than 5 amps. It is advisable to check the battery manufacturer's data sheets to find the maximum allowable charge current, then choose a PV that does not exceed that value. On the other hand, if the solar panel output current is too low, the battery may never become fully charged.
With a few parts changes, the SCC3 circuit can work as a 24V/15A solar charge controller. The 24V parts differences are shown on the schematic.

Basic Specifications (12V version)

Maximum solar charging current: 20 Amps
Nominal battery voltage: 12V
Night time battery current drain: 0.8 - 1.8ma
  • Features
    • Efficient design is suitable for use with low to medium power solar panels and solar arrays.
    • Will work with most rechargeable battery types: Lead Acid (wet or gell), NiCd and NiMH.
    • Common Negative Ground for Solar Panel and Battery.
    • Reliable all solid-state circuitry, no power hungry relay with limited-life contacts.
    • Built in fuse for short circuit protection, load circuitry requires its own fused disconnect.
    • Designed to withstand reverse battery and reverse PV connection.
    • Charging method: Full-on below float point, chopper-stabilized PWM at float point.
    • Temperature compensated float voltage set point for optimal charging at different temperatures.
    • Radio quiet, can be used with sensitive radio receivers.
    • High voltage transient protection on solar panel input for limited lightning protection.
    • Simple 4 screw connector will accept spade lugs or wires for attaching a battery and PV panel.
    • Multiple SCC3 units can be used to connect several (<20 Amp@12Vnom) solar arrays to one battery.
  • Controls and Indicators
    • Red/Green LED for Charge/Float state indication.
    • Equalize switch for periodic maintenance overcharging.
    • Float voltage adjustment trimmer pot.
  • 12V Kit Specifications
    • Nominal Battery Voltage: 12V.
    • Solar Charging Current: 0 to 20 Amps continuous.
    • Recommended Battery Capacity: 0.5 to 400 Amp Hours.
    • Photovoltaic Panel Voltage Ratings: 12V Nominal (17-24V Open Circuit Voltage, 36-48 cell typical).
    • Absolute maximum PV input voltage (not sustained): 26VDC
    • Photovoltaic Panel Power Ratings: 1W to 240W (90ma - 20A Short Circuit Current).
    • Voltage Drop During Charging: 0.5V @ 10A, 1V @ 20A.
    • Float Voltage Adjustment Range: 13V-15V (range can be altered).
    • Float Voltage Variation during charging: +/- 0.03V
    • Equalize Mode Voltage Increase: 1.5 Volts.
    • Charge Controller Temperature Compensation: -7.5mV/Degree C.
    • Night Time Battery Current Drain: 0.8 - 1.8ma.
    • Fuse Type: 20 Amp ATO automotive fuse.
    • Board Dimensions: 3.5" wide by 3.0" deep by 0.95" tall.
    • Fits into a standard 4" X 4" electrical utility box, can be mounted on the cover plate.
    • Board Mounts: 3X 4-40 screws on 1/4" spacers.
    • Assembled Weight: approximately 60 grams (2oz).
  • 24V Kit Specification Differencess
    • Nominal Battery Voltage: 24V.
    • Solar Charging Current: 0 to 15 Amps continuous.
    • Recommended Battery Capacity: 0.5 to 300 Amp Hours.
    • Photovoltaic Panel Voltage Ratings: 24V Nominal (34-42V Open Circuit Voltage, 68-84 cell typical).
    • Absolute maximum PV input voltage (not sustained): 45VDC
    • Photovoltaic Panel Power Ratings: 2W to 360W (90mA - 15A Short Circuit Current).
    • Float Voltage Adjustment Range: 26V-30V (range can be altered).
    • Float Voltage Variation during charging: +/- 0.06V
    • Equalize Mode Voltage Increase: 3 Volts.
    • Charge Controller Temperature Compensation: -15mV/Degree C.
    • Fuse Type: 15 Amp ATO automotive fuse.

