[cjthomson]

Hi everyone

I'm a novice at this stuff so please pardon any ignorance on my part!

I'm considering building a weather station using WeatherDuino Pro2. At present I have an Auriol wireless weather station and will be starting off with the RX unit to capture the data from my existing setup.

I would like to add a TX unit later when I get round to changing the wind speed and direction sensors. I'm thinking about how I'm going to power a TX unit, I don't have power in the location in question so I'm thinking about using solar panel in conjunction with a 12v battery but I'm concerned about the lack of daylight during the winter months. Does anyone one have any recommendations about might be the best combination of solar panel and battery to use?

Thanks
Chris

[hornychz]

Does anyone one have any recommendations about might be the best combination of solar panel and battery to use?

Hi, Chris,

There is very nice thread about this problem:
http://www.meteocercal.info/forum/Thread-TX-Units-power

Believe me, it gets tedious, but the best for you, if you follow these instructions resource capacity own calculations. For it you need to know solar radiation in your country, good utility is for example:
http://www.efficientenergysaving.co.uk/s...lator.html

From my experience, I recommend battery LiFePo, which is admittedly expensive, but much better for that use (you can also start with an inexpensive Pb - components remain the same).

Good luck and Regards

[werk_ag]

From my experience, I recommend battery LiFePo, which is admittedly expensive, but much better for that use (you can also start with an inexpensive Pb - components remain the same).

Are you sure that LiFePo batteries are suitable to be used with conventional solar chargers? I think solar systems are more suitable for Pb batteries.

[cjthomson]

Does anyone one have any recommendations about might be the best combination of solar panel and battery to use?

Hi, Chris,

There is very nice thread about this problem:
http://www.meteocercal.info/forum/Thread-TX-Units-power

Believe me, it gets tedious, but the best for you, if you follow these instructions resource capacity own calculations. For it you need to know solar radiation in your country, good utility is for example:
http://www.efficientenergysaving.co.uk/s...lator.html

From my experience, I recommend battery LiFePo, which is admittedly expensive, but much better for that use (you can also start with an inexpensive Pb - components remain the same).

Good luck and Regards

Thanks very much for your reply, I will have a look through that thread - sounds like it may be helpful. Likewise for the solar radiation page.

Regards

[hornychz]

Are you sure that LiFePo batteries are suitable to be used with conventional solar chargers? I think solar systems are more suitable for Pb batteries.

Yes,

I'm definitely sure about using them in meteo stations, but not with cheep conventional solar chargers.

Their application range is much greater then Pb batteries (-30°C to +70°C) and service life > 10 years. After 8000 cycles they have still more then 80% capacity. They are much lighter (maybe to 1/3) and smaller then Pb batteries ... Their main advantage is that they have the same voltage as Pb and so will not change anything on the appliance or on the side of the solar panels.

But - they are still too expensive and need more expensive solar charger, for example:
12/24V solar charger
It costs about USD 40.

And LiFePo4 battery pack 12V/12Ah PCM costs about USD 100, for example:
LiFePo4 battery pack

I'm not using the LiFePo battery yet, but this year I want to implement them into my new TX box (bigger then the old one), because their capacity during the winter time in CZ (cold and without sun).

Best Regards

[werk_ag]

I wasn't aware of those solar chargers for LiFePo4 batteries. It sounds interesting.
Thanks for that info.

[hornychz]

Hi everybody,

Today a new LiFePo4 battery has arrived at me, so I've tryied to install it. It would be pretty easy if I really read the instructions to the controller (it has to be in a manual mode to open output



The battery 12V/12Ah is incredibly light, only 1.9 kg against 3.8 kg Pb. Dimensions is 151x101x98 mm, it's the same as Pb. It would endure for 10 years. The battery has built the balancer and needed protection in. The price in CZ is about USD 80 plus VAT from local distributor: LiFePo4 12V/12Ah PCM



The controller in using is WINCONG SL02A-20A, the price in CZ is about USD 35 plus VAT. (The cheaper SL02A-10A was for long time sold.) It's too from local distributor: WINCONG SL02A-A The dimensions are exactly the same as the budget MPPT controllers, ie. outside dimension is 133x70x25 mm, installation dimensions is 126x50 mm.



If there are in the field of solar panels more pieces, it is important to connected them parallel, so that the resulting voltage of only 18V. I have two panels GWL/Sunny Poly 20 Wp 36 cells (MPPT 18 V). (2x USD 18 + VAT from local)

And here is the final installation:



Regards

[cjthomson]

Hi Hornychz

This looks excellent and is along the lines of what I'm thinking about using when I get round to doing the TX side of things. I'm starting with the RX unit which will be working with my existing Auriol weather station. But I plan to change it out for something a bit better over at some point in the next couple of months.

I have decided that a setup of a 40 Watt solar panel, charge controller and either a 12ah or 15ah battery is probably what I need to get. The prices for the parts - especially the battery are better than what I'd seen for a LiFePo4 one.

Thank you for sharing this information, it's really helpful

Thanks
Chris

[werk_ag]

Hi Zdenek

Thanks for sharing your setup.
I think that a 12Ah to 16Ah battery is enough for almost all latitudes: The most important is the solar panel, which should be around 40 to 50 Watt. Such panel even during days without strong sunlight, can power the system and at the same time give enough charge to the battery, to compensate the consumption during the night.
I'm using a 14Ah Pb battery and a 50W monocrystaline panel, and never had a problem. Last year we had here in Portugal a harsh winter with several consecutive days without clear sun.

PS: Don't tell anybody, I'm still using an "old" TX v2.50 board.

[AllyCat]

Hi,

Thanks for that very useful information. But ...

I have decided that a setup of a 40 Watt solar panel, charge controller and either a 12ah or 15ah battery is probably what I need to get. The prices for the parts - especially the battery are better than what I'd seen for a LiFePo4 one.

I'm using a 14Ah Pb battery and a 50W monocrystaline panel, and never had a problem. Last year we had here in Portugal a harsh winter with several consecutive days without clear sun.

Hmm, I wonder if you (all) appreciate how much lower is the light level in "Northern Scotland" compared with Portugal (or even CZ). Not even considering the very "Grey" days (or even weeks) that we can get in UK, the daily "insolation" (from the link in #2) for Aberdeen (not the absolute north of Scotland) in December is 0.32 kW per day, for a 1 square metre horizontal surface (I believe a typical "200 watt" rated panel). Coresponding figures for Portugal and CZ appear to be 2.0 kW and 0.7 kW respectively.

Of course there is unlilkley to be much need for power to operate "aspiration" (a fan) and Werk's panel does seem very "generous" in size. Also, the PV panel can be tilted (facing south), but the best angle can be difficult to calculate, because the slope reduces the available power from the sky (when the sun is obscured by cloud).

Whilst I do agree that LiFePO4 is an excellent technology (which I intend to use for my own much lower-power project) I do wonder if the OP should start with a much simpler (and maybe larger) SLA battery, or a much more specific power-budget calculation. A SLA could be much easier (and cheaper) to increase in capacity if required, or just to receive a "boost" from a mains charger in mid-winter, if the solar charging proves inadequate.

Cheers, Alan.