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Thread: LiFePo4 Battery Use

  1. #11
    Membership #: 142 Free member M0TCF's Avatar
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    Re: LiFePo4 Battery Use

    Just completed 'Life's a Beach' with an 817 and a home brewed antenna run up a 10m long fishing pole! I ran the station on and off, over three days, and managed it all using one properly charged internal battery pack. My radio and antenna plus a few odds and ends like spare patch leads, adapters etc. all went into one old laptop case, the fish pole doubled duty as a walking stick and my butties went in a should bag my son gave me as a gift on return from China (compete with a picture of Chairman Mao!!).

    The best bit of advice I was given about going portable was to take into consideration how long you intend to transmit for - if it takes 3 hours to climb a mountain, how long are you actually going to hang around on the top? 30 mins is probably the max, esp taking weather into consideration so a battery that last no more than an hour will be quite satisfactory (an 1800milli amp usb charged item perhaps?). On the other hand a 24 hour stint on a field day weekend might in real terms require a 15 amp hour gel battery (I never use lead/acid, not suitable for safe portable work). Having said that the old PRC320 I was issued with in the Army only had 4 amp hr batteries, each of which lasted pretty well, however mil coms are all about speed and accuracy not about having a chin wag lol.

    There comes a point, hopefully after only a few portable expeditions, that you realise just what and what isn't needed for success, and to be totally honest if you check the gear before you leave, its relatively a small amount - even running data modes these days can be done on a fairly reasonable mobile phone or a cheap tablet both of which weigh very little.
    73's & Thanks.

    Lin. M0TCF. Exeter.

  2. #12
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    Re: LiFePo4 Battery Use

    Ok. Enough of the comments please chaps.

    Everyone has their own view on what a /P station should consist of. Some of us like small, compact and low power whist others like large, extensive and QRO. We all use our /P equipment in different ways and one of the great things about the hobby is that we are able to.

    For example, I have a homebrew man pack made from an FT-857 which contains everything I need for 6 hours operation in a back pack. Full HF/2M and 70cm with batteries, digital modes and several different antenna options.

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    I also have a large "go box" style station that is far to big for back pack type operation but gets used for portable Special Event Stations, demonstration days and training activities. It's designed to be a full field station in a easy to use package. Just lift it out of the car, plug in power and antenna then away you go. Here is a picture of the beast...

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    Both are portable stations built for very different jobs. Please bear that in mind when replying to posts.

    Larry, here is a typical discharge curve graph from a LiFePo4 battery. This one is rated at 1200mAh.

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    You can see that in this case, the voltage tails off rapidly when there is only a small portion of the capacity left. I always shut my kit of at around 11.5V and have had no problems. I also have a battery monitor that beeps at me to let me know when it's time to swap batteries!

    You need a proper LiFePo4 charge controller if you plan on using PV to top up depleted batteries. The Genasun range is well regarded so maybe something like this... https://genasun.com/all-products/sol...st-controller/

    It's important to remember that almost all PV charge controllers do not have a balance input so you will still need to use a proper LiFePo4 mains/12v charger to balanced the cells every few weeks. I have a 120W PV panel on the roof at home that charges a 200Ah SLA marine battery via a normal charge controller then I use the 12v output of that battery to power a LiFePo4 charger for charging my man pack batteries. Not the most efficient method and the 200Ah SLA is never going to go anywhere in a hurry but it does let me give the LiFePo4 a proper charge from a renewable source.

    The Alpha antenna will work but please ignore all the "I worked 5000 miles using a wet piece of string" comments that you will hear. When the bands are open and good it is perfectly possible to work the world on 100mW using a wet branch for an antenna. Remember that the antenna is one of the most important parts of your station and if your going to the trouble of going /P then make the antenna as efficient as it can possibly be. A good starter choice would be to take a look at our very own Davids multiband antenna - http://www.arpoc.org/content/135-mul...enna-easy.html. That will get you off to a good start. I personally use a linked dipole that is resonant on 80M, 60M, 40M, 30M, 20M and 10M. I can then also run this through the ATU to get onto other bands at the expense of efficiency.

