Solar Calculator Tutorial
Solar Calculator Notes and Instructions.
First, the notes: We hope this solar calculator will make sizing your panels and batteries a little less painful. Keep in mind that this is only a calculator, and it will directly reflect whatever you, the user, inputs into the fields. If your base calculations are off by even a little bit, the results reflected can be skewed by quite a bit, so view this as a guide, not an absolute. With that said, here comes the disclaimer. This calculator is for educational purposes only. BatteryStuff.com is in no way responsible for the results of your calculations, and if you purchase a system based on the results of the Solar Calculator, BatteryStuff will not and cannot be held responsible for returns or exchanges for improperly sized systems. Normal RMA and exchange rules will apply to all solar panel purchases. See BatteryStuff.com policies for more info.
Now the instructions:
Field #3: This field needs to be DC watt draw only. If you are using an DC to AC power inverter, meaning your device is rated in AC amps and 110 V, you will need to convert that number into DC watts before entering it in the field. Then you will need to add about 10% due to the inefficiency of the power inverter. To get there, use the following formulas;
1 Amp AC = 10 Amps DC. (example, 2AC amps =20DC amp)
Add 10% (22 amps)
DC amps x 12v = DC watts. (22 x12 =264 watts)
264 would be entered in field # 3
Fields #6 and #12 are for how many hours you expect your equipment to run in a 24 hour period, and your input voltage (12, 24, 36?).
Fields #14 and #18 will determine what size and how many batteries you need. In #14, insert days of backup you would like your battery pack to be good for. This is minus any solar panels, which we will figure in a minute. Field #18 is based on what battery you choose. Say you want to use a 55 AH battery because you like the dimensions, or maybe you like the 21 AH battery due to its terminal configuration. Enter your chosen battery amps there. We don’t like to see any battery discharged more than about 50%, so we will automatically adjust for that.
Still with me? Good, we are almost done. The last two fields, #22 and #25 are easy. How many hours of direct sunlight do you estimate your panel will get. Be realistic. We will then automatically guesstimate for clouds, bad weather etc. Field #25 is just like field #18 in the battery section. Look at our solar page, pick a panel you like and then enter the watts here.
I am ready, take me to the calculator!
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Jimmy Really good information! Thank you sir. If I may ask a question. I have made a giant 12v battery from some saft 1.2v cells. 9p10s @ 270 ah, if my newbie math is correct. If this was a normal set up I think I could do the math but it’s different. You think a 400w panel bundle would keep this thing charged?
Thanks again, Jim
BatteryStuff Tech What you are asking is part of the math problem… A 12v 400 watt panel most likely will put out 94 to 140 amps a day to a battery. Do you believe this is sufficient given your daily draw plus accounting for backup energy for bad weather days?


Farouk i am trying to power up 1000 watts of eneregy all of them in total are lights ,i have a 2000wat inverter and two bateries 12 volt 120ah ,my question is how many solar panel i need to charge these batteries on a daily basis or do i need to purchase more bateries my lights are on 12 hours daily , thank you e7

BatteryStuff Tech Realistically I would tell you to purchase a generator. Trying to run 1000 watt an hour for 12hrs a day equates to over 13,000 watts by the time you factor inefficiencies! As most people see an average of 46 hrs of usable sunlight a day, that would mean you need an array that could collect 3,500 watts an hour!


Emme Hello!
Wow, this all makes my eyes glaze over! I’m old and was a humanities major. Please be gentle!What size panel should I get to recharge a Sears Die Hard Platinum Portable Power 1150
12 volt battery? I’m getting one as emergency back up power for a cpap machine.I think you are saying that a battery shouldn’t be allowed to get to less than 50%. How long would it take to recharge a battery from 50% to 100%?
Thank you!

BatteryStuff Tech We always try to be kind! What you are asking is a bit of a math problem, and in order to figure out your problem, you are going to need to get some specification in order to use this calculator. I would first suggest reading our article Solar System the Right Way, as this will guide you through the steps required before you attempt to use this calculator.


Douglas S. Duran Good day sir. how much solar panel will i use to power up a 2500 watts load? that can work for 12 hours of operation with that amount of load? how much solar panels, the size of inverter, and the size of solar charge controller, and the battery? thank you and god bless you always.

