My first project - Solar power computer....I need your help
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Kellez
Registered Users Posts: 21 ✭
Hello everyone, as you can see i am new to this forum and new to solar power as well. I have done some research on off-grid PV systems but i have not done any project of my own yet. Therefore this is the reason i am here today, i have decided to build my own off-grid PV system to power my desktop computer. However I am not planning to use this system to power my computer all year round but just for testing...I mostly want to get familiar with these systems and gain the required knowledge so that in the future i can build a larger system, and mostly to understand the costs behind PV systems.
Ok these are the requirements
computer specifications
Computer energy consumption: 115Wh
Operating time: 1 hour (since this is only for testing)
Computer voltage requirements: 240V AC
and this is what i am planning to use for the PV system
PV panel properties
28 cells @ 3.9W per cell = 109.2 Watt panel
28 cells @ 0.5V per cell = 14V panel
Battery sizing
The battery is sized for 1 hour computer operation per day and i would like to use a 12V battery and use an inverter to convert this to 240V AC
115Wh x 1h = 115Wh/day
Therefore the capacity of the battery is:
C = W/V = 115Wh/12V = 9.6Ah
I then double this so that i only discharge the battery at 50%
therefore
C = 2 x 9.6Ah = 19.2Ah => say 20Ah
Solar radiation
Ok now for this example lets use the irradiation value for my country in January that is the lowest: 2.78 kWh/m2/day
So with a 109.2W panel energy generation for one day is 109.2W x 2.78 kWh/m2/day = 303.5Wh
Therefore this states that i am able to run my computer for one hour each day and even more hours if my battery has the right capacity.
This is how far i have reached and i am not really sure if what i have done above is correct, please let me know if you see any crazy mistakes.
Assuming the above is correct now i need your help to decide on the size of my inverter and charge controller. Is it ok to use a 10A charge controller and a 200W inverter and how to i calculate this?
Also i want to use a pure sine wave inverter so that i do not damage my computer, i have read that if a modified sine wave inverter is used the computer can get damaged.
Thank you everyone for your time.
Ok these are the requirements
computer specifications
Computer energy consumption: 115Wh
Operating time: 1 hour (since this is only for testing)
Computer voltage requirements: 240V AC
and this is what i am planning to use for the PV system
PV panel properties
28 cells @ 3.9W per cell = 109.2 Watt panel
28 cells @ 0.5V per cell = 14V panel
Battery sizing
The battery is sized for 1 hour computer operation per day and i would like to use a 12V battery and use an inverter to convert this to 240V AC
115Wh x 1h = 115Wh/day
Therefore the capacity of the battery is:
C = W/V = 115Wh/12V = 9.6Ah
I then double this so that i only discharge the battery at 50%
therefore
C = 2 x 9.6Ah = 19.2Ah => say 20Ah
Solar radiation
Ok now for this example lets use the irradiation value for my country in January that is the lowest: 2.78 kWh/m2/day
So with a 109.2W panel energy generation for one day is 109.2W x 2.78 kWh/m2/day = 303.5Wh
Therefore this states that i am able to run my computer for one hour each day and even more hours if my battery has the right capacity.
This is how far i have reached and i am not really sure if what i have done above is correct, please let me know if you see any crazy mistakes.
Assuming the above is correct now i need your help to decide on the size of my inverter and charge controller. Is it ok to use a 10A charge controller and a 200W inverter and how to i calculate this?
Also i want to use a pure sine wave inverter so that i do not damage my computer, i have read that if a modified sine wave inverter is used the computer can get damaged.
Thank you everyone for your time.
Comments
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Re: My first project - Solar power computer....I need your help
Welcome to the forum.
Before anyone goes crazy let me point out that you are in Cyprus where the power standard is 240 VAC 50 Hz. I imagine you use the European standard 230 VAC equipment though (they have quite a broad tolerance range for that 'standard').
Well you've missed a couple of finer points on the sizing, so let's check it out.
It would be good if you could measure the computer's actual power usage. I suspect the 115 Watt hours is based on the power supply specs saying "115 Watts". How much it really uses is probably lower, possibly higher; computers use varying amounts of power depending on what they are doing at the time.
But let's go with 115 Watt hours. Now that's AC and inverters aren't 100% efficient so on the DC side the power consumption will be higher. Based on 90% efficiency it will be 128 Watt hours. Then the inverter itself has some draw, depending on what size it is. A small one like the Morningstar 300 will run the computer and use only 6 Watts to do it. Now your total power consumption from the battery is 132 Watt hours.
Divide by nominal 12 Volts and you get 11 Amp hours used. It is usually best to go with 25% DOD so that's 44 Amp hours. Batteries don't come in every size you want so you have to adjust that to what's available, preferably rounding up. Around here that would be a 50 Amp hour 12 Volt AGM.
Now for recharging it. If you went with 50% DOD you'd need twice as much panel to recharge with because of having to bring up the battery from a lower SOC in the same amount of time requiring a higher charge rate. So let's stick with the 25% DOD 50 Amp hour battery.
