Solar AA Battery Charging Kit

System
System Posts: 2,511 admin
in General Solar Power Topics #1
Hi everyone,

We have been using the setup below to charge NIMH AA batteries at base camp with good success:

http://www.solarhome.org/20wattsolarbatterychargerkitwithaccumanager20batterycharger.aspx

Is there any reason I could not purchase the Kyocera 85 watt panel to allow charging on cloudy days, or expand our operation and charge from multiple chargers? I am not very proficient with these technologies and do not want to spend $400 on a panel that will fry our chargers or batteries. Any advice would be truly appreciated.

Thanks,
Jason
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: Solar AA Battery Charging Kit

    Jason,

    I don't have any information on the charger other than what I see from the web... The charger appears to be able to plug into a standard 12 volt car battery--so current is not an issue (with a fuse to limit current to the charger as needed--many 12 volt cigarette adapters have fuse built into the DC plug--and that should be good enough).

    However, "12 volt" solar panels can reach 17 to 21+ volts depending on sun, temperature, and loading. And many 12 volt accessories for cars have about a 15 volt limit/maximum--above which they may begin to fail.

    So--I would recommend that you either contact SolarHome directly, or even ask on their forum "Alternative energy forum" and see if they can give you a better answer with respect to their kit.

    Also, a possible suggestion... If you are looking to add that much in the way of a solar panel to your charging station (100 watts total)--You may want to go the whole way and add a Solar Charge Controller and an 80-150 AH AGM, Sealed, or other lead acid battery to your system... For the most part, you will only get 4-7 hours of full sun per day on your solar panels--and many charge controller of this type will take 6-10+ hours to fully charge their batteries (they may also have a 1-2 hour quick charge too for AA / AAA batteries--I am not sure).

    In any case, your solar panels + solar charge controller charge up the 12 volt battery with the available sunlight--and your smaller DC powered battery charger (AA/C/D etc.) can get 24x7 charging from the 12 volt battery. You can then full charge in one day, and even charge overnight your NiMH / NiCAD batteries without being completely at the mercy of the sun.

    Depending on your needs, the AGM battery+Charge Controller may let you capture more useful power from your solar panels and the 24 hour per day charging ability may limit your need for a second, large, solar panel.

    Before you add a panel--you probably should monitor the current you are using today and see how efficient your charging is today (batteries charge vs available power from the current solar panel).

    The 12 volt solar charge controller + storage battery will also safely limit your maximum voltage to 14.4 volts or so (depending on the charge controller you purchase) and then you can use this to charge cell phones, computers, etc...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
    Re: Solar AA Battery Charging Kit

    i'll basically agree with bb, but i don't think you want to put a 12v battery to it. the point of the higher voltages is a concern and it would depend on the ability of the charging circuit to handle that high of an input voltage to determine if some external regulation is warranted. it is possible the supplied pv is exceeding the limits too, but i can't say for sure being unfamiliar with that charger. i can't even say adding more pv will do anything as it shows it to be limited to 700ma and if it series charges all batteries then there's no reason to expand. if however the charger can pump 700ma individually to each battery then its max input capacity would be 6 x 700ma = 4200ma or 4.2a and putting higher input current to it in that case will allow for a faster charging of the batteries which is important when dealing with the short duration of full suns for each day. (4-5hrs typically during summer in northern hemisphere depending also on positioning of the pv) most battery chargers are series/parallel in that they do it in groups of 2 in series and then parallel for some even number of batteries. each group would then probably be 700ma each and yours is indicating 6 batteries max and that would equate to 3 x 700ma = 2100ma or 2.1a.
    bottom line is we don't have enough info to say for sure.:roll:
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #4
    Re: Solar AA Battery Charging Kit

    It's probably 700mA total to the charger since that figure is taken from the wallwart's specs.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #5
    Re: Solar AA Battery Charging Kit

    what wallwart? nevermind as i see it but it said,

    "The 20W, 1.2 amp solar panel, in full sun, will power the battery charger at it's maximum charge rate of 700mA."