    Maybe you could give some content around how you intend to use the station, what bands and the locations types available to you (if you have lots of forest then you may not need a mast to get an antenna in the air!).
    Matt - M0LMK


  3. #13
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    Re: LiFePo4 Battery Use

    "'m contemplating my proposed portable station for emergency use, when mains power may be unavailable, and petrol conservation may be desirable, thus the photovoltaic system. That should be capable of powering the station indefinitely without necessity of any ancillary hardware, connections or consumables other than sunlight. "

    I'm sorry but you are in the wrong place for advice on your proposed use. Here we are interested in operating from often remote places, where vehicular access may not be possible, (and here's the key part) for FUN. Battery charging is not an issue as after a few hours of fun we pack up our gear, and head back home for our dinner :-)

    You might me more "on topic" with the Rapid Deployment Amateur Radio (RaDAR) guys over at https://plus.google.com/communities/...65808971118728

    This might be of some help as well : https://en.wikipedia.org/wiki/Amateu...tes_of_America
    Last edited by G0DZB; 5th Aug 2015 at 20:24. Reason: Added RaDAR suggestion
    Best 73 tu
    Peter G0DZB

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    Re: LiFePo4 Battery Use

    Quote Originally Posted by G4YVM View Post
    Ha ha. Good advice. Personally I can't fathom why anyone uses more than a few watts when portable either. Maybe 25 tops.

    I use my self contained kx1 with just a few watts of cw and simple aerials. It just never fails. Why use more?

    D
    Unfortunately I've never found the time to devote to learning Morse Code operation. I sincerely appreciate the functionality of CW mode, and I'm sure it's a fun mode, but probably not for me. I'm always surprised at how good a signal a few watts can provide during favorable propagation conditions, and have worked several continents with ~35 watts (exciter power), so I'm aware that power isn't always necessary for good communications. However, for reliable emergency SSB communications, I believe higher power may prove advantageous.

    I've reached seniorhood, and probably not too keen in lugging a station too far off road. So why not contemplate adding a small, solid-state amplifier for SSB use, and enjoy the benefits in signal strength it provides?

    W1CDO also constructed a KX1-based station albeit on an e-bike:.

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ID:	464 Now, that is interesting, and added power is considerably less of an issue. Range, on the other hand....

    Being a new member of this group, I'm beginning to think I've tread on a "low power" ethos extant among members. No offense intended.

    Thank you for sharing your knowledge with me, David.

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    Re: LiFePo4 Battery Use

    I love the ebike mobile!!!

    I keep meaning to fit a whip to my push bike but time..., ah time.

    Anyway, I think you will find quite a QRP stance here but please don't let us intimidate you. We really don't mean to.

    Welcome to ARPOC!!!

    D

    G4YVM

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    Re: LiFePo4 Battery Use

    Good call on the RaDAR group Peter.

    Not all of us are low power Larry. I'm not usually less that 50W when I'm out portable and most of the time I'm up at 100W. ARPOC is not a specialty QRP group, just a group dedicated to all kinds of portable operation. Each to their own. As long as you enjoy doing it your way then that is all that counts.
    Matt - M0LMK


  9. #17
    Membership #: 381 Free member G1YBB's Avatar
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    Re: LiFePo4 Battery Use

    Sounds like two types of portable operation being discussed here, backpacking where weight is a major consideration and essentially moving and base station by car, not too far from car.
    Been on both sides of the coin, portable 60 foot masts, dual long yagis, generators and valve amps, but also full backpack portable, suitable for SOTA activations.

    I use for that 4 cell LiFePo4 batteries to run my FT-857D. Voltage wise works great. I use an inline Ah meter so I can keep an eye on discharge usage.
    I tend to use >50W,mostly because I choose to but also to make a bit more noise. I have worked a few stations giving me an S1 or S2 report so they wouldn't hear me on 5w most likely.
    Antenna wise I prefer resonant antennas to save taking, connecting up and tuning a tuner. Multiband link dipoles are very light. Mine probably weighs a couple of pounds tops, and most of that is the RG58 feeder (which I prefer over lighter but lossier thinner coax).
    Car supported portable we have taken everything bar the kitchen sink pretty much. And we never had the resources of the multi trailer tower gangs!
    Steve G1YBB
    http://g1ybb.uk

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