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Old 01-15-2012, 03:16 PM   #1
Paper OP
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Solar Charging (battery top up)

I have a 12v solar charger that's sold by Harbor Freight. It's designed to plug into a cigarette lighter and sit on the dash of your car to keep the battery charged.. It throws out 1.5 amps, so it operates like a trickle charger..

All of my bikes have Powerlet outlets, so I've added a bunch of wire to the solar charger, eliminated the cigarette plug and installed a male Powerlet..

This way I can keep my bike batteries topped up without running a 120v charger..

Here's my question.. Will this drain my battery when it's dark out? I know it's charging during daylight, but is there anything that would drain the battery when there's no light..

Here's the unit.. http://www.harborfreight.com/15-watt...r-header-44768 I've mounted it on my south facing garage wall and ran the wires inside..
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Old 01-15-2012, 03:29 PM   #2
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Without some kind of charge controller between them (something with a diode that keeps current flowing in only one direction), I think it might.
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Old 01-15-2012, 03:36 PM   #3
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That's what I was thinking, too.. I've seen chargers like this, that come with a controller, and I figured that might be the case.. Mostly I was guessing the controler was to keep from over charging.

Not a big deal.. I can unplug the cord at the the plug just 1' from the panel and plug it back in when I head to work in the morning.. I was hoping to leave it plugged in and just swap it between bikes every other day or so..

Just keeping them charged during the winter when not being used.
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Old 01-15-2012, 03:52 PM   #4
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it helps to read the directions.....
Quote:
Note: You may leave the unit plugged in overnight and it will not drain your battery.
http://manuals.harborfreight.com/man...4999/44768.pdf

....and here's another handy tip.

Quote:
Outdoor Mounting 1. Although the Solar Panel (#2) and Frame (#1) are weather resistant, you should apply a bead of clear silicone sealant along the glass edges and the PVC Frame.
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Old 01-15-2012, 03:55 PM   #5
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Just about every (even cheap) solar panels have a diode in line to stop reverse current.

Worry more about the very small amount of energy any small panel will provide and do not worry about the solar panel sucking up current from your battery.
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Old 01-15-2012, 03:58 PM   #6
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Quote:
Originally Posted by bomber1965 View Post
it helps to read the directions.....


http://manuals.harborfreight.com/man...4999/44768.pdf


It also helps to read the original post..

Quote:
so I've added a bunch of wire to the solar charger, eliminated the cigarette plug and installed a male Powerlet..
The cigarette plug is where I'm guessing the controller is.. I've had this thing laying around for 2 years and the manual's been thrown away long before I thought about using it in this manner..
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Old 01-15-2012, 04:01 PM   #7
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Quote:
Originally Posted by EZman671 View Post
Just about every (even cheap) solar panels have a diode in line to stop reverse current.

Worry more about the very small amount of energy any small panel will provide and do not worry about the solar panel sucking up current from your battery.
Yes, but that diode may very wll have been in the cigarette plug, which has been removed to install the male powerlette plug..

The small panel is providing the same as the Schumacher 1.5 amp trickle charger that I was going to use..
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Old 01-17-2012, 08:35 PM   #8
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The solar panel you linked to is 1.5 watt not 1.5 amps. Using Ohms Law, that works out to .125 amps at 12 volts. It might be enough to keep the battery charged if left connected full time.
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Old 01-17-2012, 10:21 PM   #9
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What would you want to do with a "big" 1.5w (yep, watts, not amps) worth of "power"?
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Old 01-17-2012, 10:32 PM   #10
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those little solar panels aren't worth their weight, 1.5 Watt Maximum Peak power, means you might see .125 amp for two hours a day around high noon, if the panel happens to be in the right place to catch maximum sunlight
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Old 01-17-2012, 10:34 PM   #11
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To see if it's going to discharge your battery, hook an ammeter in series between the panel and battery. Expose the panel to light, you should see current flowing in one direction (positive or negative, depending on how everything's hooked up). Cover the panel up, you should see no current flowing. If you see current flowing in the opposite direction, then you know the battery is draining through the panel.

Just make sure you don't connect it across the battery or you'll wreck a fuse in your meter (if you're lucky), the meter (if you're not lucky), or blow something up/start a fire (if you're really not lucky).
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Old 01-19-2012, 08:03 AM   #12
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Quote:
Originally Posted by Paper View Post
I have a 12v solar charger that's sold by Harbor Freight. It's designed to plug into a cigarette lighter and sit on the dash of your car to keep the battery charged.. It throws out 1.5 amps, so it operates like a trickle charger..

All of my bikes have Powerlet outlets, so I've added a bunch of wire to the solar charger, eliminated the cigarette plug and installed a male Powerlet..

