Hi All,
Just to confirm that I put the repeater back on again at approx., 5:30 pm on Saturday evening, 30th.
All the batteries had been back at home being recharged and cycled, etc. All appeared to be holding a charge.
For those who have sent e-mails asking various questions, I'll attempt to answer them here. Thanks for your interest.
1. Why 24 volts and not 12 volts.
Well. All the kit runs from 12 volts, just like your 2m mobile rig. Most deal with 13.8 volts +/- 10% without too much trouble, but don't like it much when they start to see 11 volts or so.
By using a 24 volt system we can use a dc to dc converter, which can deal with a 17 volt to 32 volt swing in input voltage, and still hold a 13.6 volt stabilised output, at up to 24 amps continuous.
Using 24 volts also means that we are generating the power we need at a much higher voltage, and lower current. Easier to overcome voltage drop in the long run of cable between the turbine and the battery / converter system. The system is more efficient, overall.
2. Why 12 volt batteries and not 24 volt batteries.
Yes, as most of you concluded, PRICE.
However, physical size and weight also comes into it.
The two primary batteries are 12 volts @ 250 AH deep discharge leisure batteries, and two people can just about manage a short distance lift. I dread to think about trying to move a single 24 volt @ 250 AH Battery !!!!!!
3. The dc to dc Converter.
Yes, it's a real PWM converter, not just a linear series 24 volt to 12 volt dropper.
The unit employed is a PV24s - see Alfatronix web site.
4. Current System.
The above three points should give you a good idea as to the system, as far as the output of the dc-dc converter, at nominally 13.6 volts, which feeds the repeater.
There is another stage, which provides support at 12 volts. This having been put in when the panel was stolen.
I had been rebuilding this system, whilst the repeater was off air.
The simplistic system is 2 x 12 volt @100 AH, Gel batteries, which are connected into the 13.6 volt supply to the repeater, via a simple steering-diode network.
When the output of the dc-dc converter is there, it feeds current to the repeater and floats the 12 volt batteries, via isolating diodes.
If the output of the dc-dc converter falls below the terminal voltage of the 12 volt battery, then current is supplied to the repeater from the 12 volt battery.
The output from the dc-dc converter is therefore isolated, by a reverse biased diode and only the nominal dump-load / regulator control system current (approx., 100mA) continues to be drawn from the 24 volt system.
Thus giving the 24 volt system a chance to recharge a bit before it takes over the system again.
Hopefully that makes sense.
As I said, it is a very simplistic system, and could well be enhanced into something more robust.
Hopefully when the SP is replaced and the system is more or less back to full normality, the full technical group will get their collective heads together, and modify / replace, as they see fit.
5. Solar Panel.
Yes, this has taken quite a while to sort out, and NO, I'm not going into the details here.
However, I am anticipating a cheque to drop onto my door mat, anytime soon. I guess, in insurance company lingo, that means that it could be another 6 months .... Hi Hi.
Anyway, as soon as it arrives, have not doubt that we shall be hot-footing it to the PV supplier for a replacement panel.
That means that The technical team will then have to make a final decision about mounting method and location.
6. Current Operation.
Since returning the repeater to operation on Saturday afternoon, I have been back to the site both yesterday, and this morning to check battery and system voltages. All appears to be OK.
I will not have a hence to go back again tomorrow, but will take another look on Wednesday morning.
The system is operating at its nominal levels.
Finally, thanks to all who have offered suggestions and thanks for the effort that myself and others put into GB3JB. It is nice to know that our efforts are appreciated.
Cheers & 73's
Dave, G3ZXX
