Category: Field Day

LiFePO4 Portable Power Kit

LiFePO4 Portable Power Kit

Recently I was researching an alternative to Sealed Lead Acid Batteries (SLAB), the cause of this research…back pain. While SLAB’s have performed ok for my car portable use, I was reminded just how heavy a 50AH SLAB is after straining my back putting it back on the shelf. So having seen a number of posts and videos on the Internet about the weight advantage I needed to give alternatives some serious thought.

I suspect like me, many of you will have heard of Lithium batteries but what I hadn’t realised is that there are different types and specifications. I was looking for three things in a new battery; appropriate voltage for amateur radio use (13 to 14 volts), low voltage sag (little voltage drop when under load), and a high number of recharge cycles (reduced cost of ownership).

Lithium ChemistryNominal Voltage
(4 cells in series)
Recharge Cycles
Lithium Titanate9.6v3000-7000
Lithium Nickel Cobalt Aluminium Oxide 14.4v500
Lithium Cobalt Oxide14.4v500-1000
Lithium Manganese Oxide14.8v300-700
Lithium Nickel Manganese Cobalt Oxide14.8v1000-2000
Lithium Iron Phosphate (LiFePO4)13.2v1000-2000

 

I hope you agree that Lithium Iron Phosphate (LiFePO4) came out as the most suitable. I was also fortunate that while away on a DX’pedition to the Isle of Barra with Bob (M0KLO) he kindly lent me his KX3 and a small radio model style 13v LiFePO4 4.2AH battery pack to try. It was certainly compact in size, light weight, and an ability to maintain voltage during transmit but the total capacity of 4.2AH I felt was a bit small for what I had in mind. 

A battery of about 15AH seemed to be about the size suitable for my needs based on my initial transmit tests with a Yaesu FT-891 “field” radio which suggested about 8 amps on transmit was a good target if I wanted 3 hours of operating time on a single charge. Remember that this is not an exact science as less current is drawn when listening as to transmitting and whether you use CW, Data, or SSB.

A search on the Internet provided a range of options from which I produced a shortlist:

  1. “radio control” style soft battery packs to make up a battery of 17AH. Various comments on the Internet suggested quality control of these packs is variable. Costs today (Mar’2018) for a 8.4AH pack is £ 52.83 + p/p. Due to the manufacturing process if one of the internal cells develops a fault the whole battery is a right off. Requires a balance charger to maintain cells. https://hobbyking.com/en_us/zippy-flightmax-8400mah-4s2p-30c-lifepo4-pack-xt90.html

 

  1. Electric Golf Cart suppliers have a good selection of LiFePO4 batteries in capacities from 15-40AH available with chargers and 3-5 year guarantees. Mainly sealed units with an internal Battery Management System (BMS), while this is perhaps convenient it has the drawback that if a cell or the BMS develops a fault the battery may be a right off. Generally supplied with a simple charger. Costs depending on capacity and warranty term but are generally £150  to £300 per unit. NB: Always double check golf cart batteries, are they definitely LiFePO4?www.topcaddy.co.uk/category/batteries/lithium-batteries/

 

  1. Electric Bikes commonly use LiFePO4 packs of various sizes (8,10,12,15AH), individual cells can be purchased and made into a pack. All of the required components can be purchased online or from an electric bike components supplier. Costs increase as cells capacity increases. For 4x15AH cells + cable bits to make 13.2 battery (Mar’2018) approximately £100. Simple chargers are available similar to the ones provided by the Golf Cart suppliers, but would recommend radio model style balance chargers suitable for LiFePO4 batteries.
    LiFePO4 (UK) Battery supplier
    http://eclipsebikes.com/index.php?cPath=25_10
    ISDT T6 LiFePO4 charger
     https://hobbyking.com/en_us/isdt-t6-lite-600w-charger.html?___store=en_us
    ISDT Battery Checker
    https://hobbyking.com/en_us/bg-8s-smart-battery-checker.html

 