You want a peak current around 10% of capacity, or 5 Amps. Very easy to achieve. One panel will do it, and it doesn't have to be very big; about 88 Watts @ 17.5 Vmp. Once again you can't get panels in any size you want, so you either have to settle for a little less charge rate (85 Watt panel 4.8 Amps) or a little more panel (130 Watt panel 7.3 Amps). Around here the 130 Watt is actually cheaper, and the AGM could take the higher current without any problem. Of course you'll need a 10 Amp PWM type charge controller.
I can give you an equipment list for this set-up but that may not do you any good as it really depends on what's available where you are. -
Re: My first project - Solar power computer....I need your help
Welcome to the forum Kellez,
Your calculations and numbers are correct in the "ideal" world. In the real world, there are some issues.
First, you want to discharge the battery at a C/2 hour rate (fully discharging the battery to "dead" in 2 hours)--Flooded cell batteries really only like to be discharged at a C/8 hour rate, or at most, a C/5 discharge rate.
Also, the faster you discharge a battery, the less apparent capacity (a battery discharged at C/20 rate may appear to have a 100 AH capacity, a lead acid deep cycle storage battery discharged at C/2 rate may have an apparent capacity of 60 AH or less).
So--You have two choices, either get a larger battery to drop the discharge rate to C/8 - C/20, or change the battery type. AGM type Lead Acid batteries can be discharged at a much faster rate... Or looking at the various types of Lithium Ion chemistry type batteries (lots of choices, and you get into the whole "Battery Management System" electronics--Some/most Li-Ion battery types need a per cell voltage monitoring/charging adjustment circuit to prevent over/undercharging and damage/battery failure).
And there are two calculations we make when sizing a solar array to battery bank. The first is that there is enough charging current to properly recharge the battery bank based on AH capacity (5% to 13% rate of charge typical). And second is based on the Watt*Hours (or Amp*Hours) you use per day and the amount of sun you get.
The fact you used the "worse" average hours of "noon time equivalent" sun per day is fairly conservative--This is "average" weather--Those values can be +/- 10% over long term average, and day to day, you can have a few days or even a week+ of bad weather where the solar energy is only 5% of system capacity (dark days). So, you either have to be able to turn off the loads during poor weather or have a backup power source (typically a small AC genset).
There are options out there--But you need to pick the correct battery/system to match your needs.
Next, there are other losses--AC inverter conversion losses, battery charging/discharging losses, solar panels+charge controller derating+controller losses, etc... For a simple lead acid solar power system, roughly the end to end efficiency (solar panel to charge controller to battery to ac inverter) works out to be around 52%--Yep, you get only 1/2 of the "rated" capacity of your system.
So, what would a flooded cell lead acid battery system look like? Roughly, the calculations would look like:- 115 Watt* 1 hour per day = 115 Watt*Hours per day
- 115 WH * 1/0.85 AC inverter eff * 1/12 volts * 2 days of storage * 1/0.50 max discharge = 45 AH @ 12 volt battery bank (long life, good battery capacity for load balance)
- 115 Watts * 1/0.85 inverter eff * 8 hour discharge rate * 1/12 volt battery bank = 90 AH @ 12 volt minimum based on loads
To continue with the calculations using Flooded Cell... First need to size the solar array to battery bank AH capacity. Nominally, we recommend 5% minimum rate of charge (for good battery health) and "low usage system" (emergency backup, use system at weekend/seasonal cabin) to 13% rate of charge (full time off grid, used daily, maximum "cost effective" solar array for typical applications).- 90 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 85 Watt array minimum
- 90 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 169 Watt array nominal
- 90 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 220 Watt array "cost effective" maximum
- 115 WH per day * 1/0.52 system efficiency * 1/2.78 Hours of sun per day (winter minimum average) = 79 Watt array minimum
- 169 Watt array * 0.52 system eff * 2.78 hours of sun winter day = 244 WH per day
There are ~28 cell panels sometimes out there--But this is from the "olden days" where people wanted "self regulating" panels to charge batteries without a battery charger. Today, we always use battery charge controllers as this is more efficient and will give you better battery life/more energy (overall) from your system.
Next, the "other losses". AC inverters, even small ones, take something like 6 watts just to "turn on". If you had an AC inverter to supply your 230 VAC power that you left running 24 hours per day (did not turn off the DC power to your inverter when the AC was not required)--You would have to add:- 6 watts * 24 hours = 144 Watt*Hours per day to your load calculation
Anyway--Those are the basics. Not to say my design is "perfect" and the only answer--But it is a starting point for a reliable system that should give you many years of use with minimum maintenance/surprises.
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Re: My first project - Solar power computer....I need your help
Thank you guys, really appreciate the time you give on this, wow there's lots of info going around. I need some time to go over your replies and think the whole project all over again but i guess i will just get a bigger battery capacity since i am stack with the 3.9W cells.
