Charging Ipod docking station?

Lloydy
Lloydy Registered Users Posts: 15
Hi,
I'm pretty new to solar, 12v, electronics and everything in between.

I have recently set myself up with a small solar set up (12v 33AH battery, 20W solar panel and 4.5A charge controller) mainly for charging electronics while camping for extended periods.

My ipod docking station charging requirements are 12.9V and 1.39Amps. Can I charge straight off the battery or will there be an issue with slight mismatch of volts available and charging requirements? The battery is sitting on 12.8V at present but not sure if this will begin to drop when charging begins, potentially causing a problem? The docking station has an internal Lithium-ion battery and take minimum 6 hours to charge.

Also, am I right in saying that it would be more efficient to charge using direct 12VDC rather than an inverter?

Thanks

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Charging Ipod docking station?

    Yes it is more efficient to charge from 12 VDC. An inverter would eat up a lot of power.

    A tenth of a volt difference shouldn't be a problem. Chances are you couldn't even get a measurement that accurately with a DVM, and all voltage circuits fluctuate somewhat anyway. If the voltage from your battery was much higher, there would be a problem. Lower, the only potential problem is the Ipod won't charge fully.

    I'd say the biggest problem you have is that 20W solar panel. It probably manages maybe 2 Amps under the best of conditions? That will be short if the Ipod is drawing 1.39 A for six hours, if something else is being used as well. That panel is probably just enough to keep the 33 Amp/hr battery up. Add another draw and .... not enough power.
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Charging Ipod docking station?

    Also note: Make sure that your docking station takes DC. Many small electronics that use wall warts might use 9v or 12v AC.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Charging Ipod docking station?

    You may have fewer surprises if you get a DC Car Adapter too...

    It difficult with electronics to know what the devices actually require (frequently, everything is done; dc voltage, battery charging, etc,, in one proprietary integrated chip).

    You have to way the costs of an adapter of some sort vs the cost of the device + test for magic smoke.

    And you need to check for "standby loads too"... Does the adapter still take significant power if the device to be charged is not plugged in.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Lloydy
    Lloydy Registered Users Posts: 15
    Re: Charging Ipod docking station?

    Thanks guys.

    Firstly ipod docking station is definitely 12v. info on 240v charger says....input: 100-240V, 40/60Hz 600mA & output: 12.9V---1.39A.

    Great if i can charge with 12VDC.

    In terms of panel size, charging and looking after my battery. I've calculated (using an online amp & watt hour calculator, which I'm quite addicted to) my total daily amp hours is around 7-8. There is a 15% battery loss allowance worked into this.

    My camping spot's average daily sun hours are 6.5 (without sun tracking) x 20W panel output 1.19A = 7.735 amp/hours. Sure I would like another 40W of panels but cost/need has to be factored.

    Am i right in saying using 8A/H hours daily / 33A/H AGM battery = 24% depth of discharge, which is a perfectly normal/safe level of discharge?

    Total requirements from battery:

    -Docking station has the greatest draw but will only need charging every third day. I get 10 hours of listening from a full charge. 1.39A x 6 hours (every third day)
    -Ipod is charged from 12V-USB outlet (5v x .5A x 2 hours) every 2nd-3rd day
    -Fridge cooling fan .12A x 16 hours
    plus: Occasional personal cooling fan (if it's very hot at night) 2x .12A x 8 hours
    & 12v shower 20mins @ 1.5amps.

    Can you see flaws in my calculations? Am I missing something?

    Cheers
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Charging Ipod docking station?

    Everything you said seems to make sense...

    Your numbers seem light for Amp*Hour use--Or you are really using very little power (no radio, no lights, etc.).

    The 12 volt water pump I would hazard to guess is closer to 3-7 amps * 1/3 of an hour for 1-2.5 amp*hours.

    6.5 hours on the solar panel is pretty high for most of the US in summer.

    If, you could have 2x the solar panel you need--it would allow for poor sun days, 80% efficiency for flooded cell battery charging (90% or so for AGM)...

    Monitor your battery state of charge--don't let it sit for over a day below ~75% state of charge, try to get it above 90% charged a couple times a week...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Lloydy
    Lloydy Registered Users Posts: 15
    Re: Charging Ipod docking station?

    Camping is on the eastern seaboard in Australia. The sun is full on here and only occasionally works in your favor! We definitely should have way more solar here, but that's another story.

    No lights or radio from the battery. According to manufactures specs. on 12v shower, it pulls 1.5A. It is a pretty small pump and I imagine won't be pumping out that much water.

    A second panel would be good. see how we go? And yes, I will be monitoring the battery closely. Is the morning best? There will be nothing go in or out all night?

    Cheers
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Charging Ipod docking station?

    To measure state of charge with an acurrate volt meter--let the battery "rest" for ~3 hours then measure the "resting voltage".

    Check to see if the battery MFG has a voltage vs charge level chart, or use the table in the Battery FAQ to estimate charge level.

    If you have a good hydrometer--you can check once in a while for accurate state of charge measurements (for flooded cell batteries).

    Battery Monitors are ideal and just about mandatory for AGM/Sealed batteries (hydrometers won't work)--but probably not worth the cost for your needs... Look for a cumulative Amp*Hour meter (or Watt*Hour) like one of these (used by the Radio Control Crowd). Should work well enough for your needs.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset