Portable solar power and notebooks, and voltage differences - Page 1
Forum section: electronics / general

author: Sigmoid
author_rank: Frequent Contributor
timestamp: December 26, 2017, 12:19:09 pm
content: Heya. So I need a way to stay at least somewhat productive while out in nature (in the tropics, thankfully), and for that I'm thinking of getting an 80-100W portable solar panel to use with my rugged Thinkpad T61.Now what gives me a bit of a headache is that 90% of portable, foldable solar devices are dual voltage for 5V (USB) and 18V (barrel). The Thinkpad is rated at 20V. Now with 18V I think I can't even really use a car inverter (nor would I really want to tbh).I wonder if it's possible to run a notebook like this off a slightly lower voltage, will the internal regulator cope, or will it just tell me to go eff myself...

author: ealex
author_rank: Frequent Contributor
timestamp: December 26, 2017, 01:47:35 pm
content: 18V should be ok, but test it to be sure.battery charging might not work at that voltage.an old 19V asus could start and run as usual down to 12V but could not charge the battery at that voltage.

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: December 26, 2017, 01:59:35 pm
content: Most notebooks use an 19v supply. There is usually a volt or so tolerance either way. The reason is that they have typically to charge 4 lithium cells in series, which calls for 16.8v max.Most solar panels will output considerably more than their nominal voltage. This is because the nominal voltage allows for a worst case under very hot conditions. (OK, for Aussies that might be a normal casebut not here..) Diode forward drop being less when hot. A nominally 12v panel will often output 20v under no-load in our conditions (If your fingers aren't too stiff to turn the multimeter to the volts range, that is)You do of course need a regulator to prevent the voltage going too high, which might damage the notebook.

author: 2N3055
author_rank: Super Contributor
timestamp: December 26, 2017, 02:38:03 pm
content: 100 W panel is 1 m square... 3 feet by 3 feet..nothing portable about it....

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 26, 2017, 05:09:33 pm
content: Quote from: 2N3055 on December 26, 2017, 02:38:03 pmThe ones specifically sold as portable panels are segmented so they can fold up. Naturally, that comes at a significant price premium.

author: Gregg
author_rank: Super Contributor
timestamp: December 27, 2017, 06:36:24 am
content: You might try a buck boost converter with constant voltage and current limiting like this one:https://www.banggood.com/DPH3205-160W-Buck-boost-Converter-Constant-Voltage-Current-Programmable-Digital-Control-p-1105294.html?rmmds=search&cur_warehouse=CNThey also sell a nice little aluminum case for it:https://www.banggood.com/RUIDENG-DP-And-DPS-Power-Supply-Housing-2-Kinds-Aluminum-Housing-Constant-Voltage-Current-Casing-p-1146253.html?rmmds=detail-top-buytogether-auto&ID=514816&cur_warehouse=CNI have a couple of the Ruideng buck converters and they seem pretty well built considering they are made in China; same brand that Dave did a couple of videos about.For overall reliability, you may want to change the electrolytic caps to name brand ones before going too far away.

author: bazza
author_rank: Contributor
timestamp: April 01, 2018, 12:26:29 am
content: You need some type of PWM or MPPT solar regulator ( maybe 10 A) hooked up to a battery ( maybe 30 Ah minimum, but it depends on usage) to keep powered-up predictably.Next item is only around 4 USD:To power my laptop on solar DC for the past 3 years I have been using a DC-DC step-up converter found on ebay. Search for:DC converter 6-35V.Look for the ones in the metal casing. You can pop the lids off these things easily, which is handy too. They are just held on by pressure of the side 'walls'. Anyway, an item like this will probably work well with most low to midrange laptops as long as your laptop doesn't sip too much power. Mine is low-end.You will need to wire things up yourself. I think I am using 2.5mm squared wire which is just about the max those little terminals can take with ferrules on. I prefer to terminate the wires with ferrules for robustness and resistance to broken wire strands. Ferrules and ferrule crimpers are available online. I can't live without them.The unit itself has a dial to adjust to your desired latop output voltage, so keep a multimeter handy. Also, every unit I've ordered has had mislabelled stampings on its metal case. Just pay more attention to the PCB markings than the case markings and you should be able to discern output from input.On the laptop end you need the correct connector.I normally buy something like this first:5.5 mm x 2.1mm screw dc connector plug 10pcsThese plug in well to your final laptop plug, found with a search such as:Universal laptop power adapter set 2.1mm...on ebay.With the suitable barrel connector and the suitable voltage via the step-up converter, you should be ready to go. No silly inverter needed.

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 01, 2018, 06:59:31 pm
content: If you don't mind going to an oddball 5S pack, that will give a voltage that most modern laptops (and some mini desktops) will accept direct with no conversion. You'll probably need a converter for solar charging since there are few solar panels with a Vmp a little above the 20.5V or so it would take to charge a 5S pack to the recommended long term charge voltage.

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 19, 2018, 08:59:02 pm
content: hmmthe Thinkpad T61 is very old and Takes a lot of power. I got a new one in January this Year the work a lot longer with the default Akku Pack!!! I also have also Solar Cells but the recharche just the Accu Pack from that Company. I also will buy an Rugged Laptop who is Watertide that will be a better solution for you.