Solar Power Charger for a 9.6v TX Battery

System
System Posts: 2,511 admin
This is my 1st post here and my 1st project in a long time. I will go through the forums and try to find the info I need but I wanted to post specifics of my project.

Thanks in advance for your help and info.

I would like to build a Solar Charger for my TX. This way when I am out at the field for 8 hours I can use the sun to charge my tx.

I have done some research and it appear I would need a minimum of a 10 watt Solar Panel with at least 12v, this means I should use a Solar Panel with 36 cell modules. I would need a Diode that would block the panel from getting a reverse energy feed when the battery is fully charged. I wouldn't mind have some type of LED Light or Digital Display showing the Voltage when the battery is charged and some type of on off switch as a secondary method to stop charging should I leave it plugged in. I would also need some type of regulator (Resister, Diode, not really sure as more research is needed).

I would like this to be physically no larger than the size of my TX Case and ideally it would be permanently attached to the TX Case.

I know one person who has done this already and it is awesome. He is some type of electrical engineer and extremely bright when it comes to this stuff. I am considering talking to him next time I see him. But I see him only a couple times a year.

For those of you not familiar with the term TX, it stands for Transmitter.

A little about my electronics knowledge. Simply put it is limited, it has been nearly 20 years since I have done anything like this. I could handle this build with some guidance as to specs and maybe even a diagram / blueprint.

Any help with a parts list and the right circuitry would be appreciated. Even links to the right info would be great.

Let me know if I have provide enough info for you guys to help me out.

Comments

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar Power Charger for a 9.6v TX Battery

    i would like to know how you concluded that you need a 10w panel? you make no mention of the current draw of your transmitter and if there is a duty cycle, as in how much time it will be in transmit per hour. is this to be used only during strong daylight hours or will you need to tx during night hours too? you also don't say anything about the battery type or its capacity.
  • System2
    System2 Posts: 6,290 admin
    Re: Solar Power Charger for a 9.6v TX Battery

    Sorry, I forgot to add that info.

    The battery is a Ni-Mh 9.6v (nominal) 8xAA Cells. 1500 mah. It will only be used during the day. I am only looking to charge the battery during the down time (when the TX is not in use), so there will be no current draw.

    I would need to charge at 150 - 250 mah. I believe the wall charger is 10% of the extended life battery which is a 2500 mah but the stock is a 1500 mah. Basically I am just looking to keep a slow charge going while at the field so that I do not have to worry to much about running the battery down.

    The battery will be slow charged overnight 90% of the time.

    I came up with the 10w by reading through forums and topics about this. It may not be right but that seemed to be the common number.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar Power Charger for a 9.6v TX Battery

    many hts can have another source of power plugged into it and can in some cases send a charge to the battery at the same time. if you can charge from another source while it's in operation (like many car adapters do) then you just need to put a regulator on the small pv holding it at about say 14v or so. lm317t regulators are a great application for this. the 10w could work and it could be possibly a bit higher or lower and was a decent guess on your part, 10w/12v=833ma which is more than enough i'd say even with the ht receiving. most likely the pv won't be at that 833ma rated power due to aiming and efficiency so it will still suffice imho even at 500ma. if charging batteries seperately from the ht then some of those good fast chargers from maha that can run on 12v would be good to use. i was meaning to do this myself for my ht, but never got around to it as mine takes a 9.6v nominal voltage nimh pack too, but will operate at 12v car voltages as well.
  • System2
    System2 Posts: 6,290 admin
    Re: Solar Power Charger for a 9.6v TX Battery

    Sorry for the delayed info as I haven't felt well and have been recovering from some surgery (nothing major).

    Anyhow, I picked up a solar panel used to charge VW Car batteries.

    It's rated at around 4 watts and pushes 18+ volts at max power at 170 mah.

    What is the recommended method to limit this to 12 volts at the same mah? I would need to keep the current from the battery pushing back into the panel too. I will likely put a small LCD display into the case to monitor the voltage.

    Thoughts and comments welcome, thanks in advance for your help.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar Power Charger for a 9.6v TX Battery

    It is not real efficient--but it is easy and pretty bullet proof. Use a Fixed or Adjustable 3-Terminal (positive voltage) Regulator (PDF Application Note).

    Your maximum regulator heat dissipation would be:

    (18 volts -12 volts) * 0.222 amps = 1.3 watts

    You may need to put a blocking (Schottky?) diode on the output of your regulator--Could have some leakage current when the panel is dark. It will add 0.2-1.0 volt drop (~0.2v if you choose Schottky)--but it may not matter to you... Or you can use the adjustable regulator if you need to adjust the output voltage.

    There are switch mode regulators out there that would be more efficient (and more complex + costly)--just depends on your needs.

    -Bill

    PS: Hope you are feeling better now.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Solar Power Charger for a 9.6v TX Battery

    You might try just using a blocking diode, and connecting the panel to the battery pack. The battery pack will "load" the panel down to the pack voltage, and I suspect for your described purpose, that would be fine. Don't leave it charging with the radio off for too long though. Maybe hook volt meter on, and slowly walk out into sunlight, to make sure you only get up to 10 or 11V before the battery loads it down.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar Power Charger for a 9.6v TX Battery

    do not just put a diode on the panel as the vmp is too large for the ht to properly handle. most don't like voltages of around 15v and up (some won't do 12v) so use a 3 terminal regulator and by all means heat sink it well.
  • System2
    System2 Posts: 6,290 admin
    Re: Solar Power Charger for a 9.6v TX Battery

    hey all, i came across this post in search of help of my own building of a solar panel battery pack as well. I am tryin to have a small 12v panel charge two (2) 9.6v nicd batteries. I would like to have an LED indicator whether the batteries are charged or charging, and an output to a USB. Any help on the details? I have a small setup drawing here....not sure if it will work, or if it does i dont know the correct parts to use...
    F5LT83HG57007WW.MEDIUM.jpg

    Thanks!
  • GreenerPower
    GreenerPower Solar Expert Posts: 264 ✭✭✭✭✭✭
    Re: Solar Power Charger for a 9.6v TX Battery
    HeliRaptor wrote: »
    ...A little about my electronics knowledge. Simply put it is limited, it has been nearly 20 years since I have done anything like this. I could handle this build with some guidance as to specs and maybe even a diagram / blueprint.
    How about something off the shelf like this (just quick googling, not sure what's the electronics inside but there is inenpensive single chip IC targetting this area to make such a thing cheap, I bet they still make decent margin at that price)
    GP
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar Power Charger for a 9.6v TX Battery

    a 3 terminal regular circuit with an lm7812 is fine. in fact a diode can be used in the output to drop the voltage down about another 1/2v and it can be left to trickle charge, but try it without 1st. of course fuses need to be used and one could incorporate reverse polarity protection with diodes. a large electrolytic cap can optionally be placed at the input to smooth out sudden dropouts of sunshine. win win