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Simple,basic and cheap Solar charging of you phone,tablet etc.

  • 05-10-2021 4:08pm
    Registered Users Posts: 1,460 ✭✭✭

    I've been charging phone,tablet,etc for many years now,staying away from the mains expensive,and complicated PV Solar set ups.

    Bought a panel,say 30 Watts flexible,local garage are happy to give me free 12v car batteries, may not run a starter motor,but fine for these purposes.The Pound shop sell 12/24 v cigar USB adaptors at 2 amp.All set to charge devices.

    The panel,or panels wired in parallel for more charge current,are on the ground and can be moved to optomise the Sun direction,if you put panels on the roof,you can't turn the house round!

    As the interest grows, the system can be extended to involve running led lighting, radio,wireless speakers,and morph into using lipo laptop batteries,the local computer store are getting rid of. Soon back up supplies get involved for power failures,common in these parts,BT removing the 50vdc supply on the landline, means no power,no emergency calls.

    As the interest in Electric Vehicles grows,have had them now for 8 years, breakers yards have started to specialise in lithium battery sales, lighter and interesting balancing systems,

    Anyway it's a good place to start to learn the basics at little expense and hopefully safely.

    Post edited by Niamh on



  • Registered Users Posts: 1,935 ✭✭✭randomname2005

    Apologies for the double post

    No idea what is going on with this post. Thanks for starting this. I saw your comment on the Solar PV thread and was wondering if you had posted.

    Do you just put a panel in the window of a room?

  • Registered Users Posts: 1,460 ✭✭✭reboot

    Sorry,had posting problems getting back in again.

    Panels are feslexible type,outside where they can be moved to follow the sun. Lead acid batteries also outside,close to panels to avoid long cable runs and subsequent voltage drop.

    Don't really want to get involved with the folk spending tens of thousands and feeding into the mains etc, not for me but very worthy ble at the same time.

    To charge my USB devices I reckon its doable for around €50 ,given free batteries from the garage.

    A recent interest has been shown by the rural farming community to run the electric fences on a similar system instead of expensive non rechargable batteries which are filling my recycling ,oxymoron,centre. Thanks for showing an interest.

  • Registered Users Posts: 1,935 ✭✭✭randomname2005

    It is pretty cool. I have had random thoughts over the years about putting small panels, probably what you have or simiy, in windows with batteries/plugs to charge phones etc but never had the time to plan it properly.

    How long does it take to charge the car battery enough to charge a phone?

  • Registered Users Posts: 1,460 ✭✭✭reboot

    The phone will draw current,say 0ne amp from the battery,I try to have the phone off when charging..

    The panel I bought from Maplin,we miss them,sometimes, cost £30 and charged the battery in sunlight at about one amp.

    So it is on what's called a Float system,and a rough guess,as the phones not flat,say 20% charged in 2hrs?

    We soon get into loosing most of the audience by introducing very basic maths, maybe to be discussed later, Watts= Volts ×Amps.

    Panel is 30 Watts, output voltage,off load,20 volts. 30 divided bt 20 equals 1.5 Amps of current going into the battery,in sunlight.

    The pound shop sells a USB cigar plug which is 12/24 volt in,USB out,for €3. The longest journey and all that,good luck in the dark days ahead,but sure didn't cost much!

  • Registered Users Posts: 1,935 ✭✭✭randomname2005

    Rs or farnell probably have similar.

    Would it work to go straight from panel to the phone? This might be useful for charging things when camping, and emergency use during power outages. I have a rechargeable lantern and power bank which could be changed directly for emergencies. Hmmm

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  • Registered Users Posts: 1,460 ✭✭✭reboot

    To answer your previous question,how long would it take to charge the phone on the suggested float system ,panel charges 12v battery,which then charges phone via the 5v USB adaptor,answer same as if you were charging from mains,phone won't know the difference. In other words the Load,in this case phone,tab,lantern etc, will draw the current it needs from the battery the charger doesn't push a charge into the device.

    Your follow up question, would it work to go straight from the panel to phone,a qualified Yes, But I wouldn't recommend it for the following reason.

    The panel output,in order to charge a 12v battery,must be more than 12v,typically 20v. That's why you should only buy a cigar adaptor which is 12/24v.,must be for use in trucks which are 24v.Problem could arise if the cigar adaptor went faulty,they only cost a few Euro,from China, .What could then happen is that the full 20v panel output would appear across the phone, end of phone.

