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So my father get's me odd Christmas presents. I guess because I have everything I need already.

Last Christmas he got me this 7 watt solar cell from Northern Tools. At first I wasn't sure what to do with it. Then when the battery went dead on one of my riding mowers and wouldn't hold a charge afterwards from sitting over the winter, I came up with this idea.

I decided to mount it up against the window and use it as a trickle charger. I also decided to plumb in some lights in case I need to look for something at night which are powered off my lawnmower's batteries.

All of which is wired in parallel. The solar cell recharges the batteries, the lights also serve as junction blocks. No switches are involved (bulbs are screwed in to turn on).

Parts needed:

1) Dash mounted cigarette lighter (if you don't smoke, then a power point will work)

2) Female power point plug

3) wire (preferably 14 AWG)

4) Bulb sockets (these are intended for 110V AC but will work on 12V DC)

5) 50 watt DC light bulb (autoparts store)

6) Solar cell

7) Lag bolts

8) Multimeter, wire strippers, ring connectors, etc.

10) Whatever else you prefer to hang your solar cell from the window, wood screws.

Step 1: The Solar Cell

This one is rated at 7 watts. On a sunny day it will provide almost 16 volts depending upon which way the sun is shining. Luckily the window is facing the north so it get's sunlight most of the day.

I did not use the mounting kit that came with it. I used some shorter bolts and simply hung it up against the window using a piece of wire.

I ran two lag bolts into the wall. Then the clamps just attach to the bolts. Underneath the bolts are two ring connectors with the wires attached to them.

Step 2: The Lights

These are just standard 110V AC sockets used for a standard light bulb. The light bulbs are 12V 50 watts and are used for drop lights, RVs and campers. They also serve as junction blocks because I have two mowers. Because everything is wired in parallel, the lights do not have to be on the complete the circuit. To turn the light on, I just screw the bulb in.

Step 3:

The lawnmower:

Usually there is a cutout or plastic plug already on your lawnmower. So I just used a step down drill bit to enlarge the hole.

Now find a wire that is hot at all times (like from the starter solenoid), connect it to the center pin on the cigarrette lighter or + wire on the power point adapter. Then ground the other wire anywhere to the chassis.

Wiring it up:

The key thing to remember is to keep the polarites the same on everything! All positives connect to positives and all negatives connect to negatives! The solar cell feeds the batteries and the batteries feed the light bulbs. Also the batteries are now connected together so power could move from a stronger battery to a weaker battery.

Although I used scrap wire (some speaker wire) I had laying around and an ohmsmeter to check my polarites, it's best if you use red and black wire.

The screws on the sockets are plated gold and silver. The polarity of the bulbs do not care so it doesn't matter which wire goes to which screw as long as it's consistant. One thing I use to remind me when doing AC work is "Black Gold" or black wire goes to the gold post. So you could connect the black wire to the gold screw and the red wire to the silver screw.

Once again check your polarities at the power point and the plug in before connecting the wires together. The ones I used have red LEDs. As you know LEDs do care about polarities and won't work otherwise.

If you don't want to goto the hassle of mounting power points on your lawnmower, you could just use some clamps and connect them directly to the battery.

I have not done a long term test on this system. I'll know come spring if this solar cell did it's job over the winter.

<p>UPDATE:</p><p>So the other day I opened up my yard barn and to my disgust, my mower would not start after sitting for about a month. I checked the voltage and it was around 9 volts. </p><p>What prompted me to build this setup in the first place was the three year old battery on one of my mowers (all of a sudden) wouldn't hold a charge for more than a week during the middle of mowing season after going dead over the winter. </p><p>Knowing how expensive (and cheaply built) batteries are these days, I decided to just jump start it with a battery charger until next spring. Then when that method no longer worked, I started swapping batteries from one mower to the other one. </p><p>The only thing I can think of is three years is about the life of a lawn battery these days. </p><p>I remember the days (90s) when you could buy a cheap car battery for $30 and it lasted 5 years. Now a $110 battery comes with a 2 year warranty. Lead coated plastic plates that flake off I suspect. </p><p>My powerpoints have LEDs built into them. The solar cell provides enough power to light them but I wonder if they are discharging the battery? Now that we have less sunlight and less sunny days this time of year?</p><p>I sort of doubt it since these LEDs probably pull less than 1 amp. Less than what the memory on a car stereo would pull.</p><p>Any ideas?</p>

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Bio: I work as a chemical operator. In my off time I enjoy spending time with my family and working on my "old" Fiats and my ... More »
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