Do I need diodes!!

[rebel112r]

I have been using a 90 watt siemans panel, wired thru a NC25-12 Flexcharge controller...Has been working fine..I have picked up another 90 watt panel..I was planning on wiring it in series to the controller...Do I need diodes, if so where do they go.. These panels are being used to keep a 12 volt battery bank charged...Any help would be appreciated..

[hay4man]

If you are connecting them in series, no external diodes needed. They should already have built-in bypass diodes.

[rebel112r]

Another question

Would it be better to wire them in parallel.. These are mounted on a arch on a power boat, each panel with a few degree slope to the outside of the boat, so they slope in opposite directions. Thanks for the response.

[Mike90250]

If your charge controller is an MPPT type, you should be able to wire panels in series. If it's a PWM type, you must use parallel wired panels. Bypass Diodes should exist in nearly all factory made panels. Your charge controller should provide the night time blocking action, and so I don't think you need any extra diodes at all.
disclaimer - I have no idea what your controller is (NC25-12), since no link was provided, but your manual should indicate:
1) if MPPT or PWM
2) if nighttime back-feed protection included

Mike

[rebel112r]

Here is a link for controller

Think I will stay series, and stay away from diodes, I have had no trouble with the 1 panel discharging at night. Didn't know what 2 panels might do..Shouldn't be a problem with discharging, but would 1 panel affect the other?>

[rebel112r]

forgot the link lol!

http://www.flexcharge.com/flexcharge_usa/products/nc25a/nc25a.htm

[BilljustBill]

If your charge controller is an MPPT type, you should be able to wire panels in series. If it's a PWM type, you must use parallel wired panels. Bypass Diodes should exist in nearly all factory made panels. Your charge controller should provide the night time blocking action, and so I don't think you need any extra diodes at all.
disclaimer - I have no idea what your controller is (NC25-12), since no link was provided, but your manual should indicate:
1) if MPPT or PWM
2) if nighttime back-feed protection included

Mike

Mike,
You said that if they are commerically made, there should be diodes built in. Where would they be? On the two used 120 watt panels I found at a flea market, the small black boxes on the back of them have their backs missing. Should the diodes be inside? What if there isn't one?

To help me understand, you said that if the panels are wired in series that would mean the amps stay the same and the voltage increases. If I have enough old and new panels, if a string of 12volt panels in a series using a 90 watt, two 100 watt, and a 120 watt, and I have enough for two strings for a 48v system, I wouldn't need a diode on the positive wire of each string in case one string was stronger than the other?

Thanks,
Bill

[Mike90250]

Your charge controller is NOT MPPT, and therefor, supplying it with more than 18VDC, will be wasted - you should not series your PV's, only parallel them.

The "Bypass Diodes" are often embedded in the panel, and are not usually visible, You can look up the mfg from the sticker (if present) and find out for sure if they are there or not. Most modern panels have them, tiny chip diodes. I don't know about flea market panels. The may not even stand up to the salt air at the ocean, and only last a short while.

So paralleling panels, some say you need Blocking Diodes, and some think not. I tend to think not, as blocking diodes are only really needed when many panels are paralleled, and one panel is in deep enough shade, that the other panels attempt to backfeed it.

In series strings, the volts add up, and the current is limited by the lowest rated panel. Your 90W panel would be the limiting factor, allowing only 90W from the other 4 panels too. It's a hard concept to grasp, but think of 3, 3/4" thick garden hoses in series, and then adding a 3/8" hose in the middle. Suddenly, your flow slows down to only what passes thru the 3/8 hose, regardless of the sizes of the other hoses.

[BilljustBill]

Mike,

Way back, I took your advice about looking for a better controller and returned the 12v, 30 amp Sunforce controller. I ordered the 60amp, Tristar, mainly because it has so many voltage choices as I thought I was going to start small by adding panels at a lower speed than I've actually done.....

Going from the ground up, I thought I'd go for a 48v system. With that approach, I thought that four 12 volt panels in series would provide the 48 volts. So, are you saying that putting four 12 volt panels in series is a bad idea?


I'd planned to add a few more 12 volt panels in the future, considering how some prices seem to be dropping...... I saw an eye-opening price for a Kyocera 135 watt panel retailing for $340.00 plus shipping.

http://www.solarexpertsgetsolar.com/products/Kyocera-Solar-KD135GX%252dLP-%28135-Watts%29.html

Bill

[rebel112r]

Thanks Mike!!!

Found manual for controller online..Shows a diagram of what I have.and they are wired parallel, with diodes in the + line..I have found a source for some 8 amp 40 volt diodes sold under the controllers brand name, so will use them..The 1 panel has provided enough power to keep battery topped up, under most of my uses..Will be adding a small freezer, so need the added current.. Thanks for answering my questions..

[Mike90250]

Way back, I took your advice about looking for a better controller and returned the 12v, 30 amp Sunforce controller. I ordered the 60amp, Tristar, mainly because it has so many voltage choices as I thought I was going to start adding panels at a lower speed than I've done.....

Going from the ground up, I thought I'd go for a 48v system. With that approach, I thought that four 12 volt panels in series would provide the 48 volts. So, are you saying that putting four 12 volt panels in series is a bad idea?


I'd planned to add a few more 12 volt panels in the future, considering how some prices seem to be dropping...... I saw an eye-opening price for a Kyocera 135 watt panel retailing for $340.00 plus shipping.

http://www.solarexpertsgetsolar.com/products/Kyocera-Solar-KD135GX%252dLP-%28135-Watts%29.html

Bill

If your charge controller is an MPPT type, you should be able to wire panels in series. If it's a PWM type, you must use parallel wired panels.

This was referring to the Original Posters question for a 12V system.

Bill, did you get the Tristar MPPT or the PWM ($550 or $200?)??

[BilljustBill]

This was referring to the Original Posters question for a 12V system.

Bill, did you get the Tristar MPPT or the PWM ($550 or $200?)??

Mike,

I found the TriStar PWM and shipping for $191.00...