I just checked my cells today and they produce 0.57V which is the value they are rated at, tho means that i can build my panel using only 32 cells instead of 36. I also tested the amperage and it was only at 2.0W. are the cells overrated (rated at 3.9W) or is it just because i am not getting ideal test conditions? -
Re: My first project - Solar power computer....I need your help
Yes the 115W computer rating is at maximum CPU usage. I will also get a digital electricity meter to check the energy consumption.
From your third comment i understand that discharging the battery is not the main issue here, the only think you have to worry about is the percent of DOD......also what exactly is AGM????
therefore the main objective here is to achieve the ideal conditions for recharging the battery, i see the two panels you suggested however i have already purchased some poly cells rated at 3.9W each with 0.57V. This means that i am forced to use 32 cells to get a system of 18.24V which then gives me a 124.8W system....do you think this is a good choice of panel?
Also please do give me the equipment list of the above set-up
in addition please explain to me how to calculate the amperes required by the charge controllerCariboocoot wrote: »Welcome to the forum.
Before anyone goes crazy let me point out that you are in Cyprus where the power standard is 240 VAC 50 Hz. I imagine you use the European standard 230 VAC equipment though (they have quite a broad tolerance range for that 'standard').
Well you've missed a couple of finer points on the sizing, so let's check it out.
It would be good if you could measure the computer's actual power usage. I suspect the 115 Watt hours is based on the power supply specs saying "115 Watts". How much it really uses is probably lower, possibly higher; computers use varying amounts of power depending on what they are doing at the time.
But let's go with 115 Watt hours. Now that's AC and inverters aren't 100% efficient so on the DC side the power consumption will be higher. Based on 90% efficiency it will be 128 Watt hours. Then the inverter itself has some draw, depending on what size it is. A small one like the Morningstar 300 will run the computer and use only 6 Watts to do it. Now your total power consumption from the battery is 132 Watt hours.
Divide by nominal 12 Volts and you get 11 Amp hours used. It is usually best to go with 25% DOD so that's 44 Amp hours. Batteries don't come in every size you want so you have to adjust that to what's available, preferably rounding up. Around here that would be a 50 Amp hour 12 Volt AGM.
Now for recharging it. If you went with 50% DOD you'd need twice as much panel to recharge with because of having to bring up the battery from a lower SOC in the same amount of time requiring a higher charge rate. So let's stick with the 25% DOD 50 Amp hour battery.
You want a peak current around 10% of capacity, or 5 Amps. Very easy to achieve. One panel will do it, and it doesn't have to be very big; about 88 Watts @ 17.5 Vmp. Once again you can't get panels in any size you want, so you either have to settle for a little less charge rate (85 Watt panel 4.8 Amps) or a little more panel (130 Watt panel 7.3 Amps). Around here the 130 Watt is actually cheaper, and the AGM could take the higher current without any problem. Of course you'll need a 10 Amp PWM type charge controller.
I can give you an equipment list for this set-up but that may not do you any good as it really depends on what's available where you are. -
Re: My first project - Solar power computer....I need your helpThank you guys, really appreciate the time you give on this, wow there's lots of info going around. I need some time to go over your replies and think the whole project all over again but i guess i will just get a bigger battery capacity since i am stack with the 3.9W cells.
I just checked my cells today and they produce 0.57V which is the value they are rated at, tho means that i can build my panel using only 32 cells instead of 36. I also tested the amperage and it was only at 2.0W. are the cells overrated (rated at 3.9W) or is it just because i am not getting ideal test conditions?
You're building your own panel? Okay there's a few problems with that. One of them being that the cells you buy on the Internet tend to be one rejected by companies for not meeting specs, including shunt resistance.
Figure 0.5 Volts per cell under load; the 0.57 reading you got would be Voc which doesn't reflect actual power output. Therefor a 32 cell panel would be 16 Volts, which can be too low for a 12 Volt system. When the panel heats up (and this does not mean 'is used in desert temperatures') the Voltage goes down. More Voltage will be lost in the wiring. So with 16 Vmp by the time you measure Voltage at the battery under load the panel may not produce enough to fully charge the battery; you can easily be down 3 Volts at that point.
This is why standard "12 Volt" panels have 36 cells and a Vmp around 18. Notice that 36 cells times 3.9 Watts each comes to 140 Watts; pretty much a typical "12 Volt" panel with an Imp of 7.8.
You have to have both sufficient current and Voltage or the battery will not charge properly. Since PV is a current source it isn't difficult to come up with that; any one of those cells would produce the 7.8 Amps (3.9 Watts / 0.5 Volts) but if you don't have enough of them in series to make the proper charging Voltage under operating conditions it doesn't work. -
Re: My first project - Solar power computer....I need your help
Hello BB, yours is the biggest post with lots of info, i will have to read this one tonight and get back tomorrow, thanks a lotWelcome to the forum Kellez,
Your calculations and numbers are correct in the "ideal" world. In the real world, there are some issues.
First, you want to discharge the battery at a C/2 hour rate (fully discharging the battery to "dead" in 2 hours)--Flooded cell batteries really only like to be discharged at a C/8 hour rate, or at most, a C/5 discharge rate.