BatteryStuff Tech Our solar products are not geared to larger home installations, so I would source your question to a local home solar contractor. To give you a basic understanding of what you might be looking at i would suggest reading our article Solar Systems the Right Way. Either way your are looking at a system most would use a generator for, as a 2500 Watt load for 12hrs = 30,000 Watts!


Jorgen Hi
I have 2 car batteries of 110 amps each connected in parallel. How many solar panels and of what output do I need in order to charge this battery bank when it is at 50% discharge? How long will these panels take to charge the batteries bank to 100% considering they are not providing power to consumers during the charge period and that the panels are exposed to 8 hours of direct sunlight a day and that a controller is connected to the system?
Thank you
BatteryStuff Tech What you are asking is basically a math problem… How quickly do you want them recharged?… You know your batteries are at 50%, so you need to replace 110 Amps, assuming these batteries are in parallel. Divide the 110 Amps by the hours you want to recharge them keeping in mind that we really only see 4 – 6 hrs of usable sun on most days, so if you go over that time frame you will be into the next day. Then take the amp rating you came up with and multiply it by the voltage of the panel to get the wattage of the panel. Granted this doesn’t take into account any inefficiencies of the solar charge controller, or the precise voltage rating while at the panel’s max operating current, but it can give you a good idea.


Sohail hi.i have a 60ah dry cell batry and 2 Toyota corolla radiator 12 fans so what kind of solar panel should i need for running fans 6 hours in day and 6 hours in night? thank you

BatteryStuff Tech I would suggest reading our article Solar Systems the Right Way. This will explain how to put a solar system together, and then link you to calculators to size your system.


Sheraz Dear Team,
I have two 150w solar panels and 140ah acid lead battery. Direct sunlight duration is about 10 hours. how much time solar energy will take to fully charge my battery?

TECH You will have to look to the back of your panel for its rating, but here is a basic equation that can help:
Volts * Amps = Watts… So for our math problem you have to adjust the equation slightly:
Watt / Volts = Amps… The rating for watts you know, but the voltage rating you should be looking for on the back of your panel is the Pmax(Vmp) rating.
Our 150 watt panel has the following rating:
150 Watts / 18.38 Vmp = 8.38 Amps an hour
Please be aware this is the rating off the panel, with that high wattage panel you need to be using a solar charge. Most Solar Charge Controllers will reduce your amperage to the battery by 15%. Now you just need to know how discharged your battery is and then you can figure out how long it will take.
I hope that helps!


Michael Hello guys I just want to ask how many watts solar panel dining need To use to fully charge my 12volts 32ah battery with in 7hrs…ty

BatteryStuff Tech I would suggest using our Calculator  DC to AC amperage conversion run through an Inverter. You don’t want to discharge a battery more than 50% or risk damaging the battery’s life. This calculator will tell you how much you are pulling from a battery in an hour.

IBRAHIM K YUSUF span class="caps">PLEASE, I HAVE THE FOLLOWING APPLIENCES IN MY HOME
TV = 38W
REFRIGERATOR = 297W
3nos CEILING FAN each of 75W = 225W
6nos BULB each of 5W = 30W I am using1200W, 12V Inverter with 2nos 100AH batteries in parallel. How can I calculate the running time before all charges is discharged if all the batteries are in good condition? 
Mario Hi guys
I have a 18 ahr SLA battery (within a Powertech 6 in 1 setup) that I am looking to get a solar panel for for use on camping trips. I am looking to put aprox 6 to 9 amps of power back into the battery per day. Would a 20 watt panel with a PV controller be a suitable setup? Anything I should be mindful of? Thanks in advance.

TECH 20 Watts / 12.5 Volts (12 volt battery) = 1.6 Amps and Hour – 15% (for average controller inefficiency) = 1.36 Amps an hour to the battery. That is what a 20 watt panel will provide an hour through a controller in direct sunlight. The rest is dependent on your usable sun hours.


Barialai hi
sir I have question about solar?
1i have 20PC solar each one is 130W how many AC electricity I can make from IT?
2 how many inverter will require ?
3 how many battery will required?
4 from solar to battery how many controller will require?
Admin Due to the fact that we don’t have all the information for your system we would need you to contact us at tech@batterystuff.com so that we can ask the appropriate questions, to get you the answer that you may need.


