Here is a diagram showing the traditional way of interconnecting 4 batteries to form one larger bank. This is a method that we still see in many installations.

Method 1

Notice that the connections to the main installation are all taken from one end, i.e. from the end battery.  The interconnecting leads will have some resistance. It will be low, but it still exists, and at the level of charge and discharge currents we see in these installations, the resistance will be significant in that it will have a measurable effect.   Typically the batteries are linked together with 35mm cable in a good installation (often much smaller in a poor installation). 35mm copper cable has a resistance of around 0.0006 Ohms per metre so the 20cm length between each battery will have a resistance of 0.00012 Ohms.   This, admittedly, is close to nothing. But add onto this the 0.0002 Ohms for each connection interface (i.e. cable to crimp, crimp to battery post etc) and we find that the resistance between each battery post is around 0.0015 Ohms.

If we draw 100 amps from this battery bank we will effectively be drawing 25 amps from each battery. Or so we think.

In actual fact what we find is that more current is drawn from the bottom battery, with the current draw getting progressively less as we get towards the top of the diagram.

The effect is greater than would be expected.

Whilst this diagram looks simple, the calculation is incredibly difficult to do completely because the internal resistance of the batteries affects the outcome so much.

However look at where the load would be connected. It is clear that the power coming from the bottom battery only has to travel through the main connection leads. The power from the next battery up has to travel through the same main connection leads but in addition also has to travel through the 2 interconnecting leads to the next battery. The next battery up has to go through 4 sets of interconnecting leads. The top one has to go through 6 sets of interconnecting leads. So the top battery will be providing much less current than the bottom battery.

During charging exactly the same thing happens, the bottom battery gets charged with a higher current than the top battery.

The result is that the bottom battery is worked harder, discharged harder, charged harder. It fails earlier. The batteries are not being treated equally.

Now in all fairness, many people say “but the difference is negligible, the resistances are so small, so the effect will also be small”.

The problem is that in very low resistance circuits (as we have here) huge differences in current can be produced by tiny variations in battery voltage. I’m not going to produce the calculations here because they really are quite horrific. I actually used a PC based simulator to produce these results because it is simply too time consuming to do them by hand.

Battery internal resistance = 0.02 Ohms
Interconnecting lead resistance = 0.0015 Ohms per link
Total load on batteries = 100 amps

The bottom battery provides 35.9 amps of this.
The next battery up provides 26.2 amps.
The next battery up provides 20.4 amps.
The top battery provides 17.8 amps.

So the bottom battery provides over twice the current of the top battery.

This is an enormous imbalance between the batteries. The bottom battery is being worked over twice as hard as the top battery. The effects of this are rather complex and do not mean that the life of the bottom battery will be half that of the top battery, because as the bottom battery loses capacity quicker (due to it being worked harder) the other three batteries will start to take more of the load. But the net effect is that the battery bank, as a whole, ages much quicker than with proper balancing.

Method 2

All that has changed in this diagram is that the main feeds to the rest of the installation are now taken from diagonally opposite posts.  It is simple to achieve but the difference in the results are truly astounding for such a simple modification.   The connecting leads, in fact, everything else in the installation remains identical.   Also, it doesn’t matter which lead (positive or negative) is moved, Whichever is easiest is the correct one to move.   The results of this modification, when compared to the original diagram are shown below. Only that one single connection has been moved.

After this simple modification, with the same 100 amp load….

The bottom battery provides 26.7 amps of this.
The next battery up provides 23.2 amps.
The next battery up provides 23.2 amps.
The top battery provides 26.7 amps.

This is quite clearly a massive improvement over the first method. The batteries are much closer to being correctly balanced. However they are still not perfectly balanced.

How far is it necessary to go to get the matching equal?

Well, the better the quality of the batteries, the more important it becomes. The lower the internal resistance of the batteries, the more important it is to get them properly balanced.

So that now leaves the question of whether or not there is a wiring method to perfectly balance the batteries.

Before getting to that, it should be pointed out that doing the calculation is not actually required in order to arrive at the ultimate interconnection method. I simply did them to show the magnitude of the problem.

In order to get a better balancing it is simply necessary to get the number of interconnecting links as close as equal between each battery and the final loads.

In the first example the power from the bottom battery passed through no interconnecting links. The top battery passed through 6 links.

In the 2nd example (the much improved one), the power from the top and bottom battery both passed through a total of 3 links. That from the middle 2 batteries also both passed through 3 links which begs the question “why were they not therefore perfectly balanced?”. The answer is that some of the links have to pass more total current and this therefore increases the voltage drop along their length.

And now we get to the correctly wired version where all the batteries are perfectly balanced.

