Monday, September 7, 2015

AA NiMH Ambient Solar Indoor Charger and Night Light

Indoor Ambient Solar AA NiMH Charger & Night Light

I had previously worked on an indoor (ambient light) solar charger for 4 AA NiMH batteries, but finally have something that works fairly well for me. Turns out I have borrowed circuits from at least three other designs, and modified them. The goal was to work for four AA 1.2 volt NiMH 2500 mah batteries indoors under ambient light. After getting it working, I thought it would be good for a long lasting night light when I do not need to charge batteries.

I have seen other circuits for two or three AA batteries, but could not find anything that would charge four in parallel.I wanted to charge in parallel so that the charging would be done evenly, without the need to create a separate battery monitoring circuit.

The circuit also works in direct sunlight, but be warned, the batteries can get warm under direct sunlight. It works well if set near a window that gets at least a couple of hours of sun.
Let me see, credits should go to author P. Marian at (for his 3V boost converter), mrpiiggs and Dick Cappels at (for his 1.5 volt Solar Garden Light), and to Afrotechmods video on YouTube (for his Reverse Polarity circuits).

I plan to add a 1.2V AA low voltage indicator, but have not yet decided which circuit will be appropriate for this design.
  Main driver circuit for regulated output voltage:

AA NiMH Ambient Light Solar Charger Circuit #1 - The Krell Lab

Modifications included the addition of 547 transistors in an effort to increase the amps, the use of a toroid, and the use of a slightly larger (6V) solar panel.

  The main AA 1.2 volt indoor night light circuit:

AA NiMH Ambient Light Solar Indoor Night Light Circuit #2 - The Krell Lab
The above circuit connects to the charged AA battery bank. Alternatively, it can run from a 1.2 volt AA NiMH battery. I modified this one by using a toroid, using NiMH batteries (in parallel), the addition of a Light Detecting Resistor (LDR), and the use of a capacitor.

For a breadboard view, the overall circuit looks like this:

AA NiMH Ambient Solar Indoor Charger Night Light - The Krell Lab

That's a view from the kitchen table during daylight hours, the window is about 8 feet away. The white Tenergy batteries on the left were used to power the voltage meter only. The charged AA NiMH batteries are near the upper right hand corner.

The volatge regulation circuit is on the bottom left, the night light is on the right, and the polarity check circuit is on the upper left. The batteries are charged in parallel on the upper right.

The above voltage regulation circuit looks like this on the breadboard:
AA NiMH Ambient Light Solar Charge Regulation Circuit - The Krell Lab


The polarity check part of the circuit is below:

AA NiMH Reverse Polarity check circuit, the batteries are in parallel - The Krell Lab

And a view of the batteries in parallel, being charged from the reverse polarity check circuit:

AA NiMH battery bank of four, the batteries are charged in parallel - The Krell Lab

These are 2500 mah NiMH batteries.

This would be a view of the Night Light on a breadboard:

1.2 volt AA NiMH Night Light on a Breadboard - The Krell Lab

The circuit is able to run an 'Ultra Bright' or 'Super Bright' 10mm LED.
 Warning - Do not look directly into an 'Ultra Bright' LED.

And this would be the same night light on a perferated board:

1.2 volt AA NiMH Night Light on a PerfBoard - The Krell Lab
 This version on the perf board has a toroid wound differently, but it still works. I just happened to have this toroid on hand and haven't taken the time to wind another yet.
In this picture, I have the windings backwards, as L1 should have the more windings. Just goes to show that it still works when the windings are backwards. However, the LED is not nearly as bright, so if you are not getting a bright light, then check the windings.

I have not tried the ferrite core, as I have no ferrite cores available.

So, there you go. If you want to charge 4 AA NiMH batteries indoors, or just run an indoor night light from rechargeable batteries (or do both), then this should work for you. 

The main problem is I see is regulating the amperage, as in using direct sunlight vs. ambient light. Which is to say, without appropriate amperage, the batteries will not last long under a normal load. So, what is needed next is to test for longevity. I am thinking I may test the number of coil windings and type of coil used (Joule Thief vs. Inductor) for the voltage regulation part of the system. Or, otherwise find a way to increase the current when not in direct sunlight, and keep the default current under direct sunlight.

Update 09/16/2015:

 Using one 6 volt, 1 watt panel, it does not charge properly, and does lose charge over time.
My current thinking is that the main problem is the lack of sustained current (on the order of 250 ma).

Some of the less common parts:

 Warning - Do not look directly into an 'Ultra Bright' LED.