Joshua I have a question: I run a mobile coffee truck and would like to add a deep cycle battery (or 2) for running my small appliances occasionally through the day with out having to run my generator.
The appliances I have are a milk steamer, shaved ice machine, small brewer, and water pump.
The brewer and water pump have to run at the same time. The others will run only one at a time.
These are the amp rating for the items:
Ice shaver 3.4 amps (runs for about 5 minutes total per day)
Milk steamer 1.8 amps (runs for 20 minutes per day)
Water Pump 1.1amps (runs for 5 minutes max per day)
Coffee brewer 19.6amps (start) 14 amps (continuous) (runs for 4060 minutes per day)All are 110115 Volt
What size battery (batteries) would I need and what kind of inverter?
All the items only run when needed and not at the same time (except brewer and pump)
Also how long would the recharge take on a battery if it was plugged into a wall outlet in my home?
Thanks for your help, awesome site!
Due to the fact that we don’t have all the information for your system we would need you to contact us at tech@batterystuff.com so that we can ask the appropriate questions, to get you the answer that you may need.

Chris I have a 30 watt spotlight which will run from a 600 watt inverter for 10 hours and 2 × 10 watt lights which will run together for 5 hours from the same inverter. What size of panel, charge controller and how many batteries do i need.
Due to the fact that we don’t have all the information for your system we would need you to contact us at tech@batterystuff.com so that we can ask the appropriate questions, to get you the answer that you may need.

Ramesh Sir, I have an 25 Watts battery which should be running for atleast 12 hours an day. I have multiple 12V and 5AH solar panels. So, what is the battery specification I need to use for the above mentioned usage and also how many panels i need to use and we have an average of 10 hours sunlight a day

Enias What is a correct charge controller and inverter which is equivalent to 130 watts solar panel plus 120Ah batteries

John Please help with question and calculate :
Need to know what size solar panel would do this :
A 12 volt battery connected to 400 watt, 3.3. Amp power inverter to a device drawing 2 amps.
Would a 18 Watt , 8 Amp solar panel be enough to keep battery charged up ?….. with a avg. day sun light ?. If not, what size solar panel in watts would be needed ?. Thank you

Jeremy Fear Short answer: no.
If you look at the numbers, you have 400 watts going out (for some unspecified length of time), and 18 watts going in durring only sunlight hours. Even if the 400 watt load is only 1 hour per day, the 18 watt panel would not recharge enough to run that in an average day sunlight(it would take about 24 hours of direct sunlight).


Fitzroy If i use a 60watt 12v panel putting out about 3.5 amps what size battery should i use to power an AC water pump drawing around 80 100watts.
sun hours would be around 67hrs(caribbean area) and pump runs 24hrs. inverter is 1000w capacity.cheers

Cathy Hi sir, can a 60 watts solar panel can charge a 24 volts battery? We are working for our thesis but we have a problem because the lead acid battery is not charging, the capacity is 10Ah.

BatteryStuff Tech If you are referring to our ~60 Watt solar panel, the answer is no. Our large solar panels are rated for 12 volt systems. You should look at the specs of your existing panel to answer your question. If your solar panel is rated for 12 volts (even if output voltage is as high as 21 volts, the design is for 12 volt applications) I recommend using two solar panels wired in series for an output of 24 volts. Only this will be able to charge your 24 volt battery.


Sunil I have 5panel of 12&40watt con i directly connet to the inverter to get 240v

BatteryStuff Tech We recommend connecting the inverter to a battery source, and then use the solar panels to recharge the battery.


Mamatha Hi Sir,
I want to buy solar system for my house needs to run AC,1fan,Refrigirator, Can you please suggest howmany Watts/A/Volts in each required to meet these specification,battery capacity,panel capacity,howmany panels best and day time how can I use direct power without using batteries etc. Please provide all the required if I missed any thing about this as my vendor is going to visit my place soon,once they fixed the setup pannels,battery etc it is not easy to ask them to change the setup. Can I go ahead with upgrade to existing setup like If I will set up 100W, Can I add another 100w to existing system?

