Hurricane Season Preparation

HarryN · Jun 13, 2024

2Big2B said:
Thank you.

As I re-read this in more context, your expanation sheds some light on things. How VOC and SOC do their dance together is still a bit of a mystery, but I am working on it...

The Voc ( Voltage open circuit ) is the voltage that the panels will hit if they are in the sun and there isn't any power being pulled off of them.

When the battery is full ( 100% state of charge ), then the solar charge controller essentially cuts off the connection between the solar panels and the battery pack. ( no power being pulled off of the panels )

So at that point, the solar panel voltage will rise to Voc.

Solar panel output is a series of curves, not a fixed entity like the numbers Vmp, Imp etc imply. It is an analog device, not a digital device.

Imagine driving a car down the road without cruise control. There is an approximate relationship between your foot pushing on the gas pedal and vehicle speed, but not exact. If you are pulling a trailer, then you have to push harder on the pedal to go the same speed. If you are going up a hill vs down a hill, then you have to adjust your foot / gas pedal position to go the same speed.

In some cases, such as pulling a large load in a pick up with a heavy trailer in tow - up a steep grade, there simply is not enough power to maintain speed no matter what.

In a vehicle, you can either drive in manual mode, do your own shifting / gas pedal stuff - or if conditions are not too crazy - just use an automatic transmission and cruise control to do it for you.

Think of your solar charge controller as being a cruise control that deals with all of that for you when it comes to the real behavior of solar panels, lots of light, not much light, battery pack charging details, and SOC. Now add onto this that some cruise controls / solar charge controllers respond much faster to changes than others.

The fastest on the market is the genasun that I posted earlier, making adjustments about 10x per second. Some other cheap ones take 10 - 20 seconds to make an adjustment. Not the end of the world, but on a partly cloudy day, the light conditions change rapidly.

The bogart setup that I used in that test fixture can also work well for you.

2Big2B · Jun 17, 2024

DIYrich said:
24v solar charge controller. With 300ah of batteries, probably want at least 60 amp charge controller. Something like the Victron mppt 100/50.

Or this:

FOR SALE - Outback FM60 Charge Controller (NW Ontario, can ship from Minnesota)

Selling my Outback FM60. Approximately 6 years old. Nothing wrong with it, I've just changed my system and need something different. Please message me on here to discuss price/shipping if interested. I'm in Ontario, Canada but can get to Minnesota easily to ship from there if makes more sense...

diysolarforum.com

Get panels to match input limits of the charge controller. Assume a 400 watt panel produces 310 watts, that is 13 amps. You would want 4 panels.

At this point, taking advantage of an Eco-Worthy ebay online sale, I decided to get (4) x 130w panels instead of just 3 of them @ $70each. Hard to walk away from. I also decided to return the Victron Mppt 100 20 and found a used Victron Mppt 100 30 for $85. That way I can do 2s2p setup with 49v @ 22A max output which is probably a sweet spot for that controller.

Eco-Worthy said that they would comp me for an upgrade to the 520w Kit which includes their brand charge controller, but I wont hold my breath. They may have mis-spoken and/or will probably send me their 12A Boost Controller rather than their Mppt 100v 40A Controller, if at all.

Lets hope the Victron gets here before a major hurricane!

HarryN · Jun 17, 2024

You will want to wire the panels 2S2P for the ~ 50 volts. Wiring them in series will be too close to the max voltage.

This will also give you redundancy as well as the potential to face 2 panels in one direction and 2 in another.

While there is substantial sunlight attenuation going through your bedroom window, you might for fun try setting up 2 of the panels on the inside of the window and setting it up to do some testing / verification.

2Big2B · Jun 17, 2024

HarryN said:
You will want to wire the panels 2S2P for the ~ 50 volts. Wiring them in series will be too close to the max voltage.

This will also give you redundancy as well as the potential to face 2 panels in one direction and 2 in another.

While there is substantial sunlight attenuation going through your bedroom window, you might for fun try setting up 2 of the panels on the inside of the window and setting it up to do some testing / verification.

Thank you!

But am I also NOT over the 20A limit either way, and can I get away with that? as a matter of practicality?
Or is my math completely wrong?

I have wondered if running the panel through bedroom windows would work. That would be cool.