    it didn't say it was from the walwart and did say 700ma max charge rate, but is that for each battery? or total? or for each pair of seriesed batteries? if it's total then why the 1.2a pv? it raises too many questions because we don't have enough info to properly answer.
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #6
    Re: Solar AA Battery Charging Kit

    As I see it, it's like when you pick up a wallwart (eternity knows we all have too many) and look at the info printed on it, it always says 120VAC/60cy (in USA) and then you see 12VDC @ 700mA. Simple. But, in the past, I've been too wrong too many times. :confused:

    IOW, the electronics downstream from the wallwart doesn't want or can't handle/deliver more than 700mA. This was a clue to what the charger expected to see coming in. I'll admit that I''m groping.

    Dissecting the charger module to the point after the stepdown/rectifier is problematic. One would hope to preserve the regulatory aspects of inherent circuitry.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #7
    Re: Solar AA Battery Charging Kit

    you might be right, but it might also be what is stamped on the charger itself as i have read charger specs that differ from wallwart specs.
    we don't know as we don't have enough info.:confused:
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #8
    Re: Solar AA Battery Charging Kit

    I think this is the charger itself (where I got the specs.). There is also a little bit more in a PDF download under the extended info tab:
    12-16 VDC Input for the different Adaptors

    So--while I am guessing that this is the same/similar battery charger--it does appear to be OK to put on a 12 volt battery.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #9
    Re: Solar AA Battery Charging Kit

    bb,
    i never said it couldn't take the voltage of a 12v battery, but i just don't think it is a 12v battery he needs. if the charger says it'll take 12-16v then there better be regulation between the charger and the pv as i'm sure it will exceed 16v. if there is something that prevents damage to the charger like a regulator, that i am not seeing off hand, then that is one aspect cleared up that would allow more pv to be added. the other is if it will do any good depending on how it utilizes current as i speculated into some before.
    with that i see no more point in my addressing this thread without more definitive input from the op with the info we would need to answer him properly.
    it would seem from the link to the charger that the charger itself is limited to 700ma and i see no point in adding more pv.

    to the op,
    as bb has already said, ask those that are familiar with the charger from their forum.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #10
    Re: Solar AA Battery Charging Kit

    The two reasons I saw for the 12 volt AGM (or equivalent) battery was:
    1. stabilize the 12 vdc from the solar panel to 12-15 volts to limit possible over/under voltage to the charger.
    2. allow the charger (which may be a 6-10 hour charger) the ability to charge when the sun is not up... Adding more solar panels will not help the charger work any faster (past whatever the maximum input current limit of the charger is).
    Note, from the PDF data sheet, the charger needs to be unplugged/plugged in between each battery charging cycle (couple of microprocessors inside)... Constantly changing solar panel energy may confuse the micro's inside (I don't know what they are doing--so it is a pure guess on my part).

    A steady "12 volt source" would seem to be a good idea with this guy.

    -Bill :confused:
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • System2
    System2 Posts: 6,290 admin
    #11
    Re: Solar AA Battery Charging Kit

    Thanks all for the input! I will try the Alternative Energy Forum for more info on the charger. It sounds like the key question is if there is a regulator as part of the battery charger. Again, I am very ignorant concerning these matters, but wouldn’t there need to be a regulator as the battery charger can be plugged into a normal 110 ac outlet?

    I wanted to avoid adding a 12v battery to the equation because we do not use the system year round, didn’t want to deal with complexities of maintaining a battery. Our Eneloop LSD AAs have proved to be very stable over the last 4 years and require no maintenance outside of using them occasionally. The 20 watt panel struggles to operate the charger on a cloudy day, thus the desire for a more beefy panel. Also, more people have expressed interest in using the solution so we were going to purchase the item below in addition to more AccuManager20 chargers.

    http://www.amazon.com/LENMAR-SPP-04-Power-Outlet-Socket/dp/B00009RUGY/ref=pd_sim_auto_6

    Again, thanks for the input and the time you have taken, looks like a good forum with good folks participating. I’m off to try to better understand “current” and “mA”.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #12
    Re: Solar AA Battery Charging Kit
    • 1 amp = 1,000 mAmps (milliamps) That is just a 1,000:1 conversion figure.
    • Power = Voltage * Current = Volts * Amps
    • Voltage = Current * Resistance (Ohms)

    The battery charger is a regulator in its own right... Takes ~12-16 volts DC and feeds ~2 volts to your single cell batteries for charging.

