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Ross
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Posted: 16 March 2012 at 2:51pm | IP Logged Quote Ross

This question is to do with my power supply which runs my LPFM station. Currently using a solar set up, but after a couple of cloudy days the battery runs flat. Was thinking of also using a wind generator but don,t know how to connect wind and solar together. The solar goes through a regulator.
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RadioTech
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Posted: 18 March 2012 at 4:35pm | IP Logged Quote RadioTech

Hi Ross,

There's a few questions that need answering before a practical solution can be given.

1) How old is the battery or batteries you are using?
2) What type are they - SLA, deep cycle etc?
3) What capacity are the batteries?
4) How big is the solar panel in terms of power output?
5) What is the brand and model number of the solar regulator?
6) If you know it, what is the maximum current draw off the system?


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Ross
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Posted: 18 March 2012 at 11:45pm | IP Logged Quote Ross

The battery is a car battery. About 2 years old. 660 cca.
Solar panel is a 85 watt.
Regulator, controller is a Morning Star. Prostar 30. 15 amp.
Can,t tell you the draw off. There is a 1 watt trasmitter and 12 volt car stereo running off it.
Just wondering if I should have a deep cycle battery?
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RadioTech
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Posted: 20 March 2012 at 12:48am | IP Logged Quote RadioTech

Ok, problem #1 right there.

Car battery = no good. They are designed for starting cars. That is, they can provide a lot of current for a very short period of time.
They are no good at supplying small amounts of current over a long period.
You do indeed need a deep cycle battery.

Don't make the mistake of buying a second-hand one either unless you know its history and how old it is. Batteries have a limited shelf life and will fall in performance and output as the years go by.

Your panel should be big enough to hold the system up.

Best advice, buy the biggest deep cycle low maintenance battery your wallet can afford. As winter comes around, you will have less hours of daylight (especially on cloudy days) and the extra capacity in the battery means the system will cope better with these conditions.

I don't have the info to hand for your specific solar regulator but some need to be set depending on the type of battery that's connected to them, so check that when you go to replace it.


Edited by RadioTech on 20 March 2012 at 12:49am
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Ross
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Posted: 21 March 2012 at 3:35am | IP Logged Quote Ross

Thanks for the info. Will start looking for a battery.
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KiwiSongwriter
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Posted: 10 October 2012 at 2:53am | IP Logged Quote KiwiSongwriter

You should really be using 2 x deep cycle batteries wired in parallel, not just one. This will give you twice the amp hour current draw time, i.e total DC power supply will last twice as long in overcast conditions, therefore buying you plenty of time for the sun to reappear after adverse weather.

You also need to take into account the exact power draw of your system. I note your reply does not mention the power rating (watts) of the car stereo. Even with no speakers attached, the amplifier will still draw anything from  20 - 100 watt or more depending on make and model.

There should be no 'draw off' from current controller or power regulator itself, as it is supposed to be connected to the solar panel before the battery to prevent overcharging damage, or worse, excess gas accumulation and potential explosion.

Also, a Monocrystalline cell solar panel is the best type to use, and offers the best and most efficient solar power generation as opposed to PV cell panels

I have researched this topic extensively and will be installing a LPFM station in Marlborough after Xmas, high up in the hills with a view right over Blenheim city. Whole station will be 100% solar powered.

Hope this helps.


Edited by KiwiSongwriter on 10 October 2012 at 3:18am


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RadioTech
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Posted: 12 October 2012 at 1:44am | IP Logged Quote RadioTech

KiwiSongwriter wrote:
You should really be using 2 x deep cycle batteries wired in parallel, not just one. This will give you twice the amp hour current draw time, i.e total DC power supply will last twice as long in overcast conditions, therefore buying you plenty of time for the sun to reappear after adverse weather.


I disagree with the first part, because batteries wired in parallel do not share the charge equally.
One battery will always charge slightly more than the other. The battery with the lesser charge will never reach 'terminal voltage' and will get to the stage where it simply will not ever reach terminal voltage - i.e. it becomes compromised and won't deliver full potential to the load.

