Solar Charging (battery top up)

Discussion in 'The Perfect Line and Other Riding Myths' started by Paper, Jan 15, 2012.

  1. Paper

    Paper In need of vacation

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    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?:huh 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-solar-battery-charger-44768.html#pr-header-44768 I've mounted it on my south facing garage wall and ran the wires inside..
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  2. GoGoGavin41

    GoGoGavin41 Sokath, his eyes opened!

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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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  3. Paper

    Paper In need of vacation

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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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  4. Hurricane Bob

    Hurricane Bob Long timer

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    it helps to read the directions.....
    http://manuals.harborfreight.com/manuals/44000-44999/44768.pdf

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

    :augie
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  5. EZman671

    EZman671 Adventurer

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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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  6. Paper

    Paper In need of vacation

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    It also helps to read the original post.. :deal

    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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  7. Paper

    Paper In need of vacation

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    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.. :deal
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  8. jesse68

    jesse68 Adventurer

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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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  9. SgtDuster

    SgtDuster Long timer

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    What would you want to do with a "big" 1.5w (yep, watts, not amps) worth of "power"? :huh
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  10. RVDan

    RVDan Long timer

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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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  11. SoSlow

    SoSlow Having fun

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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).
    #11
  12. eepeqez

    eepeqez Long timer

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    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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  13. Uncle Pollo

    Uncle Pollo Long timer

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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.
    #13
  14. Paper

    Paper In need of vacation

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    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):lol3

    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.. :lol3

    So, I
    #14
  15. SgtDuster

    SgtDuster Long timer

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    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.

    Good choice, you'll do yourself a great favor VS your previous project.





    +1

    Can you imagine that this panel is sold as an "automobile, truck, or tractor" solution!? :huh
    #15
  16. eepeqez

    eepeqez Long timer

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    I have a 20 Watt panel on my sailboat to keep the 80AH battery fresh when parked on the trailer. By the time it's regulated down to 14V, I get at most 1 Amp.

    When I pulled the battery out yesterday it was at 12.4V (not flat, but certainly not fully charged either) and is going on the auxiliary battery cable in the back of my car to charge up properly. It's difficult to find a spot where boat gets good clear sunlight on the entire panel for much of the day due to tall trees around me here.

    The next boat will get a much larger panel, enough to supply useful power on the water as well as to recharge the battery during the week.
    #16
  17. Paper

    Paper In need of vacation

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    I was outside, mounted on my south facing wall, with the wires run into the eves, mounted low enough to keep it out of the rain, and in full sun.
    It's collecting sunlight very well.
    #17
  18. slartidbartfast

    slartidbartfast Love those blue pipes

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    If you have a modern float charger you'll be fine. A simple regulated trickle charger may not fully charge many modern AGM and gel batteries, although the regimen you suggest will certainly help during long storage. In an unheated garage, the self-discharge will be very low so you may hardly need to do anything for just a few months' out of service. For the best approach to extending battery life consider also hooking up a desulfator like those sold by wizbangplus for a few hours or days before or while you trickle charge (although they are best connected directly to the battery with short wires.)

    Powerlet plug idea is great. I have those or cigar-lighter sockets on most of my bikes and all the 12V accessories have in-line 2-pin trailer plugs so I can change to whatever plug I need or hook directly from battery to charger or whatever. It also means I can cut wires short on air compressor for example and plug in an extension when required.
    #18
  19. ricmachado

    ricmachado Been here awhile

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    Would this chargers be a good idea to keep a i-pod and GPS charged?

    I'm traveling with my daugther and she will be playing most of the time with her i-pod, I also have a GPS on the bike. The bike is a KLR with a sidecar (that is how she will be playing) and has all the extra lights for the sidecar already installed. I was thinking about using one solar panel like this to keep the accessories charges without overloading the bike system.

    Is it a good idea?
    #19
  20. slartidbartfast

    slartidbartfast Love those blue pipes

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    If you will be camping for example and not moving the bike for several days, it might be worthwhile. Otherwise the tiny amount of energy you gain (and the tiny bit of load you save from the bike's charging system) is not worth the expense and extra stuff to haul around IMO.
    #20