YouTube Video:

                      AA NiMH Ambient Indoor Solar Battery Charger and Night Light

Friday, July 3, 2015

Portable Solar Generator In A Battery Box

Portable Solar Generator In A Battery Box

Nothing makes it more clear that you need an off the grid type of system than when a hurricane hits and knocks your electricity out for a week. Even up here in Ohio, hurricane Ike hit us with winds that left us without power. But, I have also lived in Michigan, where we lost power more often than we lose it here in Ohio. And a portable system lets you use that power in other situations, such as camping or boating. More than that though, it's just fun to generate your own free electricity without feeling dependent upon your local power company.

I have read a number of newspaper stories about seniors who have died in extreme heat or extreme cold, so living without power even for a short time can be life threatening for some.

This post is intended to help you build your own portable solar generator. For this prototype, a battery box was used.

Meter Layout

Portable Solar Generator In A Battery Box - Meter Layout - The Krell Lab

Wiring Schematic

A general schematic of the wiring:

Portable Solar Generator In A Battery Box - Wiring Schematic - The Krell Lab


  Portable Solar Generator In A Battery Box Part 1    - The Layout
 Portable Solar Generator In A Battery Box Part 2  - Getting beyond the layout:
 Portable Solar Generator in a Battery Box Part 3 - Wiring the layout:

 Portable Solar Generator in a Battery Box Part 4 - Meters & Switches

 Portable Solar Generator in a Battery Box Part 5 - Final Layout & Solar Tracker

 Portable Solar Generator in a Battery Box Part 6 - The Solar Tracker Problem & Trouble-Shooting It
 Portable Solar Generator in a Battery Box Part 7 - Solar Tracking Problem Resolved
Wagan Wattage Guide

 Wagan includes this handy wattage guide with the 400 watt pure sine wave inverter:

Wagan Wattage Guide

Parts List

  I was able to get the box on sale for $9.00, so shop around.

  Wagan EL2601 Elite 400W Pro Pure Sine Wave.................$199.95
 I was able to get the inverter on sale for $119, so it may help to shop around.


 This controller would be for my sealed lead acid batteries. You can get one cheaper without the display.


   PowerStream HR22-12 ...........................................................$ 67.10

   However, a LiPO4 batteries twice as powerful could be used in this space.
   If you use a lithium battery, be sure to also use a lithium controller.
   Also, be careful to insulate the battery from the heat of inverter.

   I have used the Lithium Battery and Lithium Charge Controller in my portable solar generator in a File Folder box.

Blue Sea Systems Dual USB Charger Socket ...........................$ 25.98

  I was able to get this USB socket on sale for $ 16.77

Cigarette lighter fuse/circuit breaker.............................................. $  4.87

Waterproof LED Rocker Toggle Switch SPST Marine .......... $9.99 + $4.49 shipping

Battery Cut-off Switch ....................................................................$ 20.00

   I was able to get the cut-off switch on sale for $8.00

 Lighted power switch Cherry SWITCH ROCKER SPST 20A 125V ..............$1.30

 35 Amp Circuit Breaker Digi-Key Part NumberPB1049-ND ..........................$4.55

 Circuit Breaker 15 Amp 1/4" Terminals .........................................................$4.89
 Circuit Breaker Switch 20A 125VAC 50VDC .................................................$3.54


Wednesday, June 3, 2015

Portable Solar Tracking Mount

Portable Solar Tracking Mount

Folks have been building portable solar power generators for emergencies, camping trips, and boating. I have always noticed that most just find a place in the sun, and set the unit there. Few, if any had any solar tracking mount for their unit.

I bought a portable solar power generator unit, and got tired of positioning the portable solar panel, so I wanted to build a portable solar tracking mount for it. I also wanted to build a better unit on my own, or maybe two. We had a power outage for a week a couple of years back, and were without power for a week. I think it was hurricane Ike, winds hitting us way up here in Ohio.

I wanted a sturdy mount that would not fall over easily in the wind. On this day, it was windy, but nothing very fierce. It was also partly cloudy, and when the clouds cover the sun, the tracker circuit will wait for about 10 seconds for the clouds to pass, then if the clouds remain, it will search for the brightest spot in the sky. Therefore, there are a couple of times in the video where the mount appears to move back and forth briefly.


The tracking unit can be programmed to reset at night, but I do not plan to leave it out at night, so I have not set that.