    The other issue is the output of the solar panel may exceed the input rating of the NiMH/NiCAD battery charger... If your system is working well for you--then why not continue.

    Cloudy days are always a problem... Even just a high overcast can easily cut 1/2 of the amount of sun hitting your solar panels--and the way they work, the panels will output about 1/2 of their rated current with 1/2 the sunlight.

    Heavy storm clouds--you are looking at only 10% of the power reaching your panels...

    So, while you do not like the extra 12 volt battery--if you live/camp in an area with a marine layer/cloudy conditions at times--You are pretty much left with getting a lot larger panel (whose output may be wasted on sunny days) or using an intermediate battery to allow you to capture energy on sunny days and recharge your other batteries on cloudy days and/or at night.

    If you have a measurement of your actual loads when charging and how much charging you plan on doing (say 1 amp at 12 volts for 5 hours):
    • 1 amp * 5 hours = 5 Amp*Hours
    • 1 amp * 12 volts * 5 hours = 25 Watt*Hours
    You can better size your battery bank/solar panel to meet your needs.

    Ideally, you would want to use an Amp*Hour meter to measure how much power you consume with your battery charger (like one of these). That would really help you to size the system to your needs... Unless you are recharging a whole bunch of batteries--a little AGM battery (20 AH-40 AH) would probably be more than large enough for your needs (in the above example, charge dozens of AA batteries before the AGM needs recharging).
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #13
    Re: Solar AA Battery Charging Kit

    Sorry, in my last post, I forgot to add a link the the Doc Wattson / Watt's Up Amp*Hour / Watt*Hour meters:

    http://www.rc-electronics-usa.com/electrical-test-equipment.html

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • cfcw
    cfcw Solar Expert Posts: 25 ✭
    #14
    Re: Solar AA Battery Charging Kit

    I'm a novice at all this, but to me it seems like a battery, even a fairly small one, would seem like the simplest, cheapest way to enhance this system. I have a battery box with a 35ah AGM battery and morningstar sunguard charge controller it it. You can put it all together for about `$125 and would allow you to charge the batteries when you wanted to, not just when it's sunny. It would probably allow for additional night time lighting if so desired.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #15
    Re: Solar AA Battery Charging Kit

    a battery will still need the services of a controller or some other regulating circuit as there isn't any getting around that, but if one accomplished that then they really don't need the battery.
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  • cfcw
    cfcw Solar Expert Posts: 25 ✭
    #16
    Re: Solar AA Battery Charging Kit

    Will try to add a couple of picture.

    This is the battery box I take tailgating. It is a plastic MTD ammo box I bought at a sporting goods store. It has a removable tray that i store additional accessories on. I have a flexible unisolar panel I hook up to it to supplement battery power through the Anderson "hub" device I am using . I have a "watts up" to help me judge the condition of the battery system. I use this box to run an engel portable fridge which draws about 35 watts. This box weighs about 30lbs.

    [IMG][/img]CIMG0140.jpg

    [IMG][/img]CIMG0143.jpg


    I do assume you aren't packing this around and you guys have a camp. Even the addition of a much smaller,lighter battery such as a 7ah should smooth out the current going to the charger. That can't be a bad thing, can it?
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #17
    Re: Solar AA Battery Charging Kit

    "Even the addition of a much smaller,lighter battery such as a 7ah should smooth out the current going to the charger. That can't be a bad thing, can it?"

    you are correct that the battery initially could smooth out the voltage to the charger. the battery will overcharge without a controller was my point and with nothing to stop the voltage rise when the battery is fully charged the charger may have its input voltage exceeded anyway some time down the road.
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