I decided on option 3, if there was a problem with an individual cell I could replace it at minimum cost and it allowed me to take control of the management of the battery pack and individual cells. As a self-build I could also choose on different form-factors depending on requirements and components. It is also a simple task to increase the capacity of the pack by putting another one in parallel if needed at a later date. I also purchased a radio control style charger (ISDT T6).  This charger provides greater control of charging and also includes storage charge and discharge options and very importantly it allows charging of cells without a balance lead connected as I would be Bottom Balancing. Note that some LiFePO4 chargers will refuse to work without a balance lead connected. I also purchased the ISDT Battery Checker for more precise measurement of individual cell voltages on charge, storage, and discharge.

The rationale for bottom balancing is that I want the cells to converge to the same state of charge when discharged, before use and I charge the whole battery as one, rather than have the charger bulk charging the cells and top balancing them when using balance leads. I’ve included the following YouTube links for the background to bottom balance and not using a BMS. 

Bottom or Top Balancing
https://youtu.be/0KSFitqvap0

One example of how to Bottom Balance a battery pack
https://youtu.be/J2WvQre8sAQ

To achieve bottom balance I discharged the individual cells to 2.7 volts each and measured the voltage variation (after a settling period of 24hr) between the cells using the ISDT Battery Checker via the balance leads to achieve a variation between cells of a couple of mV. I then charged the cells to 3.4 volts per cell using the chargers (ISDT T6) upper storage charge setting of 3.4v and a charge current of 1/10th the pack capacity i.e 15AH divided by 10 = 1.5 Amps. The cell voltage variation at 3.4v across the pack was 8mV. I’ve found that if the individual cell charge voltage is increased to 3.6v, the cell voltage difference will also increase to 100+ mV. Also if the charge current is increased for example to 5A then the cell voltage variation will increase at top of charge. This in itself is not a problem and is predicted however monitor the voltage to make sure no individual cell goes beyond the 3.6v manufacturers specification.

My final choice was for 2×2 rather than the 4×1 cell pack, mainly because it fits neatly into a box that I subsequently purchased and it also fits better the compartment underneath the boot-floor of my car. The red/black leads with PowerPoles fitted are for the high current connection to the radio, and are also used when charging and discharging, the white leads are the low current balance leads that are used for voltage monitoring. If the ISDT T6 Lite is used to perform a discharge the balance leads are connected and the T6 will not let a cell go below 2.8v. While using the battery pack with my radio a small voltmeter is connected to the balance leads which cycles continually indicating pack and individual cell voltages during use. The audible alarm is set to 2.7v, if any cell reaches this lower limit an alarm sounds and I stop transmitting and disconnect the battery to prevent further discharge. After use the pack gets a storage charge and stored in a dry and cool place in the garage. 

Enjoy your radio
Glen G0SBN/P

A Tank For An Antenna

A Tank For An Antenna

ORIGIN

At one of the meetings of the Tynemouth Amateur Radio Club in the spring of 2006 somebody brought along some a few bits and bobs to pass on if any body could make use of them and at the end of the evening there was a green rod left.

I picked it up and was examining it when one of the members told me that it was a section of a Tank Antenna and I needed 4 sections to make an antenna for use on the Amateur bands. He told me to take it and to hold onto it as I would only need three more sections to be up and running.

A short while late I received a call from the same club member to say that he had a complete Tank Antenna and if I was interested in it I could have it for a donation to club funds.

I hot footed it around to his house and made a donation in exchange for it, the Tank antenna as previously outlined consisted of four rod sections, a top, middle and two bottom sections which measured about 4.9 metres when fitted together. The sections are constructed out of sprung steel (so I’m told), given a copper coating and painted green. They have a short broad thread on them and are pushed together and given a quick twist to join together.

MOUNTING

Having bought my Tank Antenna, I now had to figure out how I was going to mount it.

Another club member had a spare mount which he gave me. This consisted of a short metal tube that the Antenna fits into, a metal collett that tightens to secure the Antenna, and all this is mounted onto an insulator which is about three quarters of an inch in diameter and a couple of inches long.

