Cells in Series vs Parallel

Posts: 2,511 admin
I'm a bit confused now. I run 12volt trolling motor powered kayaks using 6 amp at full speed and 4amp at 3/4. I thought of using cells on top to maintain or extend the life of battery. I've found .55vdc @ 4000ma cells for 7-8.00ea.
I believed by connecting 25 of these I would have a 12vdc 4amp charging system, however researching other sites they are combining the amps along with the voltage ie. 12vdc @ 100000ma or 100 amps. This cannot be correct, right ?
In series the amps stay the same but voltage is added and parallel voltage stay the same and amps are added. Am I just completely confused..

Cells and spec are at www.plastecs.com/solar%20cells.html

Thanks for your help in my current state of confusion.

Comments

• Posts: 6,290 admin
Re: Cells in Series vs Parallel

Check out this link for the first solar-powered circumnavigation of Long Island.
http://www.sunsailor.com/
• Solar Expert Posts: 5,400 ✭✭✭✭
Re: Cells in Series vs Parallel

You are correct. Series will increase voltage, parallel will increase amperage.

Since you are in a wet environment, consider a commercial panel. I have a hunch that any home made panel would be way more trouble than it is worth, and possible more expensive. In order to just maintain the battery assuming ideal conditions, you would need a panel of at least ~60 watts.

Icarus
• Posts: 6,290 admin
Re: Cells in Series vs Parallel

So you want to build your own panel? First of all, that 4.0 amps is Isc (short circuit current) and not usable. Second, that 0.55 volts is Voc (open circuit voltage) and also not useable. When you draw current, the voltage drops. Look at a PV I-V chart.

So 25 of those would give you Voc of 13.75V if wired in series with Isc of 4A. At max power point on the I-V curve, you will probably get 10.9V and 3.2A ignoring any wiring losses or glass losses.

Compare the individual solar cell you are looking at to the SolarWorld 75W panel. The cells look similar.

http://www.affordable-solar.com/solarworld-sw75-75-watt-solar-panel.htm

Single-crystal PV panels are often made with 36 cells in series to make something suitable to charge a 12V battery effectively. If you purchased 36 cells from this place at \$7.25, it will cost \$261. You can buy a panel with a 25 year warranty for \$410. Do you think you can assemble a panel with wiring, glass, frame, and sealant for a marine environment for \$149?
• Posts: 6,290 admin
Re: Cells in Series vs Parallel

Thanks Icarus. Yeah its a father son project for keys fishing trip. Top of hull is 3/8" so thinking of embedding them slightly for a flush mount then sealing with thin plexi or vinyl. I thought it was right just had some doubt thrown in from other sites. It would be nice to have 72 watts so I could use the battery as a spare supply. Thank you for the clarity, heading to the workshop..
• Solar Expert Posts: 10,300 ✭✭✭✭
Re: Cells in Series vs Parallel

don't ignore what sage just said as your 25 cells won't be enough. funny how somebody that says something one wants to hear gets thanked while the other with perfectly good advice that one didn't want to hear got ignored.:roll:
• Solar Expert Posts: 5,400 ✭✭✭✭
Re: Cells in Series vs Parallel

With all due respect Neil,

If you look at the timing of the post thanking me, he wrote it while the other was being written. (I also didn't tell him what he wanted to hear)

T
• Solar Expert Posts: 10,300 ✭✭✭✭
Re: Cells in Series vs Parallel

tis true, but he could've seen it after he posted as it would've shown as a new posting and there was hours before i made my comment so even though there was overlap he would've seen it after he posted. this was also not to say anything bad about you icarus, but was selective on his part. he shall find out the hard way if he is ignoring good advice so i'll drop it.
• Posts: 6,290 admin
Re: Cells in Series vs Parallel

No problem here. I was just trying to toss some numbers out. Reading my comment later, it could come off as gruff. I was just in a hurry and trying to bracket the problem. I've had fun ideas like that also. He's lucky I didn't spend time trying to determine how big the wire would need to be to build a panel with the cells in parallel for a 0.55V 100A panel!
• Solar Expert Posts: 10,300 ✭✭✭✭
Re: Cells in Series vs Parallel

you gave him good advice sage so no need to worry. on the subject of the .55v 100a array, what would you do with it even if you did have the wire for it that would overcome the voltage drop? weld 2 ants together?:p
• Solar Expert Posts: 5,400 ✭✭✭✭
Re: Cells in Series vs Parallel
niel wrote: »
you gave him good advice sage so no need to worry. on the subject of the .55v 100a array, what would you do with it even if you did have the wire for it that would overcome the voltage drop? weld 2 ants together?:p

Would that good advice be "Sage" advice?

T
• Posts: 6,290 admin
Re: Cells in Series vs Parallel

Sorry guys,, No, No by no means did I not appreciate the help. My work takes me out of town a week per strech so didn't get a chance to reply.. Yeah I'm going to have to refigure looks like. The panel size is the concern, limited space on the the 10 footer my reason for using the cells. Perhaps a panel / charger would be my best bet when camping. And Thanks to all of your post
• Solar Expert Posts: 5,400 ✭✭✭✭
Re: Cells in Series vs Parallel

Don't mind Neil,

He may be an old grump,,,, but he knows his stuff!

Tony
• Solar Expert Posts: 10,300 ✭✭✭✭
Re: Cells in Series vs Parallel

sorry i'm coming off that way to you. peace.:cool:
• Posts: 6,290 admin
Re: Cells in Series vs Parallel

No problem at all. I have phpbb boards and your are right, If someone doesn't like the answer they will post it on 50 other boards until they get the answer they want. haha. No harm done. There is a little more to Solar panels then I myself was aware of. I do thank you guys for the help.... Until the next time.. Have a good one.
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