How to Estimate Solar Charge Time Solar charge time is not as simple as dividing your battery capacity (measured in Watt hours) by the power of your solar panel (measured in Watts). Even in perfect conditions, you get loss due to: Voltage drop of solar panel or Maximum Power Point is lower than rated panel voltage Energy used by circuit to buck or boost voltage Energy used to convert electrical energy into stored chemical energy – with excess lost as heat We go through two common battery chemistries and give you some rules of thumb for each. Shop Solar Panels Lithium Ion Battery Charge Time from Solar Since the charge cycle slows down considerably after the battery reaches 90% capacity, this calculation assumes full is about 90% of complete capacity. Panel Power (in Watts) / Battery Capacity (in Watt hours) X 2 Example: 6 Watt Solar Panel charging a 4,000mAh, 3.7V Battery – Time = 14.8Wh / 6 Watts X 1.6 = 3.95 hours Tip: Get a “USB Multimeter” from Amazon to verify your charge rate If you are connecting to an off the shelf battery pack, there are a number of reasons that the charge rate could be worse. We look at those in our post: “Can Your Panel Charge My Battery Pack.” Adafruit and SparkFun both offer Lithium Ion charge controllers that can work well with solar panels. Lead Acid Battery Charge Time from Solar The effective capacity of a lead acid battery is about 50% of stated capacity, i.e. you shouldn’t discharge it past 50% full. They also have a lower charge efficiency than lithium ion. For the purpose of this calculation, we will assume that the battery capacity is the true capacity. This is our favorite waterproof charge controller for lead acid batteries. Panel Power (in Watts) / Battery Capacity (in Watt hours) X 2 Example: 10 Watt, 18 Volt Solar Panel charging a 12V, 10 Amp hour Lead Acid Battery (120 Wh) from 50% full to Full – Time = 60Wh / 10 Watts X 2 = 12 hours Environmental Factors Will Likely Increase Charge Time The solar charge times above assume a 25 degree Celsius day with the panel pointed directly at the sun. Some quick rules for estimation: Heat: Power output of a panel will decrease by about 1/2% per degree over 25 Celsius. Angle: As the panel rotates away from the sun, power output drops. Angle to Sun % Output 90 100% 75 97% 60 88% 45 77% 30 61% 15 32% 0 3% Clouds: Any haze or clouds will slow down charge time, often significantly. See: Solar Performance in Cloudy Conditions. Solar for IoT and Remote Sensors Want to learn more about how Voltaic solar panels can work for your next IoT project? Contact our experienced team today to set up a consultation. Schedule an IoT Consultation 88 Responses Charles Cook November 8, 2012 Could the 16.8 Watt Panel be used to charge a 12 Volt vehicle battery? My primary use will be a laptop, cell phone, and a 12 volt battery for my hand held Ham Radio. Will one panel be enough? Reply admin November 8, 2012 Hi Charles, Yes, the 16.8 Watt panel can charge a 12V battery, but a few quick pointers. You should use a charge controller between the panel and the battery and you probably shouldn’t use a standard car battery, you’d want to use an AGM deep cycle battery. See these two posts for more details: http://voltaicsystems.com/blog/choosing-a-lead-acid-battery-for-solar-charging/ http://voltaicsystems.com/blog/charge-car-batteries/ Hope that helps / jeff Reply Jeremy December 23, 2014 what kind of charge controller was used on that second link – the images and link appear to be mostly broken inside that post. I see that an MPPT Sunsaver was used in the first post , but was hoping the second post yielded a more cost affective solution as the MPPT controllers are a little pricey Tom June 12, 2017 I have converted a mini van a Dodge Ram pro master city into a mini camper inside I built a small snack bar a installed a porta potty and a twin 24 inch wide single bed with TV for intertainment I plan to travel from California to visit friends and family in Virginia I do plan to stay at hotels at times but if I find them to costly I ‘ll stay in mini van to camp in or rest at rest stops I chose the mine van for it’s 4 celinder eng and it’s fuel efficiency the question I have is I purchased five jumper battery to use to operate a DC TV, laptop , charge a cell phone as well I want to install ring DC operated security camera to view from my cell phone if ‘someone messes around with the vans insides while I’m in a hotel room and would like to attach a solar panel to the roof rack to keep the jumper battery’s charged by the use of a cigertte DC connection plug as I driving instead of taking them out to the room for AC to DC charging but I’m not sure of what wattage solar panels to use and would I need a regulate or power controller while changing two at a time I believe I need some where in the area of a DC voltage charging