Has anyone ever used solar?

[Elopid]

Hey everyone, I'm quite interested in setting up a solar powered low power transmitter with a large 12v leisure battery and a 12v timer. Has anyone ever done anything like this with solar or a self-powered transmitter set up?

[sinus trouble]

Hello mr elopid
Ive often thought of that same idea? solar cells are very pricey and then youd need some sort of intelligent charger system to add!
In theory it can be done? 24hr operation would require you to take into account the ampere hour of your battery, current consumption of your rig and efficiency of charging based on roughly 12 hour intervals?
Being that we are in the uk? and not sunny spain? charge times will vary considerably!

[sinus trouble]

As an example!
If you have a 12v 3Ah battery? and your rig consumes 1Amp? you will be on air for around 3 hours!

[thewisepranker]

You can get 20 W solar panels from eBay for £25, item no. 262142115108.

This would be ideal for running weekends and charging throughout the week, plus a nice little top-up each running day too.

[Xerox]

Hi this is a very interesting topic for me. As i live in Italy where there are know tower blocks. And the two high blocks that there are in my area i cannot get keys for even off the firemen. I wanted to link to one of the mountains with a. Band 1link n run around 20 watt. Only weekends from 5 oclock through the night. Runnin a pirate is more risky here and is more less unheard of. Ok theres operaters on shortwave but no FM. I had same idea with panels as we have a lot of sun here. Although life was a lot easier back in Birmingham. I lost a tx last week from using the mast of a commercial station so i need another solution.

[thetufparker]

out of interest would a 10ghz link work with a battery - how would it act with the voltage drop over time?

[Maximus]

As an example!
If you have a 12v 3Ah battery? and your rig consumes 1Amp? you will be on air for around 3 hours!

Not necessarily, that's the complete discharge of the battery so there would be a considerable voltage drop.
As a general rule, I'd say it'd reliably do half of that time.

Also it's not healthy to deep discharge certain types of batteries.

You'd also need to double up on the panel power as when there is daylight, they'll have to recharge the batteries as well as power the transmitter. This is assuming that you have perfect conditions with plenty of sun and barely any clouds.

For lower powered applications it'll work fine but if you're going above 150w+ tx output then expect to spend a few £££.

The only worry I've had is people nicking the gear as a few 200w panels aren't cheap to keep replacing.


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[Maximus]

out of interest would a 10ghz link work with a battery - how would it act with the voltage drop over time?

Yes if you use one of those voltage stepper uppers. They have 12v in and 24v out. Use one of those and feed the 24v output into a 12v regulator.


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[thetufparker]

nice!

[sinus trouble]

As an example!
If you have a 12v 3Ah battery? and your rig consumes 1Amp? you will be on air for around 3 hours!

Not necessarily, that's the complete discharge of the battery so there would be a considerable voltage drop.
As a general rule, I'd say it'd reliably do half of that time.

Also it's not healthy to deep discharge certain types of batteries.

Mr Maximus is spot on!
My example was a rough guide to show Ah ratings versus consumption, i would defo recommend being very generous with the battery capacities!
With out breaking your bank balance! Lol!

[Elopid]

Thanks for answers, I've never tried this but in the summer time it's something I'd like to do.
I'm thinking of placing a solar panel as high up a tree as possible and putting that thick green army netting below it with thick leaves etc so it can't be seen from the ground. I have a 120amp battery and the transmitter is 15w adjustable power.
Would there be enough sunlight to charge through the week and run on the weekend but switching off during the early hours to save power? Roughly how long would a 20w panel take to charge a large battery like this? Thanks everyone

[thewisepranker]

It depends on how deeply discharged the battery is after a weekend on the timer.

Let's assume that your rig draws 2.5 A at 15 W output. I'll be conservative and assume that that current is at 13.8 V. This is 34.5 Wh.

Let's also conservatively assume that your battery has a total of (10.8 * 120) = 1296 Wh available. 10.8 V being the absolute minimum voltage before damage occurs.

This gives you around 37.5 hours at that discharge rate. It's not quite so simple in practice due to the nonlinear voltage over time, but it'll do.

In order for the system to work continuously, week after week, the solar cell must replenish in around 5 days, the amount of power, in Wh, that the rig uses in roughly two and a half days.

Let's say that the solar panel can output 20 W for 8 hours a day, that's 160 Wh. 5 days will provide 800 Wh.

Assume times over the weekend will be 8PM-2AM, 2PM-2AM and 2PM-2AM. This is a total of 26 hours and will consume 897 Wh - there is clearly a shortfall, however these are very pessimistic numbers. This may work in practice due to more accurate and realistic numbers... I've had to use the word "assume" lots.

[sinus trouble]

Mr Pranker pretty much summed it up!!
I suggest you do some experimenting and get some concrete figures before even thinking of installing the rig!
You could start by fully charging your battery, connect your rig and measure the load, voltage and output of the rig over a period of time!
Once you have all the data? Then you can then select a suitable charging system and solar cell to support it!
Good Luck my friend!

[Albert H]

Way back in the mists of time, I had a link repeater of about 1 Watt output on Band IV using a TV Yagi for some forward gain. It was built in a "Tupperware" box to keep the rain off, and powered with a lead-acid battery at about 13.5V. The battery was charged with a small solar panel and a little wind turbine. It was used continuously for about 5 years! The most difficult parts of the job were getting up the tree to install it all (we borrowed a cherrypicker!) and building the battery monitoring / charging / stabilisation circuits!