Theory

The circuit activation section uses op-amp IC4 wired as a comparator to switch power on for the rest of the SCC3. When the PV voltage is greater than the battery voltage, IC4 turns on and sends power to voltage regulator IC3. Diode D2 prevents damage to IC4 if the battery is connected with reverse polarity. IC3 produces a regulated 5 Volt power source. The 5V is used to power the SCC3 circuitry, it is also used as a reference for the battery float voltage comparator IC1a.
The float voltage comparator IC1a compares the battery voltage (divided by R1/VR1 and R3) to the 5V reference voltage (divided by R5 and R6). The comparison point is offset by the thermistor TM1 for temperature compensation. The comparison point is also modified by the Equalize switch, S1 and R2. The output of IC1a goes high (+5V) when the battery voltage is below the float voltage setting. The output goes low when the battery voltage is above the float voltage setting. This provides the charge/idle signal that controls the rest of the circuit.
The charge/idle signal is sent to IC2a and b, a pair of D-type flip-flops. The flip-flops are clocked by the IC1b phase-shift clock oscillator. The clocking causes the flip-flop outputs to produce a square wave charge/idle signal that is synchronized with the frequency of the clock oscillator. The two halves of IC2 operate in synchronization, IC2a is used to drive the PV current switching circuitry, IC2b is used to drive the charging state indicator LED either red (charging) or green (floating).
The clocked charge/idle signal switches bipolar transistor Q1 on and off. The Q1 signal is used to switch power MOSFET Q2, which switches the solar current on and off through the battery. The solar charging current flows through the heavy lines on the schematic. Diode D1 prevents the battery from discharging through the solar panel at night. Fuse F1 prevents excessive battery current from flowing in the event of a short circuit. Transzorb TZ1 absorbs transient voltage spikes that may be caused by lightning.

Use

Connect the solar panel to the SCC3 PV terminals, connect the battery to the SCC3 battery terminals.
Put the solar panel in the sun, the battery will charge up. In systems where the battery is frequently deep-discharged, the equalize switch should be occasionally turned on for a period of several hours to a full day. This increases the charge of the battery's weaker cells.
When the battery is low and the sun is shining, the LED will be red. As the battery reaches the float voltage, the LED will quickly alternate red/green. When the sun goes down, the LED will shut off.

SCC3 Circuit Extensions

Secondary Battery Charger

The above circuit may be used if you wish to charge a remote secondary battery. The #1156 lamp limits the secondary battery's charge current to a maximum of 2 amps, it also protects the remote wiring from high currents in the event of a short circuit. The wiring should be rated to handle more than 2 amps of current, #16 or #14 gauge wire is recommended. Other lamps may be used for setting different maximum charge current values. The Schottky diode prevents a load on the main battery from discharging the secondary battery. The diode has a .5V drop, so the secondary battery will always stay .5V below the main battery's maximum (float) voltage setting. A wet cell lead acid main battery and a gell cell secondary battery will work well in this configuration. Float voltages for gell cell batteries are lower than for wet cell batteries.

Dump Load Controller

A Dump Load Controller circuit can be used to feed excess solar power to an auxilliary load such as a heating resistor. The dump load circuit can be constructed from a second SCC3 kit using custom wired jumpers. The dump load circuit monitors the PV voltage. When the PV has charged the battery and the battery reaches the SCC3 float voltage setting, the SCC3 PV circuit opens up and the PV voltage rises. The dump load circuit detects this higher PV voltage and connects the dump load to the PV.
For 12V systems, the dump load circuit should be adjusted so that it activates at a PV voltage of around 15V. The dump load resistor should be connected across the terminals labeled "Dump" in the schematic. For the optimal dump load power transfer, the value of the dump load resistor should be chosen so that it pulls the PV voltage down to the PV panel's rated maximum power point during full sun conditions. The dump load resistor should have a power rating that is greater than the PV panel's maximum output wattage rating.
The dump load controller provides a low-quality power source. The power is only available when the main battery becomes fully charged and when it is available, it comes in pulses. Dump load power would be suitable for running a heating resistor or a catalytic electrolyzer for splitting water into hydrogen and oxygen.

 




19 comments:

ee said...

Great design, thanks

H Kassa
NCSU

ajay dixit said...

the processs is really very tough i always study about
solar charge controller
but always remain confused.

Anonymous said...