range of 12 to 14 dc charging volts but I’m not sure if anyone knows the answer I’m at Ter5@aol.com I would be very great full thanks ajmal July 15, 2013 i want to use an ac fan for 6 hours daily by a car battry and i want to charge this battry by a 40w panal. what will be the time required to charge it by this panal? plz help mn Reply admin July 15, 2013 It depends on the Voltage of your panel, the size of the car battery, your charge controller that you’re using and the weather conditions. You should be able to do it in about a day of full sun though. Please consider using a deep-cycle rather than a standard car battery, it will work better. Reply Tim November 14, 2013 I want to charge a laptop battery (about 11V, 4400 mAH) and a 9V, 2100mAH battery for a smaller device. Do I need to get two kits, one 18V and one 12V? Or can one kit charge both? I’m thinking a 12V charger will probably be okay with a 9V battery, but I don’t know about an 18V charger. Thank you. Reply admin November 14, 2013 Hi Tim, In general, we recommend using the panels to charge our V60 battery and then set the output on the battery to charge your devices. The laptop would most likely charge from the 16V setting on the V60 and the 9V battery from the 12V source. In some cases, it will be possible to charge the devices directly from the panels. Its hard to know without knowing the specs of the devices, but you would want to put 12V into the 9V battery and 18V into the 11V battery as you suggest. The key here is to make sure there is some protection to make sure you are charging safely: no over charge, no short circuit, etc. Reply webby November 16, 2013 I had a 50 watts solar panel and 12 volts battery 28 amp. how many hrs will take the battery to get fullcharge? Reply admin November 17, 2013 It depends on a lot of factors, but in reasonably good sunlight with the panels pointed towards the sun, we would expect about 17 hours. Nothing replaces field testing though! The math is: 12*28/50 * 2.5 = 16.8 Reply Junaid December 3, 2013 4-7 hours Reply Andre M December 4, 2013 I am looking to mount one or two solar panels on my cargo bike (long john) for bicycle touring. As such I wonder if I can charge my Thinkpad (it has a 20V input, but the battery itself is a mere 10.8V, 7.8Ah) with one or two of your panels and how I would go about setting it up. I doubt it could take 36V input if I took two of your 16.8 and wired them in series, and I wonder how it would do with two of your 16.8 panels wired in parallel? I will probably buy the V60 battery, but in order to save losses I would prefer to be able to charge the laptop directly. Reply admin December 5, 2013 Hi Andre, It might work directly from the panels if wired in parallel, it is hard to tell without testing. In general laptops/tablets have fairly sophisticated charge circuits and are looking for something pretty close to spec. It will definitely work from the battery. Reply Andre M December 7, 2013 Thank you, that was quick. I might just give it a go and see what happens. Now, to find the money 😀 Eddie January 31, 2014 I have the 13 watt battery charger from harbor freight charges at 12 and 24 volts. I got a 40 amp charge controler and a 1.2 amp inverter that plugs into a cigaret lighter socket, the panel kit came with a cigaret lighter socket that I can this plug into. The question is ….will this supply suffecent power for a power tool charger to and charge an 18 volt battery? Specs of the charger:120 VAC, 60 watt. Or… Can I connect the 18 volt battery direct to the battery charge port on the charge . And… What is the average amps hours on 12 volt battery? Thanks for your kind response. Reply siva May 22, 2014 how many hours are taken to charge 12v battery useing 10w,12v solar panel Reply Kumar August 24, 2018 What is the Amp hour (Ah) for battery. if you have battery Ah then apply below formula 12V x Battery Ah ============== Solar panel W (10) Reply Mark June 9, 2014 Hi, I am going to install a 50 watt solar panel, control charger, 2000 watt continuous/4000 watt peak power inverter, and a group 29 deep cycle flooded battery, what will I be able to run with this set up? I would like to run a 15 amp chest freezer and a 22 inch tv, and one house fan will this be enough and if so how long will I be able to run this before battery runs out? Reply Brent June 11, 2014 I just bought a Coleman 6W solar battery charger. I am looking to use a 12V battery during the night to run 2 lights, a small fan, and some small speakers. My plan is to use a 400W inverter attached to the battery at night, then use the solar panel to trickle charge the battery at night. Most likely a car battery, possibly a marine gel battery. Does anyone know if my plan will work? Trying for 4 days/4 nights. Im guessing the solar panel will have a good 12+ hrs in sunlight to charge each day