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I want to buy my first solar panel and I have some questions


Alexander12
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Hello guys, I am a Swiss highschool student and I would like to buy a solar panel 100W, 12v.
I am very curious about this field and I really would like to use in the future 100% renewable energy.😊

So I need to go step by step and my first step is to buy a 100W/ 12v solar panel to can charge my laptop and my phone.So this solar panel is enough to charge a laptop right?

Here are my other questions:
For a 100W, 12V solar panel, do we need a charge regulator, a 12V battery, as well as a 300W voltage converter, from 12V to 230V (for example), to be able to charge a laptop ?

If the solar panel produces less than 12V due to little sunlight, does the battery not store anything anymore because it is a 12V battery or can it still store? If it does not store, that would mean in this case, that I should take a battery with a lower voltage such as 6V for example? Can it then store enough energy or is it “full” very quickly?
In this case, would that mean that the charge regulator and the voltage converter must also be able to accept 6V? How can I mesure the voltage of a battery?

How long does it take ~ for a 12v battery to be fully full without using it at all?

Also, I am not sure I understood everything about the inverter, which kind of inverter should I use for a 100W/ 12v solar panel? (I prefer the inverter than the DC power supply because it seems easier). Can it be like that if I want to charge my laptop? (Sorry it is written in french...)
20201123_180128.jpg

Also, so for the battery I have better to choose a 6v battery for my solar panel like this one?
20201123_180629.jpg20201123_180617.jpg
Or it isn't a good idea?
( I would like an inverter and a battery cheap but which work quite well even if they are not expensive, if it is possible)
Last question: How do you link several batteries together?
These are my main questions and I apologize for bothering you with them.
 
Have a nice day!🙂
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10 hours ago, Alexander12 said:

How can I mesure the voltage of a battery?

Most cheap PWM charge controllers have an LCD screen that can display voltage. Otherwise use a voltmeter or multimeter.

 

10 hours ago, Alexander12 said:

Also, I am not sure I understood everything about the inverter, which kind of inverter should I use for a 100W/ 12v solar panel? (I prefer the inverter than the DC power supply because it seems easier). Can it be like that if I want to charge my laptop? (Sorry it is written in french...)

The inverter pictured should be fine if you don't want to look for DC chargers. Your battery system voltage would need to be 12V. You can use two 6V batteries in series to give 12V but I would suggest you just get a 12V battery. In addition it is likely you could find car chargers for your laptop and phone that work on 12V if you don't want to use an inverter.

10 hours ago, Alexander12 said:

Last question: How do you link several batteries together?

You connect batteries in two ways, series and parallel. When connecting in series you add the voltage together e.g. 6V+6V =12V but the total current supplied by the batteries remains the same (i.e. the storage capacity will stay the same) e.g. if batteries are 12V 10Ah you will still only have 10Ah stored but at 24V. When connecting in parallel the voltage stays the same e.g. 6V||6V = 6V but the current supplied by each battery adds together so for the same voltage the amount of stored capacity adds together e.g. if batteries are 12V 10Ah you will have 20Ah stored but at 12V. See the examples below.
 

Series-Parallel-Series-Parallel-Connecti

 

9 hours ago, Vassen said:

It also depends on whether you want to only use your laptop during the day when the sun is out or after sunset as well.

To expand a little on this: power would effectively be taken straight from the solar panel if you are running during the day as long as the panel is producing power. If the panel is producing less power than the load is drawing the battery will "top up" what extra is needed. Only when your panel produces more power than the load would the battery charge.

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13 hours ago, Vassen said:

Yes, you will need a charge regulator because even though the sole panel says 12v, the actual voltage that it can supply is more like 15 to 22v. This will very quickly damage your battery and anything else you connect to it. 
if you are only planning to charge a laptop and phone, it’s better to try to get a 12v laptop charger and a car phone charger. It’s much better than trying to convert the 12v to 220v and then back down to whatever your laptop requires. The inverter uses some standby power which will just drain the battery unnecessarily. 

Okay, thank you very much for your reply!

But I am not sure I understood everything about the car phone charger? How do I know which one I need? And how does it work?

13 hours ago, Vassen said:

It depends on the size of the battery and the charge controller you have. The cheap pwm controllers are probably around 60-70 % efficient. The solar panel itself is not 100% efficient and will vary depending on the orientation of the panel compared to the sun.  A very simple calculation is 100w x 60% efficiency  = 60w. 60w at 12v = 5A. So a 12v 50Ah battery will need roughly 10 hours to charge. Bear in mind you have roughly 5 to 6 hours of good sun depending on or location. 

How do you know that it will take 10h to charge? Which calculation do you do?

 

13 hours ago, Vassen said:

Those batteries that you posted in your link will not be sufficient for your load. 
 

So I have better to use this kind of battery?

 

20201124_131826.thumb.jpg.bc5a681339aa6b712c1bbffc7dc6d04c.jpg20201124_131914.thumb.jpg.91942b210dbf9448224059e4121b1c6e.jpg

It has 60Ah.

And so which device do I have to use to know how much energy my battery has and when I am bellow 50%?

