Solar Panel: Too Big ?

[Nicholson58]

RFI is certainly a consideration. Bill, where was your MPPT situated wrt the antenna? does it make a difference how far away? Did you talk to Outback? I searched this issue when I switched out all of my IC lights for PWM. the newer lights are 30 KH or higher and do not effect my radio. My 110 AC LED replacement lights are a disaster (Home Depot & Lowes). seems like the manufacturers of the PWM units would know this. Is a shield possible? I'll be calling Blue Sky tomorrow with this and other questions regarding our plans.

[noelex 77]

Originally Posted by Nicholson58

There are panels made now with zones on diodes. typically 3 zones. Not all are made that way

They are sometimes not mentioned in the sales brochure, but I have never seen a 12v mono or poly boat panel without bypass diodes.
The maximum , without causing damage, is about 15 cells per bypass diodes for silicon cells. A 12v 36 cell module without bypass diodes would be very vulnerable to hot-spot damage.

There are now many home made, or small scale commercial, solar panels starting to appear. If you find one that genuinely does not have any bypass diodes they should be avoided as there life , particularly on a boat, would be short.

[stevensuf]

I've looked at quite a few of the cheaper panels and many don't have any diodes (18-21v panels). i am limited to running in parallel as my mppt controller only does to 40v any the panels have an oc voltage of 21v (4 panels) , i think ill throw away the physics and do a test in the back garden before fitting, connect them in series to a dump resistor and in parallel and measure both, then cover one with a towel and measure again.

[bill good]

Nicholson 58 I did some investigations today & if the MX60 had been located well away from all but the input & output wires it may have been easier to reduce the interference. So install it as far away as you can from radios, aerial coax run & switch boards. I did mount it close to a switch board with lot of both DC & AC circuits close & will now consider relocating the unit & try RF shielding. Other makes & models may have different outcomes. Also remember with panels mounted flat will involve reduction in performance achieved. If you can get what you need without hi tech controllers then why use them. Running a coax & using a VHF aerial on the back rail seemed to reduce the RFI into the VHF radio to a workable level. Checked with a handheld today & found RF even on the the diamonds & mast. Thats my thoughts.

regards Bill

[stevensuf]

you could try mounting the controller with its back towards the vhf and coating the back area with tinfoil or metal to reflect the rf.

[s/v Jedi]

Originally Posted by stevensuf

I've looked at quite a few of the cheaper panels and many don't have any diodes (18-21v panels). i am limited to running in parallel as my mppt controller only does to 40v any the panels have an oc voltage of 21v (4 panels) , i think ill throw away the physics and do a test in the back garden before fitting, connect them in series to a dump resistor and in parallel and measure both, then cover one with a towel and measure again.

Like I showed in my previous posts, shading one panel doesn't really make a difference in series or parallel setups. It is when you start partially shading multiple/all panels that it makes a difference.

When your panels do not have the diodes, you will find that they will not last very long like noelex77 explained. Sometimes cheaper isn't better. Also, for shading you would need to add your own diodes to bypass the full panels when in series. If you don't do that, you also don't have to do the test because output will drop to 0 when in series without bypass diodes. The shaded panel will go to high impedance and block current from the other panels from passing through. So yes, your panels without internal diodes will only work in parallel... a setup that you are forced to already by the maximum Voc of your controller.

ciao!
Nick.

[s/v Jedi]

@Bill

So you have the same level of interference on a handheld VHF that is operating from it internal battery without charger attached? In that case, the interference is not from DC power system but truly electromagnetic (EM interference). This relatively easy to deal with. Is the housing of your controller connected to ground?

ciao!
Nick.

[Therapy]

Originally Posted by noelex 77

Bypass diodes are fitted to all rigid panels that are likely to be used on a boat (and have been for as long as I can remember). They are necessary to prevent damage, so its difficult to imagine a poly or mono cell of 12v or above could be constructed without them.
The better panels do tend to have more bypass diodes which helps in both the shade tolerance and the durability of the panel. Most of the Kyocera panels have 8 bypass diodes fitted, cheaper panels often only have 2 or 3.
If connecting panels in series there is some theoretical advantage to fitting extra bypass diodes between the panels. This reduces the voltage loss that can occur with shaded panels connected in series.
Unfortunately most of the research and data on solar systems is directed to domestic systems where partial shading of some panels in a string is rare. On boats it is very common, so we are left to ponder such fundamental questions.

Thanks for that.

[noelex 77]

Originally Posted by bill good

Just a comment on MTTP units. Check to make sure radio interference is not an issue!!
I was extra cleaver in using 80V supply from solar & used an outback mx60 to do the charge job. All very good for charging BUT THE RADIO INTERFERENCE IS BAD!!! (VHF wipe out.) I would opt for a simple 12v panels & NO MTTP if starting today. In the mean time still investigating how to fix the RFI problem I have - before making it a part of my ground tackle!!

My advise KISS

Regards Bill

I have an Outback FX60 slightly updated, but almost identical to your MX60.
I have not noticed any interference with the VHF. I just tried turning the FX60 off and cannot detect any change in the VHF background noise (with the squelch off) as I turn the FX60 off and on.
I am not sure this helps a lot, but does suggest the problem may be due to installation, or a faulty unit.

[bill good]

Update to RFI. Relocated unit as close as poss. to the house batteries & fitted ferrite beads & clipons to all leads in & out.Fitted clipon ferrite to the primary & secondary windings of the 2 internal transformers reduced the radiated Rf to less than 5uv/m so all is well. Shielding had nil effect. (the RFI was worse on CH 77 & 78)

Regards Bill

[Hyprdrv]

My question is you charge your batteries and they are topped off, no more solar power going into them. Can the solar power now be directed to the 12v house panel so you can continue using the free power for house needs?

[noelex 77]

Originally Posted by Hyprdrv

My question is you charge your batteries and they are topped off, no more solar power going into them. Can the solar power now be directed to the 12v house panel so you can continue using the free power for house needs?

Yes all solar regulators will do this automatically. When the batteries are charged the regulator will maintain a float voltage of around 13.8v. If you turn on an appliance the regulator will increase the current from the solar panels, so the solar panels will run the appliance and the batteries will stay at 100% (if there is enough solar output to do this)

[Nicholson58]

Some charge controllers can charge multiple banks. some have the ability to pick the bank that needs it the most and some can split the output. Most, however do not. If you add in a battery selector switch you can divert power to any battery. Usually, your starting battery is only used for starting and will not need charging if the engine ran long enough.

Our system will be three Sanyo 235 watt panels and a Blue Sky MPPT. I have two 24 VDC house banks of 480 amp hours each. I use either one for starting. There will be a battery selector so I can charge either bank.

[Seahunter]

Originally Posted by Nicholson58

Our system will be three Sanyo 235 watt panels and a Blue Sky MPPT. I have two 24 VDC house banks of 480 amp hours each. I use either one for starting. There will be a battery selector so I can charge either bank.

Are you sure you have HIT-N235SE10's? The last I heard they were not available in NA. You could get the in Euro and OZ late 2010 but not here. Are you sure they're not HIT195BA20's as the max V of the 235 is 43V and the 195's is 56V perfect for a 48V system. By the by, most higher end charge controllers can manage multiple battery banks with a battery switch. Only the Outback can sense the higher voltage and charge to 12 or 24V.