A better option is to use just one battery that has double the capacity of the original single batteries.
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KiwiSongwriter
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Posted: 12 October 2012 at 5:41pm | IP Logged Quote KiwiSongwriter

Yes you are 100% correct if only using one charge controller, perhaps I should have mentioned a separate voltage charge controller is needed for each battery i.e. 2 x charge controllers for a twin battery parallel wired installation. When you use a separate charge controller for each battery, the issue of un-equal charging does not exist. Controllers are not expensive either.

Deep cycle batteries are designed to be discharged down as much as 80%. Although these can be cycled down to 20% charge, the best lifespan vs cost method is to keep the average cycle about 50% discharge, even during prolonged overcast weather conditions. Even here in Marlborough with the 2nd highest average annual sunshine hours in NZ, I would not risk using one battery alone, as it could likely mean you are discharging deeper and therefore damaging your battery.

This is the primary reason one should consider using 2 x batteries instead of one to achieve more current reliably. It is the recommended method by all solar power experts worldwide. This is not to say you can't use only one battery. You can. But at what cost?

See, at this point we still don't know what Ross's true loading is, but I would suspect it will be 20 watts minimum + transmitter, say 21 watts p/hr. This calculates to 42.8 Amp Hours per day. Allowing for 24hrs broadcast transmission, 10 direct sunshine hours per day, 3 days backup power and 50% discharge depth, you would need a 'single' battery capacity of 250 amp hours (20 hour rated).

That is a very expensive battery, at around NZ$1,000.00. You would also need to upgrade to a 100w Solar panel for charging this battery. It's far cheaper to run two smaller capacity batteries in parallel, and be done with it.

You can do the calcs here: http://www.batterystuff.com/kb/tools/solar-calculator.html



Edited by KiwiSongwriter on 12 October 2012 at 5:42pm


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RadioTech
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Posted: 13 October 2012 at 4:57am | IP Logged Quote RadioTech

KiwiSongwriter wrote:
Yes you are 100% correct if only using one charge controller, perhaps I should have mentioned a separate voltage charge controller is needed for each battery i.e. 2 x charge controllers for a twin battery parallel wired installation. When you use a separate charge controller for each battery, the issue of un-equal charging does not exist.


Ok, now you have my attention... LOL.

If you have two batteries connected in parallel, and you have two charge controllers, how does each controller know which battery it is dealing with, as both batteries are connected together and will appear as one load.
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KiwiSongwriter
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Posted: 13 October 2012 at 4:47pm | IP Logged Quote KiwiSongwriter

LOL. Watch this video... http://www.youtube.com/watch?v=bfvLcTxgvzo

Go to approx 0:36 and watch from there. They are using ac charging, but the same principal applies. It's easier than you'd think. You then wire each controller to either a separate smaller solar panel for each battery, or you can parallel wire them both back to a single larger capacity panel.

Subject to frequency availability, there could be solar LPFM's springing up from every hillside around the country after this thread. Lol.


Edited by KiwiSongwriter on 13 October 2012 at 4:51pm


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Posted: 14 October 2012 at 2:21am | IP Logged Quote RadioTech

KiwiSongwriter wrote:
LOL. Watch this video... http://www.youtube.com/watch?v=bfvLcTxgvzo

Go to approx 0:36 and watch from there. They are using ac charging, but the same principal applies. It's easier than you'd think. You then wire each controller to either a separate smaller solar panel for each battery, or you can parallel wire them both back to a single larger capacity panel.



Right. Watched the video. The problem still exists. They showed charging the two batteries in parallel configuration, with ONE charger feeding both.

As per my post above, the two batteries will not charge equally in this configuration. One will charge slightly less than the other and will not reach full capacity.

Then they suggested separating the two, so you effectively are just charging each battery on its own - no problems there, except you now no longer have them in parallel.


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