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Need help! Why my solar panel will not charge my laptop batt

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Newbie level 6
Sep 4, 2009
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how much current a laptop need

I had came across many solar charger products whereby they use a battery pack to store the solar energy and charge it to their laptops.

I had in mind thay i want to use the solar energy going to through regulator to charge my laptop battery.

I am using a 20w solar panel which generates a short circuit voltage of 12 to 13v and the short circuit current will generate a max of 1.6A depending on the sun intensity.

The solar panel is connected to the Dc-Dc converter and to the laptop.

I am using two sets of 4 solar cells in series connected in parallel therefore my panel consist of 8 solar cells.

The dc converts any input voltage between 12-13.8 volts to a range of 16v to 24v.

Since my compact laptop requires 18.5V , i set it to 19V, because the converter only have specific range like 18, 19 ,20etc..

The question is I was wondering why the laptop battery does charge not as the charging indicator does not light even with an solar current output of 1.10 A ?...

By the way the converter has an efficiency of about 85%.

Does it mean there is insufficient current to charge the laptop battery?..

I had this concept whereby any amount of current will charge the battery depending how much it takes to charge eg: trickle charge, float charge..

Correct me if i am wrong ..thx for reading...

Will adding another 4 cells in parallel solve the problem?

my laptop battery has a capacity of 4400mah

Today as i was testing, the solar cells are generating a range of current from 0.64A to 1.10A. Most of the time its generating 1.10A.

The light of the converter activates for the whole time as there is sufficient voltage..

I am curious there are some products such as solar rolls are able to trickle charge a laptop directly from the sun.

i have attached a link below:

how to charge a laptop battery with solar

most probably your laptop requires 2A or more to begin to charge.
since panels can produce only 1 A max, which when upconverted becomes only approx. 0,5 A, such current is far too small to charge the laptop.
I would suggest charging 12 V battery with panels and plug DCDC to the battery, which allows more current.

solar panel laptop

hmm i have a spare lead acid battery and solar controller intended for a back-up plan..

by the way my university's project requires me to provide a solar charger that is able to extend the life shelve of the battery without the addition of the extra battery pack..

i had done about 3 mths of research and basic testing testing in the lab. I did measure the current going in my laptop is 1.88A when i connected the laptop adaptor to the ac supply with the battery intact . Althought the adaptor has a voltage rating of 18.5v and 3.5A which i think is the maximum current it can deliver to the laptop..

I did power the laptop without a battery, using a external dc supply which takes a spike of 1.7 plus Ampre to power up and a constant of 1.072A to maintain the on status of the laptop.

Does 1.88- 1.072 = the charging current?..

possible to charge laptop using solar pannel

The difference is charging current of the battery, which however is not always the same, but is dependand on the battery fullness state. Also currents 1.88 and 1.072 are not always the same - depending on the laptop power consumption and again battery state.

In any case in order to charge the laptop you need approx 2 A - that is if you want to charge it, while using it. Charging current of battery you can measure by measuring the current, while laptop is shut down...

how to charge a laptop from solar panel

Today i found certain stuffs to determine the cause.

1. Initially the Dc-Dc converter out was 18v which was insufficient, i adjust it to 19v.

2. The solar panel was able to barely charge in which the charge indicator on for about 4 seconds and off . The proccess was repeated many times. By than the current generated by the panel was about 1.2A and when its goes in the converter about 15% was lost.

3. Adding a 4 new cells in series only did increase the current to about 1.8A which also generate in the same result.

4. I did try a fully charge 7Ah lead acid battery and it was able to charge the laptop like the adaptor. I can say the current was insufficien to generate the charge.

5. I did measure the charging current from adaptor to the battery. It takes spike of about 1.7 plus Ampre to power up the laptop. After, it takes a constant of 1.072A to maintain the on status. This is without the battery.

6. When i attached the battery and measure the current flowing from the adaptor to the laptop is about 1.88A tp 2.4A whereby the laptop battery will charge. so the charging current is determine by the current measured minus 1.072A. This could varied depending of the amount of percentage the battery will charge.

Correct me if i am wrong for my observation...thx

My new plan is to use a solar controller to charge my 4Ah lead acid battery . The lead acid battery is connected to the dc-dc converter and to the laptop. Any suggestions thanks..

charge laptop dc solar

If the laptop only needs a very short burst of high current then a large capacitor could be used. If the laptop needs the high current for a few seconds then a battery of some sort would be needed to supply the longer period of high current. PV cells have a limited amount of current which drops the voltage very fast when loaded beyond the MPP point so some kind of storage is needed for the higher current bursts.

charge laptop with sun

Hi John90,

May I know how long (hours) do you let your solar chagers to charge the laptop baterry in your testing? only a few minutes? 1 hour? or you have been leave it for 4 hours? As I know the laptop adaptor chager ampere will be higher as you know most of the application at home or in office, users will plug the adaptor to charge the battery an at the same time they are using the laptop for their work, so the adaptor at the time will need to supply the current for the laptop consumption and few amperes (e.g 500mA) to charge the battery. If you are working with your laptop for 8 hours, means 8 hours * 500mA will charge the battery.

So do your application of solar chager panel is same like the adaptor?(charging while using the laptop) or just leave the charger to charge the laptop without using the laptop? If that is the case, try to leave the charger to charge.

Futhermore, one more information I need to know, if you had full charged your labtop battery, how long it could last for a normal ON stage consumption without plug in the adaptor, give me the approx number of hour e.g 2~2.5 hrs. My labtop I am using now could only stand for one(1) hr. That could be the different rating of charging time needed for yours.

how much solar panels needed to charge laptop

Hi there, i let my solar charger do the charging till my laptop battery goes flat typically around an hour or so. I was only surfing the net and doing some emailing.

