Man Portable Comm Power

Discussion in 'Survival Communications' started by Falcon15, Mar 6, 2013.

  1. Falcon15

    Falcon15 Falco Peregrinus

    Here are some options for "man portable" HAM comms - long distance comms. Bear in mind, this came from a discussion regarding the near infamous Chinese hand cranked surplus generator. After much research, I have determined that setup will NOT WORK as it stands, and would need to be heavily modified, as it only outputs 6.3V DC. You need 12V DC. An electrical engineer has posted some mods on the internet, if you or your group is bound and determined to buy a hand cranked generator, you can look them up yourself.

    All information is based on some basic math and knowledge of the systems being discussed. I try to give easy to understand breakdowns.

    Using a pair of 7 amp hour (7aH) gel cell batteries (similar to the ones used in alarm systems, and uninterrupted power supplies). This is exceptionally portable, and if you throw in a solar panel with charging attachments, silent and literally free energy. Note: the radio (or electrical gizmo) needs power pole connectors for the battery pack. You add some weight with the gel cells, but it gives you more transmit/reception time. The 7aH batteries are really cheap as well (about $20.00 each). However, research has shown that a 12v 1.5w 120mA output solar panel from Harbor Freight which, while it runs under $20.00 requires about 66 hours of good daylight to charge one 7 aH battery to full.

    Based on extensive research, I provide the following options. Always remember "Fast, good, or cheap", pick 2.

    Option 1: "Good and cheap"

    At under $100.00 you can run portable, with extremely light weight.

    Pros: Extremely portable (panel is 13.75"x4.75"x0.5"). Free energy from the sun (no labor needed), can charge the batteries while on the move.

    Cons: exceptionally slow charging speed. Cannot run a small radio directly from the panel.

    Break down as follows:
    1.5 Watt Solar Panel: $12.99 (trickle charges a battery. Will fully charge [from 0 charge to full] a 7 aH in approximately 66 hours under full sun - 1.5 watt/12 V = approx .112 Amps. 7 aH/.112 A = 66 hours In direct sunlight.)
    Connector wire set: $8.99
    2 Qty. 7mA hour Gel Cell batteries: $40.00
    Total cost, minus tax or shipping: $60.00

    Option 2: "Fast and good"

    Allows for faster charging, more flexibility and a bit more cost. For just over $120.00 you can have a larger portable solar panel (14 Watt) that charges faster, and it comes with a connector wire set.

    Pros: Extremely portable. Free energy from the sun (no labor needed), can charge the batteries while on the move. Charges the battery in 1/10 the time of the smaller, lower powered cell. Can potentially run the radio (as long as TX power is in the 4-5 AMP range, you are golden, as the radio draws less than the 14 Watt output of he panel) without any battery source during daylight hours. At 9 and 15 AMP TX you would drain a battery fully in .75 and .5 hours of constat transmission (approximate).

    Cons: Larger solar cells (20"x15"x1.5"). Higher price point.

    Break down as follows:
    "Briefcase" Solar Panel: $79.99 (trickle charges a battery. Will fully charge [from 0 charge to full] a 7 aH in approximately 6 hours under full sun - 14 Watt/12 V = 1.1666 Amps. 7 aH/1.1666 amps = 6 hours In direct sunlight.)
    2 Qty 7aH gel cell batteries: $40.00
    Total cost, minus tax or shipping: $119.99

    Please note, these charging times are very conservative as all panel ratings are calculated using winter time sunlight. Sunny locations with more daytime hours will give higher Amps, thus shorter charge times. One of the heftier 14 Watt portable panels will fully charge a standard car battery (40 aH) in 34 hours.

    Also to note, the larger panel can be used to charge NiCads, relatively quickly with an adapter and battery charger hooked in (I have one that is cigarette lighter adaptable, and the large panel comes with a 12V DC "cigarette lighter female adapter"), or a separate charger can be bought.
    I took the time and built two of the option #2.

    I housed the batteries in surplus ammo cans (water tight and nearly indestructible) and connected the batteries in parallel, thereby doubling the amp hours of the bank, while maintaining the Voltage (14 aH at 12vDC as opposed to 7 aH at 24vDC). I lined the bottom of the ammo cans with 1/2" thick styrofoam. I installed 6" tall 3/4" dowels as "legs" in each corner of the box, and installed a cover plate of 1/8" balsa ply with a power switch. I screwed through the outside of the ammo can into the legs to anchor them tight into the structure. Sealing them with silicone, I painted them olive drab to match the outside of the can.

    The foam and dowels keep the batteries tight in the box, yet keep an airspace around the batteries to help keep them cooler during use and charging.

    The switch (which is recessed approximately 1/2" below the ammo can lid) allows me to turn the power on or off as I need. I ran a female "cigarette lighter" 12vDC connector with a cover cap to the outside of the box (sealing around the wire with silicone), wired to this to a charge controller (mounted under the wooden plate), switch, and then batteries.