Something else I am conflicted about is whether anything below a 29.5v output (e.g. 24.5v + the required 5v Victron overhead) , regardless of the 22 theoretical amperage, would charge anything or not? What becomes of a 15v @ 22A output?

HarryN · Jun 17, 2024

2Big2B said:
Thank you!

But am I also NOT over the 20A limit either way, and can I get away with that? as a matter of practicality?
Or is my math completely wrong?

I have wondered if running the panel through bedroom windows would work. That would be cool.

Something else I am conflicted about is whether anything below a 29.5v output (e.g. 24.5v + the required 5v Victron overhead) , regardless of the 22 theoretical amperage, would charge anything or not? What becomes of a 15v @ 22A output?

I have done a little work with the Victron chargers but not enough to consider myself an expert. Will leave that to others.

What I do know is that they tend to get pretty warm / hot so if it were me, and I wanted to stay with a victron solar charger, I would go up a size to a 100 / 30 vs running anywhere near their limits. When you use electrical stuff, try to use it at 50 - 70% of the rating, not at the rating, especially when it comes to current / amps.

The ratings on those is a pretty hard limit as far as I know, and I do know people who have had to buy replacements as a result of pushing them.

__________________

All solar charge controllers have a minimum voltage to make them work.

For a PWM controller like a bogart, the input voltage from the panels only needs to be 1 - 2 volts above the battery pack voltage to turn on and start to work, so that is why it is a good choice for overcast skies. ( The Vmp of a panel varies more than you might think in the real world )

For most "buck" / voltage reducing MPPT controllers like the Victrons, I "believe" that it needs the panel voltage to hit ( battery voltage) + ( 5 volts) to turn on charging. The higher this difference, the better, within the limits of the controller.

Some brands of controllers need to hit ( battery voltage) + ( 10 volts ) to turn on, so if the batteries are at 25 volts, then they will wait for 35 volts to turn on. The effect is that some will turn on earlier or stay on later than others.

It has to hit the minimum required voltage to turn on.
___________________

Think of a panel not connected to anything in dim conditions. As the sunlight starts to increase, the first thing that happens is the voltage on the leads starts to slowly rise from ~ 0 volts until it hits Voc.

Same panel, in full sunlight, and you short the leads to each other, then the voltage will go to 0 and the current will be Isc ( short circuit current )

Everything in between, the solar charge controller uses the built in algorithm to calculate how to run it.

It can be fun to play with a panel, and a clamp meter to see what actually is happening.

2Big2B · Jun 18, 2024

HarryN said:
I have done a little work with the Victron chargers but not enough to consider myself an expert. Will leave that to others.

What I do know is that they tend to get pretty warm / hot so if it were me, and I wanted to stay with a victron solar charger, I would go up a size to a 100 / 30 vs running anywhere near their limits. When you use electrical stuff, try to use it at 50 - 70% of the rating, not at the rating, especially when it comes to current / amps.

The ratings on those is a pretty hard limit as far as I know, and I do know people who have had to buy replacements as a result of pushing them.

__________________

All solar charge controllers have a minimum voltage to make them work.

For a PWM controller like a bogart, the input voltage from the panels only needs to be 1 - 2 volts above the battery pack voltage to turn on and start to work, so that is why it is a good choice for overcast skies. ( The Vmp of a panel varies more than you might think in the real world )

For most "buck" / voltage reducing MPPT controllers like the Victrons, I "believe" that it needs the panel voltage to hit ( battery voltage) + ( 5 volts) to turn on charging. The higher this difference, the better, within the limits of the controller.

Some brands of controllers need to hit ( battery voltage) + ( 10 volts ) to turn on, so if the batteries are at 25 volts, then they will wait for 35 volts to turn on. The effect is that some will turn on earlier or stay on later than others.

It has to hit the minimum required voltage to turn on.
___________________

Think of a panel not connected to anything in dim conditions. As the sunlight starts to increase, the first thing that happens is the voltage on the leads starts to slowly rise from ~ 0 volts until it hits Voc.

Same panel, in full sunlight, and you short the leads to each other, then the voltage will go to 0 and the current will be Isc ( short circuit current )

Everything in between, the solar charge controller uses the built in algorithm to calculate how to run it.

It can be fun to play with a panel, and a clamp meter to see what actually is happening.

Update:

I am upgrading to a Victron MPPT 100 30 instead, now that I better understand the math using VOC.