This way I can keep my bike batteries topped up without running a 120v charger..

Here's my question.. Will this drain my battery when it's dark out? I know it's charging during daylight, but is there anything that would drain the battery when there's no light..

Here's the unit.. http://www.harborfreight.com/15-watt...r-header-44768 I've mounted it on my south facing garage wall and ran the wires inside..
There are several different potential issues here that people seem to be confusing with each other.

  • A solar panel will need a diode in series to prevent the battery discharging back through it. Almost all larger solar panels have this included in the terminal block for you. This panel evidently has some circuitry in the cigarette plug, so doubtless the diode is in there.
  • A solar panel without a voltage regulator can reach an open circuit (no current) voltage high enough to damage your battery. The battery basically keeps charging until the voltage reaches the open circuit voltage. The open circuit voltage of this panel is 22.5V. However, generally speaking, where the output of the panel is very small relative to the battery size, the battery will not be overcharged.
  • Which brings us to the real problem here. This is a 1.5 Watt panel, which has a closed circuit current of 120mA. Your bike probably has a battery somewhere between about 5 and 20 AmpHours, depending how big they are. 120mA for a couple of hours a day won't really make much impression on a 20AH battery.

What is making your batteries go flat? Do you have some parasitic load which is on all the time, like the clock or remote central locking in a car?

I knew a doctor in a rural area who had an electric start generator with a 15 AH starting battery identical to my BMW R65 battery, a remote control receiver that consumed about 50mA, and a 120mA (in bright sunshine) solar panel to keep it charged. She couldn't seem to grasp that 50mA for 24hours a day (=1200mAH) was way more than the panel was putting back in. Quite simply the load would flatten the battery in about 10 to 15 days even in good weather.

But then she couldn't grasp that a mains battery charger would keep her battery fully charged just fine so that she could start the gen when the power went off. She seemed to think the charger needed to work with no mains power or that the battery would suddenly go flat when the power went off. And yes, the generator also charged its own battery when running, but not very fast.

She was a bit odd.
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Old 01-19-2012, 10:09 AM   #13
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Hey Paper, this is Alejo.

I REALLY want to rig up a simple electric bicycle and use solar power to charge the battery, so I am here to follow your project.
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Old 01-19-2012, 03:13 PM   #14
Paper OP
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Quote:
Originally Posted by PolloAsesino View Post
Hey Paper, this is Alejo.

I REALLY want to rig up a simple electric bicycle and use solar power to charge the battery, so I am here to follow your project.
Well, as pointed out earlier, I made a mistake of the 1.5w, not amp. All I'm after is to keep batteries charged during the winter while the bikes are in storage (my garage) and to keep the batteries topped up without the need for removal from the bikes.

My bikes (three BMW's and a KLR) all have Powerlet outlets, so I should be able to just plug and forget..

What brought this all on was I was going to just use a 1.5A trickle charger.. While looking at trickle chargers, there were full blown solar chargers in the same area.. I thought they were amps, but they are 1.5, 5, and 19 watt chargers with controllers.. Since I had this Harbor Freight item at home, I figured I could just use what I have (remember, KLR rider here)

But, as mentioned, I don't have what I thought I did.. (seemed too good to be true)..

So, I'll scrap my solar project and go back to just hooking up the 1.5a trickle charger up on each bike for a day, once every other week or so..

Thanks everyone for the help.. At least I know my wiring and male Powerlet works.. I've lit a LED fog light with the simple solar panel I have in place. Not brightly, but I know it works.. With the Powerlet plugs, I don't have to mess around lifting seats, tool boxes, side covers, etc.. The female Powerlet plugs on each bike is wired directly (fused) to the battery..

Live and learn.. At least I didn't wreck anything..

So, I
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Old 01-20-2012, 01:13 AM   #15
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Quote:
Originally Posted by Paper View Post
All I'm after is to keep batteries charged during the winter while the bikes are in storage (my garage) and to keep the batteries topped up without the need for removal from the bikes.
Solar panel and closed storage (garage) are not friends...even if the cord is long enough to put the panel right against a window, you won't catch every bit of sun rays available outside.

Quote:
So, I'll scrap my solar project and go back to just hooking up the 1.5a trickle charger up on each bike for a day, once every other week or so..
Good choice, you'll do yourself a great favor VS your previous project.





Quote:
Originally Posted by eepeqez View Post
Which brings us to the real problem here. This is a 1.5 Watt panel, which has a closed circuit current of 120mA. Your bike probably has a battery somewhere between about 5 and 20 AmpHours, depending how big they are. 120mA for a couple of hours a day won't really make much impression on a 20AH battery.
+1

Can you imagine that this panel is sold as an "automobile, truck, or tractor" solution!?
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