Solar charge station

[ItsMinJunLol]

Hi! I want to power my laptop + phone off a solar panel. I have next to no knowledge about how to use solar panels. I just know that they generate energy by the sun, and they require some kind of rectifier to provide DC power. I am on a pretty tight budget of approx. 100$, in which I need a solar panel, something that allows me to use the solar panel's power to charge the 12 18650 2500 mah cells I'm planning to use and something that allows me to use the 18650 cell's power to power my laptop and stuff. I'm not sure what I need to use. I don't have any parts list or anything, but I know that I want at least 20,000 mah of storage, and approx. 75W of power. 

 

I will be using samsung's INR18650 25R cells, which I know they can comfortably provide me with 15-20A of current, which will be enough for me to power everything. (if calculations are correct, they can provide ~650W of power).

 

What else do I need? I'm pretty sure 99% won't understand what I just said (my writing skills are retarded) so I'll ask again. What do I need to build a solar charge station that can do AC? I will be using 12 INR18650-25R cells and I need approx. 75W of power coming out of the AC port + 3 USB 5v 2a ports. Please help me get a parts list. Thanks!

[knightslugger]

35 minutes ago, ItsMinJunLol said:

they require some kind of rectifier to provide DC power.

well you're wrong about that. they supply DC power right off the leads.

 

If you need to convert DC to AC, then you need an INVERTER. which usually comes off the battery and not the solar panel itself. you do need a battery in-between the panel and the inverter (or some sort of capacitor), and between the battery and the panel you need a charge controller, otherwise you run a very real risk of over-charging the battery. 

[Cyracus]

Well you need the solar panel, Last time I looked you could expect to get like a 30w panel for ~$100 you might be able to find more for less but didn't seem like something to bet on. You'd also need an inverter to go from dc to ac which will run you a fair bit of change, not sure you'll be happy with what $100 will get you, but well best of luck

[knightslugger]

well the good news is that you don't need a super high output panel as all the amperage will be drawn from the battery, not the panel. the panel is there to collect the energy, the battery is there to store it. while the battery is not being discharged, the solar panel will be replenishing any lost amperage.

 

If it's under constant load, THEN you need a high output panel or array, which will cost you in excess of $500. each.

[mariushm]

You'll need to pick the solar panel first.  Each panel has a different voltage and different maximum output ... for example the solar panel may advertise maximum 100 watts but in reality with no clouds at all and sun above the panel you may only get 80-85 watts. As the sun goes up and down, if there's clouds moving, the amount of energy will vary. 

So you need a circuit that can work with a wide range of input voltage and produce a steady voltage that satisfies the conditions required to charge lithium batteries.

 

Then, the next part is to either make some circuit which converts the voltage coming out of your batteries into AC voltage, or create a DC voltage the laptop expects , like let's say 19v

 

Your batteries will not be able to provide so much power.  Your laptop and laptops in general have have six of those batteries  inside the battery pack.

They take two at a time and connect them in parallel to get a battery that has twice the capacity, so your 3.6v .. 4.2v 2500mAh batteries become a single 5000mAh battery.  Then, they take these 3 sets of batteries and connect them in series to get higher voltage ... so 3 x 3.6v..4.2v =  10.8v to 12.6v at 5000 mAh

 

The batteries you mention are designed for power tools, which mean they're great for producing a lot of current for brief periods of time but the batteries are not designed to output a lot of power continuously.

Here's the datasheet : http://dalincom.ru/datasheet/SAMSUNG INR18650-25R.pdf

 

You can see there :

 

3.1 Nominal discharge capacity : 2,500mAh
				Charge: 1.25A, 4.20V,CCCV 125mA cut-off,
				Discharge: 0.2C, 2.5V discharge cut-off
3.2 Nominal voltage 3.6V
3.3 Standard charge		CCCV, 1.25A, 4.20 ± 0.05 V, 125mA cut-off
3.4 Rapid charge 		CCCV, 4A, 4.20 ± 0.05 V, 100mA cut-off
3.6 Charging time 		Standard charge : 180min / 125mA cut-off
				Rapid charge: 60min (at 25℃) / 100mA cut-off
3.7 Max. continuous discharge	(Continuous) 20A(at 25℃), 60% at 250 cycle

 

So what they're saying is that they're meant to be charged with a current of 1.25A  and discharge continuously at only 0.2C (charge current), or 0.2 x 2.5A = 0.5A

yes, they can discharge at up to 20A as long as you keep them cool (at 25c) but after 250 cycles of discharge and charge and usage in this behavior , the manufacturer says they estimate the batteries will hold only about 60% of their original capacity.  Since power tools aren't used often and they're usually charged at the end of the day or once every few days, it's not a problem that the capacity will drop after about 150-250 charges... they'll last more than their 1 year warranty.

