Hello from new guy and solar panel question!

[littlefurious]

Hey I'm new to most forums in general and electronics forums in particular. I hope to learn alot about electronics in general... parts, what they do, how they do it, etc. First question... I have an electric scooter... custom-made, twin-engine, massively powerful. It's being worked on and improved at the moment, and at some point soon i'll probably exchange the old lead-acid batteries for lithium-ion to save weight. I normally charge it via a DC converter that plugs into the wall. Do you think I could get a big enough solar panel area to charge this thing on a fairly regular basis... would I have to buy or build it.. building is cheaper and more fun but less reliable in my case. I can't remember the amps or volts it uses...I'll ask my dad who's having a guy work on it, but for batteries with that much power... could I make a solar converter to at least trickle charge it on sunny days? Thanks! Oh and anyone who wants to PM me and teach me about any specific electronic device, or get my email to do the same is welcome... i'm here to learn!

 

[magickaldan]

Hello and welcome to the forums. If your up to a lot of soldering you could try and buy some individual solar cells and tie them together to make a good size panel (search on ebay). Sometimes they'll be about 1/4th the price of an assembled panel, just a lot more work. I havn't done it yet but plan to, and I've heard about alot of people doing it so it can't be that hard. And if your not sure about something on ebay post a link here and see what others say just to be on the safe side.

But anyways once you find out how big the batteries are, then you can design something to charge them safely. But without the specs of the batteries not much we can help you with on determining size of charging system. Try searching to find that out.

Edit: also if it's one of those small scooters with the small 12v lead acid batteries then it wouldn't need to be too big of a system to charge them. Then there probably between 4 and 12 AH rating. Not for sure exactly at what amperage you could charge them though.

 

[littlefurious]

Yes I'm quite familiar with soldiering and have several guns for it and several types of solder. So I'll probably just make my own then, once I know what size I need. Thanks for the answer! Now... any idea, once I get the voltage/amperage I need( assume I'll need a testing unit to make sure of that?), how will I feed the lines into the batteries in the same configuration as the AC/DC converter it came with and will I need some kind of protector so I don't overcharge the batteries? Thanks again!

 

[littlefurious]

Oh and what kind, size, and type of solar cells should I be looking for on ebay? What are the differences?

 

[magickaldan]

Heres a link to some (**broken link removed**) There 36 6x6 cells about .5 volts each so total of about 18volts should charge a 12v battery nicely. Price averages about $1.50 U.S. per watt. Which if you bought an assembled unit would be about 3.50 to 4.75/watt. But search around there might be better deals. And for instructions on how assemble and what all other stuff you'll need search google I'm sure you'll find tons of info.

But pretty much after you get it built it's just a matter of having a charge controller, between the solar cells and batteries. Google is your best friend this has been done over and over, and there's tons of info on it.

 

[HarveyH42]

**broken link removed**

There are quite a few guides on hooking up raw cells, even broken ones. Which, if you aren't familiar, very thin and fragile. Soldering them is a little tricky, and you should find some very thin, high tin solder. Might consider getting a few extra, so you are covered for breakage, and soldering practice.

Container of Broken Solar Cells-The Electronic Goldmine

This site use to have better deals on broken cells, you could practice on. They have this soldering guide, https://www.electro-tech-online.com/custompdfs/2009/08/SolarCellInstructions.pdf which might help some.

 

[littlefurious]

Thanks for all the info... soon as my dad remembers to ask the guy what volts and amps he used, I'll start the project. Or do I need to wait? Could I not just build a larger panel that can produce at least 24v in case for some reason he used a 24v battery system? Or maybe I could just get a small package and practice, and when I find out how much voltage/amperage I need, I'll just add on Thanks again!

 

[HarveyH42]

I'd suggest getting some of the broken pieces, or check the site for some better ones to practice on. You should really get a little experience working with these, before going large. Wasn't kidding about how delicate these cells are, and you have solder and mount quite a few. The housing needs to be rugged enough for outside conditions as well, can't bend or flex. You might find that ready made panels are worth the price. Really depends on how commit you are to building from scratch, or if you really just want to save the money. If you just want something that's going to work, and last for years, the ready made isn't such a bad value.

 

[magickaldan]

Also if you have the AC-DC Charger with you just read the specs on it to see what amps and voltage you need to supply the batteries. Most have a label with output voltage and amps on them.

 

[littlefurious]

Yeah all the equipment is 800+ miles away with the scooter So until my dad gets in touch with him again, hopefully today, I won't know. Any idea on whether I should get some practice in soldiering together solar panels? I've done it before for projects and know how fragile most are... they snap like.. well, like super-thin glass! And I'll need a volt/ammeter I suppose to measure what kind of current I'm getting from the setup each time I add a cell. Any good sites to find cells to practice on, and any good outlines or "how-to" manuals out there on correctly doing the job? Thanks for the answers amigos!

 

[littlefurious]

So I'm good on pretty much everything once my dad gets the info on the volts and amps the system runs on... probably monday and probably 12/18/24volts. I'm pretty sure the batteries themselves were 12v. Anyway, to charge this, do I need to connect in series for more voltage, or parallel for more amperage? Or will that really not make a difference, as the actual current or wattage will stay the same? I was going to connect in series as that seems to be what most people do to charge batteries but just thought I'd check! Thanks again for the help!