My application is not the same as the adaptor. It is becausemy solar panel is only able to provides a max about 1.6A when the sun intensity is the best. Usually, it only output an current of 1.2A and when it goes to the laptop there will be a lost of 15 percent.

I am using the solar charger to charge the laptop while i am using.

Typically an hour to about 1.5 hrs. With just basic use not activating the cd-driver inside but using wireless so i supposed the laptop will consume slightly more current.

What i am puzzled is the charging light and it flicks off after about a few seconds. The process is repeated.

charging a laptop with solar panel


Do you mean the charging light flicks off when you are using the laptop while charging it? Try not to ON your laptop while charging, and leave it about 4 hours to charge, and see what happen. Singapore wheather is quite hot now, I know :D

my solar panel energy singapore

I had tried out the second plan, it was working. I just had to take note of some pointers.

1. prevent the lead acid battery from being overcharge and discharge.

2. had to fully-charged the battery frequently ( at least one or twice monthly) to prevent it from getting permantly damage.

i will try the plan you had mentioned earlier after i complete my testing for my second plan.

help solar panel

hi there,
U did mention that ur solar panel only produce 0.64 to 1.1 Amp of current. Does this current u measure while charging ur laptop or only short circuit current that produced by ur solar panel? Since ur solar panel is only 20W and 1.6A max current.

how to use solar controller to charge laptop

i connected the solar panels to the converter and to the laptop. From there i measured the current.

i was wondering should the lead acid battery be charged to 13.8V because 12.7 is the nominal votlage where it was charged finish.

Today i did some testing with a 12.7 nominal voltage , and after a few minutes my controller shut it off at 11.6v. My laptop battery is 100 percent charge. I tried to implement the lead acid battery similarly to as the ac adaptor.

My lead acid battery is 4ah. Is there a possbility that the current drawn is too huge?..usually my laptop draws the charging current about 0.4 to 2 plus A depending on the state of charge of the laptop battery? ..

From the theortical calculations, it should last about 1 hour plus to 2..

getting long hours of charge on solar

Hi there,
If i'm not mistaken that u said ur laptop battery required about 18.5V right? And u are using a 20W solar panel which produced 12/13V and 1.6A. I think to charge a 18.5V of battery, ur solar panel should produce at least 19V with only 1.05A at maximum of sun intensity by using 20W solar panel. 1.05A is the maximum of ur solar panel can produce but as u said ur solar panel only produced about 0.64~1.1A and this may take about 6~3 hour to fully charge the battery (depend on the current produced at the time). Please correct me if i'm wrong.

solar panel not working

i had modify some changes to my testing. Presently, i am using a 25 W panel which was connected to a solar controller to charge a 12v 4Ah lead acid battery. The load output of my controller was connected to a converter which steps up the voltage to 19v which was than plug into my laptop.

Previously, there was no lead acid battery and controller. It did charge the laptop after increasing the solar panel wattage but it was very inconsistent. I felt that the only way was to store the solar energy in a battery.

If the open circuit voltage of the battery is 13.8V
and the working voltage is 12.7v does it mean that the lead acid battery is fully charged?..

testing measuring solar panel

Hi there,
owh i see... If u think that ur battery is already fully charged, u have to disconnect the battery from charger and leave it about 1hour to get the actual of ur battery voltage. Normally the voltage u measure while charging will drop after charging. So better u disconnect the battery and measure the battery volatge after an hour.

how to charge using 16v solar panel

k thx will take note of that. Usually i measured the open circuit voltage during the next day before beginning my test. I am awared that would be some self-discharged.

I was quite concern with the battery capacity. Since a lead acid battery discharges 80 percent of it capacity which in turn a 4 ah lead acid battery will discharge 3.2A.

After it passed through my converter there would be a 15 percent loss of current which would result to 2.72A.

If i were to charge the laptop battery when it was 10 percent remaining and it would required about 2.12A plus an additional 1.072A to power the laptop similarly to the ac supply. That would severely discharge my battery quickly which the controller will cut off at 11.6V.

I feel it can only be used to charge the laptop battery when it is off and act as a ac supply when the laptop battery is 100 percent charge.

it consumes 1.072A to keep the laptop in the on state, the 4 AH battery will supply the current for about close to 3 hours ? ( including conversion lost)

correct me if i am wrong thdx..

solar charge my laptop

Hi there,
First of all, u can't assume solar power battery charging as using ac supply since we know that solar power is not constant as ac supply. Ur controller will cut off at 11.6V because the battery is now at 20% state of charge and also to protect the battery from over discharge. To keep ur battery longest life, ur battery should remain at 40% state of charge n above. I might say that ur 20W/25W of solar panel is not enough to charge the battery while turning on the laptop because the laptop it self required 1.072A otherwise the solar panel only can produce 1.1A. 3hour standby is enough for 4Ah of battery. Is that any point to help u? :)

lead acid laptop extend


this are very easy.(only thinking u can charge an 12V Car Battery with 6V) .ur Outputvoltage from the Solarcell are only about 12V..ur Notebook Battery about 18.5V ..or other talking the inputVoltage must be 18.5V ur Batterie at the laptop must have an lower voltage as the input voltage...
How to do...u need an Booster (ec. like LTC3780) from about 8V to the 18.5V...and some protection circuit...,if u need i have done this Converter...2"*2" with 150W output Power...
The problem are the power of the cell u have only 20W.. u need 18.5V..ur Input about 12V ..the converter have about 95% ...ur useable output current are 1,02A..
mean u need about 4h for charging..

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