    Why not play safe and charge the powerbank from the float system.

    With the darker days coming,I doubt if a panel ,less than 20watts output would be much use inside a window? Best to live with panel outside for maximum solar gain. Keep camping during our Indian Summer!

  • Registered Users Posts: 1,935 ✭✭✭randomname2005

    Makes sense regarding failure of charger.

    I'm thinking of this from a convenience perspective. Realistically I could get family members to plug in a device close to a window where there are plug sockets in close vicinity. Having a panel in a window wired to a power bank would maybe be a comprise.

    I'm not seeing dragging a car battery in and out of of the house to charge/use going down well.

    Will check out cost of 50w panels. WFH means I could put it on the window ledge outside on calm days and charge a few things at night from a power bank when people are sleeping.

    Thinking 50w because it might also work inside the window on windy days.

    Although I would probably need a battery in-between for safety for charger failures.

  • Registered Users Posts: 1,460 ✭✭✭reboot

    Makes sense,no argument here.power banks are expensive,fine if they do the job. I've power banks around which are say 10 amp hour,

    Meaning you can draw an amp for 10 hrs,or half an amp for 20 hrs,before it's flat. The heavy lead acids stay outside with a wire coming inside,I know tricky.But they are typically 80 amphrs. Lot more bang,sorry,for no buck.

    Sure start with a panel,at least 20 Watts inside a south facing window and see how it goes.

    Lidl sometimes sell small,but vert bright rechargeable worklights,which are around 5v USB at 2 amp output,a powerbank in effect,for around €25.

    Hope we haven't lost the other half of audience with too many maths!

  • Registered Users Posts: 6,194 ✭✭✭Ubbquittious

    RS solar panels (and most other stuff) very expensive

    Ali express or ebay ones woudl be a lot cheaper

  • Registered Users Posts: 1,460 ✭✭✭reboot

    As you would say,they're everywhere.

    I haven't looked recently,but in recent years have favoured flexible panels,having broken a fair amount of glass in winter storms..

    They don't last forever,my oldest glass panel 50watts has been working for about 30 years,courtesy of BP.

    Others developed faulty connections in the sandwich below the glass,making it very difficult to remake the almost cigarette packet aluminium foil,impossible to solder.Prices don't seem to drop much in our Winter,guess the Sun's shining somewhere else.

    Thanks for info and interest shown.

    Randomname must have a big window he doesn't need to see out of if he'sputting a 50 watt panel in it!. There are ofcourse see through panels,and various hybrids,

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  • Registered Users Posts: 1,935 ✭✭✭randomname2005

    On a sunny day stuck in the box room working from home I definitely don't want to be looking outside!

    Haven't even checked sizes!

    Do you think the older panels were better quality or just circumstance that kept it going more than others?

  • Registered Users Posts: 1,460 ✭✭✭reboot

    50 watt will be maybe a metre by half.There are new materials just around the corner for the past 5 years.

    Panels only work on some colours/ frequencies.

    BP petrol giants made professional panels for ngo projects in places like Bangladesh ,decades ago.

    I wouldn't buy older panels today,but sure a meter at about €10 will read the o/p of any panel you buy,strangely they don't like heat and are less efficient if too warm.

    In winter you'll need to let all the vitamin D into thar boxroom you can get!

  • Registered Users Posts: 1,935 ✭✭✭randomname2005

    Fair enough, wasn't really thinking about size. I figured if nearly 400w is 2m x 1m then 50w would be much smaller, but things don't always scale that way.

    Food for thought, and need to figure out how to make it work.

  • Registered Users Posts: 1,460 ✭✭✭reboot

    Last time I saw panels in a local sop was Halford, they know how to charge,sorry, mostly aimed at caravan folk I guess.

    It does morph into other small projects even in the dark days,worth persisting

  • Registered Users Posts: 1,935 ✭✭✭randomname2005

    I will have to fight a battle on this and need to be able to show benefits and convenience for every day use. Payback not massive issue but having a way of charging tablets, AA/AAA batteries at night in an easy way will be the way to fight it I believe.

  • Registered Users Posts: 1,460 ✭✭✭reboot

    We could debate this for a long time with folk,but they either see it,or they don't and that's fine I'm shocked at how little knowledge our 18 year olds have on electricity upon leaving school,you can't google everything.