 

For storing solar power and stuff, you don't want these batteries, you want batteries that are more optimized for higher continuous current.  For example, if you make a battery pack out of 3 sets of batteries in series and you want to power a laptop that uses a 65w laptop adapter, you'd need batteries that can provide a peak continuous current of 65 watts / 12.5v = ~ 5 A

So each set of batteries in the pack must be able to output 5A, or 2.5A per battery if there's two in parallel, or about 1.75a per battery if you have 3 in parallel and so on.

 

Compare them with Panasonic NCR18650A 2900mAh which can discharge at rated for 1c discharge instead of 0.2c :  http://industrial.panasonic.com/cdbs/www-data/pdf2/ACA4000/ACA4000CE254.pdf

 

 

[ItsMinJunLol]

8 hours ago, knightslugger said:

well you're wrong about that. they supply DC power right off the leads.

 

If you need to convert DC to AC, then you need an INVERTER. which usually comes off the battery and not the solar panel itself. you do need a battery in-between the panel and the inverter (or some sort of capacitor), and between the battery and the panel you need a charge controller, otherwise you run a very real risk of over-charging the battery. 

 

 

 

What do you mean? Don't I need a charging circuit that has overcharge protection to limit the charge volt+current and it will automatically stop charging at 4.2V?

8 hours ago, Cyracus said:

Well you need the solar panel, Last time I looked you could expect to get like a 30w panel for ~$100 you might be able to find more for less but didn't seem like something to bet on. You'd also need an inverter to go from dc to ac which will run you a fair bit of change, not sure you'll be happy with what $100 will get you, but well best of luck

 

 

 

I'm happy to spend a bit more but here in Indonesia, it's the cells and electronics that are expensive. Solar panels are fairly inexpensive. I can get this 50W panel for ~50$ LINK.

8 hours ago, knightslugger said:

well the good news is that you don't need a super high output panel as all the amperage will be drawn from the battery, not the panel. the panel is there to collect the energy, the battery is there to store it. while the battery is not being discharged, the solar panel will be replenishing any lost amperage.

 

If it's under constant load, THEN you need a high output panel or array, which will cost you in excess of $500. each.

 

Ok, how many watts of power do I need? I can get a decent amount of sunlight during the day. I'll probs only use this at night when the cells are charged.

8 hours ago, mariushm said:

You'll need to pick the solar panel first.  Each panel has a different voltage and different maximum output ... for example the solar panel may advertise maximum 100 watts but in reality with no clouds at all and sun above the panel you may only get 80-85 watts. As the sun goes up and down, if there's clouds moving, the amount of energy will vary. 

So you need a circuit that can work with a wide range of input voltage and produce a steady voltage that satisfies the conditions required to charge lithium batteries.

 

Then, the next part is to either make some circuit which converts the voltage coming out of your batteries into AC voltage, or create a DC voltage the laptop expects , like let's say 19v

 

Your batteries will not be able to provide so much power.  Your laptop and laptops in general have have six of those batteries  inside the battery pack.

They take two at a time and connect them in parallel to get a battery that has twice the capacity, so your 3.6v .. 4.2v 2500mAh batteries become a single 5000mAh battery.  Then, they take these 3 sets of batteries and connect them in series to get higher voltage ... so 3 x 3.6v..4.2v =  10.8v to 12.6v at 5000 mAh

 

The batteries you mention are designed for power tools, which mean they're great for producing a lot of current for brief periods of time but the batteries are not designed to output a lot of power continuously.