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4 hours ago, Shadders said:

You connect batteries in two ways, series and parallel. When connecting in series you add the voltage together e.g. 6V+6V =12V but the total current supplied by the batteries remains the same (i.e. the storage capacity will stay the same) e.g. if batteries are 12V 10Ah you will still only have 10Ah stored but at 24V. When connecting in parallel the voltage stays the same e.g. 6V||6V = 6V but the current supplied by each battery adds together so for the same voltage the amount of stored capacity adds together e.g. if batteries are 12V 10Ah you will have 20Ah stored but at 12V. See the examples below.

So I guess it is better to have 6v but 20Ah right? Because I can store more energy?

 

4 hours ago, Shadders said:

Most cheap PWM charge controllers have an LCD screen that can display voltage. Otherwise use a voltmeter or multimeter

So thanks to this device I can know how much "full" in % my battery is?

Thanks again for your very well explained answers!

 

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49 minutes ago, Vassen said:

the charge controller normally has a screen that will tell you the voltage. For these batteries, the capacity is based on the measured voltage. So you will need to check what the safe voltage is when it's 50% discharged. It needs to unfortunately be done manually as far as i know but im not 100% sure about this. Its only the expensive controllers that can automatically switch off. 

Okay thanks, but it shows you the % or you have to figure out alone? Like with ...volts would I be at 50%?

 

 

50 minutes ago, Vassen said:

that connects directly onto the 12V battery. 

And so I can put this charger directly in my laptop, like I don't need anymore the charger I am using now or I still need it?

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2 minutes ago, Vassen said:

No, it will just show you a Voltage and you need to calculate based on that. Remember, this is the cheapest possible way we can do it. If you want to automatically shutdown, then you need the more fancy inverters... but then your costs and equipment needed becomes a lot more. 

Okay thanks. How can I calculate it? Is it like you explained before?

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On 2020/11/24 at 7:20 PM, Vassen said:

You could use something like this. It will at least show a red led when battery is low

Normally on these, at least on the cheap chinese Juta ones, it will automatically cut the power to the load terminals when the battery is low. On the Juta ones with an LCD screen you can program at what voltage this happens at.

 

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15 minutes ago, Shadders said:

Normally on these, at least on the cheap chinese Juta ones, it will automatically cut the power to the load terminals when the battery is low. On the Juta ones with an LCD screen you can program at what voltage this happens at.

 

Okay thanks and generally it is like at 12.2V, but it depends? And generally when it is like at 12.6V it is fully charged?

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For lead acid batteries those are decent operating voltages yes. I've tried to find the data sheet to see what the Varta recommended values are but could not find it. The Varta LFD60 has a life span of 200 cycles @ 50% discharge (if you do 1 cycle a day that's less than year) so it's not really designed for regular deep discharges. It will be a decent start though.

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Just now, Shadders said:

For lead acid batteries those are decent operating voltages yes. I've tried to find the data sheet to see what the Varta recommended values are but could not find it. The Varta LFD60 has a life span of 200 cycles @ 50% discharge (if you do 1 cycle a day that's less than year) so it's not really designed for regular deep discharges. It will be a decent start though

Clarification to the above: a fully charged battery would be around 12.6-13.2V under no charging or load. You normally would charge them at a voltage of 14.2V to 14.6V during cyclic use depending on what the battery manufacturer recommends.

 

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On 2020/11/24 at 2:27 PM, Alexander12 said:

So I guess it is better to have 6v but 20Ah right? Because I can store more energy?

No, you have the same amount of energy in both systems. If you have a constant load of 10W at 6V you will be drawing 10/6 = 1.67A but at 12V you will be drawing 10/12=0.83A and if you do the mathematics you will get 12hours on both systems.

Higher voltages are used to reduce losses by decreasing the current. If you go through your formulae to calculate power you get P=I^2*R and the resistance would be a constant dependent on your cable so the power lost as heat in a cable is heavy affected by the current flowing in it. If you reduce your current by a factor of 2 you reduce the power lost as heat by a factor of 4!

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21 minutes ago, Shadders said:

For lead acid batteries those are decent operating voltages yes. I've tried to find the data sheet to see what the Varta recommended values are but could not find it. The Varta LFD60 has a life span of 200 cycles @ 50% discharge (if you do 1 cycle a day that's less than year) so it's not really designed for regular deep discharges. It will be a decent start though.

Okay thanks, so I should think for something else because I would like to have this battery for at least 2 years. (By using it every day)

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6 minutes ago, Shadders said:

No, you have the same amount of energy in both systems. If you have a constant load of 10W at 6V you will be drawing 10/6 = 1.67A but at 12V you will be drawing 10/12=0.83A and if you do the mathematics you will get 12hours on both systems.

Higher voltages are used to reduce losses by decreasing the current. If you go through your formulae to calculate power you get P=I^2*R and the resistance would be a constant dependent on your cable so the power lost as heat in a cable is heavy affected by the current flowing in it. If you reduce your current by a factor of 2 you reduce the power lost as heat by a factor of 4!

So with a 12v battery there is less losses because it is higher?

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