Also, the faster you discharge a battery, the less apparent capacity (a battery discharged at C/20 rate may appear to have a 100 AH capacity, a lead acid deep cycle storage battery discharged at C/2 rate may have an apparent capacity of 60 AH or less).
So--You have two choices, either get a larger battery to drop the discharge rate to C/8 - C/20, or change the battery type. AGM type Lead Acid batteries can be discharged at a much faster rate... Or looking at the various types of Lithium Ion chemistry type batteries (lots of choices, and you get into the whole "Battery Management System" electronics--Some/most Li-Ion battery types need a per cell voltage monitoring/charging adjustment circuit to prevent over/undercharging and damage/battery failure).
And there are two calculations we make when sizing a solar array to battery bank. The first is that there is enough charging current to properly recharge the battery bank based on AH capacity (5% to 13% rate of charge typical). And second is based on the Watt*Hours (or Amp*Hours) you use per day and the amount of sun you get.
The fact you used the "worse" average hours of "noon time equivalent" sun per day is fairly conservative--This is "average" weather--Those values can be +/- 10% over long term average, and day to day, you can have a few days or even a week+ of bad weather where the solar energy is only 5% of system capacity (dark days). So, you either have to be able to turn off the loads during poor weather or have a backup power source (typically a small AC genset).
There are options out there--But you need to pick the correct battery/system to match your needs.
Next, there are other losses--AC inverter conversion losses, battery charging/discharging losses, solar panels+charge controller derating+controller losses, etc... For a simple lead acid solar power system, roughly the end to end efficiency (solar panel to charge controller to battery to ac inverter) works out to be around 52%--Yep, you get only 1/2 of the "rated" capacity of your system.
So, what would a flooded cell lead acid battery system look like? Roughly, the calculations would look like:- 115 Watt* 1 hour per day = 115 Watt*Hours per day
- 115 WH * 1/0.85 AC inverter eff * 1/12 volts * 2 days of storage * 1/0.50 max discharge = 45 AH @ 12 volt battery bank (long life, good battery capacity for load balance)
- 115 Watts * 1/0.85 inverter eff * 8 hour discharge rate * 1/12 volt battery bank = 90 AH @ 12 volt minimum based on loads
To continue with the calculations using Flooded Cell... First need to size the solar array to battery bank AH capacity. Nominally, we recommend 5% minimum rate of charge (for good battery health) and "low usage system" (emergency backup, use system at weekend/seasonal cabin) to 13% rate of charge (full time off grid, used daily, maximum "cost effective" solar array for typical applications).- 90 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 85 Watt array minimum
- 90 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 169 Watt array nominal
- 90 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 220 Watt array "cost effective" maximum
- 115 WH per day * 1/0.52 system efficiency * 1/2.78 Hours of sun per day (winter minimum average) = 79 Watt array minimum
- 169 Watt array * 0.52 system eff * 2.78 hours of sun winter day = 244 WH per day
There are ~28 cell panels sometimes out there--But this is from the "olden days" where people wanted "self regulating" panels to charge batteries without a battery charger. Today, we always use battery charge controllers as this is more efficient and will give you better battery life/more energy (overall) from your system.
Next, the "other losses". AC inverters, even small ones, take something like 6 watts just to "turn on". If you had an AC inverter to supply your 230 VAC power that you left running 24 hours per day (did not turn off the DC power to your inverter when the AC was not required)--You would have to add:- 6 watts * 24 hours = 144 Watt*Hours per day to your load calculation
Anyway--Those are the basics. Not to say my design is "perfect" and the only answer--But it is a starting point for a reliable system that should give you many years of use with minimum maintenance/surprises.
-Bill -
Re: My first project - Solar power computer....I need your helpFrom your third comment i understand that discharging the battery is not the main issue here, the only think you have to worry about is the percent of DOD......also what exactly is AGM????
Also please do give me the equipment list of the above set-up
AGM: Absorb Glass Matt. Sealed lead-acid battery with very low amount of electrolyte (sometimes called "starved electrolyte battery").
Off-the-shelf pick of major parts for the design I was suggesting:
Battery: Universal 50 Amp hour 12 Volt AGM http://www.solar-electric.com/unbamo45agms.html
Inverter: Morningstar 300 Watt 220 Volt version of this http://www.solar-electric.com/mosu300wasiw.html
Solar panel: Kyocera 140 Watt 17.7 Vmp 7.9 Imp http://www.solar-electric.com/kyocera-kd140gx-lfbs-140-watt-polycrystalline-solar-panel.html
Charge controller: Morningstar SunSaver 10 Amp PWM http://www.solar-electric.com/ss-10.html -
Re: My first project - Solar power computer....I need your help
Ok then i will use a 36 cell panel that is final.
I want to ask you one question regarding the cells i bought...there are some small burns at the sides of the cells, see the picture below, is that normal? don't worry about the broken part i did that.