Reply Robin July 21, 2015 I have a small 4amp fan i wanted to run 2-3hrs a day. I have a 2.2 amp trickle charger..Can I put the trickle charger on the car battery while running my fan to maintain the car battery? Any info would be helpful. Reply Tony Kauffmann July 27, 2015 probably not, the voltage might not be high enough Reply Catherine February 24, 2016 Hello I am a novice here. What is the least watt/volt solar cell that is needed to charge an iPhone, etc.? How does the size of the solar cell fit in to the equation? Reply Voltaic Systems February 24, 2016 We typically recommend 3.5 as the smallest panel for charging an iPhone. Smaller than that and you will typically be frustrated with charge times. Reply Edwin March 26, 2016 Is it possible that a 5 watt 18v solar panel can charge a smartphone? Reply Voltaic Systems March 28, 2016 It is if the panel has a regulator. The output needs to be close to 5V, 1A to charge a smartphone. In most cases, our batteries function as the regulator, but we also have a 5V regulator for direct charging from our 6V panels. See – https://www.voltaicsystems.com/solar-usb-regulator Reply mathsongroup March 29, 2016 Pls, i want set up a solar pv phone charging centre in my house (village) to charge about 6 phones (3.7v and 2.5w each) at a time. do i need inverter and controller? pls let someone help me for the calculation of the components; panel, inverter and controller. Reply Voltaic Systems March 29, 2016 You don’t need an inverter. Everything can stay in DC. For this sort of application, you could use the 9 Watt Kit which includes a 9 Watt solar panel and the V44, 12,000mAh battery and 2 USB ports. If you really wanted to reduce costs, you could just get the 9 Watt panel and the USB regulator. This would work to charge phones on sunny days, but you wouldn’t have any power storage if you skip the battery. See: https://www.voltaicsystems.com/9-watt-panel https://www.voltaicsystems.com/9-watt-kit Reply mathsongroup March 30, 2016 Thank You for the instruction. Pls how many female usb regulators or phones can be connected to the output of the 9w panel? Reply Voltaic Systems March 30, 2016 Up to 2 if you use a splitter – https://www.voltaicsystems.com/f3511-splitter Reply olayinka May 5, 2016 I have a need to set up a 30 phone capacity charging station. What kit do I need to have i.e panel, battery, inverter, charge controller Reply Voltaic Systems May 5, 2016 It is certainly possible to do without an inverter / charge controller, but you could also do it that way as well. Using our equipment, you could get 7-8 x 9 Watt kits which have a 9 Watt panel and V44 battery. From each V44 you could run a USB hub so that you could charge 4 phones from each V44 battery. In this way, you skip going from DC to AC and back to DC. Or you could get a large panel, say 100 Watts and connect it to a battery over 200 Watt hours with a built in inverter and run lots of USB chargers out of that. Have a look at earthtech products for a range of products in this category. Reply Selina Zhou May 7, 2016 How long would it take to recharge a IPhone 6s, fully, using a 100 watts solar panel? Reply Voltaic Systems May 9, 2016 Same time as from the Apple wall charger, assuming you have a regulated USB output of 5V, 2A. The iPhone has a maximum charge rate so you won’t be able to charge faster than from a wall. Reply M faisal khan June 23, 2016 I have 150 Watt soler panel and 105 amp battery. What time is required to charge my 12 volt battry. Reply Gurpreet July 20, 2016 I want to purchase a 13000 mah 5 V power bank but company donot mention how long it will take to charge power bank fully in a good sunny day…any idea ahow approx it will take to charge it fully? Reply Voltaic Systems July 20, 2016 It depends on how efficient the battery charges from solar power and the size of the solar panel. If we assume that the battery charges efficiently from solar, a reasonable estimate is (Battery Capacity in Watt hours) / (Power of Solar Panel) * 2. You need to take the size of the solar panel, divide by 48 Watt hours (the voltage of the internal battery is actually 3.7) and multiply by 2. Reply raja August 17, 2016 i had 12v 10w panel and 12v 40w panel how much capacity battery and Amps charge controller are require please help me I planning for an led garden light Reply Tony Kauffmann October 26, 2016 How much capacity of the battery you need depends on the power consumption of your light and how long you want the light to run. Reply DEEPANKAR September 22, 2016 how can we charge a small solar panel fast. can we use other things to charge without a Sun? Reply Tony Kauffmann October 26, 2016 All of our voltaic universal batteries can also be charged from a wall power outlet, either through a USB port or through the included 18V AC charger for the V72. So you don’t need to sun