BatteryStuff Tech You can always add more solar panels. However, we cannot tell you what kind of power requirements you need. Only you can figure that out. I suggest looking at all of the equipment you want to run, add up the power ratings, and then use that information as input for our solar calculator.


Mike i am planning a large system, k00kw solar.
we want to have battery backup of 1500 amp , 48 v (hupsolar one battery, lead acid )
how long would it take for the grid to charge the battery 50 hz, 600v transformer
and how long would it take a generator to charge the 400 kw.
BatteryStuff Tech I‘m sorry, but can you clarify. Will you be using an AC plugin charger? Or are you suggesting charging your battery from the 600 volt transformer? Also, the generator probably does not put out 48 volts DC to recharge the batteries with. You will need a charging unit rated for 48 volts. This unit will determine the length of charge time.


Howard Heath Shop and well wired for 220. Want to convert to solar power. How do I find out how big of a system I need? According to electric bill approx 55 kilowatt hours used last month. Concerned about burning up well.

BatteryStuff Tech If you can narrow down how much power you consume in a 24 hour period, that would be most helpful.


Sunil can some body tall me ,ihave around 700 watt load in my house i have invarter 650 watt i want solar panal also for back up ,i need to know how big or how mouch watt soler panal need for charging 110ah 12 volt battery can gate 8 hours back up

BatteryStuff Tech A 650 Watt Inverter is too small for a 700 Watt load. Seems to me like if you want to pull 700 watts for 8 hours long, and if you have 8 hours of direct sunlight, then a 700 Watt solar system will be minimal to simply keep up with your home usage.


Ron trying to use a solor pannel to run a heater element like to use the 12 volt pannel can you hook it up direct say a 100 watt pannel what size heater element could i use

BatteryStuff Tech If you use a 100 Watt solar panel directly on a heater element (bypassing a battery) please use a heater element that takes less than 100 Watts to run.


Naeem sir we have refrigerator, tv, and fans, energy saver 24watt
from all the above things who many things i can run same time.
BatteryStuff Tech Please provide the power ratings for said refrigerator, TV, and fans. Then you will know if a 24 watt solar panel is enough to run any of them or not.


Naeem sir
i want to buy solar panels of these specifications
6 by 6 inch Mono crystalline solar cells 4.2 watt each(Solar eneger)
These cells have following specifications
Power 4.2 watt
Ampere 8.4
volt 0.5
do you understand or not
BatteryStuff Tech I understand you want to buy solar panels. My question to you is what you want to do with them? You asked ‘how many things i can run with this power’?
My answer is this: It depends entirely on those ‘things’. You might not be able to run a microwave for very long with 420 watts of solar power, but maybe a few lights you can. What is it you are trying to do?


Naeem sir solar panels

Naeem *6 by 6 inch Mono crystalline solar cells 4.2 watt each(Solar eneger)
These cells have following specifications
Power 4.2 watt
Ampere 8.4
volt 0.5
sir if i buy 100 piece i get 420 watts how many things i can run with this power
can a charge a ups with it or not
please tell me in detail
thanks in advance
BatteryStuff Tech What kind of ‘things’ are you referring to?


Naeem Sir i have a Question
Power 420 watt
Ampere 840
volt 100
How many things can i run with this power
Can i run TV, Energy saver, fans etc….
i have a ups of 2000 watt and two butteries can i charge these butteries using ups.
BatteryStuff Tech span class="caps">UPS usually uses batteries as a source of power. Are you asking if you can recharge the same batteries, through the UPS? That‘s circular reasoning, and it will not work.


Naeem Sir my Question is that if i have
Power 420 watt
Ampere 840
volt 100
who many things i can run plz tell me in detail
Can i run TV, fan, energy saver etc
BatteryStuff Tech I‘m confused by your specs. 100 volts x 840 amps does not equal 420 watts. What do you mean by this? If you are referring to batteries, inverters, solar panels, or equipment, please specify.


Dharmendra Malviya can i ues 220amp tubular battery on my solar system. my system have1kw.

BatteryStuff Tech If your solar system is rated for 12 volts nominal, and if your battery is a 12 volt battery, then the answer to your question is yes. I strongly recommend the use of a solar controller with such a large solar charging system.