Here's the datasheet : http://dalincom.ru/datasheet/SAMSUNG INR18650-25R.pdf

 

You can see there :

 

3.1 Nominal discharge capacity : 2,500mAh
				Charge: 1.25A, 4.20V,CCCV 125mA cut-off,
				Discharge: 0.2C, 2.5V discharge cut-off
3.2 Nominal voltage 3.6V
3.3 Standard charge		CCCV, 1.25A, 4.20 ± 0.05 V, 125mA cut-off
3.4 Rapid charge 		CCCV, 4A, 4.20 ± 0.05 V, 100mA cut-off
3.6 Charging time 		Standard charge : 180min / 125mA cut-off
				Rapid charge: 60min (at 25℃) / 100mA cut-off
3.7 Max. continuous discharge	(Continuous) 20A(at 25℃), 60% at 250 cycle

 

So what they're saying is that they're meant to be charged with a current of 1.25A  and discharge continuously at only 0.2C (charge current), or 0.2 x 2.5A = 0.5A

yes, they can discharge at up to 20A as long as you keep them cool (at 25c) but after 250 cycles of discharge and charge and usage in this behavior , the manufacturer says they estimate the batteries will hold only about 60% of their original capacity.  Since power tools aren't used often and they're usually charged at the end of the day or once every few days, it's not a problem that the capacity will drop after about 150-250 charges... they'll last more than their 1 year warranty.

 

For storing solar power and stuff, you don't want these batteries, you want batteries that are more optimized for higher continuous current.  For example, if you make a battery pack out of 3 sets of batteries in series and you want to power a laptop that uses a 65w laptop adapter, you'd need batteries that can provide a peak continuous current of 65 watts / 12.5v = ~ 5 A

So each set of batteries in the pack must be able to output 5A, or 2.5A per battery if there's two in parallel, or about 1.75a per battery if you have 3 in parallel and so on.

 

Compare them with Panasonic NCR18650A 2900mAh which can discharge at rated for 1c discharge instead of 0.2c :  http://industrial.panasonic.com/cdbs/www-data/pdf2/ACA4000/ACA4000CE254.pdf

 

 

 

Thanks! That was super helpful. I was thinking of a 50w peak solar panel w those cells but now I think I need to change out those cells, but the problem is cost. 12 of the INR18650-25R costs the same as 4 NCR18650A. Not sure why. It should be the other way, but I guess Indonesia's pricing is just retarded. Is there anywhere I can cheap out? Thanks!

 

P. S. for me, the rated discharge rate won't matter as much because I will probs save up enough to replace all the batteries to a good one.

[mariushm]

That particular panel has the specifications :

 

Rated Max power (Pmax): 50w

Current at Pmax : 2.85A

Voltage at Pmax : 17.6v

Open Circuit Voltage 22.5v

 

That 50w is the theoretical maximum power the panel can provide (imagine it in a laboratory, with a "sun" a few centimeters above the solar cells with no fog, no clouds, nothing interrupting the light. In real world, you never get that much.

You are not at the ecuator where light would fall straight down on the solar cells, and during the day the angle on which light falls on the panel will change and affect the maximum power the panel can provide.

So in reality, expect that panel to provide between 15 watts and maybe 40 watts throughout the day.  With the brightness of the sun, the voltage value of the solar panel will also change, you won't always have 17.6v , the voltage may vary between minimum let's say 12v and maximum 17.6v depending on how bright is outside. 

 

Also, solar panels have a particular property that if you try to suck too much energy out of them (too much current), the voltage will drop and you won't be able to pull that energy out of them. For example, let's say it's cloudy outside and the solar cells output 30 watts  at 15v ,so a maximum current of   (30w / 15v = 2A) . If you try to consume more than 2A, the solar panel can't handle it and the output voltage of the solar panel will drop to let's say 14v and now you get 14v and let's say 2.1A , but not the same 30 watts, it would be slightly less.

So to get the ideal maximum output power, whatever you connect to solar panel must be smart enough to monitor how that voltage changes depending on how much power it takes ... for example, take 0,5A and check the voltage, everything's ok so go up to 1A , everything OK so go to 2A , everything's OK so try going to 2.5A ... ooops i see voltage dropped down if I try to "suck" so much current, so let's go back and limit ourselves to 2A because that's the best efficiency.

This is called "power tracking"

 

That particular panel would be more suited to be used with a power converter circuit that would convert that varying amount of energy and store it into a lead-acid battery like  regular 12v car battery (or a UPS or motorbike) etc. Such batteries will charge as long as the voltage they see is about 13.8-14.5v (for a 12v battery) , no matter the amount of current.  Lithium batteries are more difficult to charge, they should be charged with a constant minimum current (let's say 100mA) if you want them to last a long time so if the panel outputs a very low power (let's say under 10 watts) maybe you wouldn't even be able to charge the batteries, unlike with the classic heavy lead acid batteries.