to charge these batteries. Reply aivazquez October 5, 2016 I don’t agree. Look at: http://defyingnormal.com/2013/07/06/review-voltaic-systems-fuse-10w/ Reply RockAndHardPlace November 3, 2016 I know someone living in their vehicle and they need a cpap machine while they sleep. They have an inverter, and it runs their machine 6-7 hours from the car battery before shutting off. When it shuts off, there is still enough of a charge on the battery to start the vehicle. I think the inverter won’t allow them to run it dead, but it let’s it go until that’s all that’s left. He is about to buy a solar setup from a private party that has a total of 32 watts in two solar panels, and has a charge controller with it. Where we live, it is always completely overcast or raining. Would the panels still charge the battery to full in the 8 hours or so that we have daylight? Reply Voltaic Systems November 3, 2016 There are a lot of unknown variables. a) the size of the battery inside the CPAP machine and b) whether the battery inside the CPAP will charge effectively. However, it seems like you could be short on power given the conditions. Solar won’t work as well When it is raining, the power output of the panels will likely be about 5% of its rated output or 1.5W. However, the CPAP may not accept this low amount of power so it could be zero. The easiest way to figure it out would be to test on a fully drained CPAP machine. Reply Idris December 16, 2016 How may watt solar panel that will charge 400Ah battery with 5kva inverter 75% load during sunning time and for how many hours Reply sunny January 7, 2017 hi can I charge a 18v laptop using 20v 7w solar panel? Reply Voltaic Systems January 9, 2017 It won’t work. The panel produces so little current that your laptop will not recognize it. In addition, charging laptops directly from a panel is challenging as they expect a very steady flow of current which solar does not provide. You could connect your panel to our V72 battery (https:/www.voltaicsystems.com/v72) and use that to charge your laptop. 7 Watts is well below our smallest system for charging laptops which is a bit over 10 Watts so you should be prepared to be patient or get a larger solar panel (in Watts). Reply Andrea March 7, 2017 Hi Jeff, Following your example it means a 4,5V solar panel could charge a 3,7V 2500mah lipo battery? And in how much time if the panel has 3,2W and about 20% of efficency Reply Voltaic Systems March 7, 2017 Without some sort of boost circuit, we believe 4.5V is too low of a peak voltage to charge a 3.7V battery. It will charge reasonably well when the battery is flat (3.7V), but as it starts to charge, its voltage will increase and the charge rate will slow down and may not charge it completely full. Over the complete charge cycle, 5-6V (we use 6V) will charge the battery faster. The efficiency of the cells in the panel doesn’t matter in this case. What matters is the total power produced by the panel as well as the voltage. In your case (and assuming you use a 6 Volt panel) your 3.7V 2500mAh battery is 9.25 Watt hours. Approximate time to charge would be 9.25 Watt hours / 3.2 Watts * 2 = 5.8 hours. This will vary based on cloud conditions, shading, angle to the sun and temperature. Reply Andrea March 7, 2017 Thank you very much Jeff, adding a mppt controller is usually make any difference in term of faster charging? Or it is better to have just a simple controller to reset panel when weaked sun or cloudy? Voltaic Systems March 7, 2017 Hi Andrea, MPPT chips can improve performance, but may simply add cost without significant gain. Where we see them most effective is in either very large systems or when space is highly constrained and the circuit needs to get every available bit of power. We’ve seen lots of these circuits under-perform so it is really only worthwhile for expert engineers or someone who is going to put in a lot of time testing output under a range of solar and environmental conditions. Andrea March 7, 2017 Forgot to say: Thanks for your time Reply Andrea March 7, 2017 Thanks a lot Jeff I hope I could buy some beers one day Reply rakshit March 12, 2017 Can a 12v and 2w solar panel charge my mobile battery? Reply Voltaic Systems April 28, 2017 It most likely won’t work. You can get a regulator to drop the 12V down to 5V, but the 2W panel is so small that your device will ignore it and won’t charge. Reply James March 12, 2017 I’d like to charge a deep cycle car battery (this one http://www.odysseybatteries.com/batteries/pc1500t.htm) with the Arc 20 panel. How would you recommend going about this? Reply Voltaic Systems March 13, 2017 Hi James, I would get something like the Phocos CM04 charge controller. Connect from the Arc 20W panel with this extension: https://www.voltaicsystems.com/extension-with-exposed-leads Connect from the charge