Here, I am testing with 10 AA batteries (12 volts) just to look for problems. After I am happy with it, it will simply plug it into my portable solar generator.
I hope to do a video later showing "How To' build it.
Here, the mount is single axis, but I am thinking it could become a dual axis by replacing the vertical support with a very small actuator (or just strap another servo to the vertical axis). Not to forget, the tracking circuit requires a limit switch if you use an actuator.

General Design



Portable Solar Panel Mount motor side view - Krell Lab

Portable Solar Panel Mount back view - Krell Lab

Portable Solar Panel Mount base side view - Krell Lab

 Time Lapse Video

See also the story at the ServoCity blog:

   Building a Portable Solar Tracking Mount

Some of the parts used for the mount:

Adjustable Speaker Stand 80lb Capacity    $ 27.59

1 3/8'' Speaker Pole Mount Adapter         $1.89

What I like about the stand is that it should hold up to winds, and it telescopes to 7 feet.
In the winter, the area within the time lapse video is in a shaded area, and raising the mount to 7 feet will enable it to capture the sun during the winter months. It will support up to 80 pounds, is lightweight (7 pounds), and can be carried with or without the carrying case.

Solar Panel

RENOGY® 30 Watt 30w Monocrystalline Photovoltaic PV Solar Panel UL Listed Module 12v     $64.99
13.5x23.8x1 inches - mine is larger...464mm (18.27") x 556mm (21.9") x 35mm (1.38"), It puts out 1.8 amps

Currently unavailable.
I don't know when or if this item will be back in stock.
Tracking circuit


SBE Solar Tech 12V Digital Solar Tracker Control Board MK3.1  ......$39.00 + $4.62 shipping by SBESolarTech

SBE Solar Tech Sun Tracker Weather Enclosure  ......................$14.99 + $4.62 shipping
by SBESolarTech

 If you use a larger panel, or different servo, you may need to add the tracker relay circuit:

Support Beams (that attaches to panel):

Menard's or Ace Hardware

Plated Slotted Steel Angle 14 Guage 1-1/2" x 2 foot  $ 5.79 each
Motor, base, & rotating mechanism

(8871T31) 1/4 inch Bore Clamping Motor Mount             $ 1.99
(638154) 2 RPM Gear Motor (RZ12-1500-2RPM)               $24.99
       * Weight: 0.27 lbs. each
(9753K65) Gearmotor End Cap                              $ 0.89
(9753K66) Precision Gearmotor End Cap                    $ 0.99
(615206) 80T, 32P, 1/2 inch Bore Aluminum Gear           $12.99
(615270) 32 Tooth, 32 Pitch, 6mm Bore Pinion Gear        $12.99
(585438) Round Base A                                    $ 6.99
(585440) 1.50 inch Aluminum Channel                      $ 2.99
(635256) 6 inch length x 1/2 inch dia. Aluminum Tubing   $ 2.69
(633110) 1/2 inch Shafting & Tubing Spacers (12 pk)      $ 1.69

Plus miscellaneous parts: beams, screws, washers, nuts, etc.
I will try to get the "How To" build it video out later with instructions

Thursday, May 28, 2015

How To Build an MPPT Solar Charge Controller with Arduino

How To Build an MPPT Solar Charge Controller with Arduino

Julian Ilett has a series of 20 YouTube videos that show you how he built an MPPT solar charge controller with Arduino. Maximum Power Point Tracking (MPPT) is electronic tracking that enables the charge controller to compare the output of the panels to the battery voltage. It then figures out what is the best power that the panel can put out to charge the battery.

What that usually means that it tries to increase the charge on cloudy days (or in the mornings if your panel is not pointed to the sun) so that you can get the most from your panels.


Arduino MPPT Solar Charge Controller by Julian Ilett

 What is nice about this one is that he walks you through "How To" build the graphic display.

MPPT Solar Charger Graphic Display by Julian Ilett

There are 20 videos in Julian's video series, and they start here:


MPPT Solar Charge Controller #1 - Introduction and Voltage Measurement

At video #14, he changes the name of the series:

Arduino MPPT Solar Charge Controller #14 - Stable Current Measurements

 And, if you would like to see where he ended with the videos on this topic, here is #20:

Arduino MPPT Solar Charge Controller #20 - Inductor Discontinuous Mode

California Nonprofit Offers Free Solar Panels to Its Poorest

California Nonprofit Offers Free Solar Panels to Its Poorest

Photo: Michael Macor, The Chronicle via SFGate Magazine

A new California program by the Oakland nonprofit Grid Alternatives will install home solar arrays in disadvantaged neighborhoods and aims to make solar power available to lower-income families — using money from the state’s fight against global warming. 

