MPPT Charge controller

[SV Demeter]

Check out the Outback Flexmax 60. I have been very pleased with mine and everyone I have spoken with has given them high marks.

[bobofthenorth]

The big advantages of MPPT technology are:
- in low light or partially shaded conditions the MPPT controller may extract more power from your panels
- if you wire your system intelligently, the higher voltage coming from a series string of panels to an MPPT controller will allow for smaller gauge wiring for the same watts output

The drawback of an MPPT controller is that you should use identical panels which may make adding panels more difficult.

[SV Demeter]

Originally Posted by bobofthenorth

The big advantages of MPPT technology are:
- in low light or partially shaded conditions the MPPT controller may extract more power from your panels
- if you wire your system intelligently, the higher voltage coming from a series string of panels to an MPPT controller will allow for smaller gauge wiring for the same watts output

The drawback of an MPPT controller is that you should use identical panels which may make adding panels more difficult.

Oh no, you had to mention series wiring. The parallel wiring folks will be coming for your head now...

[Celestialsailor]

Originally Posted by SV Demeter

Oh no, you had to mention series wiring. The parallel wiring folks will be coming for your head now...

Then let me start...Just received my 2, 100 watt "Grape" solar panels yesterday. I got them from Global Industrial. But before I ordered them, talked to the manufacturer in Oregon. They are manufactured overseas but not in China as I do not support their unfair trade practices.
When I received them and looked at the wiring, they show 2 in series with a MPPT. It goes against everything I was taught. I'm sure if it was wired with an old style charge on/off regulator, parallel wiring would be the way to go.
So I wonder why the series and if I do it that way, how do I add a third panel? I'm sure my panels can be wired in parallel but what is the difference to series?

[senormechanico]

Parallel has a disadvantage of having to use larger wire gauge for a given power transfer, but series requires identical panels, all of which which receive sunshine unless equipped with bypass diodes. Not all do have them.
I have two Aurinco 100 watt panels and one 120 watt rigid panel from Solar Boulevard.
They're all wired in parallel and work just fine with the MPPT.

Basically, unless you can be sure you don't get shading on one or more panels when others are in the sun, you might be better off wiring them in parallel.
This applies especially if you add panels with different current ratings.

Just my 2 cents.

[sailorchic34]

Series increases the voltage at the mppt controller so there is more net gain converting say 27 volts to 14 volts then 17ish volts (panels in parallel). Three panels might be a problem if the mppt controller can't take the higher voltage. Then you would need two sets of two panels, each two sets wires series and then tied parallel together.

Or just wire all three parallel and live with it. Me I keep mine at 17 volts, so if the controller dies I can still hard wire the panels to the batteries for bulk charging, while watching the battery voltage. Oh the propane sensor will alarm too, if the panels are hard connected and left too long, due to hydrogen off gassing.. sort of a poor girls reminder to turn the bypass off . I use a bypass switch to bypass the controller to do a manual equalization of the batteries too.

[Celestialsailor]

Well...It sounds like I would be best off wiring in parallel then for the reasons just stated...(thanx Senor and sailorchic)
1) Both 100 watt panels will live on the top of the hard dodger which can be shaded at times. That's just life on a sailboat.
2) I will add a different shaped (square) panel on the radar tower on the back of the boat. It will be another 100watt or smaller as I am going to be using a controller of handling a max of 25 amps. I=P/V (25% safety)
Speaking of which SV Demeter recommended the Outback Flexmax 60. I've learned over the years that if I want to go cruising in an exceptable frame of time given my financial resources, I have to budget the systems. The Bluesky 2512i is $161. So you see the extra $400 will go a long ways for batteries and what-not.

[goboatingnow]

Originally Posted by senormechanico

The sky was very overcast, the mode was "Bulk".

So?

Nothing to do with mppt, that's everything to do with your batteries.

Your mppt controller would normally as your in bulk be tracking the power point. It's when the panels don't need to be at full output that mppt doesn't matter.
Dave

[senormechanico]

I don't meant to hijack the thread, but that was exactly my point.
The system was trying to stuff as much current into the batteries as it could.
The sun location was not even visible due to the extremely heavy overcast, but the output current from the controller was MORE than what was coming in from the panels. Therefore, the MPPT controller was in boost mode even at low current.

[noelex 77]

Originally Posted by senormechanico

I don't meant to hijack the thread, but that was exactly my point.
The system was trying to stuff as much current into the batteries as it could.
The sun location was not even visible due to the extremely heavy overcast, but the output current from the controller was MORE than what was coming in from the panels. Therefore, the MPPT controller was in boost mode even at low current.

With a MPPT controller the voltage conversion always takes place. Many controllers will keep tracking and using the MPPT even when the power needs to be reduced to avoid overcharging the batteries.
The MPPT technology will boost the current even when the battery is in float mode. Boost is normaly a term used to describe the situation where there is no regulation. The MPPT will always " boost" the current, but describing it as such can be confusing.

[Celestialsailor]

Just received the Bluesky 2512. One thing I did not like about it is that it was not a sealed unit. It has open electronics mounted on the back of the face plate and they give you a standard 4 11/16" X 4 11/16" galvanized box. It found a stainless box that I will use instead.

[goboatingnow]

Originally Posted by senormechanico

I don't meant to hijack the thread, but that was exactly my point.
The system was trying to stuff as much current into the batteries as it could.
The sun location was not even visible due to the extremely heavy overcast, but the output current from the controller was MORE than what was coming in from the panels. Therefore, the MPPT controller was in boost mode even at low current.

At the basis of an MPPT is a DC to DC convertor. Thats always working converting the working panel voltage into something that the battery can use. Just like your mains charger is converting mains voltage to 12V ( nominal). The ability to track the MPP, is an added bonus.

MPPT ( or more correctly DC DC conversion) is always useful as it avoids the issue of pulling a panel with a high working voltage to 12v and loosing much power in the process.

Dave

[Fluenta]

Looking for some guidance on my first solar install. We have a 245 panel over the davits controlled through a Blue Sky 3024i MPPT. The remote is showing a voltage well above where it should be - up to around 17V and it drives the battery bank voltage to about 15V before I noticed and pulled the fuse. It does not seem to leave "bulk mode".

Waiting for Blue Sky to open again on Monday but any ideas in the meantime ?

Thanks

[Jon Hacking]

Fluenta, welcome to Cruisers Forum! The solar panels should be running at ~16-17v (depending on cell temperature). But the batteries should not be above about 14.7v unless you're doing an "Equalization" charge. There's a switch for that which you should probably check. Also, do you perhaps have it set for 24v?

For new solar installations, you might want to read our Solar Panel page for cruisers.

[noelex 77]

Welcome to the forum Fluenta.
Jon has given you some good advice. I would also double check the wiring the basic things are often wrong.
A friend a mine was involved in repairing a particular type of electronic equipment used in operating theatres. He used to get emergency calls in the middle of the night to fix stuff. I asked him what the most common problem was and his reply was.
The equipment was not plugged in.

I have never forgotten the message and always start troubleshooting any electronic problem by checking the basics.