Rolando Bruno I have 600 watts solar panel an 30 amps charger controller an 1 4000w inverter an two 1000w inverter how many battery I need tto run my refrigerator an few mashines



Lance I gave a rating of 3 on this article, because while knowledge may be present, it is also presented as a 10th grade science presentation, instead of an Electrical Technician format. I worked as the Director of Engineering for a major RV manufacturer for years, and one of our greatest headaches was DC power systems and regeneration systems. We installed solar panels, gridtiein converters with battery chargers and conditioners, generator power transfer systems, and serialparallel battery bank systems; all in the name of meeting the customer‘s demand for wanting 24hour power at megawatts per pennies. As a result of this, we spawned a complete RV electronics subgroup within our engineering department to address battery construction, demand and regeneration vectors, as well as complete ‘working system’ analysis to determine system configuration around specific customer ‘lifestyle’. I say all this, because in the beginning, one of the things that beat us to death until we better understood it was the effect of Peukert‘s Curve on our DC power system efforts. I‘ve played with your calculator a bit, and I‘m not quite sure you are compensating for the Peukert effect in your calculations (the result is either rounding, or not staying consistent versus my calculator). Your ‘n’ value is definitely set higher than the efficiency of most deep cycle batteries, and I am not sure you are taking into effect actual ‘total depletion’ versus ‘real world depletion’ rates as a function of cell life. You also don‘t address the function of temperature on both charge and discharge, nor do you offer any temperature compensation variables (I‘m not talking 5°F here, but the difference between discharging at 32°F and charging at 72°F, etc.). It also appears you didn‘t take into account the 10hour rule in ‘fastrate’ charging (which can be somewhat overlooked with ‘more exotic’ cells, such as AGM and jelltypes).
T = (C/((I/(C/R))^n) * (R/C))
{it‘s the theory that is hard to beat}
BatteryStuff Tech We have another calculator for recommending specific battery capacity based on demand which uses Peukert‘s Constant, temperature, and age of the batteries in the formula. This calculator is a helpful reference for those who don‘t much about solar power. It‘s a good starting point to help point people in the right direction. If you need help with more accuracy than this calculator can provide, please call our tech line or email us.


Solar Air Conditioner I have read somewhere about solar calculator, but was not fully aware about how it works. The instructions given helped me to understand it better. Thanks for this very well explained information.

Scott If i have a 24 V 32 Amp hour batter supplying power to something which requires 24V 5amp how long will the battery last?

BatteryStuff Tech To maintain a safe 50% discharge level, please do not use for more than 2 hours and 31 minutes.

John “To maintain a safe 50% discharge level, please do not use for more than 2 hours and 31 minutes.”
Just wrapping my head around solar and battery drain calculations.. With 24V 32Ah battery, and 24V 5A load, doesn‘t this equal 3.2 hours to 50% drain? (32 / 5) * 0.5 = 3.2? Thanks!

BatteryStuff Tech Battery capacity is not a linear relationship. Amp Hours is usually rated for 20 hours at a time. Therefore, 32 AH means that during a period of 20 hours, the battery provided a total of 32 amps. That is not the equivalent of 1 amp per hour. The greater the draw amount, the less realized capacity you will perceive.

John Aha, that makes sense, thanks for the help. In the spirit of teaching a man to fish, is there a nonlinear equation to work out rough numbers?





BEN how many 1kw solar panels required to electric vehicles like NISSIAN LEAF.It has a motor running at 80kw with lithium ion batteries of 24kwh and on board charging required is 3.3kw.what value should i consider for running of the vehicle?

BatteryStuff Tech Just to clarify, do you want to put solar panels on top of your car to RUN IT live while you‘re driving? Or are you looking for something to RECHARGE the batteries while the car is parked?


Nihon Thanks sir for your answer.
I did use your calculator but still i have confusion about #3 Total watts per hour (DC) where can i get this DC watts?
53V x 3 Lights 7 hours a day
37V Wi Fi 24 hours a day
500W O/S 19 hours a day
I will use 12V 600Ah battery, 240W solar panel. #14 2days backup power required #22 6 sun hours per dayThanks a lot for your help.I am glad to find your website.

BatteryStuff Tech DC Watts is the same as AC Watts. Watts is total power, you can pull from it at different voltage, whatever is available for you. Are your numbers, 53 volts? 37 volts? I will hesitate to believe that these devices run on such varying voltages. These are probably the Wattage ratings for the devices.