Full story by David R. Baker at SFGate Magazine:

Wind Turbines With No Blades

Wind Turbines With No Blades

A prototype of the Vortex Bladeless wind turbine from Wired Magazine 

"A Spanish company called Vortex Bladeless is proposing a radical new way to generate wind energy that will once again upend what you see outside your car window."

If you happen to see one of these, and are wondering what the heck it is....

Full story at:

How To Build a Solar Cabin For Under $2000

How To Build a Solar Cabin For Under $2000

Nice video by Lamar Alexander, includes links to plans.

It is a 14' x 14' cabin with loft, providing about 400 square feet.
Power system is 580 watts Solar electric and 400 Watts wind power which powers a 12 volt fridge, lights, water pump, TV's, laptop and many gadgets. 
Heat source can be propane or wood stove. 
Toilet is solar assisted composting.

Wednesday, May 13, 2015

How to Build the SolN1 Portable Solar Generator for Safety

How to Build the SolN1 Portable Solar Generator for Safety

LaserSaber came up with the idea of a light-weight mobile solar power generator with his video on YouTube.

However, the original SolN1 is missing the controller, and that controller should be compatible with LiFePO4 batteries...

Also, if you use the flat LiFePO4 batteries, you really need a Protection Circuit Module (PCM) for charging the four (flat) LiFePO4 batteries.

Here's a video from John Strabismus where he has the LiFePO4 controller and PCM:

The charge controller is needed so that you do not overcharge the battery. If you overcharge the battery, the LiFePO4 batteries tend to swell up, and can emit some dangerous fumes. In the worst case, they can even catch fire.
The battery management system is required because combining batteries for total power can cause a discharge at different rates per battery. This can cause problems when charging, leaving some of the battery pack undercharged, and others overcharged.

Regarding sizing of the PCM module, John Strabismus says:

"The main thing to keep in mind with your PCM choice is the size of the inverter you will be running. LaserSaber chose a 150w inverter, fully loaded it will pull close to 15amps continuous and surge a bit higher, that's why the surge rating on the PCM is higher than needed, as the inverter starts up with load it will pull more amps briefly then settle to its load draw, so the 16amp PCM matches the 150watt inverter, if you go higher like a 200 watt inverter you will be over the 16amps draw fully loaded and this will more than likely cause the PCM to shut down the load , so using a 20amp PCM for a 200watt inverter will match the components better."

So, you should remember that the PCM chosen should be based upon the power of the inverter.

You can find the PCM circuit boards on

  - PCM for a 150 Watt inverter:
Protection Circuit Module (PCM) for 4 cells (12.8V) LiFePO4 Battery Pack at 16A limited  
Part Number: PCM-LFP12.8V16A

PCM for a 200 Watt inverter:
Protection Circuit Module (PCM) for 4 cells (12.8V) LiFePO4 Battery Pack at 20A limited
Part Number: PCB-LFP12V25A


Part Number: PCB-LFP12.8V20A


The "Flat" type of LiFePO4 batteries can be found on AliExpress:

3.2V 20Ah A123 LiFePO4 Prismatic APP72161227 PHEV/EV/E-REV Rechargeable Battery      $33.88 each x 4

3.2V 5C   20Ah
Nominal Voltage:    1.2V
Nominal Capacity:    20Ah
Size:    7x166x227mm       (.276" x 6.54" x 8.94")
Package Size:    10cm x 10cm x 5cm (3.94in x 3.94in x 1.97in)
Cell Weight:    About 496 g   (1.09 pounds ea.)
Cell Capacity (minimum, Ah):    19.6A
Charge voltage:    3.75V
Power:    Over 2,400 W/kg and 4,500 W/L
Continuous discharge rate:    5C 100A
Peak discharge rate:    20C 400A (10 seconds) 

The original SolN1 videos:

 DIY Build Session SOLN1 Portable Solar Power:

 SOLN1 - Amazing all in one free energy portable solar unit:

DIY Build Session SOLN1 Portable Solar Power

SOLN1 - Amazing all in one free energy portable solar unit.

Real Time SOLN1 Making-of + Other Updates

SOLN1 Version 3 - Solar made easy!

SOLN1 Update - Testing the Mini Boostpack

Battery Free Solar! Real Time Solar - Nano BoostPack + SOLN1

SOLN1 25 Kit Build Video - 20Ah Version