Enough solar for a modern laptop

[TernVI]

Yes, it's my work laptop and the task it does is my job
....o they don't actually have better battery life or smaller batteries (45Wh here and runs all day, ....

If you'd said you needed 45Wh to do a day's work in the first place, instead of

"probably uses less than 20W average so I'm thinking around 2A draw "

you might have got answers you liked more.

The whole thing is a 'how long is a piece of string' kind of question.
Depending on how far into the winter you want to work, what batteries you are prepared to buy, what estimates of how many dark days in a row, you can get any answer you want.
Baggy's approach is sound, but in the limit, there will come a dark rainy week where you have to run the engine to charge the batteries. Doing that occasionally is not the end of the world.

 

[lustyd]

I didn't say I needed 45Wh, I said the battery is 45Wh and will run all day. That'll take more to charge from the domestic bank, which will take more to charge from solar. None of this is an exact science, I was looking for guidance before embarking on a project and got exactly that - it's clear that the minimum amount of solar for the usage will make it unfeasable given the other constraints at play. I may later change those constraints, I could easily fit an arch if I didn't hate the look of them for instance, but right now I've avoided some lengthy work to get to a dead end so feel like that's a win

 

[lustyd]

I had to be a little creative in placement, but have managed to find room for 3x40W panels on my 23 footer.

I think even that would be more of a compromise than I'm willing to make. I may end up giving it a go with this kind of capacity, but keep them in a locker and deploy while at anchor. I could happily put in a deck socket to make this possible. For the time being though I may just see how long I manage on the domestic bank

 

[Kelpie]

really nice write up, thanks. Now if we can get that 300W down to 50cm x 50cm and have it work in the UK...

You must be able to fit more solar than that on a 36ft boat. Maybe a panel on each side of the cockpit, hung on the guardwires?

 

[lustyd]

I can, I just don't like the look or the windage . As I said that might change some day but at the moment this was more useful for the learning as I've not looked at it before. If I end up working on board a lot then I may have to go full liveaboard style

 

[Pete7]

I can, I just don't like the look or the windage . As I said that might change some day but at the moment this was more useful for the learning as I've not looked at it before. If I end up working on board a lot then I may have to go full liveaboard style

If you ware at anchor so stationary, there is one trick you can do to help boost the solar panels and that is have them loose on deck. Until it slipped and smashed, we had a 60w suitcase panel in addition to our other solar panels. Moving it around the deck to face the sun made a huge difference for a couple of minutes work and some string 3 times a day.

In addition to 300w on an arch which I know you will hate, we also have one of these now. The regulator is junk and I ditched it for a Victron MPPT which I can now see via bluetooth, so when it starts to tail off, its time to move it again. If you are at anchor the tide will mean you need to move the panel. Will it last 25 years and still give 80%? no chance but its cheap and cheerful so if it lasts 5 years that's fine. Also the canvas cover is less damaging when getting it out of the companion way and storing it again compared to the aluminium folding type.

110W Foldable Solar Panel with 20A Solar ControllermodulFür Travel Camping Car 12V Battery Charging | Wish

Be warned though, solar is addictive, we started with 45w, then 80w, next 150w and now 300w. for the fridge and freezer. Now there is some space on the rails, hmm.....

 

[lustyd]

That might be a pretty good solution actually. At 110W and positioned properly it might be just about enough juice for topping up

 

[Pete7]

Nah, you need the really big boys toys

Dokio 220W 12V Folding Portable Solar Panel Kit For Phone/Car battery/Camping/Caravan | Wish

 

[Norman_E]

I use a small inverter that I plug into a "cigar lighter" socket. Recently "upgraded my laptop" to something that I can run for eight hours on battery and never use it underway.

Its more efficient to use a DC to DC boost converter like this. Power Supply 12V Car Battery Charger Adapter +Plug 2 For Notebook Laptop 80W | eBay

I bought one of these from a UK supplier some years back and it works very well on either of my laptops.

 

[jac]

I didn't say I needed 45Wh, I said the battery is 45Wh and will run all day. That'll take more to charge from the domestic bank, which will take more to charge from solar. None of this is an exact science, I was looking for guidance before embarking on a project and got exactly that - it's clear that the minimum amount of solar for the usage will make it unfeasable given the other constraints at play. I may later change those constraints, I could easily fit an arch if I didn't hate the look of them for instance, but right now I've avoided some lengthy work to get to a dead end so feel like that's a win

How discharged is that 45 W battery - it's a fairly small battery in 12v Domestic Battery bank terms and that's what you need to understand . Assuming it's something like a 12v battery ( It's probably more) Then you're looking at a 4Ah battery tops. That suggests that a 20W panel would probably do it in summer but doesn't get around the winter problem or take into account the full demands of the boats domestic systems

 

[Kelpie]

We have a 100w rigid panel (£70 off eBay) hung on the guardwires, like a dodger. When anchored on in calm conditions underway it is swung up to whatever angle catches the most sun- in fact I actually take a certain pleasure with fiddling around with it through the course of the day and watching the extra power coming in through the charge controller.
I plan to fit a matching one on the other side next year. It's so cheap is seems a complete no-brainer.

 

[catlotion]

I'm facing the same challenge next year when I abandon the extortionate marina.

Has anyone mounted a solar array on their tender? I thought of a folding pair of panels I can deploy once aboard...?

 

[stevie69p]

I have a fixed 80w rigid panel on the hatch garage but not many other good places for having more fixed panels, so I have another 80w folding semi flexible that I can position wherever the sun is shining to best effect. I don't have a fridge mind you, but maybe a fixed and moveable combination might be in order.

 

[lustyd]

I'm going to answer my own question in case anyone else stumbles on this thread in the future. My Surface Laptop 3 will happily charge from a USB-C socket - I just bought one of these - https://www.amazon.co.uk/gp/product/B07R8JV1LX
According to the battery monitor this is pulling 17W from the system while the battery is charging, which is the limit of the socket. I can use the laptop at the same time and it continues to charge the battery. When fully charged it uses 13W during use which seems reasonable.

That means that with this socket and a pretty small solar install I should be able to work comfortably on board if I don't use the fridge. A 50W panel should suffice in the summer and should give enough for lights etc. too. My plan now is to have a portable 100W panel and connect it as and when required at anchor.

 

[PhillM]

How abut using a lithium battery? I was told by a friend that you can take almost all the charge from them and they also accept more charge more quickly so you get more bang for your Solar bucks. Apparently. I'm sure someone will be along soon to correct me!

 

[lustyd]

Battery capacity on the boat will just extend time away from power, whether that's shore or solar. With a 50W panel I can comfortably work all day on the laptop and stay charged so I don't think capacity will be a problem until I switch the fridge on, but that will then raise the requirement for panels to 300W or more which would need a proper installation. The draw has now dropped to about 6W with the laptop running so I assume it was still charging a bit last time I looked.