Meanwhile the kind folks at Eco-Worthy sent me (FREE) a care package with all the kit items to augment a 3 panel 390w system that includes all the cables and their 12a Boost MPPT charge controller. I will find something creative to use it for, I'm sure. I could hook up 3 panels and be up and running with it, and use the forth panel with this thing to run a 12v fan to cool the panels! Fun to play with anyway.

Whaddaya' want for nuthin' ? "- rubber bisquit?"

Delmar · Jun 18, 2024

2Big2B said:
So far the best I could come up with was 1/2" pvc pipe with fittings for about $100 for all 4 panels.

1/2" seems kinda weak. I used 1-1/2" PVC pipe and only bolted through the glued fittings. The double-wall thickness is very strong to prevent cracking. My panels have to survive bouncing along the road. I also edge-bolted the panels.

2Big2B · Jun 18, 2024

Delmar said:
1/2" seems kinda weak. I used 1-1/2" PVC pipe and only bolted through the glued fittings. The double-wall thickness is very strong to prevent cracking. My panels have to survive bouncing along the road.

I abandoned that idea...

2Big2B · Jun 29, 2024

HarryN said:
You can use a solar panel hung at least partially over your bedroom window to generate power as well as to cut some of the heat coming in. Depends a lot on access to hang the panel.

Power is needed all day long, not just when the sunlight is coming in during mid day. Especially when you are living off of what is the in the battery, it really helps to have some power being generated early in the morning and as late in the day as possible. More or less you are trading off solar panels generating power vs battery storage cost and panels are cheap by comparison.

Well I just had my first experiment. I hung a 130W Eco-Worthy flex panel inside my porch sliding glass door, facing out. It was late afternoon with the porch in shade, but otherwise fairly sunny outside.

I was getting about 17vdc from it. But at what amperage?

I don't know how many watts the panel is producing.
Is there any math that works with two of the three variables missing from Watts = Volts x Amps ???

(??? watts / VMP = ??? Amps ??? --> NFG

I am assuming that the 135W capacity of the panel is irrelevant, right?

Sure, 130w / 21.1 vmp = 6.16A, just as it says in the specs. But that is at 100%. capacity.
So I don't know if I am getting Amps ir Milliamps ...

Without a DC clamp meter, there is probably no way of knowing much, short of using light bulbs ? ...

I probably need to hook up the Victron. That will be my next task.

I have a 8-80v 100A shunt w/monitor that I use for my "fuel guage" on my wheelchair, as well as a hall monitor that I lost patience with. I could probably use them, but the Victron is probably the better thing to do. I want to start figuring it out anyway. I figure I will set it on 12v and use one of my old, taken out of series, 12v 55 amp AGM wheelchair batteries as a test platform and see how that works.

I also have that Eco-Worthy 12A boost charge controller I can test: by putting a pair of those batteries in series and experiment to see if the boost controller would actually trickle charge a 24v battery using just one panel by boosing the voltage. It was my understanding that the Victro cannot boost charge, thus will not charge at all until the panel output exceeds nominal battery voltage + 5v. Hence it would take 2 panels minimum.

Yet the Eco-Worthy 12A boost charge controller can?

??

HarryN · Jun 30, 2024

Your understanding is correct.

1) Some electronic circuits are designed to "boost" the voltage. ( Watts in ) - ( minor losses ) are still ( watts out ).

2) Some electronics circuits are designed to "buck" / lower the voltage. ( watts in ) - ( minor losses ) are still ( watts out )

Just the voltage has changed.

A few circuits can do both - but usually are significantly less efficient, so the losses are higher.

Here is an article on the concept for some more in depth reading. Life with electronics is to either just accept what they do at a black box, or do the big dig reading.

Buck converter - Wikipedia

en.wikipedia.org

______________

In our everyday lives, we tend to see more of ( 2 ), but hidden deep inside of consumer electronics, are both types.

__________-

Sounds like a good test arrangement with the AGM battery.

HarryN · Jun 30, 2024

Here is an output curve generously provided by a user on wikipedia.

Here is the link to the article on solar panels. Very helpful.

Solar panel - Wikipedia

en.wikipedia.org

The output of a solar panel is a series of curves of current vs voltage. Notice at the extremes ( open circuit ) the voltage is at maximum, but current is zero. ( Voc )

Q-Dog · Jun 30, 2024

All I care about are watts into or out of the battery through the shunt/battery monitor. I set the maximum charging rate and let the MPPT worry about the panels amps and volts.