Attachment not found.Cariboocoot wrote: »You're building your own panel? Okay there's a few problems with that. One of them being that the cells you buy on the Internet tend to be one rejected by companies for not meeting specs, including shunt resistance.
Figure 0.5 Volts per cell under load; the 0.57 reading you got would be Voc which doesn't reflect actual power output. Therefor a 32 cell panel would be 16 Volts, which can be too low for a 12 Volt system. When the panel heats up (and this does not mean 'is used in desert temperatures') the Voltage goes down. More Voltage will be lost in the wiring. So with 16 Vmp by the time you measure Voltage at the battery under load the panel may not produce enough to fully charge the battery; you can easily be down 3 Volts at that point.
This is why standard "12 Volt" panels have 36 cells and a Vmp around 18. Notice that 36 cells times 3.9 Watts each comes to 140 Watts; pretty much a typical "12 Volt" panel with an Imp of 7.8.
You have to have both sufficient current and Voltage or the battery will not charge properly. Since PV is a current source it isn't difficult to come up with that; any one of those cells would produce the 7.8 Amps (3.9 Watts / 0.5 Volts) but if you don't have enough of them in series to make the proper charging Voltage under operating conditions it doesn't work. -
Re: My first project - Solar power computer....I need your help
Cells get rejected for many reasons, including cosmetic ones like that burn mark. If it doesn't affect the output it's not particularly relevant. -
Re: My first project - Solar power computer....I need your help
If you are going to "push" performance/cost/reliability/etc.... You need to really research battery technologies. Lead Acid flooded cell deep cycle batteries are used a lot because they are relatively cheap and reliable. They are heavy, need maintenance, and don't like to sit around discharged for days/weeks/months and do not like to be heavily discharged (below 50% state of charge) very often.
Here is a nice AGM Battery FAQ from our host (I actually have not seen it before):
http://www.solar-electric.com/agm-battery-technology.htmlWhat is AGM, and what makes AGM technology better?Absorbed Glass Mat batteries are constructed differently than the traditional flooded battery. This write up covers mainly the Concorde Sun-Xtender AGM's, but also applies to most other brands of deep cycle AGM batteries.In AGM batteries (also called starved electrolyte), there is a thin ultra-fine fiberglass mat sandwiched between the plates that are saturated with battery acid to about 95% of what they can hold. This mat is then packed in between the plates and slightly compressed, then welded/soldered in place. Because the plates and mats are packed fairly tight, they are almost immune to vibration.AGM (Absorbed Glass Mat) sealed battery technology was originally invented in 1980, and developed and introduced in 1985 for military aircraft where power, weight, safety, and reliability were paramount considerations. The Concorde AGM batteries a VRSLAB (Valve Regulated Sealed Lead-Acid Battery). Sometimes referred to as VRLA (Valve Regulated Lead-Acid). Several manufacturers now produce AGM batteries, but Concorde was the first to develop the technology for commercial non-military use.AGM - Deep Cycle Or Not?An important thing about AGM - Just because a battery is AGM does NOT make it a deep cycle battery. Several companies, such as Optima, have adopted AGM for starting batteries and other non-deep cycle applications. Those still have the advantages of AGM, but are not deep cycle. It is primarily plate thickness that makes a battery deep cycle, not whether it is flooded, gelled, or AGM.The Concorde SunXtender batteries are essentially the same construction as the Concorde Lifeline, Chairman, and other Concorde AGM batteries. The major difference is that the Sun-Extender batteries have bolt-on terminals instead of the common post type. We feel that bolt on terminals give a much more reliable connection. We also stock many of the Concorde "Chairman" (designed mainly for wheelchairs) batteries and some "LifeLine" (marine & RV) batteries.Battery Efficiency:This comparison is important, and is critical for high charge or discharge rate applications. Internal resistance of a battery denotes its overall charge/discharge efficiency, its ability to deliver high currents without significant drops in voltage, and is a measure of the quality of the components and construction.Battery Internal Resistance Losses:Losses from internal resistance shows up as heat, which is why batteries tend to get warm when heavily charged or discharged for a while.Internal resistance losses in standard flooded Lead-Acid batteries is usually around 10% to 15% for a new battery, and can be as high as 25%+ for older batteries. This can vary considerably, depending mainly on the age and quality of the battery. In general you get what you pay for - cheaper batteries with thinner plates and internal connections tend to be less efficient.Gel batteries are better at approximately 12% to 16% internal resistance so would require around 115 amp-hours of charge for every 100 amp-hours used.Concorde AGM has the lowest internal resistance of any commercial battery that we know of - only 2 percent in a new battery. In solar electric systems, this is the same as getting an extra 10 to 15% out of your panels. This also allows Concorde AGM batteries to be charged much faster if needed and also to deliver higher currents when required. Owners using high output alternators, operating inverter banks, or relying on solar panels can benefit significantly when using Concorde Advanced AGM batteries with their equipment. Concorde AGM's are more efficient.Heat: Better efficiency means much less heat is developed in the batteries - any current that does not actually go to charging a battery turns into heat. That is why some batteries, especially older flooded batteries (and even some non-deep cycle AGM), can get very warm or even