Nihon I am new to solar system and i would like to know.. 53V X 3 Lights, 37V WiFi and 500W oparation system. I want to run this all 19 hours a day. How many watts solar panle, how many Volt and amp battery, Inverter, controler do i need? to run this 3 things well for all season. looking forward to hear from you. thaks a lot.

BatteryStuff Tech Are you unable to input these numbers into our calculator? Use your demand (lights, wifi, etc) and fill in the first field in the calculator with the total watts. Enter 19 hours into the next box. And fill in the remaining boxes with the correct information (system voltage, what size batteries you will use, etc) and it will tell you how many batteries and solar panels you need based on the information you put in.


Lutz I have a system drawing 700ma 24v for 24 hours a day. I use 2×12v 90ah gell batteries in series and 2× 130watt 12v panels in series to keep the batteries charged.
Is this configuration sufficient to keep my system running 24/7/365.
BatteryStuff Tech 700 mAh for 24 hours a day is 16.8 Amps. 130 Watts will charge at a rate of 5 watts per hour of direct sunlight. Therefore, if you have at least 4 hours of good sunlight everyday, then your system will be suficient.


Ham DIYer Hi, I am a bit confused. I want to continuously run a small remote router which runs at .24A DC from a 12v source. Using your calculator it would seem that a 7aH 12V battery and a 5 watt panel would do the trick and give me several days of reserve. Plugging .24 into the first box works. But then I see the “x12” in the description. Is that just for AC? or should my number be 2.88 in which case I need a much larger system. Size counts. I want to keep this as compact and light as I can. Thanks.

BatteryStuff Tech The first box is watts, which is amps x volts. With total power, Watts, AC or DC is irrelevant. But since this solar system is 12 volts DC, we‘re using 12 as our conversion factor. Therefore, the first box should be 12 x .24, which is 2.88.


Iqbal Singh hey i want to have some more of knowledge about solar power. is there any way that i could talk to you nd clear my doubts. i need it very urgently as i am working on a solar project and want to have more technical details. so plzz i need you to give some of ur valuable time. thanks.

BatteryStuff Tech You are more than to welcome to call our tech line at 5414744421 or email us at tech@batterystuff.com


David Hi, i want to run 4 × 30W LED flood lights for 5 hours a night, i want to run a 12vdc solar system to run them, how many amp hours of battery should i have, and how many watts solar system would i need to fully recharge battry every day and allow enough in reserve for cloudy days etc etc./

BatteryStuff Tech Please fill in the solar calculator with this information. If your having trouble with the calculator, please refer to the solar calculator tutorial to explain what the fields mean. From your comment, it seems to me like you have all the information you need. You just need to put in the numbers in the calculator in order to give you your answers.


Jj I am purchasing a home with 1860 watts of solar, 24 volt system charging 16 trojan 6 volt batteries in series. will this keep everything running except for the furnace, (will use wood heat)?no electricity availible, owners have been using this system for 10 years with upgrades they have 2 referagerators running and one freezer

BatteryStuff Tech Without knowing the amount of draw of the appliances, I cannot tell you if the system will be enough or not.
If you could provide detailed information about the amount of draw, the duration of the draw, and the number of sunlight hours, please email our tech department for an answer at tech@batterystuff.com.


F Hello Guys,
I wonder how or where to get the Worst Weather Factor of 1.55?
Please advise.
Regards

BatteryStuff Tech Worst weather factor guesstimates for days with clouds, rain, fog, etc. This of course will drastically reduce the amount of sunlight the panel will receive. When sizing systems, it‘s important to keep in mind that not everyday will be perfectly sunny. It‘s better to be safe than sorry. Going larger on a solar system will help protect from the inefficiencies of bad weather.


Beginner What is high rate battery? Its hard to get true solar batteries locally so we have been using with a UPS battery sealed lead acid battery (Unigy HR1500) which is described a high rate battery of with a 33 Amp hour rating.

BatteryStuff Tech A “high rate” battery means that it can take a higher rate of discharge. The battery is designed to handle large loads. But keep in mind, the higher the load, the shorter the perceived capacity of the battery will be.


