Adding more solar

[AJMike]

I currently have 3 100 watt flexible SunPower solar panels on the roof of my 2018.5 Winnie Fuse and that pretty much takes up the available space. If I add any more flexible panels I will lose the ability to walk around so I have to find some other way if I want to increase the available solar power.

One of the solar installers around here suggested that I add rigid panels over the flexible ones. That would add more power since the rigid panels provide more power and if they are added on top of the flexible panels it would not take up more space or, if the panels are larger, it would not take up much more space. He suggested adding 2 200 watt rigid panels, replacing the flexible connections with the rigid ones and leaving me with 500 watts (2 x 200 watts + 1 x 100 watts).

The problem, if it is one, is that the rigid panels are higher wattage and a different voltage than the flexible ones and I don't know if that is OK or not. All are currently connected in parallel so is it OK to mix different wattage and different voltage panels? Or would I have to disconnect the remaining flexible panel so that the remaining 2 panels would match?

[DavidM]

Mixing a couple of 200 watt, 24V nominal high voltage panels with one 100 watt 12V nominal low voltage panel while using same the wiring and the controller won't work.

You can install the 200 watt panels but use separate wiring and an MPPT controller.

David

[AJMike]

Originally Posted by DavidM

Mixing a couple of 200 watt, 24V nominal high voltage panels with one 100 watt 12V nominal low voltage panel while using same the wiring and the controller won't work.

You can install the 200 watt panels but use separate wiring and an MPPT controller.

David

I thought that the 200 watt panels were close in voltage to the 100 watt flex panels. The installer said that the 200 watt panels were about 21 volts and the specs for the flex panels specified 18 volts.

In particular I was told that mixing wattage was OK if the panels were wired in parallel and mixing voltage was OK if the panel voltages did not vary by too much. The term "too much" was not defined.

Are you saying that different wattage panels can not be used in parallel? Or different voltage panels can not be used in parallel? Or both? Or something else?

[creativepart]

Most “12v” Solar Panels put out between 18v and 22v. This is totally normal and is handled by your solar charge controller. Zero worries there.

You’ll notice in the comment above he was referring to “24v nominal” panels. You’ll want 12v panels and they would put out 18v to 22v.

[AJMike]

Originally Posted by creativepart

Most “12v” Solar Panels put out between 18v and 22v. This is totally normal and is handled by your solar charge controller. Zero worries there.

So is mixing wattage OK? Will 2 200 watt panels in parallel with 1 100 watt panel give me 500 watts?

[Winterbagoal]

This video might be helpful. Or not?
It describes some wiring options, and results, for mismatched panels (W/V).

https://www.youtube.com/watch?v=vj_VyVmCSQU

It will probaby require you upgrade your charge controller from the PWM (do you have the Zamp ZS-30A PWM CC?) to an MPPT. I think the video suggests that it might function better. Also, if you have one, the ZS-30A CC has an input limit of <510W or <30A. You'll be pushing the limit with 500W of panels.

Just curious. Why do you want more than the 300W of solar you have now? I get that when it comes to off grid power, more is better, but 300W on a good sun day will produce ~ 15A of charging. That's not too bad?

[creativepart]

Originally Posted by AJMike

So is mixing wattage OK? Will 2 200 watt panels in parallel with 1 100 watt panel give me 500 watts?

Yes, and yes. Well, keep in mind that you’ll seldom see max watt output. You’ll have 500w of panels but, typically see less than that.

One thing to note! If you have a 30-amp charge controller now you are theoretically limited to 440w of panels to not surpass 30-amps. Most people with a 30-amp controller don’t go beyond 400w of panels. Though as I said you’ll seldom max out the wattage.

I believe everything in your system is sized for 30-amps.

To safely go past 440w most would upgrade all the components to 40-amps or more. So, I doubt you’d want to do that.

[creativepart]

AJmike, taking in to consideration all you’ve said in other threads, for your RV, battery bank storage capacity is your number one limitation.