hot. In extreme cases you can get " thermal runaway", which can be dangerous. If you have ever felt the side of a battery under heavy charge, you have probably seen that they can get very warm.Concorde batteries far exceed the US Coast Guard test for thermal runaway: These MW-SPEC (Military Specification) tests involve fully charging a battery, heating it to over 130 degrees (Potential Thermal Runaway Conditions) and then overcharging the battery to simulate a shorted cell. (16V for a 12V battery).AGM Batteries Are Not Gelled Batteries:Concorde AGM batteries are NOT a gelled electrolyte. It is considered a "Recombinant Gas Absorbed Electrolyte" battery. This cuts water loss by up to 98%. Loss of charge due to self-discharge is 3 to 10 times better than with conventional gelled, and 5 to 50 times less than with flooded batteries. The gasses recombine almost 100% within the battery, reducing Hydrogen emissions to a level far below most battery types, and less than half the lower explosive limit for Hydrogen. In addition, they do not have the charge and discharge current limitations that most gelled batteries have.Concorde AGM battery technology has continued to develop and offer improvements over other sealed battery technologies. AGM technology has become the next step in the evolution of both starting and deep cycle sealed batteries for marine, RV, and aviation applications. These are the same batteries that the US Military uses in many of it's armored and standard vehicles. This "next generation" technology delivers increased safety, performance, and service life over all other existing sealed battery types, including gel technology. All Concorde AGM batteries carry a one-year full warranty - most gelled cells carry only a 90-day warranty.AGM batteries have much better resistance to vibration and shock due to their construction than most flooded batteries. The plates are packed in with the glass mat, reducing plate movement and vibration to nearly zero. In addition, because the glass mats are not totally saturated and the liquid does not expand to cause plate and case damage, AGM batteries can withstand freezing - you will get little or no output from a frozen battery, but at least it will not ruin the battery or break the case.Concorde AGM batteries meet MIL-SPEC B8565J and FAR 23.1353, 25.1353(c), 27.1353, 29.1353(3), 25.853(a). All Concorde AGM batteries are shippable without restriction by any means of transportation, including air. Hazardous labeling is not required.In AGM sealed batteries, the acid is absorbed between the plates and immobilized by a very fine fiberglass mat. No silica gel, as is used in gelled, is necessary. This glass mat absorbs and immobilizes the acid while still keeping the acid available to the plates. This allows a fast reaction between acid and plate material. Even if the battery is broken, no electrolyte will be spilled.The AGM battery has an extremely low internal electrical resistance. This, combined with faster acid migration, allows the Concorde AGM batteries to deliver and absorb higher rates of amperage than any other sealed batteries during discharging and charging. In addition, AGM technology batteries can be charged at normal flooded lead-acid regulated charging voltages, therefore, it is not necessary to recalibrate charging systems or purchase special chargers. Concorde AGM batteries can be bulk charged at high rates without damage - up to 10 times as fast as most gelled cells, and 4 times as fast as flooded batteries.AGM batteries are not the best choice for all applications - they are rather expensive compared to flooded batteries. However, their safety and design features make them the battery of choice for many applications, such as:- Where you cannot have fumes or hydrogen, such as in poorly ventilated areas, or where fumes may cause corrosion to electronics, such as repeater and cell phone sites.
- Where resistance to shock and vibration is important.
- Where spilled acid from leaking, tipped, or broken batteries cannot be tolerated.
- When installed in a location where maintenance would be difficult or expensive, such as remote communications sites.
- Where the batteries may be subject to freezing (-40 degrees F or lower).
- Anyplace where you need a reliable totally sealed battery for safety or environmental reasons - wheelchairs, medical standby power, inside RV's, computer room UPS systems, or in enclosed spaces in boats.
Even a "simple thing" like a lead acid battery has many (probably hundreds) of design/manufacturing parameters that can be tweaked to obtain the optimum performance for any specific type of operation.
Just buying a car battery from the local auto parts store is usually not going to give you good "deep cycle" performance that is needed for off grid power system usage.
Some more reading:
http://www.windsun.com/Batteries/Battery_FAQ.htm
http://www.batteryfaq.org/
http://batteryuniversity.com/
More or less, I like to describe the battery bank as the heart of your system. Design the battery to support your loads, and design the charging system to support your battery bank.
And, I agree with Marc/Cariboocoot--Don't try to build your own 140 Watt panels. Besides them not working as well as you would expect (typically seconds of solar cells from panel production lines), it is difficult to build a reliable/safe panel outside of lab/commercial environment. Here is an example of some sort of panels built cheaply (and possibly in a factory) that did the home owner no favors:
Panel Fire Question
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Re: My first project - Solar power computer....I need your help
I wouldn't worry about it with building one panel for learning/experimental purposes. But if you were looking at constructing a larger off-grid system you'd soon see what a tedious nightmare panel construction is. And how much more expensive it is than commercial panels these days!
Yet you still see the ads: "Build your own panels for as little as $2.99 per Watt! Save money!"