Method 3

This looks more complicated.  It is actually quite simple to achieve but requires two extra interconnecting links and two terminal posts.   Note that it is important that all 4 links on each side are the same length otherwise one of the main benefits (that of equal resistance between each battery and the loads) is lost.   The difference in results between this and the 2nd example are much smaller than the differences between the 1st and 2nd (which are enormous) but with expensive batteries it might be worth the additional work. Most people (myself included) don’t consider the expense and time to be worthwhile unless expensive batteries are being fitted or if the number of batteries exceeds 8.

This method isn’t always so easy to install because of the required terminal posts. In some installations there is simply no room to fit these. So, thanks to a colleague, we can also present another wiring method that achieves perfect battery balancing.

Conclusion

I’ll be opting for method two, as its simple to install, and with the three batteries I’m opting for the difference in amperage between batteries will be somewhat lower than as above. Once installed I’ll take a few photos

Ok it has 500 potential recharge cycles at 70% usage, but running it flat I’m going to really deplete that potential and thus I’ve come to the conclusion that I need another two.

With three batteries in the boot, with about 300amp/h between them, I shouldn’t need to have to start the engine to apply a charge. The main car battery is disconnected by means of a relay; thus when the engine is off the batteries now in the boot are isolated from the rest of the car.

You might wonder, why not just run the engine? Well despite all my efforts of finding an ex police Range Rover, applying additional ferrite filters to a lot of the loom at some expense, there is still on 20 meters a lot of noise which no doubt is coming from the ignition.

I’ve recently purchased from high quality Magnecor HT leads which I’m hoping will reduce the problem. They are Silicone competition leads which promise “excellent RFI and EMI suppression”. Fingers crossed that coupled with some new spark plugs (well why not) the issue of RFI will be gone.

I also need to get a move on and find a way to mount the solar panel to the roof. I’m currently seeking a Expedition Roof Rack to enable me to mount it on. Being a 40watt job, it should address the issue of battery discharge when doing very little and keep everything primed without the need to remove the batteries and trickle charge them.

Basically where the vehicle is parked, its half sticks out of the underground car park. So it seems a shame to not make use of the light and charge it up not only when static at home, but also when on a beach or on top of some hill. It will hopefully ensure that whilst receiving at least, the amount of powering being used won’t exceed what the panel is generating (I wish).

Setup a YP3 Beam in a Bag on a Racal pneumatic mast.

Flex receive is fantastic, however the radio at times refused to transmit, not could the ATU match up. Despite the Antenna having a very good VSWR reading on the MFJ Analyiser.
Switched back to the Icom 706 which is on the dash, and made a good few contacts.

Will have to investigate why the Flex is temperamental

I decided on Com0Com as the virtual com port driver, thus downloaded it from http://com0com.sourceforge.net/

Installation went ok until I got up a nice message about unsigned drivers, similar to this:

(Note that’s not exactly the same error as the driver is different, but the message and problem are)

Basically in Windows Vista x64 you cannot allow unsigned drivers to be installed. Even using BCDEdit to allow unsigned drivers doesn’t work as Microsoft has applied a number of security patches to prevent it. The only way to do it, is to press F8 on window boot and select the option which allows for unsigned drivers.

I don’t want to be pressing F8 every time I reboot the computer, as after all its designed to be in the car and getting the keyboard each time will soon become tiresome. Luckily I came across ReadyDriver which lets you boot from a CD Image, USB Stick or Floppy and it basically presses F8 and selects the options for you. That said I dont want to boot from a CD or any other external device. A bit more research and I was sent a copy of ReadyDriver Plus which basically installs a bin boot image and extends the Windows Boot Manager to boot into it and does the rest for you.

I’ve uploaded version 1.1 of the software, as it got sent to me and I’m not sure where from.

http://www.2w1etn.com/wp-content/uploads/2009/06/SetupReadyDriverPlus.exe

I won’t even mention the £260 I had to pay in customs charges

Let’s hope that’s the only hitch I get. Looks quite tidy, I’ll do a full review when I get it all setup.

I got delivered the server for repair which had originally been donated by another Amateur. Formerly used as a rack mounted media server, no doubt to which it was very suited. But in terms of keeping something you want to maintain online for as close to 24/7 as possible then from the outset it was naturally the wrong choice.

Reading other repeater websites, it seems whilst groups have been forthcoming with funds for the ICOM hardware there has been a general over optimist approach to hardware dependability. Consider that in the first 4 years hard disks of server quality will fail at a rate of 10% a year. After 4 years this increases significantly year on year. Consider the user of lower quality, cheap consumer hard disks and you’re asking for trouble. The lack of any form of RAID on the original GB7CD installation was regrettable as without access to a working system or a backup of the user registered accounts you create yet more work for yourself when you come to reinstall the server.

