Solar Panel Question ....

[themexicandoctor]

On the side, its not possible except on the driver's side.

Unless you suggest removing the 80 watt panel up front?

[booster]

Originally Posted by themexicandoctor

NIC,

Do you have mismatched panels?

Do you have two controllers?

Does that video mean even though I believed that I saw an increase in watts produced, at a voltage level, I was getting less valuable yeild?

I usually just give all this to my Guru & have him work it out, that last video was a slap in the face.

Bottom line; it says if I dont go through the expense of 1. paying someone to wire them in series 2. I either add another $150 Victron & pay to have that done or 3. I just cut the connection to the 80 watt unit?

Does that sound accurate?

So as to the two controllers of I went that way of buying anothrr Victron 75/15, would I be able to, or not be able to, track the fridge usage or would it just give me the yield from the 80 watt but no history?

I have an email & a call into my guy who has now retired & I don't blame him. I might ask him to describe here exactly the thinking behind his theory.

As it is, as part of adding the Victron 30/100, I gave him my 75/15.

The guy as I said is an Electrical Genius, I paid him $500 to rewire everything because another quality rv guy but without the Electrical background had two negatives/earths with the dual batteries & it was throwing off the BMV712 - he was reluctant to add the 80 watt but I was so enthused at the idea of perfect batteries & free power I had him choose the panel versus adding another Go Solar unit as he felt his purchase was a better product.

I am sure he chose wisely & installed as such.

I think I am getting lost in this discussion, so a couple of questions to clear up where we are?


Do you have the specs on the two panels as in max power point current and voltage? Don't consider any rewiring until you see those specs to determine if it is needed.


What is driving the discussions on two controllers and/or monitors? A single controller will use the information it gets so what it says you got in energy should be correct. If you put two monitors on the battery they are going to read the same unless you figure out a way to isolate the grounds and charging or put the shunt in the lines only from the two controllers, and neither would show battery SOC or power use.


Using two controllers really doesn't have a lot of benefit unless you need it for extra rated capacity. Two controllers (or any charge sources) will almost always interfere with each other unless they are specifically setup to pair (if they have that capability). It is commonly said that you would use too so they are more accurate in their algorithm control, but other charging makes the algorithm unable to determine how much power is going to the battery.


Is the amount of harvesting for the day being taken from the monitor or the solar controller (the best place)? The monitor is really only concerned with the SOC and such of the battery and is not really interested in where the power is coming from or going to it's shunt.


IMO, the comments repeating the very simple solution to the parallel or series are the best. If the max power point voltages of the panels match you use parallel. If the max power point amps match use series. One controller and one monitor is really all you should require, unless I am missing something.

[themexicandoctor]

I just got up there & measured, no room unless I used the flat, non-frame panels but they would be getting shadow from both existing raised units.

The other day when I gave an installer my 3 Way Fridge, he thought a very thin, long unit might work on the driver's side but that it would be at risk of damage from trees as it would extend out past the edge of the van.

I live & work in Los Angeles & always at risk of parking where trees can take off or damage panels.

Hence the little unit up front at the time, felt like a Smart Choice. The same 170 unit is 10-12 inches too long if placed sideways as the Roadtrek narrows at the front.

[themexicandoctor]

BOOSTER,

Thank you also.

Going to talk with my Guru next couple of days - we have the same Roadtrek, would you put another 170 watt panel in a horizontal position or as I determined, would it "stick out" too much.

If I was going to do anything, I think this would be the most feasible option & have them connected in parallel rather than trying to add to/bump up/put another controller on the 80 watt unit.

Living in LA has its challenges, parking isn't often available for even a normal sized vehicle & securing ANY* parking sometimes comes with the risk of trees.

*hence the need for a DC Fridge that doesn't need leveling.

PS. Are my options accurate from what you can decipher?

[Nic7320]

I tried flexible panels on my Roadtrek. They were great at first, but both failed over time. It looks like they get too hot in the sun and break some internal connections. Sometimes they have some output, and other times it's zero. The overlay glazing also hazed up quite a bit. They were not a name brand panel with any warranty.

Heat is always a problem when there is no air space underneath the panels to cool them. I liked the flat panel idea at first; why compromise fuel mileage with an array of raised panels? It just didn't work out.