Yeah? You can buy 'em with warranty for $1 per Watt - and they work right out of the box. -
Re: My first project - Solar power computer....I need your help
Well how would i know that the output is not affected? i have checked the voltage which is fine but i am not sure about the wattage. Can you please explain to me how can i check a cell if its fine to be used for a panel? for example how shall i know if there is a problem with the shunt resistance of the cell? -
Re: My first project - Solar power computer....I need your help
Ok guys thank you for your time i need to go right now, i will get back tomorrow, thank you -
Re: My first project - Solar power computer....I need your help
You won't be able to check the shunt resistance (at least I can't think of any easy and accurate way to do it), but you can check the Isc (short circuit current).
You need a multimeter that can handle 10 Amps DC. Put it across the cell's output. Apply sunlight. Read Amps. It should be in the neighbourhood of Imp or ideally just above. It will not read properly if there isn't bright sun directly on the panel; change the angle, change the current.
Possibly you can measure the resistance in the dark with an Ohmmeter. I've never tried. -
Re: My first project - Solar power computer....I need your help
The cells you have are probably all "rejects" from either a mfg. or solar panel builder... Either by lot and/or individual inspection.
Here is one way a mfg. would inspect for cell defects:
http://www.flir.com/cs/emea/en/view/?id=41872
http://www.sensorsinc.com/photovoltaics.html
Obviously, while I would love a FLIR camera for many reasons--I would be hard pressed to justify the costs for a hobby.
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Re: My first project - Solar power computer....I need your help
Project Update
Hello guys, i decided not to use my desktop computer for this project since it will require a pure sine wave inverter and getting a good quality one is very expensive....therefore i will use my laptop which can be powered through a modified sine wave inverter with no problems. This will also allow me to buy a good quality MSW inverter.
Can anyone please suggest any good brands non-chinese that make quality MSW inverters?
One more thing regarding the charge controller....please check the calculations below
Minimum Amps required by the controller is determined by PV module power (W) divided by the battery voltage (V)
therefore
36 cells at 3.9W = 140.4W
12V battery
140.4W/12V = 11.7A minimum for the charge controller
I know this is a different calculation from what you suggested but what do you think about this? I found this in a book. -
Re: My first project - Solar power computer....I need your help
The charge controller rating also depends on the type of charge controller. For a PWM:
140 watts / 17.5 volts Vmp = 8 amp controller minimum PWM controller current rating
For an MPPT type controller:
140 watts * 0.77 panel+controller derating / 14.5 volts battery charging = 7.4 amps minimum "cost effective" MPPT controller
What size of MSW power supply are you looking for? How much do you want to spend?
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Re: My first project - Solar power computer....I need your help
I want to use a 200Watt MSW inverter up to $40-$50.
in the above calculation
140 watts / 17.5 volts Vmp = 8 amp controller minimum PWM controller current rating
why did you use 17.5V and not the 12V for the battery? -
Re: My first project - Solar power computer....I need your help
For a PWM controller, it is simply an "on/off" switch--The controller does not "change" the current available from the solar panel.
More or less, solar panels are roughly constant current devices... Once they are at Vmp, the output current is almost the same between Vmp and zero volts. (technically, at zero volts, or short circuit, Isc~Imp*1.25)
-Bill.Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Re: My first project - Solar power computer....I need your help
ok therefore i need a 10amp 12V charge controller and a 200watt inverter MSW, can you suggest a good cheap MSW inverter?
good about this charge controller?
http://www.solar-electric.com/ss-10.html -
Re: My first project - Solar power computer....I need your help
Always check the data sheet for charge controllers--The calculations I gave are minimums--But sometimes there are temperature or other deratings by the mfg. or NEC (NEC wants a 1.25*1.25=1.56 charge controller deratings--I think this is overkill and if the mfg. does their job correctly, there should be no NEC derating requirement).
Samlex (and Cotex, same/very similar models) are good quality inverters out of Taiwan (or China these days). But they are TSW and cost more than $50.
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Re: My first project - Solar power computer....I need your help
well since this is just a test and i will only be using my laptop with out any fear of damaging it, i prefer to go with a cheap solution. If i don't manage to get an inverter and a charge controller for around $120 (non-chinese) then i might as well go with the chinese -
Re: My first project - Solar power computer....I need your help
I finally decided to go with this cheap chinese controller...nothing could go wrong at this price, if it brakes, its not a big a loss.
http://www.aliexpress.com/item/20A-20-Amps-Solar-Charge-Controller-with-light-and-timer-controller-PV-battery-Charge-Regulator/825239480.html
has anyone tried this before?
Am i allowed to post links to other products ? i am asking this because this a store forum -
Re: My first project - Solar power computer....I need your help
Yep, you are OK to post links when asking/answering questions... We try to avoid xyz.com is having a 1/2 off sale today type posts and spam (boy, there are lots of spammers out there).
Here is a similar looking controller:
Wellsee MPPT
Don't know if it is the same internals or not.
