# PV (solar panel) and charge controller with battery

Depending on where you are you might want electricity.

Solar power is a convenient, low maintenance way to get electricity if you have sunlight.

For this example I will consider a 80W 12 V solar panel and a charge controller capable of 6A at 12 Volts.

The panel

80 W  (maximum power)

12V

P = VxI

P/V =I

80/12 = I

6.66 A =I (maximum current)

The charge controller

12V

6A

P= VxI

P = 12 x 6

P =  72W

Close enough to matched, remember the panel lists it maximum power not typical power rating.

A charge controller is a fancy battery charger which can put unused solar power into stored energy into a battery.

Usually there is a load circuit for things you want to run directly off the solar panel and a battery charging circuit. For this example there is a maximum load of 72 watts from the controller load wires.

For a larger load than the controller allows disconnect the battery from the charge controller and use the charged battery.

There is often a wet type battery for flooded lead acid cells check you documentation as to whether it is connected to the positive(+) or negative (-) terminal of the flooded battery.

A typical arrangement:

PV charge controller and battery wiring diagram.

For 12 Volt setups the car cigarette plug and socket system of connectors is a good idea, simple and common. There is also a wide variety of electrical items made especially for this connector format.

The connectors on solar panels are waterproof, the connections on the charge controller are not, make sure they are waterproofed or kept away from water.

# Repair: Examples – Small solar battery block in rain water

I have a bed side lamp I got from IKEA years ago, it’s solar powered with a removable block of batteries. So I did something dumb and inadvertently left the block out in the rain. Thinking the unit was well sealed as I retrieved it it made a sloshing sound, obviously not that well sealed. The 2 slots for the power output of the battery were it’s Achilles heel, and let the water straight in. As I unscrewed the block, water dribbled out of the screw hole, this repair/salvage job started looking dicey. The real risk was if there were complex charging circuits in the block. I finally opened it after almost losing 2 of the 4 screws bouncing on my wood floor.

Solar battery block with 3 x AA (1200mAh?)

After about 5 minutes of using a hair dryer to dry the water away, I discovered there was apparently only a fuse as the sole electronic component. Fuses do tend to survive water quite well.

Quite a relief really. Other things I found out were there were only 3 AA cells (I had guessed 4) and they were stamped with  1200A, I speculate that means 1200mAh, low on the capacity spectrum of rechargeable batteries.

The things you learn once you have the audacity to pop open the case.

Amazingly enough, once dry the unit worked.

Solar lamp in working order

Got to get information.

Access to information is very important and radio, while an old technology now, is likely to be one of the best sources of information during a crisis. AM radio is a particularly good source because of its range and likelihood of operation.

DEGEN DE13 Solar / windup/ 5V DC powered. Radio AM FM SW, LED flash light, red flashing LED, USB power output, and alarm.

This is a really great radio, packed with features.

A radio? You may think that because your mobile phone has a radio you’ve got it covered. Well partially. Mobile phones generally only receive FM radio and usually only with headphones attached as they double as the antenna.

FM is a relatively short range radio signal so if you are far from a transmitter you wont hear anything.

AM radio stations use large amounts of power and have large capacitors in order to operate, so that when the power goes off to radio stations FM stations only have generator reserves. AM stations will have a few days of electric reserves in their capacitors on top of generator reserves, so an AM receiver will be more likely to give you information and for longer. AM stations also have much longer range in reception as well.

Shortwave SW radio has enormous range, you’ll realize this when you start hearing languages other than English on them. Shortwave radio receivers are somewhat uncommon these day also.

Powering it.

Solar: A nice little polycrystalline panel.

Wind up: 60 turns of the handle for 1 hour of radio.

AAA cells: 3 AAA cells are an option.

micro USB port: the 5 pin connector, connect to a computer or other 5V DC source.

Lithium battery: Just like what is in cordless phones.

Features:

3 LED light, a pretty good light for shorter range illumination.

Red flashing LED, this is meant to be for reading maps at night, the red doesn’t affect you night vision too much.

Siren: I’m not sure how this is useful but its there.

USB output: I think this runs from the wind up only,  and has output limited to low current for charging older mobile phones or small electronic devices, but better than nothing (though the manual doesn’t specify).

Down sides.

Not waterproof, this can be mitigated buy using a small water proof container or bag.

Not dust proof, if your operating environment is very dusty of silty you could have trouble.

Antenna clasp is a bit fragile, fortunately this is not a critical component.

Battery case cover for the 3xAAA compartment seems a little flimsy.

No clock, one of the few products where the addition of a clock might have made sense, radio shows are scheduled to start at certain times, thought announcers do tend to quote the time often enough.

The instruction manual that comes with this device is pretty vaguely written, a bad translation from Chinese, it’s almost a throw away manual.

There is not form of charge indicator, just  charging LED (green) and a discharging LED (red).

Short wave radio stations sometimes talk about transmitting on X meters rather than a frequency.

This length distance they are talking about is the wave length of the radio wave, wavelength is usually given the Greek letter λ

c is the speed of light in a vacuum 299 792 458 m / s , you’ll notice this number is close to 300,000,000,  300 million or 3 x 10 ^8.

Frequency: f , measured in Hz (Hertz).

For example if someone was transmitting on 19 meters:

c  = λ  *  f

f =  c / λ

f = 300,000,000/19

f = 1,000,000   *  300/19

f = 1,000,000   *   15.79 Hz

f   = 15.79 MHz  (or 15,790 kHz )

This radio can detect that short wave frequency and those between 5.8 MHz and 18.2 MHz (51 to 16.5 meters in wavelength).

It should be noted that some SW bands are not in the frequency region where they should be due to some historical conventions.

You should create a series of notebook entries listing for each location you plan to be in which frequencies are operational and what type of information is given.

ie

location 1

AM  frequency  information types

station 1             music and hourly news

station 2             news and weather (mostly prerecorded)

FM  frequency  information types

station 3        music  (infrequent news)

SW frequency  information types

station 4        Chinese language (shipping?)

A great deal of information can be inferred from which stations are still broadcasting also with what information they are giving.

This handy radio comes in several colors; dark green(pictured), lime green fluoro, and white, though I’m sure almost any color is possible

Can be bought from many internet sellers for about \$30.