On the issue of multiple solar controllers -- most of us have multiple sources charging the battery. There's the alternator through a diode isolator or smart relay, an AC to DC charger drawing from shore power, and... the solar charge controller(s). All of these are "single quadrant voltage sources," i.e. they do not fight each other, they only provide battery current when they think they need to. My two Victron MPPT controllers don't synchronize perfectly and, as it turns out, they don't really have to. One will operate in bulk mode a few minutes longer than the other, even with the BMV712 feedforward data on the network going to both.

Perhaps your solution is to find three slightly shorter matched panels that fit your van. Solar panels are not that expensive, so do the most with the space you have. There is not such thing as too much solar!

[themexicandoctor]

NIC,

Thank you.

This is what I have in the 170.
https://gpelectric.com/products/170-watt-solar-module/

This is the 100 watt from same company.
https://gpelectric.com/products/100-watt-solar-module/

Unfortunately I would go to the expense of removing the 80 watt only to replace it with a 100watt before filing with other issues.

I have no space for 2 x 100watt units side by side.

[Nic7320]

Don't worry too much about shadows. Your peak solar sun-hours are high noon plus or minus a couple hours, when shadows aren't an issue.

In the early morning or later in the evening, the sun goes through so much more atmosphere that the solar radiance is greatly reduced, and that's when your shadows from roof-top vents are present.

So concentrate on when you get the most solar power.

My plan with the Roadtrek is to keep two panels on the roof and deploy flexible solar panels on PVC frames when I need to. But I need to add some aluminum backing to keep the flex panels from getting flexed too much and damaged from wind flutter.

[booster]

Originally Posted by Nic7320

I tried flexible panels on my Roadtrek. They were great at first, but both failed over time. It looks like they get too hot in the sun and break some internal connections. Sometimes they have some output, and other times it's zero. The overlay glazing also hazed up quite a bit. They were not a name brand panel with any warranty.

Heat is always a problem when there is no air space underneath the panels to cool them. I liked the flat panel idea at first; why compromise fuel mileage with an array of raised panels? It just didn't work out.

On the issue of multiple solar controllers -- most of us have multiple sources charging the battery. There's the alternator through a diode isolator or smart relay, an AC to DC charger drawing from shore power, and... the solar charge controller(s). All of these are "single quadrant voltage sources," i.e. they do not fight each other, they only provide battery current when they think they need to. My two Victron MPPT controllers don't synchronize perfectly and, as it turns out, they don't really have to. One will operate in bulk mode a few minutes longer than the other, even with the BMV712 feedforward data on the network going to both.

Perhaps your solution is to find three slightly shorter matched panels that fit your van. Solar panels are not that expensive, so do the most with the space you have. There is not such thing as too much solar!

I think you are missing the point on the multiple charging sources.


Yep, we all have multiple sources, and they all effect each other unless they are non smart chargers running only on timers or running completely off of shunts.


If the solar is holding the voltage above about 12.8v with batteries that aren't full, many shore chargers or other solar chargers will not run a charge cycle when activated, and go right to float so no help in filling the batteries is just one example. In the case of two solar controllers, when the sun comes up if one of them activates first and goes into bulk, holding the voltage up above the same 12.8 approx volts, the other solar charger may see it and go directly to float and not contribute to the charging. If you have the van engine running when you drive out of a dark garage, the solar may go to float directly no matter if you need charging or not because it sees alternator voltage. If you get to a campsite with low batteries but with a little surface charge on them, if you plug in right away the shore charger will likely go right to float.


Many smart chargers look at things like rate of change of voltage or current to set their algorithm for that charge cycle, so having other sources on line alters their calculations, usually shortening the cycle too much.



If one charger has absorption at 14.0v and another at 14.4v, the 14.0 on will essentially be shut off unless the load is big enough to drag the system down to the 14.0 level, then both chargers will be contributing.



About the only charging sources that would truly be independent would be chargers that do a complete charge cycle at every activation and control it by reading the battery amps at a shunt. Those chargers will always do the correct charging regardless of whatever else is also charging. I know of no other way to do it without the different sources affecting each other.


The point of my statements is not that the charging sources won't run or put out charging ever. The point is that you can often not get as much charging as you should get (as in the solar discussions), or you may not get a charging cycle at all, just float voltage. I have watched all the above things happen in the real world, as they were happening.