For several weeks I pondered on how I was going to mount the Antenna with or without the mount that I’d been given. While looking at mounting options in my garden one thing that really struck me was that it has a low impact visually.

I now had to decide how I was going to mount it. Looking on the internet you will see vertical antennas on the market that are mounted close to ground level so that was an option. There is a lot said about Stealth Antennas and I thought that it might be a good antenna to mount at the top of the fence and couple it to an auto ATU.

In June 2006 a couple of us from the radio club decided to go out for the day and play radio, it was planned to go to a farm that we have been lucky to gain permission to use for our various field days.

With this planned it made me work a bit quicker to sort out a way of mounting the Antenna.

Looking at the insulator there is a hole underneath and I wondered if it would sit on top of a section of fishing Pole. It would but there would be too much flex and it would probably fall to the ground. The insulator would fit inside a Swaged pole and also inside a section of fishing pole.

I had a couple of spare sections off a fishing pole that was broken as a result of my son using the pole to retrieve his Frisbee out of a tree, he took it apart and put it back together again the wrong way around and trying to sort it out damaged a few sections of the pole, so I now had two spare sections.

I decided to mount the antenna at ground level and cut one of the poles down and fitted the mount inside. I had a Ground Spike from another manufactured Portable Antenna, so I decided to use that, and the Pole fits nicely inside the tube attached to the ground spike.

The Antenna was now mounted and supported.

RADIALS

The next thing that the Antenna needed was Radials.

The Antenna is about 4.9 metres long, so you don’t have to think too hard to work out that it was around a quarter of 20 Metres. Thinking back to a talk given by the Chairman of the club at the time on ground planes and radials I remembered various points discussed and using these principles I made up 12 radials. In the talk given to the club it was mentioned that a good number of radials to use was 120. I couldn’t manage 120 so I decided on 12.

I mounted the radials on a bolt that was connected to a short earthing strap and that would then be attached to the Spike or Pole. I have a SOTA beam which comes with a length of coax with a BNC connector on one end and lengths of wire soldered to the centre core and outer braid of the coax cable with crocodile clips attached to clip onto the antenna. I had made up another similar length of coax with a PL 259 plug on the end, so I used this and connected the centre core of the coax to the metal collet on the antenna mount and the outer braid to the earthing strap which was connected to the radials.

I made the radials slightly longer than the antenna with the intention of folding them back until I got the SWR right and I would then cut them to length. I attached automotive connectors onto the radials in order to thread them onto the bolt.

      

OPERATION

On the 8th June2006 along with the other two members of the club Tony and Glen we went to the Farm to play with our Radios and Antennas.

The three of us have Yaesu FT 817’s and we were going to have a QRP day.

I took along the Antenna, my 817, an SWR meter, an ATU and a small amplifier because on my previous attempt at portable QRP operating I didn’t have any success with SSB with the antenna that I used on that day and I had people who were using higher power bleeding over the top of me (Glen).

To power this entire set up I also took along a Leisure Battery, over the top I know but I wasn’t going to take any chances and if I wasn’t successful with the QRP I was going to use the amplifier, so the extra power would be handy.

I set the Antenna up, connected it to the radio and switched on. Immediately I was receiving good clear strong signals.

I hooked up my SWR meter and checked the SWR and it appeared to be spot on, the needle only moved a fraction on the meter.

I called Tony and Glen over and checked the SWR again to show them how good it was (I expected to be fiddling on with the radials for some time to get the SWR right).

When the needle hardly moved Glen said,

It’s broken”.

I kept the SWR meter connected to the radio, but I could have actually removed it.

I made only made 12 contacts but at a fairly leisurely pace, it was also a social event with plenty of chat.

My first contact came after a couple of CQ calls and was with Ian G3PHD in Tilbury, Essex who gave me a 5 & 7. I had one 59 report, a couple of 57 and a lot of 55 reports which when you actually take time to understand the RST system of reporting 5 by 5 reports are perfectly satisfactory. On this first outing I contacted a German station DQ2006S who gave me a 55 report and he obviously found it hard to believe I was running only 5 watts, he kept asking me to confirm I was QRP I confirmed it and he came back to tell me that he was running 500 watts.