controller to the lead acid battery with hookup wire. It is labeled pretty clearly on the charge controller what connects to what. Reply Luke Davis April 3, 2017 Hi, I have the array 10 volt back pack. It works great in full sunlight, it charged my phone from 45 % to 90 % in 2 hours. I charge through window panes, but a lot slower than when in full sunlight. However I still havent figured out how to store power. As soon as i take the kit away from the sunlight, the phone stops charging. How do I store power from the sun Am i doing something wrong ? Reply Voltaic Systems April 28, 2017 Hi Luke, can you send us a picture of your setup and submit a support request here: http://tech-support.voltaicsystems.com/customer/portal/emails/new Reply Travis April 20, 2017 Hello, I Currently have a 12v 12 AH battery that runs a 12v 4 amp water pump. Normally I have to plug the battery in to charge it but was hoping a solar panel could eliminate this. Assuming this pump runs for no more than 2 hours total a day, what size solar panel would I need to purchase? I know their are outside factors so I would rather be safe than sorry. Any help is appreciated! Thanks Reply Voltaic Systems April 28, 2017 Hi Travis – assuming that the pump uses the full 4A (you’d have to measure to be sure), your pump draws 48 Watts. If you run it for two hours, the pump consumes 96 Watt hours a day. Not every day is sunny so I would tend to overdo it with a 50-100 Watt panel from your local big box hardware store. They are not that expensive, but that will charge the battery in 1.5 – 3 hours of good sun a day. Reply Erik April 29, 2017 I’m building a remote APRS weather station. I draw about .5amps per hour to run the system. What size battery and what size solar panel do I need if I want it to be able to run year round. The charts for my area show 5 hours of sun per day average. (Eastern washington). Reply Voltaic Systems May 23, 2017 Hi Erik – 0.5A at what voltage? If at 5 Volts, that is 2.5 Watts (0.5 * 5V) and 60 Watt hours per day. We tend to assume that you are going to get a batch of bad weather vs. 5 hours of sunlight a day. To plan for that period, we tend to recommend scaling the system so that it can run on 2 hours of sun a day and run for 5 days without any sun. For important systems, be even more pessimistic. I would suggest using something around a 60 Watt panel and a 200 – 300 Watt hour system. You can of course experiment with something smaller or tolerate times when the system goes down during periods of bad weather. Reply Chelsea Inglis May 15, 2017 Hey there, I have been using the 20 watt solar panel with the v72 battery just testing it out. When the battery first arrived fully charged it charged all of my devices with juice to spare. I tentatively have been putting the panel out my window behind a screen and charging it that way. The battery now lights up as fully charged but lasts maybe 10 minutes. Why is it lighting up as fully charged if it isn’t? Thank you! Reply Voltaic Systems May 23, 2017 Hi Chelsea, the V72 won’t charge well from behind a window. Make sure you put the solar panel outside and without any shade. It should take about 5-6 hours in full sun with the panel pointing at the sun. What may have happened in this instance is that the V72 gave a false positive of being fully charged. We are working on making the charge indicator more accurate. Reply Hozefa July 17, 2017 Hii I want to charge one laptop and 3 smart phones i want to charge with solar panel so how much watt panel i should buy and what voltage output battery i use??? Reply Voltaic Systems July 17, 2017 Our most popular laptop charger is the Arc 20W Kit – https://www.voltaicsystems.com/arc20w-kit The voltage setting depends on the AC charger that your laptop uses, see: https://www.voltaicsystems.com/solar-laptop-charger#faq_3 For your smartphones, just connect into the USB port on the Voltaic battery. It always outputs 5V. Jeff Reply gryann January 12, 2018 Could a 6v solar cell be used to charge a 3v battery? Reply Voltaic Systems January 12, 2018 Yes. The important things are that it charges safely (no overcharge, no short circuit) and efficiently (doesn’t waste too much power). We use 6V open circuit panels to charge 3.7V LiIon / LiPo cells in a lot of our products. Reply Nicholas April 5, 2018 Can a 5 watt to 10 watt solar panel charge up a 9 volt battrry .. I have a caline echo effects pedal that uses a 9 volt battery to operate . It also has the 9 volt input for an AC power adapter .. I have a USB to 9 volt adapter cable to connect a solar panel to the caline echo pedal .. But I need to know what’s the least amount of watts from the solar panel needed to power up the echo pedal that uses 9 volts .. Thank you Reply Voltaic Systems April 5, 2018 What kind of battery? Is it a rechargeable or non-rechargeable. I think