MPPT Charge controller

[Celestialsailor]

I have ordered 2, 100 watt solar panels and will probably add a third in the near future as I finish the electrical system. So I'm looking for a charge controller and I hear a lot on here about the MPPT controllers. To be honest, I don't even know what that stands for but it is rumored to allow a more efficient charge to the batteries. I think I will need 30A. Capacity of 3 panels will put out around 21A.
I use to use a Flexcharge controller because I liked the feature of the leg that kicked out power to an auxiliary load when the batteries were topped up. Do any of these MPPT's do that? Also, is there a brand better than another?...Thanx

[Target9000]

The Bluesky 3024i will handle 30amps and it has a "duo option" that will allow it to dump excess load but it doesn't work the same way as the flexcharge.

You basically connect your wind gen (or water gen) to the batteries directly and the 3024 detects when something is overcharging the battery and then dumps some of the load to a resistor load.

From all the stuff I've read though you can just put the wind gen on its own regulator instead of bothering with doing all that.

I've also heard really good stuff about the outback controllers.

[Celestialsailor]

I went down the windgen road with my last boat and didn't like it. Just solar this time. I usually have computer fans over my ceiling vents and it keeps the boat fresh when they come on with the divert leg. Never a mold problem that way.

[senormechanico]

Think of a MPPT (Maximum Power Point Tracking) controller as an automatic transmission. Every few seconds, it looks at the available voltage, current, and load and it changes extra voltage from the panels to extra amperage for the batteries.

Some people say they're not of any use unless you have x power worth of panels because the boost circuitry won't work at low levels, but I disagree.
Even when the sky is very overcast and I have seen solar input of as low as 1.0 amp, the controller shows 1.2 or 1.3 amps coming out. The Blue Sky 2512X IPN Pro remote has a page which will show both input and output on the same screen.

[stevensuf]

mppt controllers claim to gather a little extra energy wasted by normal controllers, most will have a dump load option for when the batteries are fully charged.

[Celestialsailor]

Originally Posted by senormechanico

Think of a MPPT (Maximum Power Point Tracking) controller as an automatic transmission. Every few seconds, it looks at the available voltage, current, and load and it changes extra voltage from the panels to extra amperage for the batteries.

Some people say they're not of any use unless you have x power worth of panels because the boost circuitry won't work at low levels, but I disagree.
Even when the sky is very overcast and I have seen solar input of as low as 1.0 amp, the controller shows 1.2 or 1.3 amps coming out. The Blue Sky 2512X IPN Pro remote has a page which will show both input and output on the same screen.

Good info...I have noticed some other brands such as Sunforce, Instapark and Rohr advertise that they are MPPT's but not. I was impressed that Bluesky was a US company and not Chinese like the others claiming to be MPPT's. I found a 2512i online for $161. That's only $50 over the Flexcharge and I feel it's well worth that for an extra 30% charge efficiency.

[djmarchand]

There is no nead for a "load dump" capability on a solar charge controller. That is because solar panels, unlike wind generators, don't mind being "disconnected" momentarily. Nothing happens when the circuitry does this, the solar panel voltage rises to its maximum Voc and stays there even while putting out zero amps.

David

[Celestialsailor]

Originally Posted by djmarchand

There is no nead for a "load dump" capability on a solar charge controller. That is because solar panels, unlike wind generators, don't mind being "disconnected" momentarily. Nothing happens when the circuitry does this, the solar panel voltage rises to its maximum Voc and stays there even while putting out zero amps.

David

I know but it is an option on the Flexcharge to do something with the excess power while the batteries go into float mode. You can connect it to a 12v hot water heater or overhead fans or whatever.

[Target9000]

Originally Posted by Celestialsailor

I know but it is an option on the Flexcharge to do something with the excess power while the batteries go into float mode. You can connect it to a 12v hot water heater or overhead fans or whatever.

Why not just turn on the heater or fans whenever you want to use them if the battery is topped up?

[Celestialsailor]

Originally Posted by Target9000

Why not just turn on the heater or fans whenever you want to use them if the battery is topped up?

Because with the overhead fans, it is automatic during the times I,m not onboard. Trust me the reduction in mold is well worth this option. I had a Tartan 37 with a white fuzzy problem and after a bleaching and the fans, it never came back.

[goboatingnow]

Originally Posted by Target9000

Why not just turn on the heater or fans whenever you want to use them if the battery is topped up?

Exactly why have a "dump" mode just turn on an appliance

Dave

[goboatingnow]

Originally Posted by senormechanico

Think of a MPPT (Maximum Power Point Tracking) controller as an automatic transmission. Every few seconds, it looks at the available voltage, current, and load and it changes extra voltage from the panels to extra amperage for the batteries.

Some people say they're not of any use unless you have x power worth of panels because the boost circuitry won't work at low levels, but I disagree.
Even when the sky is very overcast and I have seen solar input of as low as 1.0 amp, the controller shows 1.2 or 1.3 amps coming out. The Blue Sky 2512X IPN Pro remote has a page which will show both input and output on the same screen.

Mppt only works when the load requires the panel max power. If the load is low mppt adds nothing to the party. It simply can't. ( that's why it's called the " max power point" .

Dave

[goboatingnow]

Originally Posted by Target9000

The Bluesky 3024i will handle 30amps and it has a "duo option" that will allow it to dump excess load but it doesn't work the same way as the flexcharge.

You basically connect your wind gen (or water gen) to the batteries directly and the 3024 detects when something is overcharging the battery and then dumps some of the load to a resistor load.

From all the stuff I've read though you can just put the wind gen on its own regulator instead of bothering with doing all that.

I've also heard really good stuff about the outback controllers.

Two charging sources with there own regulators work fine on battery systems. There was a good "water" based analogy posted some time ago on CF.

Let's try to put this to bed.

A battery especially with a low SOC ( state of charge)presents a very low impedance , lower for bigger banks. This impedance is much lower then the output impedance of the various charge controllers.

Due to this low impedance the battery is basically determining the terminal voltage

In bulk mode multiple charge sources simply contribute all the current they can muster. As the SOC rises, so does the effective battery impedance. Hence the terminal voltage rises. At this point ( absorption mode) there is a division of current amongst the charge sources, there is in effect a lazy one(s) and a busy one. BUT, it doesn't matter the battery is still getting the full absorption mode treatment. It only matters if you must control which charge source actually finishes the battery. to even put our control which source finishes, you need current control signals between the sources.

Eventually the absorption mode exists ( though some two stage charge controllers remain at absorption levels permanently , especially cheap solar ones )

Charge controllers don't interact. They can't , it's the battery that's in effect doing the controlling.

Dave

[Celestialsailor]

Thanks everyone for your input. I see that a MP PT would never need a dump mode as the throttle themselves to keep the batteries at max efficient charge. As to my ceiling computer fans. I'll just put them on a timer and run them a few times a day for a few minutes each time.

[senormechanico]

Originally Posted by goboatingnow

Mppt only works when the load requires the panel max power. If the load is low mppt adds nothing to the party. It simply can't. ( that's why it's called the " max power point" .

Dave

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