Sticking in any form of cheap desktop computer with little more than desktop components even for a short time is pointless. You have to register users on it, do you really want to have to register them again if it fails a week later?
 

The Right Hardware

Quite frankly the number of people in Amateur Radio that are “experts” in computing never astonishes to amaze me. Before you decide to go build your own computer out of bits you have floating around, consider that you can obtain cheaply, maybe even free a quality rack mounted server 2 to 4 years old from many companies and corporations. On eBay even decent boxes are floating around for £150 to £400 with ample abundant parts should something go wrong. You might wonder why you obtain quality servers at prices cheaper than a comparable desktop. Its simple. Newer servers are more energy efficient. Imagine you are the Halifax bank and you have an installation of 1000 HP DL580’s; If you could replace those servers with hardware that’s maybe using 200 watts less and has more computing power, wouldn’t you drop the old ones too? 

What you’re looking for in server hardware is at least redundant disks and redundant power supplies. Depending on the server manufacturer and model you might have 2 to 3 power supplies all hot swappable. I’d suggest you have a spare sitting there in case one goes, reducing the time your machine doesn’t have a online spare. Notice I’m talking about keeping your box online for as long as possible. Surely that’s got to be the goal, and is it really justifiable to let the server fail for the sake of a few parts that together wouldn’t cost more than £50.

Cooling as with the RF side is important, hot swappable fans are generally the norm in server larger than the smallest 1U form factor, again keep a spare one or two so should a couple fail you don’t have to take it offline to protect the hardware.

Considering the low disk usage of the D-Star gateway software RAID 5 seems a bit like over kill. Opting for Mirroring with a hot standby seems more sensible, you should have improved read access and the ability to lose two hard disks.

Other options include getting servers with redundant ram and even redundant CPU’s. That’s where I drew the line, having a good pick of servers to chose from I did consider something like a HP DL580 with redundant RAM but it’s probably a bit overkill. I opted for an IBM x360. 2GB of ram installed and 4CPUs plus mirrored disks. I see no reason it won’t be running for the next 5 years without major problem. It needed before being installed on site a new FAN and a new Hard disk which were found for less than £50 for both on eBay.

Some pictures that might interest you:

I was getting a lot of messages like" link attempted while linking currently prohibited" in dplus.log resulting in the repeater not being able to connect. Rebooting would sometimes result in it working and enable the dplus functionality of being able to connect up the repeater to other boxes.

Robin AA4RC pointed out in an email that port 20001 UDP needs to also be open, which was sadly lacking from a lot of documentation.

At present the current ports are open which after seemed to cure the problem:
20001 UDP
20002 TCP
20002 UDP
20003 TCP
20003 UDP
20004 TCP
20005 TCP
40000 UDP
40001 TCP

Through eBay I’ve picked up 10 Motorola MRF150 RF Mosfets, some research on the web lead me to a number of projects specifically the amp of k0gkd, and it’s from his website I’m basing my project. I’ll be posting everything I discover whilst building it, so you should be able to replicate what I’ve done.

Amateur Radio is about more than just communicating. After all anyone can grab a copy of Skype, MSN Messenger or YIM and start chatting with new people. In my view the Internet has meant that people become Radio Amateurs for very different reasons than a large proportion did say pre 1998.

Despite the efforts of the governing bodies to reduce the technical standard and exam burden on new amateurs with the introduction of easier licensing requirements Amateur Radio as I see it has no choice and is already becoming more technical. The end goal may well remain the same for many Amateurs but today it’s not just about making contact its far more about how you make contact. Perhaps infact we are returning to far more original goals and objectives of experiments and developing new technology.

Amateur Radio in all reality started at the dawn of the 20th Centenary, with the 1920s the hobby developed into what we know today as Amateur Radio with the introduction of voice. Its directly through the efforts of Radio Amateurs that a lot of technology was developed and therefore made contributions to very differing industries.

Today we see Radio Amatuers from almost every country on world, the exception being the odd closed state. Women, Children and everything inbetween is welcome and can often be heard onair.

In many countries, amateur licensing is a routine civil administrative matter. Amateurs are required to pass an examination to demonstrate technical knowledge, operating competence and awareness of legal and regulatory requirements in order to avoid interference with other amateurs and other radio services.  Generally there are a series of exams available, each progressively more challenging and granting more privileges in terms of frequency availability, power output, permitted experimentation, and in some countries, distinctive callsigns. Here in the United Kingdom we have for some time began requiring a practical training course in addition to the written exams in order to obtain a beginner’s license, called a Foundation License.