As a fun club event on the 15th of July that year a few of us organised a QRP Barbecue come QRP competition. The basic idea was that we would have a day out at the farm, do some operating and have a barbecue. The competition side of events was that Glen erected a wire dipole for 40 metres and I took along the Tank antenna for 20 metres and we both took our 817’s. Competitors would have a 15-minute slot on each antenna and the person with the most contacts was the winner. There was an adjudicator sitting with each competitor to verify the number of contacts.

It was a great day out with fantastic weather, good food (if I do say so myself), good company and overall it was good fun.

DEVELOPMENT

Since that first outing and success with my antenna I have made another coax lead with automotive connectors on to tidy up the connection between the coax and the antenna, I have also tidied up the connection with the radials. I have also shortened the section of fishing pole which sits inside the ground spike, it was initially too long and one windy day with it moving about it split the fibreglass tube and fell over. Lowering it takes away that strain on the tubing.

During another day out on the farm in mid-February 2007, my first contact of the day was with PT7CB in Brazil! Wow I was over the moon; this was using the internal batteries on the 817. I also had a contact with CN8PA in Casablanca which was a first for me, so I was also very pleased with that.

Initially the Antenna was not intended to be used solely for QRP and it could certainly be used with more power or as a home base antenna, but I get such a buzz from making a contact using it on QRP that I am now totally hooked, and I would always keep sure that I have a Tank antenna for portable work.

Coming up to date in August 2018 twelve years on from when I first used the antenna.

I still have the antenna; the connections and radials are still working perfectly, and it has been used on many occasions at various power levels. The only further development that I have made with it is a tripod mount for use when I’m on a hard surface and cannot hammer the ground spike into the ground. It is a camera tripod that I was given with the tilt/mounting head on a central pillar that can be raised or lowered in the tripod. I simply took the tilt head off and the section of fishing pole with the antenna mount attached slides over the top of the pillar.

If you have a moment come and ask me about my Tank antenna, I’ll be only too pleased to tell you about it.

Enjoy your radio… 

 

 

 

 

 

 

Graham M0GAE

 

 

Field Day – July 2018

Field Day – July 2018

Sat 21st July, A day that will be long remembered, by me at least… !

It was the summer Tynemouth Amateur Radio Club Field Day, one of a few we have planned over the summer, which in fact so far is proving to a proper corker of an English summer

There were 6 vehicles and 7 members present in total and an amazing array of kit and antennas ! Everything from an 80m Doublet to a 2m Beam was present and almost everything in between.

I was operating with my friend Carl Gorse (2E0HPI) using the DXCommander vertical antenna which I find is an excellent all round vertical that covers multiple bands. Initially we set out to use my TS590SG which turned out to be a no go at anything over 10 watts as the car 12v system just could not provide the current and the radio simply shut down each time TX over 10 watts was used.. Luckily ! I had my trusty KX 3 and LifePO battery box at hand which I normally take on portable ops with Carl so we reverted to that and blasted out our mighty 15 watts LOL !!

We did well with a total of around 18 in the log, mainly from Europe but we had some great craic in the sun, eating sandwiches and talking radio with the other members, I took along my restored WWI Lancaster bomber radio, a marconi R115A receiver so we could listen to AM broadcast radio just for some entertainment !

The log for the day read like this :

40 Meters

(7.160 Mhz)
G4SQA
M3FEH
(7.096 Mhz)
F4FMU
ON7RN
F2YT
ON3EA
2E0WDX /M
(7.144 Mhz)
F4HXC /P
(7.180 Mhz)
ON6OO
G7VQE
F4HZR
MM0JEL
G0FVH
DK0WK /P
DL4ABN

Echolink (2 Meters)
M1PVF /M

17 Meters

(18.144 Mhz)
DG4FCN