    A comparison I think about is a household spending €50 to operate the USB small charging project,and NIE/ESB supplying that 5v USB to the same house. They start,in my case 70 odd mile away,generating 44,000 volts AC, which then has to be converted to 5v DC in the house.I know they do that for all mains supply needs.

    We can,with the little power wall as Elon Musk calls it, supply our own 203v AC with a 12v DC in inverter, I do this because the fishpond pump is mains voltage only in.

    Someone wrote that if every household changed one tungsten light bulb to LED, one power station could be closed.

  • Registered Users Posts: 1,935 ✭✭✭randomname2005

    For size and practicality, would an alarm battery work as well, or not enough capacity from what you use?

    Something like this:

  • Registered Users Posts: 1,460 ✭✭✭reboot

    Interesting how the picture displays a 12Amp hour battery,but the one for sale is 7ahr?,just over half the capacity. Meaning you can draw one amp,roughly a modern smart phone charge,for 7 hrs,more than enough.

    Need to be slightly careful on the charging,the purists might be a bit unhappy about overcharging,and constant currently charge etc.

    I would start the longest journey with this project,and as the clocks go back,and we are too far north of the sun,don't think you'll be overcharging any time soon.

  • Registered Users Posts: 1,935 ✭✭✭randomname2005

    I just copied the first link I found as an example. Something small like this will be easier to hide than a big car battery.

    Time to plan some more

  • Registered Users Posts: 1,460 ✭✭✭reboot

    Agreed,think the best plan is to start at the other end from the panel/battery setup.

    By that I mean,where do you want to use,in this case the 5v USB socket,and how much current do you want to draw and for how long,

    ie,Ampere hours,as marked on the gel pack sealed 12 7Ahr battery.

    That way you can just spend what you need,and keep it simple.

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  • Registered Users Posts: 1,460 ✭✭✭reboot

    Samsun TV remotes, have had a little solar panel on the back for some time now,and have moved on to charging the new models from the WiFi router in the house.

    A small antenna is fitted to the remote which receives the RF signal from the hub.

    Obviously we may only be talking micro Amps in and miliamps out,but with most hubs on 24/7, seems like a game changing idea?

    Once again small scale is worth looking at.

  • Moderators, Home & Garden Moderators Posts: 5,906 Mod ✭✭✭✭graememk

    Remotes use so little power and so infrequently..,(well depends!) It's an ideal use case for it

  • Registered Users Posts: 1,460 ✭✭✭reboot

    I've read that one billion AA batteries are dumped each year,this as you say is a small wattage presumably a tuned circuit,and a welcome start.

    Been launched at CES LV,and can be read on BBC technology page. Thanks

  • Registered Users Posts: 1,460 ✭✭✭reboot

    Perhaps other remotes may follow, and who knows what else?

    Electric toothbrush, razor,and you should see the panic in this house when the firestick remote fails,and needs new batteries,which can't be found in the dark!

  • Moderators, Home & Garden Moderators Posts: 5,906 Mod ✭✭✭✭graememk

    Hard to see anything with motors being able to harvest enough power.

    Although most of them are rechargeable anyway.

  • Registered Users Posts: 1,460 ✭✭✭reboot

    Your right of course to mention any items that draw a lot of current,relativly speaking.

    But I guess if they're not on for long,and sitting receiving a small charge 24/7?

  • Registered Users Posts: 1,460 ✭✭✭reboot

    No battery in remote,simply a capacitor.

  • Moderators, Home & Garden Moderators Posts: 5,906 Mod ✭✭✭✭graememk

    In the meantime, we changed our tv, we have one of them remotes now!, Comes with a normal remote too.. useful when the little one disappears every so often..

  • Registered Users Posts: 1,460 ✭✭✭reboot

    Spooky action at a distance!

    Can't see it coming to a firestick anytime soon.

    But certainly a step forward,when you consider

    millions of AAs dumped every year.

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  • Registered Users Posts: 1,460 ✭✭✭reboot

    Relevancy of this idea of small scale solar charging may becoming of more interest with the war in Ukraine and electricity rationing being talked about?

    I've recently be told the Norther Ireland Office,NIO ,are looking at the possibility of bringing in Generator Ships!

    I didn't know there were such things.