One of the really odd things to watch on our system is when we are driving. The van alternator often runs slightly higher voltage than the solar does in absorption, so going down the road, the solar is showing no output at at to the batteries (it reads the amps off a shunt like a monitor), so most controllers would go right to float because the voltage is up and they are delivering no current to the batteries unless they are timer only models. Ours does not go to float because even though it is not putting out any amps, it is seeing the alternator amps going through the shunt to the batteries and stays in absorption with no output until those amps reach it's fully charged setpoint. Very strange to see, or even think it could happen that way.

[booster]

Originally Posted by themexicandoctor

BOOSTER,

Thank you also.

Going to talk with my Guru next couple of days - we have the same Roadtrek, would you put another 170 watt panel in a horizontal position or as I determined, would it "stick out" too much.

If I was going to do anything, I think this would be the most feasible option & have them connected in parallel rather than trying to add to/bump up/put another controller on the 80 watt unit.

Living in LA has its challenges, parking isn't often available for even a normal sized vehicle & securing ANY* parking sometimes comes with the risk of trees.

*hence the need for a DC Fridge that doesn't need leveling.

PS. Are my options accurate from what you can decipher?

I don't think I can say unless see the specs on the panels to be able to know how they should be wired. We have 300 watts on our Chevy 190 all behind the fan, and like you not hanging out or up to get snagged, as IMO that is a big issue.

[themexicandoctor]

Would love a photo of your install on top, behind the fan.

[themexicandoctor]

By the way, my Solar reads 0 also when driving.

This question may give you insight into my electrical savvy;

I have never synchronized the BMV712 & I know it's needed occasionally however since it is only* a Meter giving me the State of Charge & has nothing to do with charging the system, I have left it alone.

*the Distributor made this point abundantly clear when I was having issues with the multiple Earths.

Plus I always believed the numbers I saw were sufficient to determine my state of charge.

Is this thinking correct?

Or should I be calibrating my system as often as they suggest?

[themexicandoctor]

Its 3.10pm on a very, very hot LA day.

(with the fridge not in the cut out there is very little ventilation coming in through the rear windows, its all being sucked up through the lower & upper ventis directly into the Fantastic Fan)

I have driven my vehicle twice for about 15 minutes each time.

Ran the inverter for 45 minutes.

My Yield so far has been 480 watts with a P.Max of 121 & a V.Max of 21.30 volts.

Battery minimum was 12.45 & my Max was 14.55 volts.

In Bulk for 2 hours 43 min
Absorption for 1 minute*
Float for 6 hours 37 minutes.

*very unusual, its typically in Absorb for about an hour per day - remember the fridge hasn't been installed yet & with these temperatures I am again second guessing the Novakool upright versus the Engel chest unit.

Noticed something for the first time; when I am scrolling through the BMV712 Screen I see its reading 76 A*

*must mean watts?

But at the same time the Smart Solar is only reading 61 watts.

And the meter on the Bluetooth of my phone reads current at 73 with 10 watts of Power.

Could the 12 watts difference be the Fantastc Fan at high setting?

So like you Booster, as soon as the motor starts my Solar drops to 0 & the volts go to 14.30 & it goes to Float but it was in Float anyway

[booster]

Here is a link to a thread on our 300 watts behind the fan,

https://www.classbforum.com/forums/f...olar-3407.html

I have seen recently some super efficient panels that would have 330+ watts in a single panel that would also fit that area. I won't be doing that improvement as the single panel is too heavy for me to be able to get on and off by myself like the single panels.

Re the synchronizing. Maybe a Victron user can chime in, but most monitors are set up to automatically synchronize, calibrate, reset, whatever you call it, every time you get a full battery. If that isn't happening, you either are never getting a full charge, or the Victron has the wrong settings in it. If it never synchronizes it will get less accurate with every charge cycle and be too far off to be of decent use.

[themexicandoctor]

I went ahead & synchronized it.

[GallenH]

Watching with interest. Good discussion. My Renogy 100W solar suitcase consists of 2 hinged 50W panels. I've thought about using these in addition to straight 100W panels. The 50W would fit around areas on the roof and the 100w could fill in the more open areas. Not sure if I would go with extra solar or an additional alternator or both. So I enjoy the discussion. Thanks.

[themexicandoctor]

Windrat,

Was trying to find a way to email you - what are you thinking after seeing all this, any opinion?

[SteveJ]

Originally Posted by GallenH

Watching with interest. Good discussion. My Renogy 100W solar suitcase consists of 2 hinged 50W panels. I've thought about using these in addition to straight 100W panels. The 50W would fit around areas on the roof and the 100w could fill in the more open areas. Not sure if I would go with extra solar or an additional alternator or both. So I enjoy the discussion. Thanks.