 

[bryan1]

Hello littlefurious,
If all you want to do is trickle charge a scooter battery don't bother trying with ebay PV wafer cells, they are so fragile you'll endup breaking a heap of them.
I have said in previous threads in this RE forum trying to make your own panels will endup costing more than buying a PV panel and for longterm use personally I'd just buy a panel suitable. Those small amorphous trickle pv solar might only what you need and they should be available at any auto store.

I have lived off the grid for over 5 years now so my suggestion will endup saving you a heap of money and pain of spending more money on wafer cells and finding out you were better of just buying a panel.

If I can help anymore fell free to PM me and I'll gladly help you out.

Regards Bryan

 

[littlefurious]

Thanks but no thanks... I've used those cells before and out of over 100, never broken one yet. I am careful bro. This way is much cheaper and I can adjust the voltage and amperage to what I need almost exactly, or a little more actually so even in dimmer light I can still get what I need. And who knows, if this turns out well I might try bigger panels. If you aren't going to even try to answer my question at all, why did you answer btw? If you can get a trickle panel premade for 10 bucks let me know

 

[magickaldan]

You can get one for about 15 to 20 dollars. But most output only 1 to 5 watts of power at 12volts. The one i just seen on ebay was $20 and for 2.2watts. So 2.2watts/12v=.183 amps. So if you calculate price per watt = $9.09/watt. Now there are some auctions where you can find them a lot cheaper. That was just one of the first one's that showed up on ebay. Such as the 5 watt ones. I looked at some are 9 dollars and 30 dollars shipping and some are 39 dollars and free shipping. lol

But anyways lets say you have total 7 amp/hr capacity on your scooter. I'm assuming it's a 24v scooter with two 12v 7a/h batteries in series. Most small scooters are this way but vary a lot such as 24v, 36v, 48v... upward just more batteries in series.

So if you buy two of those small panels (because you'll need 24v not the 12v one panel can give) and hook them up. It will make 2 panels equal 24v with .183 amps. Lets say the batteries are 50% discharged (7/2=3.5) that's 3.5a/h +/- that need to be pushed back into the batteries. If our cells are putting out .183 a/h then it will take 19+ hours to charge them. (3.5/.183=19.125) Or about 2 1/2 days of 8 hour sunlight.

Or if you bought two of the 5 watt panels which would cost around 39*2=78 dollars or $7.8/watt.
10watts/24v=.416amps. 3.5/.416=8.4hours. So you might get lucky and be able to charge your batteries in one good day of light. That's if all my math is right. Anyone who thinks it's wrong tell me why please.

 

[littlefurious]

Well that didn't help AT ALL magicaldan... lol. If your math is right, and i don't care to check, I never liked doing math although i'm good at it, that wasn't my question. I have cancer and am waiting on surgery so I have a lot of time on my hands... a project is what I need. I just wanted to know if I needed to hook up the whole panel in series for max voltage or hook some up in series and some in parallel so I can get more amps, less volts? I mean it's the same current either way, I know that much, voltsxamps=current I think I remember, but i never took any electronics. So please stick to the topic and try to stop persuading me to just buy a premade panel. I just want to make my own and keep my hands and mind busy thinking about that, and not about whether I'll get to keep my liver or have to take immunosuppresants for the rest of my most-likely foreshortened life. Thanks.

 

[magickaldan]

Well there's a minimum voltage you'll need to even begin charging the batteries and not knowing what voltage your battery pack is kinda limiting factor. Say there arranged to be 24v then minimum charging voltage should be 25.8v and max should be 28.2v.
Roughly 2.15v - 2.35v per cell, and a 12v battery has 6 cells, and 24v has 12 cells. and so forth.

Volts*Amps(which is the same as current)=Watts When hooking up your cells in series you will increase the voltage while keeping the current the same. And when hooking up in parrallel you will increase current while keeping voltage the same. So say your cells are .5volt cells you will need 24 cells in series to produce 12v.

But anyways I would shoot for making several 12v panels as a starter then you could hook them up in series to gain voltage for whatever your battery pack is.

Check out this site for charts on voltages to charge Sealed lead acid batteries. How to charge sealed lead acid batteries. Custom battery chargers for OEMs in a hurry from PowerStream Which is most likely what type of battery you will have in the scooter.

 

[littlefurious]

Yes they're sealed lead-acid... was looking at upgrading them at some point to lithium-ion to save weight when the price drops on Li-Ion batteries that size. So you're saying I don't need to have any cells hooked up in parallel, I just need to have voltage slightly above what my system runs on? Or would it make a difference? Say I had enough extra cells, I make 3 12v panels... hook 2 up in series to get 24volts or slightly more... can i hook the 3rd one up parallel for extra amperage and charge faster? Voltage should stay the same if the 3rd panels cells were all hooked up parallel right? I'll start on some 12V panels tomorrow when I pick up a voltmeter to test the cells... I'm using unbroken cells first so shouldn't need to do anything but solder them together. When I get to the broken cells though(though they are not really broken, they're 3x3 and worst i've seen is a TINY chip off a corner of one... maybe 5% of the surface area gone), do you know a good place to get a conductive pen to redraw the conductive lines if they're missing? Or would conductive silver paint be better? Thanks for the helpful answers!