RICH hi, no one seems to know what their on about on other sites intill i seen this one, i need some help please ,
ive got…. one 110 ah deep cycle battery , 30a charge controller , 500w inverter , an 5 solar panels at 11.13v each (minimum everyday)linked pos neg in connection box going in my charge controller at 12.06v too 12.68 no higher, i run six 11 watt lights at 230 volts from inverter,
ive asked lots of people but no one knows my question is,
why does my battery start on 12.67v then soon as i switch lights on it drops to 12.21v an falls 8v first few hours, 6v after then steady 5v every hour till i switch it off after 6 hours give or take (battery now on 11.73 ish)i need it at lease 8 hours a day,anyone helps ill give a big pat on back

BatteryStuff Tech Sounds like a bad battery. Under a load, especially 11 watt lights, the voltage should never go below 8 volts, or even 10 for that matter. When the voltage drops under a load, it‘s usually a sign of an internal defect. A weld piece (solder point) is probably becoming disconnected under the prolonged heat of the load. This will cut current. But when the load is off, the metal cools and touches again, giving you a “false” voltage reading. If the battery is under warranty, it should be replaced.

RICH do you think my solar panels are giving enough out? i made them myself, 20 cells in one 1.5 watt each (or so they say) i have 5 panels,which is best for me, parallel or series just need to know what best for my system, my battery is brand new ive rung them but they say i might need another battery (is that selling or what, any ideas how to get the 8 hours i want for 6 11 watt 230 volt lights ?? thanks for replying,

BatteryStuff Tech 1.5 watts each? That gives you a total of 7.5 watts of power. This translates to roughly 1/2 amp of charge every hour of direct sunlight. If your lights are rated for 11 watts, and you have 6 of them, I believe there is not enough solar power to recharge the batteries after being used.
With your lights, you‘re pulling about 1 amp an hour from your battery. If you want to recharge, you‘ll need at least 15 watts, but better with 20 watts of solar, to be safe.


RICH do you think my solar panels are giving enough out? parallel or series is better for my system, my battery is brand new any ideas how to get the 8 hours i want for 6 11watt 230volt lights ?? thanks for reply

BatteryStuff Tech If the solar panels are rated for 12 volts, then I recommend parallel to keep the voltage system in tact. 12.68 is kind of low for the battery. Typical charging voltage can be as high as 14.2 volts, and floating at 13.2 volts. The higher voltage is needed to bring the voltage up to the battery. At fully charged state, you should be reading 12.8 – 13.2 volts for a new battery.
As far was the solar goes, you didn‘t specify how many watts of solar panel power you have collectively. You simply stated you have 5 panels at 11.13v each. This is low voltage, and it would help to have either amperage or wattage rating on the panels. Without this information, I cannot confirm if your system is going to work or not.




Mark Hi. Your website is so informative. Thanks a lot for that.
I have a spare diesel car battery (12V ~100A). I would like to use it for lighting and/or cooking. What are my best options? Use 12V appliances or buy an inverter and hook into it something 240vish?
I am thinking of connecting the battery to a trickle charger.
Thanks & regards,
Mark

BatteryStuff Tech 100 CCA, or AH? As long as it‘s a deep cycle battery, and not just a starting battery, then it‘s fine to use. You will see best performance if you use 12 volt appliances. Using an inverter causes a loss of efficiency.

Mark Actually it‘s 105AH.



Bo I need help. I want to run a small off the grid cabin. I currently have 8 12volt 100amp deep cycle batteries, 1 60watt solar panel, 1 charge controller and a Tripp Lite PV2000FC DC to AC converter. I want to run a small Frigidaire 5000BTU air conditioner rated at 565 watts and 1 60 watt incandescent light bulb for two consecutive days (approx. 67 hours per day). I‘m having issues where the Tripp Lite PV2000FC starts showing low power after a few hours on the first day then turns off the power. What do I need or what is wrong with this setup?
Thanks in advance for the help!

BatteryStuff Tech Your AC and light together draw from the battery at a rate of roughly ~63 amps an hour. Having 800 AH from the batteries is good. But a 60 Watt solar panel will only deliver ~4 amps of charge an hour. To keep a safe 50% discharge level, I recommend using your batteries to run your cabin for no more than 6 hours and 4 minutes. But the solar panel you have will not put back the power you used in a single day. A good rule of thumb is this: 15 watts is equivalent to 1 amp of charge. To keep up with your draw for 6 hours of sunlight, you will need a ~800 Watt solar system, with a much larger controller.