    My briefcase solar panel can be plugged directly into the batteries using the male 12vDC connector. any 12vDC item can be plugged into the system. If you know what kind of amerage your equipment draws, you can easily figure out how long you can run on this battery pack. This was designed as a portable power pack for comms, but it can have many uses. I will be building another battery box, and will post pictures as I progress.
    melbo likes this.
  2. Falcon15

    Falcon15 Falco Peregrinus

    FYI, all of the links are to the pertinent items I listed and, in the case of set-up #2 bought and used.
  3. Gunny Highway

    Gunny Highway Hard Work and Sacrifice blessed by God's Grace

    Falcon - this kind of thing is why I LOVE THIS BOARD !!! Awesome stuff
  4. melbo

    melbo Hunter Gatherer Administrator Founding Member

    Great info!
    I'm researching some non man portable power options tonight
  5. Falcon15

    Falcon15 Falco Peregrinus

    It all comes from a personal need, and then a desire to share what I learned. Enjoy.
    Melbo: what kind of non-portable power? Gennies?
  6. BTPost

    BTPost Stumpy Old Fart,Deadman Walking, Snow Monkey Moderator

    Good Job Falc... At 100 watts RF output on HF You will get 45 minutes of of Tx time before the system goes flat. A judicious use of Tx Power would seem appropriate, for this Man Portable Power System, thus extending operating time. A. PSK Modem will reduce Tx the Power required, as well as allow for Data Messages that can be encrypted, and sent with Error Correcting Protocols. The modem power requirements will be much less than that saved by the reduced Tx Power needed to complete the Comm Link.
    Falcon15 likes this.
  7. melbo

    melbo Hunter Gatherer Administrator Founding Member

    Upgrading the battery system on a travel trailer and replacing the stock Converter with a Magnum inverter/charger- ultimately adding solar.
  8. Silversnake

    Silversnake Silverback

  9. stg58

    stg58 Monkey+++ Founding Member

    Check around there are 20% off Harbor freight coupons in the papers.

    Here is an online coupon.

    20% Off Coupon
  10. stg58

    stg58 Monkey+++ Founding Member

  11. Falcon15

    Falcon15 Falco Peregrinus

    That is the briefcase solar panel set, yes. I am building another battery box next weekend, I will snap pictures and post them.
  12. stg58

    stg58 Monkey+++ Founding Member

    Picked one up today.

    Thanks for the tip.
  13. kellory

    kellory An unemployed Jester, is nobody's fool. Banned

    I would like to see these battery boxes.
  14. PapaGrune

    PapaGrune Inside the firestorm

    Harbor Freight's web site has monthly sale fliers on them. Just print it out, or the page your item is on ant take the sale price to the store. They will give you the Corp fyler price. You can also sign up and they will email you different sales too. I get sales-fliers in the mail when I signed up with a business I no longer have. Several ways, pick one that will fit your needs. I have a junk email account, that I have had for many years and that is where I have most of those things sent to.
  15. natshare

    natshare Monkey+++

    Harbor Freight is pretty good about sending out 25 to 30 percent off coupons in e-mail, too. :cool:
  16. Falcon15

    Falcon15 Falco Peregrinus

    I will be assembling another battery box sooner than later. Full photographs to follow. Please be patient. This second box will live in the family main vehicle for backup power for my portable HAM.
    kellory likes this.
  17. Tevin

    Tevin Monkey+++

    I know this is an old topic, but since someone "bumped" it, I thought I'd sound off. I am drawing on my 20+ years professional experience as an electronics technician, ham operator, and someone who runs a good chunk of his house on a solar power system I designed and built myself, as well as having hand-built a 135 watt portable solar station.

    The statement "Sunny locations with more daytime hours will give higher Amps, thus shorter charge times." is inaccurate. Solar panels do not produce more current in the summer. Given equal light levels, a battery that takes x hours to charge in the winter will still take x hours in the summer. Whether done all in one day or split up over several days doesn't matter...the total net charge time is constant. I think the original post meant to say that you get more watt-hours in the summer. There isn't more current and nothing goes "faster', it just gives you a larger window of opportunity each day to charge your batteries.

    Solar panels do not like hot temperatures. They are more efficient in the cold, although the advantage is negligible in small systems. The Standard Test Condition (it's on google, by the way) is 77º F and efficiency above and below that is neither flat nor linear. Efficiency drops very quickly above STC and increases below that point.

    The calculation that a 1.5 watt solar panel in full sun would need 66 hours to charge a 7.00 amp-hour battery is mostly right (it assumes 12 volts; it's more in the 15-18 volt range)...except that in the example given, two batteries are used. So now we are up to 132 hours at prime conditions. At that rate you are barely overcoming the internal resistance of the batteries. In a real-world application you would never see a full charge. This is not even vaguely close to being an effective setup.

    The other systems described in the original post have the same serious miscalculation: Charge times are based on a 7.000 aH battery, but then he goes on to specify two batteries for the project. So at minimum, you must at least double the charge times given. It does not matter if you charge them individually or wire them together in parallel; we are still dealing with 14.000 aH total capacity.

    A 14 watt solar panel cranks out about 0.85 amps in full sun. Running the numbers, it would take nearly 20 hours to charge 14 amp-hours worth of battery. Even in summer, that would mean several days of good sun. I do not consider that an effective system, either.

    The general rule of thumb for larger solar plants is that you should have one watt of solar for every amp-hour of battery. This formula assumes you are not running your batteries totally dead. My home and portable systems roughly follow this parameter and even in the winter I typically get enough sun to replace what I used off the battery overnight. Small systems that are intended to literally bring batteries back from the dead will need to have a watts to amp-hour ratio much higher than 1:1 in order to get reasonable charge times.

    Bottom line: No matter what else you do, get a solar panel big enough to refill the battery faster than you drain it.
    Last edited: Dec 15, 2013
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