It’s up to you but if it were me that’s where I’d work on improvements.

Of course, you may feel totally different. I certainly don’t want to interfere with your decision making process. I just thought it might help you examine your options.

[DavidM]

I have never seen a 200 watt, 12V nominal panel. When they get that big they always go with 24V. The biggest 12V nominal panel I have seen is about 160 watts.

But if you can find two 200 watt, 12V nominal panels then you can wire them in parallel but then you will have a huge voltage drop in your 12 gauge wire.

Why not wire them all in series and feed them to a 100 volt rated controller? Well this might be a solution but you are pushing beyond the wiring specs as well as the 100V rating of the controller. Your open circuit voltage with two 24V and one 12V panels in series will be 100+V.

David

[AJMike]

Originally Posted by Winterbagoal

do you have the Zamp ZS-30A PWM CC?

Yes.

Originally Posted by Winterbagoal

Also, if you have one, the ZS-30A CC has an input limit of <510W or <30A. You'll be pushing the limit with 500W of panels.

Not too long ago I called Zamp to ask about upgrading the solar panels and I asked if their controller could handle 510 watts (3 of their 170 watt panels). Theoretically, given Ohms Law, that should be 30 amps and they told me that they do a lot of exactly that configuration. That is why I was thinking about using 400 watts of rigid panel with 100 watts of the existing flexible panels. If that is too close to the 30 amp limit I guess I could add only a single rigid panel which would give me 400 watts, although that does not seem to be all that much more than I currently have at 300 watts.

Originally Posted by Winterbagoal

Just curious. Why do you want more than the 300W of solar you have now? I get that when it comes to off grid power, more is better, but 300W on a good sun day will produce ~ 15A of charging. That's not too bad?

Of course it depends upon just how sunny it is and what time of year it is, but we have seen just shy of 20 amps coming out of our 300 watts of solar. My understanding was that the 3 panels would produce no more than 17.7 amps under ideal circumstances, but I have seen 19+ amps coming out regularly if the batteries are low and there is a lot of overhead sun. But any clouds cut into that figure dramatically and when the day got even a little cloudy that 19.9 amps dropped down to about 10 amps. Given that I thought more solar would be good.

But I suspect that this is going to end up being a slow crawl of upgrading our RV. First I will have the battery monitor installed so I have some idea of our power usage. Our Norcold DC compressor refrigerator really uses quite a bit of power. Then, probably, the upgraded AGM batteries. If I am having trouble keeping the current 130AH battery pack charged with our solar I will have even more issues with a 230 AH battery pack so we will end up using our generator when we can to top off the batteries. Finally we will probably end up adding more solar.

There is a strong temptation to do it all at the same time, just to get it over with, but I think it is probably better to do this slowly so as to make sure the next step really needs to be taken.

Lithium would have been nice but we don't do enough dry camping or boondocking to warrant the cost and trouble, let alone worry about the claims that our changes may have voided our warranty.

[AJMike]

Originally Posted by DavidM

I have never seen a 200 watt, 12V nominal panel. When they get that big they always go with 24V. The biggest 12V nominal panel I have seen is about 160 watts.

I will see the guy that gave me that information on Monday and will ask him again. Perhaps he was wrong or perhaps I heard what I expected to hear and not what he said.

The responses in this thread make me think that perhaps I should just let it top off at 400 watts to make sure I am within the limits of the Zamp 30A solar controller and I will probably be doing this all in a series of upgrades rather than all at once. The battery monitor should tell me how much power I am using and how much I am actually adding to our current batteries and give me more information about upgrading to a higher capacity battery bank.

My biggest concern in terms of power usage is the DC compressor refrigerator as I am sure that is what is using the large majority of power in our RV. Until I know how much power is being used I don't suppose I really know how much power I need in the batteries.