Just something to add to your dilemma, consider keeping the portable as a portable. This will give flexibility when you don't want to or can't park in the sun.

[themexicandoctor]

What do you far more knowledgeable members think of this Absorption figure collected from the Solar MTTP Controller*

*I presume this doesn't take into account any Alternator charging from driving.

1. Is the above presumption correct?

#######

2 x 100amp Lifeline AGM's in excellent condition.

No DC Fridge installed yet. No heavy loads.

########

I set the Absorption on the Magnum 1012 to 4 hours.

I set the preset on the Victron Control to 4 hours.

Today was a perfect day & a sunny day in LA & in that its almost 3pm & I have been using Solar only since I parked around 11pm.

On average, my Batteries reach Float (13.4) as much time as they are in Bulk (14.4) with the Absorption of about 1 hour only each day.

2. So presuming that all the power going into the batteries is from Solar only, is this Absorption Time sufficient?

[booster]

Originally Posted by themexicandoctor

What do you far more knowledgeable members think of this Absorption figure collected from the Solar MTTP Controller*

*I presume this doesn't take into account any Alternator charging from driving.

1. Is the above presumption correct?

#######

2 x 100amp Lifeline AGM's in excellent condition.

No DC Fridge installed yet. No heavy loads.

########

I set the Absorption on the Magnum 1012 to 4 hours.

I set the preset on the Victron Control to 4 hours.

Today was a perfect day & a sunny day in LA & in that its almost 3pm & I have been using Solar only since I parked around 11pm.

On average, my Batteries reach Float (13.4) as much time as they are in Bulk (14.4) with the Absorption of about 1 hour only each day.

2. So presuming that all the power going into the batteries is from Solar only, is this Absorption Time sufficient?

Therein lies the major dilemma with the timer based systems like you are describing. Optimum absorption times are not consistent as the they change with depth of discharge, length of time the batteries have been discharged, temp, etc. There is also a very long (relatively) absorption time needed to do the last 10% or so of charging, probably in the 4-6 hours after you get to 85-90% full. Unfortunately, you can't set the timers for that long a time as then you would overcharge badly on a shallow discharge cycle.



4 hours of absorption for shore chargers of reasonable size is pretty common if you are using the 14.4v absorption voltage. Solar would normally be similar if the solar can charge as fast as the shore charger to have that long to use for absorption during good sun conditions. Again 4 hours would probably be appropriate but it may not get to float all the time which is OK and better than going to float even earlier unless shallow discharges.


One issue to watch for would if the two chargers stack two full cycles on top of each other. This could happen coming off of a night of shore power where the shore charger just finished and solar did a full charge on the full batteries. This speaks to the interactions between charging sources I mentioned earlier.

[themexicandoctor]

Thank you Booster.

This far I presume that I have yet to have both Chargers stack on top each other the cycles.

Starting to get a better handle on this & just got off the phone with The Other Guru & he said that he matched the voltage of the 80 watt addition to the 170 watt, at most it might have been the difference of 2 volts if at all & there is my inefficiency.

*he mentioned at the time the newer 80 watt unit was more efficient than the Go Power 170 watt, better technology.

He also mentioned the way Roadtrek designed the older One Battery system behind the tire plus adding the optional battery 3 feet away in front of the tire means 6 feet of wire which can mean a difference in battery performance & charging, sometimes as much as 5-10amps which cumulatively adds up.

Ideally, if it appears I need it once the Fridge is in there, those connections should be removed & two or even three new units put in under the sleeping area.

Or increase my Solar which means scrapping my present system & going to Booster's 3 x 100watts behind the fan (what dort of cost would that be Booster?).

I should add that rarely do I ever use Shore Power, when I do its usually once every couple of months & only to run a Equalization Cycle at 15.5 with Lifeline AGM's.

Unfortunately my system is not being taxed by the demands of a DC Fridge so many of the parameters are not in front of me yet.

Ie; Equalisation times, etc.

I agree that Solar is not the only driver of battery charging & therefore my equation is also not clear.

And that my present solar as it is configured, along with the older Roadtrek dual battery system, is probably not adequate but for my driving.

I believe that I have the standard Roadtek Isolator(?) & an upgraded single Alternator after my last one died.