Add a Solar Panel to Keep Your Backup Battery Topped Up

Just a few weeks in the past, I wrote about
building a simple, home backup power system for
charging telephones throughout prolonged electrical energy outages — like that which occurred throughout storm Sandy.

Add a Solar Panel to Keep Your Backup Battery Topped Up

Nonetheless, there’s a limitation to any battery system, and that’s that any battery energy
provide will ultimately grow to be depleted. I reckon to get a theoretical 13 days out of
mine. What occurs, in a catastrophic occasion, if grid energy is not restored on the finish of
13 days?

The reply is fairly easy. It is easy to harness the solar’s rays and hold the battery
topped up with an electricity-producing photovoltaic photo voltaic panel.

Here is how to go about it.

Step 1: Calculate Your Wants

Match the photo voltaic panel to the battery. Solar panel output is measured in watts. A rule of
thumb is to select a panel with roughly the identical variety of watts because the battery has amp

Return to the battery article for a refresher on amp hours in case you want it — however a 55-aH
battery just like the Optima we used can comfortably pair with a 55-watt, or barely greater
output panel.

A versatile laminate amorphous panel just like the one we’re utilizing right here pumps out 68-watts in full solar.

Step 2: Select Your Panel

Portability and value are the 2 main elements. All panels on the low
finish of wattage output, just like the one we’re working with, output at 12 Volts DC — accurately
matching the voltage of the battery.

Add a Solar Panel to Keep Your Backup Battery Topped Up

UniSolar Versatile Solar Panel

Versatile panels are nice for backup energy as a result of you possibly can fold them or roll them up
till you want them. They’re additionally tougher to break, in contrast to just like the permanent-install glass
sorts. The issue is that foldable panels are typically very costly.

I’ve sourced a low-cost rollup panel, manufactured by now-bankrupt Uni-Solar, that was
designed for sticking to metallic roofs.

I like to recommend it for this answer. The U.S.-based firm went bust partly as a results of
low-cost imports and slowing financial system — not as a result of the product was no good. Receive one
from SoldonSun (about US$189 on Amazon and eBay).

Tip: Two 30-foot runs of solar-specific extension cable are helpful if finances permits,
so you possibly can hold the battery within the protecting shade (about $44 at Amazon).

Step 3: Collect the Remainder of the Elements

Predominantly, you may want a cost controller.

Cost controllers cease the battery from changing into overcharged — and consequently
broken — by limiting the output of the panel. They’ll additionally carry out neat battery tips
like interrupting energy to the load within the occasion of low battery.

Add a Solar Panel to Keep Your Backup Battery Topped Up

Morningstar SunSaver Cost Controller

I am utilizing well-regarded Morningstar’s SunSaver 10 amp controller (about $48 on
Amazon by way of SoldonSun).

Tip: The cost controller ought to exceed the output of the panel by at the least 25 %.

A tough, ballpark calculation for the controller is to divide watts-by-voltage to get the amps
delivered by the panel. On this case, dividing 68 by 12 supplies 5.66 amps.

Examine along with your producer, although, as a result of photo voltaic panels will present greater than
12 volts below sure circumstances, thereby rising the amp load, leading to beefier
cost controller wants.

Different components you will have: 12-AWG automotive wire, referred to as “main wire”; a pair of
battery terminals — the marine type with wing nuts is finest for this job; yellow color-coded wiring spades; giant ring terminals and butt connectors; two pigtailed automotive-style fuse holders; two most 20-amp fuses; and related instruments like probe
voltmeter, wire stripper and crimper.

You may supply all of those supplies from automotive shops like Autozone and
electronics shops like

Step 4: Hook It All Up

There may be an order to all of this — fuses being final.

The Load

First, lower the alligator clamps off the tip of the cigarette lighter plug we used on the
battery mission and discard the clamps.

Then strip a quarter-inch from the ends of the retained wires and be a part of a fuse-holder
pigtail to the crimson, constructive lead with a butt connector. I get aesthetically fancy right here and
additionally heat-shrink the connection, however you do not have to.

Add one spade to the opposite finish of the constructive fuse-holder pigtail and one spade to the
finish of the black lead from the cigarette lighter.

Connect the black lead to the controller’s unfavourable screw labeled “Detrimental Load” or
related, and the crimson to the constructive screw labeled “Constructive Load.”

The cigarette lighter plug is now linked to the cost controller.

The Solar Panel

Cowl the panel with its delivery paper, or roll it on itself to keep away from arcing cables, after which
hook the photo voltaic panel to the “Solar” terminals on the cost controller.

Laborious-to-work-with solar-specific MC3 plugs are generally provided on this atmosphere.

Nonetheless, you possibly can simply snip the MC3 ends off solar-specific cables on the cost
controller finish, and crimp spades to make the connections if you would like. No fuse is required
right here.

Tip: Examine for polarity along with your multimeter probes and multimeter set to DC earlier than
connecting. Expose a little of the panel to generate some energy, and examine for a unfavourable
image within the multimeter show that signifies incorrect polarity. Right if mandatory.

The Battery

Comply with the wiring method directions within the earlier “Load” paragraph to make battery
connections for the controller terminals labeled “Battery.”

Add a pigtail fuse holder on the constructive wire inside 6 inches of the battery. Crimp ring
terminals after which join the black and crimson wires below the corresponding battery wing
nuts — constructive first after which unfavourable.

Step 5: Discover a Sunny Spot

Place the photo voltaic panel in a most solar location, avoiding shade. Place the battery and
cost controller subsequent to one another within the shade, observing any heat-reducing orientation
necessities from the cost controller’s instruction guide. I’ve mounted mine
vertically on the aspect of a battery field.

Then insert the fuses, inserting load circuit fuse first, then battery circuit. Observe the power-up
mild sequence from the cost controller’s guide.

Plug your telephone charger into the cigarette lighter socket together with telephone, and watch the
telephone’s charging-in-progress indicator — eternally.

Tip: Amorphous panels just like the one talked about will work in shade — it will simply take
longer to cost the battery.

Need to Ask a Tech Query?

Is there a piece of tech you want to understand how to function correctly? Is there a gadget that is acquired you confounded? Please
send your tech questions to me, and I am going to strive to reply as many as attainable on this column.

And use the Talkback function under to add your feedback!
Add a Solar Panel to Keep Your Backup Battery Topped Up

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