HarryN · Jul 4, 2024

We are already having power outages here locally from heat and heavy demand. Multiple grid out failures in the SF bay area. Heat, county fair, and EV charging I guess. It is hot enough that they cancelled 4th of July activities.

I decided to slightly edit my work bench power system - so of course we lost power at home.

We plugged the refrigerators into the power system in the explorer. Same setup - 2 x Lifeline 100 amp-hr AGMs wired 24 volts, 1 kW inverter. Bogart PWM controller. Only 1 each 150 watt solar panel, so not nearly enough to keep up long term, but lasted just fine through the outage.

Just kept things on the back up system for 10 hrs for a fun test.

Get that system up and running. You won't regret it.

2Big2B · Jul 4, 2024

HarryN said:
We are already having power outages here locally from heat and heavy demand. Multiple grid out failures in the SF bay area. Heat, county fair, and EV charging I guess. It is hot enough that they cancelled 4th of July activities.

I decided to slightly edit my work bench power system - so of course we lost power at home.

We plugged the refrigerators into the power system in the explorer. Same setup - 2 x Lifeline 100 amp-hr AGMs wired 24 volts, 1 kW inverter. Bogart PWM controller. Only 1 each 150 watt solar panel, so not nearly enough to keep up long term, but lasted just fine through the outage.

Just kept things on the back up system for 10 hrs for a fun test.

Get that system up and running. You won't regret it.

Well, I have four Eco-Worthy 130w flex panels w/ kit that includes all the wires and a spare 12A Boost charge controller , Victron 100 30 MPPT, three fully charged 24v 100a LiFePo4 battery packs, an 800w 24v Samlex inverter & a 1500w 24v Samlex inverter. I am presently bench testing everything. I am just about ready.

Bring it on !!!

2Big2B · Jul 4, 2024

HarryN said:
I have done a little work with the Victron chargers but not enough to consider myself an expert. Will leave that to others.

What I do know is that they tend to get pretty warm / hot so if it were me, and I wanted to stay with a victron solar charger, I would go up a size to a 100 / 30 vs running anywhere near their limits. When you use electrical stuff, try to use it at 50 - 70% of the rating, not at the rating, especially when it comes to current / amps.

The ratings on those is a pretty hard limit as far as I know, and I do know people who have had to buy replacements as a result of pushing them.

__________________

All solar charge controllers have a minimum voltage to make them work.

For a PWM controller like a bogart, the input voltage from the panels only needs to be 1 - 2 volts above the battery pack voltage to turn on and start to work, so that is why it is a good choice for overcast skies. ( The Vmp of a panel varies more than you might think in the real world )

For most "buck" / voltage reducing MPPT controllers like the Victrons, I "believe" that it needs the panel voltage to hit ( battery voltage) + ( 5 volts) to turn on charging. The higher this difference, the better, within the limits of the controller.

Some brands of controllers need to hit ( battery voltage) + ( 10 volts ) to turn on, so if the batteries are at 25 volts, then they will wait for 35 volts to turn on. The effect is that some will turn on earlier or stay on later than others.

It has to hit the minimum required voltage to turn on.
___________________

Think of a panel not connected to anything in dim conditions. As the sunlight starts to increase, the first thing that happens is the voltage on the leads starts to slowly rise from ~ 0 volts until it hits Voc.

Same panel, in full sunlight, and you short the leads to each other, then the voltage will go to 0 and the current will be Isc ( short circuit current )

Everything in between, the solar charge controller uses the built in algorithm to calculate how to run it.

It can be fun to play with a panel, and a clamp meter to see what actually is happening.

Harry, I love the way you explain things. You have a real talent.

"Same panel, in full sunlight, and you short the leads to each other ..."

That's not a really good idea though, is it?
Unless, I suppose, you want to use the panels as a barbeque grill?

I have also wondered if a solar panel could be used as a directional antenna....

Well, this gives me some food for thought. The implication is that, with the Victron buck charge controller, I need enough sunshine to kick on ANY charging. Hence, in dim light it won't charge at all.