Well, please post the link to the original site, when its not ur design. At least, people who really worked on this need some appreciation.
Kumar-9739887744

Anonymous said...

frnd. . . Nice work, can u mail me detailed design? My mail id, monikaprakash146@gmail.com, plz plz

Anonymous said...

Sory, its monikaprakash143@gmail.com thanks

Anonymous said...

I asked her, as fashion to make men fall in love with you has been my internet quizzes.
It was the extended Memorial Day weekend.

Check out my weblog :: web hosting and design

Anonymous said...

I'm truly enjoying the design and layout of your website. It's
a very easy on the eyes which makes it

much more enjoyable for me to come here and visit more often.
Did you hire out a developer to create

your theme? Great work!

Look at my web-site :: barcelonaman

Anonymous said...

It is the best time to make a few plans for the long run

and it's time to be happy. I've learn this post and if I
may I desire to suggest you few attention-

grabbing issues or suggestions. Perhaps you could write next
articles

regarding this article. I want to read more

issues approximately it!

Feel free to surf to my homepage irc.helios-Matrix.net

Anonymous said...

Wow, awesome weblog structure! How

lengthy have you ever been blogging for? you made running a blog

look easy. The total glance of your website is magnificent, let alone the content material!


my web blog teaching in spain

Anonymous said...

I really appreciate this post. I’ve been looking everywhere
for this! Thank goodness I found it

on Bing. You have made my day! Thank you again

Here is my website http://intranet.escolaarrels.com

Anonymous said...

With everything that

seems to be building inside this specific subject

matter, a significant percentage of

viewpoints are generally

very exciting. Even so, I appologize, but I can not give credence to
your

whole suggestion, all be it exciting none the

less. It would seem to me that your remarks

are generally not completely validated and in

reality you are generally your self not wholly convinced of your assertion.
In any case I did appreciate reading it.

my homepage; Bandera Andalucia Jpg

Anonymous said...

Hi there! I'm at work browsing your blog from my new iphone

4! Just wanted to say I love reading through your blog and look forward to all your

posts! Carry on the superb work!

my homepage; www.diysolarheatingspain.com

Anonymous said...

I as well as my guys were found to be looking at the excellent thoughts on the website and then quickly developed an awful suspicion
I had not thanked you for them. My young boys

appeared to be absolutely very interested to read

them and already have seriously been using these things. Thanks for getting considerably thoughtful and for

considering such incredibly good subjects millions

of individuals are really desperate to understand about. Our own honest regret for

not expressing gratitude to you sooner.

My web page: Property Costa Blanca

Anonymous said...

Simply desire to say your article is as surprising.

The

clearness in your put up is simply nice and i could think you're a professional on this subject. Well with your permission

allow me to take hold of your RSS feed to stay updated

with drawing close post. Thank you one

million and please keep up the enjoyable work.

My website ... malaga spain weather trends

Anonymous said...

Hello! Do you know if they make any plugins to assist with

SEO? I'm trying to get my blog to rank for some targeted keywords but I'm not seeing very good

results. If you know of any please share. Thank you!


Here is my blog: visit the following page

Anonymous said...

Excellent web site. Lots of useful

information here. I am sending it to a few friends ans also sharing in delicious.

And obviously, thanks for your sweat!

Feel free to visit my page - diy solar

Anonymous said...

It's a pity you don't have a donate button! I'd definitely donate to

this outstanding blog! I guess for now i'll settle for

bookmarking and adding your RSS feed to my Google account.
I look forward to new updates and will share this website with my Facebook group.

Talk soon!

My blog post; jumbo jobs spain

Anonymous said...

Hi, Neat post. There's a problem with your website in internet explorer, would test

this… IE still is the market leader and a big portion of people will miss your magnificent writing because of this problem.

my blog post; suze orman buying real estate

Anonymous said...

In a online classes cheap consisting of 25 students or
50 students or 60 or even 35 students, it is hardly a statistic
worth shouting about. 31, 2013, in New Orleans, site of Sunday's Super Bowl. Always tipped for stardom contemporaries still think it will distract them and help them sleep are actually doing the exact opposite.

Take a look at my site :: Log-logs.Blogspot.com