 

Lead acid batteries are also able to output that amount of current you want for long periods of time (let's say 100 watts or 100w / 12 = 9 A of current) .. and for brief periods of time such batteries can output 30-50 A of current (that's how much a car pulls when you start the car)

[ItsMinJunLol]

2 hours ago, mariushm said:

That particular panel has the specifications :

 

Rated Max power (Pmax): 50w

Current at Pmax : 2.85A

Voltage at Pmax : 17.6v

Open Circuit Voltage 22.5v

 

That 50w is the theoretical maximum power the panel can provide (imagine it in a laboratory, with a "sun" a few centimeters above the solar cells with no fog, no clouds, nothing interrupting the light. In real world, you never get that much.

You are not at the ecuator where light would fall straight down on the solar cells, and during the day the angle on which light falls on the panel will change and affect the maximum power the panel can provide.

So in reality, expect that panel to provide between 15 watts and maybe 40 watts throughout the day.  With the brightness of the sun, the voltage value of the solar panel will also change, you won't always have 17.6v , the voltage may vary between minimum let's say 12v and maximum 17.6v depending on how bright is outside. 

 

Also, solar panels have a particular property that if you try to suck too much energy out of them (too much current), the voltage will drop and you won't be able to pull that energy out of them. For example, let's say it's cloudy outside and the solar cells output 30 watts  at 15v ,so a maximum current of   (30w / 15v = 2A) . If you try to consume more than 2A, the solar panel can't handle it and the output voltage of the solar panel will drop to let's say 14v and now you get 14v and let's say 2.1A , but not the same 30 watts, it would be slightly less.

So to get the ideal maximum output power, whatever you connect to solar panel must be smart enough to monitor how that voltage changes depending on how much power it takes ... for example, take 0,5A and check the voltage, everything's ok so go up to 1A , everything OK so go to 2A , everything's OK so try going to 2.5A ... ooops i see voltage dropped down if I try to "suck" so much current, so let's go back and limit ourselves to 2A because that's the best efficiency.

This is called "power tracking"

 

That particular panel would be more suited to be used with a power converter circuit that would convert that varying amount of energy and store it into a lead-acid battery like  regular 12v car battery (or a UPS or motorbike) etc. Such batteries will charge as long as the voltage they see is about 13.8-14.5v (for a 12v battery) , no matter the amount of current.  Lithium batteries are more difficult to charge, they should be charged with a constant minimum current (let's say 100mA) if you want them to last a long time so if the panel outputs a very low power (let's say under 10 watts) maybe you wouldn't even be able to charge the batteries, unlike with the classic heavy lead acid batteries.

 

Lead acid batteries are also able to output that amount of current you want for long periods of time (let's say 100 watts or 100w / 12 = 9 A of current) .. and for brief periods of time such batteries can output 30-50 A of current (that's how much a car pulls when you start the car)

 

Ok, so if I get one of these (solar panel monitor), most of my solar power issues will be solved? LINK

Also, I probably won't be using lead-acid batteries because I have a fairly small room that I do everything in. I believe lead-acid batteries create hydrogen gas, and I really don't want my room to turn into an explosive when I light up my soldering iron (I have a butane one).

[knightslugger]

1 hour ago, ItsMinJunLol said:

Ok, so if I get one of these (solar panel monitor), most of my solar power issues will be solved? LINK

Also, I probably won't be using lead-acid batteries because I have a fairly small room that I do everything in. I believe lead-acid batteries create hydrogen gas, and I really don't want my room to turn into an explosive when I light up my soldering iron (I have a butane one).

what you linked to is a charge controller, and it will be required to charge the battery. That it has an Ammeter built into it is a nice feature to have. however if you plan to use this all night long, you are going to need a lot of storage, and wet cell lead acid batteries offer the best Ah per Rp. a Deep cycle battery would be best. don't worry about hydrogen gas venting. you should be ventilating when soldering anyway, and the amount of hydrogen gas produced is very little to none. the accidents you hear about stem from over-volting the battery, which is mitigated by the charge controller.

[mariushm]

True. 

