Solar power ~ no more running the engine

[Cruisingdad]

Originally Posted by foggysail

Is this the right thread to ask what others are doing for controllers? I purchased a junk so called MPPT controller from China that I am now attempting to sent back...more on that later. My options as I type include installing a reverse protection diode and just connect my two each 145 watt panels to the batteries with fuses and switches. The next option is to see if I can purchase an inexpensive pulse width modulated buck converter to get by the rest of the season.

So what are others doing?? OH-- the panel output voltages ar in the 21vdc range with current in the 8 ampere range/panel

Foggy

I sure wouldnt be pumping 21 vdc into my batteries. Those panels are too large not to use a controller.

I use an Outback MX60 MPPT. Has worked flawless for years. Best thing I have installed. I know others have used Bluesky and I think Maine reccomened Morningstar but I have no first hand experience with them.

Brian

[foggysail]

Cruisingdad (Brian)--

I know enough about these panels now to be dangerous........that even scares me! Now back to the 21vdc. I understand that the panels are current sources so the voltage reallys should not matter when working into a short or lower voltage unless their internal impedance , causes the panels to heat up.

The voltage drop will be across the panels, not the batteries because their internal resistance is too low. For example, if you charge a depleted battery and place say about 14vdc across its terminals, you would need to supply MANY amperes depending on the state of charge. If the battery was in the low 12vdc range and not sulfated, that thing could accept as much as 50 amperes DC but a panel can only supply 8 amperes on a good day.

Now if the battery is fully charged, that is another matter! It might enter a state of equalization.

Yes, I share your concern but my concern is with the panel not the battery unless the battery is left completely unattended. I might install the panels along with the wiring next week without using them to charge anything. I don't want to damage them before I even get to properly use them. Thanks for sharing your concerns--

Foggy

[Cruisingdad]

Originally Posted by foggysail

Cruisingdad (Brian)--

I know enough about these panels now to be dangerous........that even scares me! Now back to the 21vdc. I understand that the panels are current sources so the voltage reallys should not matter when working into a short or lower voltage unless their internal impedance , causes the panels to heat up.

The voltage drop will be across the panels, not the batteries because their internal resistance is too low. For example, if you charge a depleted battery and place say about 14vdc across its terminals, you would need to supply MANY amperes depending on the state of charge. If the battery was in the low 12vdc range and not sulfated, that thing could accept as much as 50 amperes DC but a panel can only supply 8 amperes on a good day.

Now if the battery is fully charged, that is another matter! It might enter a state of equalization.

Yes, I share your concern but my concern is with the panel not the battery unless the battery is left completely unattended. I might install the panels along with the wiring next week without using them to charge anything. I don't want to damage them before I even get to properly use them. Thanks for sharing your concerns--

Foggy

I'd sure watch that water level and make sure tehy aren't bubbling. I wouldn't do it. Maine was sharing with me about a 10watt panel cooking a group 27. That sure shocked me as I have always seen them too small to matter. Your batteries are no doubt larger, but your panels are too.

I am curious what happens. Let me know.

Brian

[Maine Sail]

Originally Posted by foggysail

Is this the right thread to ask what others are doing for controllers? I purchased a junk so called MPPT controller from China that I am now attempting to sent back...more on that later. My options as I type include installing a reverse protection diode and just connect my two each 145 watt panels to the batteries with fuses and switches. The next option is to see if I can purchase an inexpensive pulse width modulated buck converter to get by the rest of the season.

So what are others doing?? OH-- the panel output voltages ar in the 21vdc range with current in the 8 ampere range/panel

Foggy

You NEED a controller with those panels or you will cook the batteries when the get charged. Anything from Morningstar is good and even an inexpensive PWM would be FAR BETTER than nothing. The ProStar 15 is an excellent controller for the money.

ProStar 15

Search around you can likely find it for even less. Fried batteries will cost a lot more than a PWM controller....

[Cruisingdad]

Originally Posted by Maine Sail

You NEED a controller with those panels or you will cook the batteries when the get charged. Anything from Morningstar is good and even an inexpensive PWM would be FAR BETTER than nothing. The ProStar 15 is an excellent controller for the money.