Asad Hi, I have 4 solar panels 130 watt each, 2 in series. My battery and inverter system is 24 volt. at peak it produces 8.28.4 amperes. I have two 180 ampere batteries in series. Solar panels charge the consumed battery in 24 hours. The rest of the day the house runs on direct out put saving the battery current for the night. The question is how much energy can I spend at day time without any loss from batteries.

BatteryStuff Tech How many hours of sunlight do you have left over after the batteries have been recharged? Are you going to run your house directly off the solar panels during the daytime?


HPC Hi, interested in learning more about solar power, and that‘s how I found you….. I‘ve been doing some research in alternative ways of getting myself around other than gas vehicles… well, I found something that uses a 78v 20ah battery, my question is, if i had a solar panel battery charging setup that had output amps of 5a, would it still be 4hrs or so? does the size in volts makes a difference in charge times?

BatteryStuff Tech If you have a 72 volt battery system, you will need 72 volt solar system. Like batteries, this will require wiring in series a total of at least six 12 volt solar panels to make it work. If you need 5 Amps of output, you‘re look at least 360 Watts of total solar power. Since your battery bank capacity is 20 AH, 4 hours is a good estimate.


Ajmera ok thanks a lot i will let you know if it works!!!

Ajmera hi there,
i have a battery with specs 12V 7.0AH Cycle use 14.514.9V stand by use 13.613.8 and initial current is less than 2.8A..
And i am having a solar panel is of 12V 4W…
How can i charge the battery with this solar panel?
How much time it will take to charge the battery?
I am running 100LED‘s of 3.5V 20mA?
Please suggest me how the thing will work because i need the bed should be able to work even in nights mmm its almost 15 hours a day i want the led turned on…
Appreciate your help….
thank you
BatteryStuff Tech A 4 Watt panel will deliver roughly 300 mAh of charge an hour, in direct sunlight. Connect the positive and negative output cables from the panel to the matching terminals on the battery to charge it. With a rate of 0.3 Amps, it would take approximately 25 hours to fully charge from a discharged state. This is roughly 4 days worth of sunlight (67 hours a day). Your LED lights are rated for 3.5 volts, your power source is 12 volts. You need to match up the voltages, it‘s important to keep the system the same. After you accomplish that, please us our other online calculators to help you determine either a proper size battery, or load runtime.


Duke Your example calculation converting AC amps to DC Watts adding 10% for inverter inefficiency escaped me.
10% of 2AC amps = 0.4DC amps? Shouldn‘t this be 0.2DC amps added to 20DC amps (20.2 amps)?
So 2AC amps=242.4DC watts. Did you mean to use a 20% inefficency adder instead?1 Amp AC = 10 Amps DC. (example, 2AC amps =20DC amp)
Add 10% (20.4 amps)
DC amps x 12v = DC watts. (20.4 ×12 =244.8 watts)

BatteryStuff Tech You are correct, the numbers in the example are incorrect. 2 Amps AC x 120 Volts AC = 240 Watts. 240 Watts / 12 volts DC = 20 Amps DC. 10% of 20 Amps DC is 2 Amps DC. 20 Amps DC + 2 Amps DC = 22 Amps DC. The final Wattage rating, given the 10% inefficiency rate, should be: 264 Watts.

Midge So why not correct the math example above? It has been 3 months since this was first recognized.

BatteryStuff Tech Sorry for the delay. I don‘t know why this hasn‘t been fixed yet. I‘ll make sure we get it done ASAP.




Zakir 1 Amp AC = 10 Amps DC …. you have written this for 110 Volts AC ….. what will be the conversion factor if we are on 220 Volts AC ???

BatteryStuff Tech 1 AMP AC x 110 Volts AC = ~110 Watts. 110 Watts divided by 12 Volts DC will give you ~10 (9.1) AMPS DC. Volts x Amps = Watts. Therefore, 1 AMP AC x 220 Volts AC = 220 Watts. 220 Watts divided by 12 Volts DC will give you ~20 (18.3) AMPS DC.