With the Eco-Worthy 12A Boost charge controller it is my impression that I can set it up to start charging with minimal voltage, hence trickle charge a 24v battery with just one 130w 24.5 voc panel. It doesn't need all that voltage overhead. NO ?

Is there a situation where that boost controller would out perform that buck converter, such as a long duration of overcast skies?

HarryN · Jul 7, 2024

A good example of a way to use the "boost" controllers is your wheel chair.

If you wire it directly in, then you could just bring along with you one solar panel. Maybe there is a time when you might want to be in the shade and put the panel in the sunshine while enjoying a beverage and it will add a little charge to the battery.

I have not used the boost controller model that you have, but I have used the original version offered by genesun in some projects. Both in 24 volt and 48 volt systems.

Genasun – Sunforge LLC

sunforgellc.com

__________

The trick with most boost controllers is that they can be over loaded by too high of input voltage, so they will try to burn that off with internal resistors. This is not completely obvious in the way they are specified on the data sheets. I would not put the panels in series and then feed it into the boost solar controller.

2Big2B · Jul 7, 2024

HarryN said:
A good example of a way to use the "boost" controllers is your wheel chair.

If you wire it directly in, then you could just bring along with you one solar panel. Maybe there is a time when you might want to be in the shade and put the panel in the sunshine while enjoying a beverage and it will add a little charge to the battery.

I have not used the boost controller model that you have, but I have used the original version offered by genesun in some projects. Both in 24 volt and 48 volt systems.

Genasun – Sunforge LLC

sunforgellc.com

__________

The trick with most boost controllers is that they can be over loaded by too high of input voltage, so they will try to burn that off with internal resistors. This is not completely obvious in the way they are specified on the data sheets. I would not put the panels in series and then feed it into the boost solar controller.

What I am asking is this:

If I have overcast are shaded conditions where I cannot generate enough voltage to activate the Victron at about 30v to charge my 24v LiFePo4 battery, could I overcome that by using a boost controller instead?

If I place a 130w 24.5v panel inside my window facing out to indirect sunshine, and if it only produces about 17 volts (and I still don't know at what amperage but I assume it isn't very much) could I still charge a 24v battery with it using the boost controller, albiet as a very slow trickle charger? Is that a practical application for a boost controller. If so, then I wonder if I could use 3 or 4 panels to trickle charge during all daylight hours. Not very efficient maybe, but would that work?

Also, I believe I read a thread somewhere that one would not combine using an MPPT Boost charge controller to drive an MPPT Buck charge controller, because it would be self defeating. Is that assumption correct?

HarryN · Jul 8, 2024

2Big2B said:
What I am asking is this:

If I have overcast are shaded conditions where I cannot generate enough voltage to activate the Victron at about 30v to charge my 24v LiFePo4 battery, could I overcome that by using a boost controller instead?

If I place a 130w 24.5v panel inside my window facing out to indirect sunshine, and if it only produces about 17 volts (and I still don't know at what amperage but I assume it isn't very much) could I still charge a 24v battery with it using the boost controller, albiet as a very slow trickle charger? Is that a practical application for a boost controller. If so, then I wonder if I could use 3 or 4 panels to trickle charge during all daylight hours. Not very efficient maybe, but would that work?

Also, I believe I read a thread somewhere that one would not combine using an MPPT Boost charge controller to drive an MPPT Buck charge controller, because it would be self defeating. Is that assumption correct?

1) Don't use a boost and buck type solar charge controller from the same panels at the same time.

2) If you can only use 1 panel for some reason, then you will need to use the boost solar charge controller with that panel.

3) Any time that you can use 2 panels wired in series - feed them through the Victron 100 / 30. Period.

4) If you have 3 panels ( like the type that you have), your best bet is to wire them 3 in series and feed them through the V 100 / 30.

5) If you were to try to use 1 panel with the boost solar charge controller and 3 in series with the V 100 / 30, it may or may not work out. When 2 solar charge controllers are both trying to charge a battery, there can be times when they interfere with each other.

I have made it work - but I really had to trick it all to work and it is not something that I share with others. It is very dependent on the exact controllers, wiring and settings.

If you can do it using methods 1 - 4, that is ideal. Maybe required. There is no benefit for you to do it any other way. Method 4 will work in less light than 3, but I doubt that you will be able to tell much difference.

There are some other panels on the market that work in extremely poor lighting conditions / through a window, but you would not like the price or output all that much.

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