Author Topic: Need advice on power bank please.  (Read 702 times)

Offline kid_couteau

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Need advice on power bank please.
« on: April 18, 2018, 07:55:06 AM »
Hi All

I am tossing together a small power bank for my HF rig.

Reason for plan: I am on the local ARES team and we are responsible for the area of Aroostook county Maine.

Towns are few and far between. We have a repeater in the area about 20 miles from where I live. But we practice simplex for if power goes out. We can cover a lot of distance using 2 meter and simplex but when you need to cover a distance of about 47 miles from one EOC to another EOC [by road not as the RF flies] it gets harder to do.

I got to thinking that if we used HF for some of it we could cut down on leapfrogging the signal.

Sooooooooo here is what I am thinking please feel free to critique.

Radio: Yaesu 891 on 20 watts probably 20 meter so the antenna is not huge. On 20 watts should use 8.3 Amps per hour if always transmitting.

Battery 12 volt 20AH

50 watt solar panel to help maintain battery.

Please understand this would be a go kit so it needs to be smaller.

Could I safely get 2 hours of use before the battery is down to 11 volts? Hopefully it will be sunny the day I need it.  :P

Thanks
Kid

Offline armymars

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Re: Need advice on power bank please.
« Reply #1 on: April 18, 2018, 09:13:48 AM »
  On MARS we find 60 meters works best during the day. The antenna doesn't need to be more then 7 feet off the ground so length is less important. 60 meters is under used so having only 5 channels is not a problem. At night you need to go lower. During this sunspot cycle low I've had to drop as low as 160 meters.
  A 100 foot dipole, open wire feed, tuner and 9 to 1 unun. By adding or removing the unun you can cover all the bands from 160 up. 

Offline Carl

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Re: Need advice on power bank please.
« Reply #2 on: April 18, 2018, 09:18:58 AM »
Hi All

I am tossing together a small power bank for my HF rig.

PLEASE...PLAN to build it,just tossing it together will not be so effective.
For auto transport or is it to be hand carried?


Reason for plan: I am on the local ARES team and we are responsible for the area of Aroostook county Maine.

Towns are few and far between. We have a repeater in the area about 20 miles from where I live. But we practice simplex for if power goes out. We can cover a lot of distance using 2 meter and simplex but when you need to cover a distance of about 47 miles from one EOC to another EOC [by road not as the RF flies] it gets harder to do.

I got to thinking that if we used HF for some of it we could cut down on leapfrogging the signal.

Sooooooooo here is what I am thinking please feel free to critique.

Radio: Yaesu 891 on 20 watts probably 20 meter so the antenna is not huge. On 20 watts should use 8.3 Amps per hour if always transmitting.

Battery 12 volt 20AH

50 watt solar panel to help maintain battery.

Please understand this would be a go kit so it needs to be smaller.

Could I safely get 2 hours of use before the battery is down to 11 volts? Hopefully it will be sunny the day I need it.  :P

Thanks
Kid

While HF is known for real distance capability and 20 meters is a great choice to use for Maine to talk to Florida,Texas,The West coast....it is worthless at the shorter distances you need for direct contact as it must bounce of the ionosphere (about 50 miles up)  and return to earth to be heard beyond LINE OF SIGHT distance. It can be used effectively for point to point over mountains and into valley type contacts though with NVIS ( Near Vertical Incidence Sky wave) Same radio ,but used on 40-60-or 80 meters with a low to earth HORIZONTAL antenna. The antenna is most important...Your 20 or 33-35 Amp hour battery will do better with SSB HF than with a VHF FM radio  and a 20  (18 amp hour is common size) battery with 50 watt solar...one can operate many hours and many days.. I have posted many NVIS how to threads and antennas in the forum...and will answer any specific questions here as to not put people to sleep with details.