[AJMike]

Originally Posted by creativepart

One thing to note! If you have a 30-amp charge controller now you are theoretically limited to 440w of panels to not surpass 30-amps. Most people with a 30-amp controller don’t go beyond 400w of panels. Though as I said you’ll seldom max out the wattage.

We were getting just short of 20 amps with our 300 watts of panels so 450 watts would seem to be the max. I think you are right about topping off at 400 watts, just to be safe.

Originally Posted by creativepart

I believe everything in your system is sized for 30-amps.

To safely go past 440w most would upgrade all the components to 40-amps or more. So, I doubt you’d want to do that.

Yes. I am sure the wiring is set for no more than 30 amps so that is a hard limit unless I am willing to have them rewire the solar stuff and I am not really interested in that. Besides, we don't go out for a week or two of boondocking. Our dry camping is generally limited to 2 days max and usually only one day.

And I can usually run the generator if there is not enough solar to fully charge the batteries. My wife does not like the sound, but you do what you have to do.

[creativepart]

I think most of use go the "slow" route, one at a time upgrade. Though I read a forum post on irv2.com where one guy added 2400w of solar, 10-lithium batteries, 4-solar charge controllers and 2-3000w inverters all in one big upgrade. Though he had at $800K 45' coach.

There's two ways to look at the 30-amp limit.

1. It's common practice for most people to limit their solar to between 400w and 450w
2. You suspect you'll never see a full 30-amps from 500w of solar so pushing it to 500w shouldn't really be an issue.

But you get to make that call. Just be fully aware of it. That's all. Your solar installer that gave you that recommendation may not be aware of the wiring choices and solar controller already installed on your RV. So, he may not even be thinking about that. Maybe he thinks you'll let him install a new higher limit charge controller once he starts the job???

[DavidM]

Maybe you answered this in one of your previous posts, but how much battery capacity in amp hours do you have? If you only dry camp for two days at a time I am surprised that 300 watts of solar won't do the job for you if you have decent battery capacity.

You say you run a compressor fridge. That of course is your biggest load. I would suspect that you use about 75 amp hours each day but everyone is different. That should be easily handled with 200 Ah of batteries and a little solar input, maybe 25 amp hours each day. You should get that even on a mostly cloudy day.

Your statement above tells it all "Until I know how much power is being used I don't suppose I really know how much power I need in the batteries." Truer words were never spoken about RV power use and replacement.

How do you find out how much you are using? Send me a PM and I will give you my phone number and we can talk about ways to figure this out.

David

[creativepart]

Originally Posted by DavidM

I have never seen a 200 watt, 12V nominal panel. When they get that big they always go with 24V. The biggest 12V nominal panel I have seen is about 160 watts.
David

There are quite few 200w 12v solar panels available on Amazon.

However, one thing to look out for is the sizing of the 200w panels is fairly large and may not be appropriate for a smaller RV like the Fuse. So that could be a limiting factor that AJmike's solar installer isn't considering.

[creativepart]

Originally Posted by DavidM

Maybe you answered this in one of your previous posts,

Yeah, he has mentioned that he has two Group 24 batteries and 130aH total capacity, or 65aH usable (limiting his draw to 50% SOC).

[AJMike]

Originally Posted by DavidM

Maybe you answered this in one of your previous posts, but how much battery capacity in amp hours do you have? If you only dry camp for two days at a time I am surprised that 300 watts of solar won't do the job for you if you have decent battery capacity.

You say you run a compressor fridge. That of course is your biggest load. I would suspect that you use about 75 amp hours each day but everyone is different. That should be easily handled with 200 Ah of batteries and a little solar input, maybe 25 amp hours each day. You should get that even on a mostly cloudy day.

I currently have 2 65AH AGM batteries for a total of 130AH. But given the restriction on how low you should run a wet battery that is only about 65AH. What I have found is that although the battery shows as full at 6pm when the sun starts going down I am down to somewhere between 11.9 and 12.1 volts the next morning.