you’d have more luck if you used a solar panel to charge a USB battery (like our V44), you can use that USB to 9V adapter to run Caline pedal. Reply Future Aztec April 23, 2018 Is it ever possible to use a tablet while hooked up to a battery bank that is hooked up to a solar panel. In principle this is problematic — is there any way around it, or are we still stuck with a 2 step process of charge and use, instead of using the battery while charging a battery from a weak source like the sun (as opposed to a wall outlet). Reply Voltaic Systems April 23, 2018 Hi – if your battery has pass through charging (all of Voltaic battery packs have this), then yes, you can use the tablet while hooked up to a solar panel. Reply Future Aztec April 24, 2018 Well I have an Anker PowerCore 20100 battery pack and a BigBlue 28w solar panel. The battery pack has two usb outputs, one I have hooked up to a usb hub, the other is poweing my ipad. When I plug the solar panel into the battery pack, both the USB hub and the iPad start to pulse with the incomming power from the solar panel. This surprised me because I thought I could, in a way, slow the draw from the battery pack by feeding it power from the solar panel. I expected that the power from the battery pack would be constant, even though the solar power from the pack is not. In my understanding this is cause by the fact that the solar power to the battery is less than the draw from the battery to the iPad. But I am not certain. It seems like what is happening is that the battery is getting bypassed and the power I am receiving is direct solar — or, at least, it behaves that way. I want to make sure it isn’t some error I have made in how I have things hooked up. Or, that there is some kind of module I can implement in my setup to fix this issue. I did see a post on a forum thread of a business selling Goal Zero products that, with their equipment, it is possible to have a battery hooked up to a solar panel while using the battery to power a device. I got in contact with Goal Zero and the tech confirmed this. Since I had just ordered an Anker battery pack and was not able to figure out how to do this with their product, I contacted Anker to inquire about the issue and see if they had a product that could address it. The tech there told me that it is not common for a battery pack to do what the Goal Zero battery can do. So I was surprised to see you write that, “if your battery has pass through charging (all of Voltaic battery packs have this), then yes, you can use the tablet while hooked up to a solar panel.” Can you recommend a product that would allow me to charge an iPad Mini 4, while powering a USB hub rated at 5V2A? And if so, my current Anker battery says it will charge an iPad Mini 4: 2.5 times. What sort of comparable volume would a suggested product provide? Voltaic Systems April 24, 2018 Most battery packs don’t charge well from solar and don’t do pass through charging well, see: https://www.voltaicsystems.com/blog/can-panel-charge-battery-pack/ A couple of comments: – Most companies are extremely optimistic in the number of times they can charge a device – they assume there is zero loss going from one battery to the next, but 2.5X into the Mini from the PowerCore 20100 seems about right – The Arc 20W Kit http://www.voltaicsystems.com/arc20w-kit is the closest fit – same battery size, slightly smaller panel Future Aztec April 25, 2018 I really appreciate your help. I was on the phone with Rev Power today explaining what my needs were and how my Anker battery was not doing the job. The person on the phone didn’t listen well to what I was say straight off the bat and seemed to be annoyed that I had specific needs I was trying to cover. Then I was put on hold for 15 minutes — I ended up just hanging up. I have a couple more questions about your battery banks. Would my 28 watt BigBlue solar panel be wasted on the V72 that I see in the kit you linked to. The panel there is only 20 watts. I am sure it is a better panel than the BigBlue, but I think that this 28 watt panel I already have will be fine — at least I hope. The other thing I am concerned about is I don’t want my iPad or USB hub to receive a pulse. This causes the charging message to pop up every few seconds and my USB hub to flick on and off. If I were to order the V72 would I get a steady charge from the battery while the battery itself received the usual intermittent charge from the solar panel? Finally, to make sure. I want to plug in an iPad and a USB hub at the same time, my setup seemed to work well with 2 usb outs (as I already have the cabling to route this correctly), the V72 only has one USB — will I be able to just plug the iPad into the laptop port and the usb hub into the usb port at the same time? I have been trying to get this figured out and drew a picture