 :) I bet MARS is beautiful this time of year! :)

Offline Smurf Hunter

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Re: Need advice on power bank please.
« Reply #3 on: April 18, 2018, 10:25:36 AM »
We are really discussing a couple common problems:

1) mode of communication
2) how to provide portable/backup power for our chosen mode

If you can achieve #1 using 2 meter VHF simplex, you should.  Lots of people have mobile installations, hand helds, etc.  It's logistically a winner. While you can build/buy a directional antenna for VHF (yagi, etc.) most of the time we're not diving into deep discussions about radiation patterns or VHF antenna designs.  Everyone has an omni directional vertical for the VHF. Whereas for HF antenna design is MOST of what we discuss.

It's kind of the difference between pistols and rifles.  The pistol you carry is largely just personal preference, but when you get to rifle selection, the distance and terminal ballistics desired dictate your options.

The good news about battery banks, one that can support 100 watts on HF can of course handle your 50 watt mobile VHF. Something as simple as a small fleet of SLA batteries that you can rotate, and have a couple methods for charging seems a good place to start. 

For example, if I had two of those 35AH SLA harbor freight "solar" batteries...
I can use a 120v mains power smart charger when grid power is available.  I use a 6amp Shumacher that Carl suggested.
If I lose grid power, I can recharge from a running vehicle, or use my 100 watt solar panel/charger.  The panel isn't really portable, but it's on a wheeled cart that can be moved around my property at least.
But most important to me, is I have a few hundred amp hours in total I can access depending on the circumstances.

Maybe I'm loaning a few batteries to the EOC during an emergency.  It's really hard to predict, so plan to be flexible.

Offline armymars

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Re: Need advice on power bank please.
« Reply #4 on: April 18, 2018, 12:53:14 PM »
 Way back in May 1990 I had to put together a drill for MARS. I gave everyone a heads up of what was coming, but not when. On the day of the drill I told every one "You have just lost power, now check in." About half did. Two of the stations built extension cords that ran from their cars to their radios. Some stations always ran on batteries and would charge them between nets.
  When I ran a net portable for four years, I used a car battery on the floor of the passenger side of my car. Because I ran only 100 watts for one hour a normal car battery worked fine. The nets were mostly voice nets so no real deep discharge.
  Sealed lead acid batteries are nice for moving around, but they can weigh twice as much for a size.(dimensions). I've lost some by charging them wrong.
  The newest battery chemistry is a joy to carry. so much lighter per amp hour. Again watch how you charge them.
  Last everything Carl wrought about NVIS should be required reading. Using WWV and VOLCAP and you can calculate the best frequency to run.   

Offline Carl

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Re: Need advice on power bank please.
« Reply #5 on: April 18, 2018, 01:08:32 PM »
ARMYMARS...KARMA for agreeing with me  ::)

I have a thread or ten posted about Ham radio and battery operation as few fail when asked ...BUT a 100 watt HF SSB radio ,with voice ,actually needs 20-25 amps PEAK amperage from a battery and an AVERAGE of only 7 amps  while a Yaesu 70 watt or so VHF,at full power needs an average of 17 to 20 amps ...the HF SSB radio is much more efficient on power though I do agree that the numbers are more in favor of VHF for your needs as more local stations can act as members in relay of messages,especially those in high locations or with tall towers...Maybe the value to the community of a solar powered battery for the repeater is also easy to maintain and justify?? I have had good success with as small as 12 amp/hour batteries (one for each 3 to 4 hours of operation...If economy of TX time is used) and most HF (or VHF) radios will operate for a typical day of operation without solar or vehicle charging. As I am to old to carry big batteries,I often operate with a 100 or 125 AMP HOUR battery in my auto and a inverter to extension cord to power supply for radio as it is quick and easy to set up and squeezes the most out of the battery as most radios begin to fail when battery reaches 12 volts and the inverter will keep a radio stable,and at full power,until battery reaches 10.5 volts under load...so the inverter offers a bit more stability and run time.
« Last Edit: April 18, 2018, 01:24:47 PM by Carl »