ProStar 15

Search around you can likely find it for even less. Fried batteries will cost a lot more than a PWM controller....

That's what I thought too. But hey, I am the same guy who said you don't need one for a 10w panel.

Brian

[hellosailor]

"I know enough about these panels now to be dangerous"
Not yet but you're getting there.(G)

The voltage from the panels will vary with the load they are connected to, and a battery in different states of charge presents different loads. If the panels are small enough (compared to the battery capacity) you don't need a controller. But funny things happen, and a controller is cheap compared to new batteries or a fire. With nearly 300W of panels, you really want a controller. If you consider that an MPPT controller can give you 10% more power from your panels, ask yourself, what would an extra 30-40W panel cost you? Could you use that added power? If the answer is "yes", then an MPPT controller is worth buying. If you've got more power than you know what to do with, the answer is no.

[tdw]

I've amended HelloSailors post to read "10% more power" I'm pretty certain he slipped on the 'shift' key.

[Hartley18]

Originally Posted by hellosailor

The voltage from the panels will vary with the load they are connected to, and a battery in different states of charge presents different loads.

That's actually not correct, HS: The voltage from the panels will vary with the amount of sunlight falling on the cells. It's the current that varies with the load it's connected to.

That's why it's important to have a controller of some form on even the smallest of systems - since, unless a battery is used regularly it's still possible to overcharge ("boil") it during long summer days if directly connected to a solar panel.

Several of the smaller 'maintenance charging' panels on the market now have basic PWM controllers built-in - so it can become tricky for the layman to work out whether he needs a controller or not.

[foggysail]

Come on now guys--- there are two things happening here. First was the discussions on risk where I believe the largest risk is with the panels, not the batteries IF THEY ARE WATCHED.

The second thing that folks are missing resides in one of my last sentence from above:

" I might install the panels along with the wiring next week without using them to charge anything. I don't want to damage them before I even get to properly use them. Thanks for sharing your concerns-- "

Years ago when I was an electrical design engineer there were many discussions about how a circuit would work by folks in both management and marketing. I learned that there is no way to ******** physics. Later in life as an engineering manager, I drove that base into younger engineers so often that one Christmas they handed a plaque to me that read "YOU CANNOT ******** THE CIRCUIT!"

So what does all this mean to our current discussion. I firmly believe the greatest risk are with the panels...because I am just learning this stuff rather than the batteries IF THE BATTERIES ARE WATCHED. There is little doubt in my mind that once they are fully charged, overcharging will result in them being forced into equalization along with boiling the water out of them...as someone just cautioned so overcharging must be prevented.

Now getting back to my YOU CANNNOT B----- gets to the heart of all this. Things happen!! Surprises happen!!! If the model is wrong things can smoke. That was why I backed away earlier by saying I might (if time permits) install teh panels along with the wiring BUT NO WAY do I intend to connect them to the batteries. There will be a controller of some type installed.

Now on the POS MPPT that was just delivered yesterday, I am banging on the seller for a refund. Yeah, I know, good luck. But the seller has a refund policy that does not mention that the item must be defective before it can be returned. Hey, I intend to squawk and squawk loudly to try forcing the issue. OK, I paid $80 for the POS that I refuse to connect to my new collectors. $80 is $80, it is far from ruining my life. I just resent getting screwed.

Foggy

[foggysail]

Originally Posted by Maine Sail

You NEED a controller with those panels or you will cook the batteries when the get charged. Anything from Morningstar is good and even an inexpensive PWM would be FAR BETTER than nothing. The ProStar 15 is an excellent controller for the money.

ProStar 15

Search around you can likely find it for even less. Fried batteries will cost a lot more than a PWM controller....

OK, a good suggestion! I do have a concern although it is more so related to specs-. The Prostar 15 might be border line with panels rated at 8 amperes or so maximum. But then again most of the time the current will be less.

I am giving this controller serious consideration, I might order one in the morning. If so I will get the one without the meter. I just purchased a couple of hall current sensors that I need to build up. It needs a simple op amp plus a digital meter which I have several in my office. I prefer using I2C meters but for this application, a simple directed reading LCD volt meter should work fine with hall sensor.

MORE LATER--

Foggy