And down past the middle in this thread, one person apparently has your same controller:
Tri star charge controllers
In the end, just accept that you are experimenting and that some of the experiments will fail.
Charge controllers (and power electronics in general)--To be long lasting need good components & design, as well as good sized heat sinks/forced air cooling. High temperatures and thermal cycling are the death of electronics.
As the systems become larger and more mission critical (i.e., cabin/home in the wilderness, emergency backup power after an ice storm) and hours from any stores/suppliers, you will probably start looking for more reliable (and more expensive) components. At some point, saving a few hundred dollars is not worth the time, effort, and expenses to constantly repair the system/run a genset for backup power.
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Re: My first project - Solar power computer....I need your helpI finally decided to go with this cheap chinese controller...nothing could go wrong at this price, if it brakes, its not a big a loss.
Nothing could go wrong, unless it malfunctions allowing your batteries to be severely over or under charged, thus causing them to have a shortened lifespan.Paul -
Re: My first project - Solar power computer....I need your help
Those threads are what i was looking for thank you very much, i will through them tonight. are there any similar threads comparing charge controllers?
also check out this inverter, what do you think?
http://www.amazon.co.uk/Inverter-inverter-notebook-emergency-MRI3013J2/dp/B008HOECP0/ref=sr_1_5?s=electronics&ie=UTF8&qid=1398606065&sr=1-5&keywords=inverter+for+12v+batteryYep, you are OK to post links when asking/answering questions... We try to avoid xyz.com is having a 1/2 off sale today type posts and spam (boy, there are lots of spammers out there).
Here is a similar looking controller:
Wellsee MPPT
Don't know if it is the same internals or not.
And down past the middle in this thread, one person apparently has your same controller:
Tri star charge controllers
In the end, just accept that you are experimenting and that some of the experiments will fail.
Charge controllers (and power electronics in general)--To be long lasting need good components & design, as well as good sized heat sinks/forced air cooling. High temperatures and thermal cycling are the death of electronics.
As the systems become larger and more mission critical (i.e., cabin/home in the wilderness, emergency backup power after an ice storm) and hours from any stores/suppliers, you will probably start looking for more reliable (and more expensive) components. At some point, saving a few hundred dollars is not worth the time, effort, and expenses to constantly repair the system/run a genset for backup power.
-Bill -
Re: My first project - Solar power computer....I need your help
lets hope the one i get its not the defective one -
Re: My first project - Solar power computer....I need your helpThose threads are what i was looking for thank you very much, i will through them tonight. are there any similar threads comparing charge controllers?
also check out this inverter, what do you think?
http://www.amazon.co.uk/Inverter-inverter-notebook-emergency-MRI3013J2/dp/B008HOECP0/ref=sr_1_5?s=electronics&ie=UTF8&qid=1398606065&sr=1-5&keywords=inverter+for+12v+battery
Mate,
Listen to someone who has been there, and tried to go with substandard parts.
Above, Coot gave you a link to a reliable inverter.
While personally, I am not crazy about MorningStar's customer service (I will be polite and just say that it is less than acceptable), I have yet to hear a negative word concerning their 300 watts inverter. Plus, it has some killer features.
So, if you are going to do this, don't do it half-arsed. Do it right the first time, and you will have fewer issues down the road.
That's my 2 cents. Take it for what it's worth.Paul -
Re: My first project - Solar power computer....I need your help
Some thoughts on equipment.
The Samlex/Cotek inverters are fine for what you want to do: http://www.solar-electric.com/samlex-pst-series-pure-sine-wave-inverters.html
Your desktop computer would probably run fine on MSW unless the computer is junk; their power supplies are meant to clean up bad input power.
The laptop will use significantly less power than the desktop.
There's not much point in buying an MSW inverter as the price difference is no longer that great.
If you buy poor quality equipment to begin with you may be discouraged and not do anything more with solar. If you buy good quality equipment you may become addicted to it.
My experience with low-end stuff has been tossing it to replace it with something that works. (There's a fellow on our lake who is really keen on Chinese junk and has talked several people into buying the stuff. Then they have to spend more money to get something that works. I even had to fix his own brother's system which was saddle with defective components.)
No I do not work for NAWS nor any of the companies that make the equipment. -
Re: My first project - Solar power computer....I need your help
One thing to watch with "12 volt car" adapters and battery clips...
A typical "cigarette lighter" plug is good for around 10 amps... 10 amps * 12 volts = 120 Watts--Not the 300+ watts the inverter is rated for.
Similar for battery clips. They are not really good enough to run your inverter at higher current levels... How high? You should be planning on:
300 Watts * 1/0.85 inverter eff * 1/10.5 battery cutoff * 1.25 derating for wiring/fuses/breakers = 42 amps minimum (40 amp internal inverter fuse supplied)
And the inverter is good for ~750 Watts surge--So, you are looking at wiring, connections, and battery can can sustain ~84 amps surge--Why battery clips do not work hardly at all.
Always use heavy enough cable (and keep it short), will solid bolted up connections back to the battery.
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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