You can also get SLA batteries (SEALED lead acid batteries) which are sealed as the name says ... so they won't produce any gas. Commonly used in UPS products.

 

And, if you're so paranoid, there's also lead crystal batteries, which are slightly lower capacity than lead acid batteries (for the same volume), but they can handle more deep discharge-recharge cycles and they can be discharged to lower voltages compared to lead acid batteries (with lead acid batteries you don't want them to go below around 11v) without damaging them.

 

See http://leadcrystalbatteries.com/media/wysiwyg/NewDatasheets/12V/6_CNFJ-12.pdf

 

 

[ItsMinJunLol]

21 hours ago, knightslugger said:

what you linked to is a charge controller, and it will be required to charge the battery. That it has an Ammeter built into it is a nice feature to have. however if you plan to use this all night long, you are going to need a lot of storage, and wet cell lead acid batteries offer the best Ah per Rp. a Deep cycle battery would be best. don't worry about hydrogen gas venting. you should be ventilating when soldering anyway, and the amount of hydrogen gas produced is very little to none. the accidents you hear about stem from over-volting the battery, which is mitigated by the charge controller.

 

I guess I should get that controller, but another problem is that I also sleep in that room. I think I should get sealed ones or a deep cycle battery that you're talking about. Thanks for the help!

21 hours ago, mariushm said:

True. 

You can also get SLA batteries (SEALED lead acid batteries) which are sealed as the name says ... so they won't produce any gas. Commonly used in UPS products.

 

And, if you're so paranoid, there's also lead crystal batteries, which are slightly lower capacity than lead acid batteries (for the same volume), but they can handle more deep discharge-recharge cycles and they can be discharged to lower voltages compared to lead acid batteries (with lead acid batteries you don't want them to go below around 11v) without damaging them.

 

See http://leadcrystalbatteries.com/media/wysiwyg/NewDatasheets/12V/6_CNFJ-12.pdf

 

 

 

I'll probs get those. Are these the ones you are talking about? I think I can get these in my local ACE hardware. Also, quick question. How do these not have any hydrogen gas? Thanks for the help!

[knightslugger]

3 hours ago, ItsMinJunLol said:

I think I should get sealed ones or a deep cycle battery that you're talking about. Thanks for the help!

sure, but remember, you are going to need very large batteries to keep something going all night long, and remember that it's going to take a long time to recharge what you use the night before. I think it should be clear by now that what you want to do is not a $100 solution.

[ItsMinJunLol]

4 minutes ago, knightslugger said:

sure, but remember, you are going to need very large batteries to keep something going all night long, and remember that it's going to take a long time to recharge what you use the night before. I think it should be clear by now that what you want to do is not a $100 solution.

 

Hmm, I'll be charging my 2 10,000 mah powerbanks (usually at around 50% or 75%), mac air late 2015 and a samsung galaxy s7 edge. I think around 30,000 mah will do.

[knightslugger]

4 hours ago, ItsMinJunLol said:

Hmm, I'll be charging my 2 10,000 mah powerbanks (usually at around 50% or 75%), mac air late 2015 and a samsung galaxy s7 edge. I think around 30,000 mah will do.

remember they can only push as much voltage as they can balance. you need more voltage on the supply side than on the receive side to actually transfer electrons.

[mariushm]

Phones like Samsung Galaxy S7 edge can use fast charge or can do regular charge but at high current. By going with lead acid batteries, you could use a car charger (they have to work with anything between 11v and 30v ( because the car's voltage is usually around 12..15v) and charge your phone more efficiently and faster compared to charging it from power banks. It would be definitely more efficient than plugging your phone charger into an inverter that would be connected to your battery.

 

With regular lead-acid batteries it's also super easy to just add more batteries when you need by connecting them in parallel to the old ones. They aren't as sensitive as lithium batteries when it comes to charging them.

 

And last.. keep in mind that there are already a lot of inverters made for cars, campers and so on, basically they're designed to work from 12v and produce 110v or 230v, allowing you to power your laptop as if it runs from mains power.So you should be able to find an inverter quite cheaply, but my advice would be to not go for the cheapest you can find. Try buying one from a brand name if at all possible.

 

You linked to a 7Ah battery, those are regularly used for UPSes. If you're going this route, I'd recommend going with at least a 20Ah battery, but if you can only afford 12Ah that would be fine.