of my current setup. Here is a link just to try to be more clear on what I am doing. At the moment everything works awesome, until I plug the solar panel into the battery pack. https://forum.audiob.us/uploads/editor/fb/bzvckecmber0.png Reply Voltaic Systems April 25, 2018 The BigBlue outputs USB, it will not charge our V72 laptop battery which requires ~18 Volts. As long as you don’t need 12V output (it sounds like you don’t), you could get 2 x V44 battery packs and that would give you: a) redundancy b) more overall output for all your devices – each battery can output 3A To split the output from the panel you have into 2 x V44, you would need: 1 xhttps://www.voltaicsystems.com/3511-musb 1 x https://www.voltaicsystems.com/f3511-splitter 2 x https://www.voltaicsystems.com/f3511-5521 Reply Ann September 14, 2018 I want to charge a car battery by solar panel. I use one to charge my motorcycle 10W panel that works as trickle charger when fully charged. Just curious what wattage would be needed as a panel for a car battery. Reply Voltaic Systems September 14, 2018 You don’t need a lot of wattage, you need the right voltage, which is somewhere between 14-18 Volts. You can search on Amazon for solar trickle charger and you will see a large range of options. You could certainly use our 9 Watt panel, but you would need to add some extra electrical components (blocking diode or charge controller) to make it work. Reply Lee September 24, 2018 Hello, I am trying to determine if a 200W (two solar panels approximately 2 x 4 feet in size) will be enough to keep 2 (Everstart 29DC from Walmart) deep cycle batteries charged while I am running an ARB 50 quart refrigerator that takes about 1 amp per hour to operate in hot weather along with led coach lighting at night and a couple of hours of running a small led tv. Is 200W too much or could I get by with less or would I need more? Any additional tips or information would be greatly appreciated. Thank you. Reply Spencer September 24, 2018 How long will it take for 30 x 300w solar panels take to charge a battery bank of 6000ah? Reply Tosin November 13, 2018 Devices and equipment list 1. 24v 200mh lithium batteries; 2. 60A MPPT charge controller; 3. 2.5kva solar inverter; 4. Average daily sunlight: 9hrs; 5. Backup time after sun down 9hrs; 6. Total estimated load: 550watts; Please I would like an advice on required panels of 300watts monocrystalline solar panels to charge the batteries and equally engage the inverter Reply PMP December 26, 2018 Hello, I’d like to power a modem and cellular device similar to a phone but is meant for ‘country’ internet that will be in a sealed box from the elements. Elements: summer up to +35-40 degrees Celsius. Winters down to -35 degrees celcius. The modem will be connected to a ubiquity dish over PPoE. My home is in a ridge where cellular signal is very weak and this box will sit on top of that ridge and relay internet via dishes to my home. The latency has been taken into account and is minor. Any suggestions to help accomplish this goal would be greatly appreciated. Should more information be needed it can easily be provided. Thank you. Reply Voltaic Systems December 31, 2018 To determine how big of a solar system you need, you first need to figure out the average power draw of your device in Watts. You can connect it up to a multimeter or talk to someone from the company (you’re not looking for the rated draw of the charger, but the actual power consumption). Once you know that, then you can properly size the system. Reply Vibhor February 21, 2019 Hi, Can you explain this calculation please; what is 1.6? Also, what is the voltage assumed for the 6W panel? Panel Power (in Watts) / Battery Capacity (in Watt hours) X 2 Example: 6 Watt Solar Panel charging a 4,000mAh, 3.7V Battery – Time = 14.8Wh / 6 Watts X 1.6 = 3.95 hours Thanks Reply Voltaic Systems February 25, 2019 Vibhor, looks like a typo. We’ve updated the text on the Example. Note that we have gotten faster charge times especially with MPPT in good conditions, but doubling is a useful shorthand. Reply Lucian March 2, 2019 Nice article.Though I have tried to understand the charging batteries time forumla,I kinda don’t get it..So if I have a total number of panels summing 600W(12v) and I want to charge 6KW summing batteries, in how many hours would those batteries be charged.(90% charging type batteries.) In a sunny day. Any help would be much appreciated.Thank you. Reply Mario March 15, 2019 I have installed a Truck fridge in my Westfalia. It takes on average 2 amp/hour with 12 VDc to keep it cold. What size of solar panel and battery you recommand to keep it running. Reply Leave a Reply Cancel Reply Your email address will not be published.CommentName* Email* Website This site uses Akismet to reduce spam. Learn how your comment data is processed.