That is a little low but I could probably live with it, but it assumes I can get a decent solar charge during the day. Most of the time that is true but we also regularly camp in the New Mexico mountains at a mineral water spa and that is dry camping in a heavily treed area. The overhead foliage is so thick that barely any sunlight gets to the solar panels and we are not allowed to use the generator so I find the house batteries nearly dead in the morning. Since we generally stay for 2 days I have had to close up the RV, retract the slide, raise up the stabilizers and drive out of the camp to go somewhere where I can run the generator and only return when we have a charge. That is what I have been trying to fix.

Originally Posted by DavidM

How do you find out how much you are using?

I assume that is what the battery monitor will tell me. It should give me a figure of all of the power being consumed by all used devices, including the refrigerator, and that should tell me what I need in terms of power. For a while I played around with the idea of getting 2 100AH Lithium batteries as surely they would provide enough power for 2 days, even without any significant solar input, but the cost is just too high. Not the cost of the batteries themselves (which is high enough) but the added cost of the DC-DC charger, a new charge controller and the installation. The installation costs are about as high as the batteries, effectively doubling the cost, and it is just more than I am willing to spend for batteries.

We dry camp or boondock perhaps 40% of the time, but not for longer than 2 days at a stretch. Since we generally travel at least every other day, or are camped where we have shore power, I can usually count on the alternator or the shore power to fully charge our batteries and, if not, then the generator will do that. As I mentioned, it is only when we have no sunlight and can not use the generator that we have an issue. But since that is the one place my wife really wants to go, and since we do that a couple of times a year, it is an issue that I need to address.

[DavidM]

Ok, here is a somewhat expensive solution, but you seem to be boxed in to living with your existing solar.

Replace the two Group 24 batteries with two Group 31 Firefly batteries rated at 100 Ah. You can draw these down to 20% with no harm. This means you have 160 Ah of usable capacity, more than double your current 65 Ahs usable. That should easily carry you for two days with a little solar thrown in on top.

Fireflys aren't cheap though, about $500 each but half of lithium batteries.

David

[AJMike]

Originally Posted by DavidM

Ok, here is a somewhat expensive solution, but you seem to be boxed in to living with your existing solar.

Replace the two Group 24 batteries with two Group 31 Firefly batteries rated at 100 Ah. You can draw these down to 20% with no harm. This means you have 160 Ah of usable capacity, more than double your current 65 Ahs usable. That should easily carry you for two days with a little solar thrown in on top.

Fireflys aren't cheap though, about $500 each but half of lithium batteries.

David

So how do these react with a system alternator and a charge controller? The Lithium batteries required either a new installation (DC-DC charger) or a replacement (charge controller). What about these?

And how do they work as RV coach batteries? They are listed as marine batteries. What solar controller setting is appropriate? Wet Cell? AGM? Lithium? Those are the only choices I have on my Zamp controller. And are there any local distributors?

[DavidM]

Firefly is a small company and sells direct, although Walmart just finished a special last month at $800 each.

They act just like most FLA or AGM batteries in so far as charging parameters are concerned. They require no special charging algorithm like LPOs do for best performance. Yes you can get more charging out of a B2B charger from your chassis alternator, but if your current batteries work ok, these should too.

From what you describe: two dry camping days at a time, you shouldn't need to run your generator or charge with your chassis alternator for that period.

They have two characteristics that set them apart from normal AGMs, otherwise they act the same. They can be discharged down to 20% with no harm and they can be left at a partial state of charge for extended time with no harm. For your use the 20% discharge is the most important.

They are not really a marine specific battery (is there such a thing- don't think so) but they have been mostly marketed to and installed on boats. FWIW the marine use is a tougher market- they are scared of lithiums, so Fireflys are a good alternative.

Go to https://sprinter-source.com/forum/sh...ad.php?t=84526 and read the comments about Firefly batteries. Some have installed them on RVs and they work fine.

David