New Flex Solar DIY Project

[RaymondFitz]

Hi everyone,

We are starting a new solar project on our 2014 23D and we are looking for some advice and wisdom. Here is our plan:

Flex Solar Panels
2x100 watt flexible panels - looking at the Renogy® 100W Monocrystalline Bendable

1 Combiner box, we know we will need to make a hole in the roof. We are looking at the AM solar black combiner box.

Here is where it gets a little tricky, we are running the standard group 24 stock batteries right now but we do plan on upgrading to Lithium Ion very soon. So we have to keep this in mind when we decide on the charge controller. I've already gotten some great feedback from Lewster, alano, and Scout1. Just looking to really get this going. We are just wondering what else we really need to start and complete the project:

Charge Controller - Must support Lithium, PWM or MPPT
Shunt controller or series controller?
Charge Controller Remote.

We are planning on buying the LiFePO4 Lithium batteries locally.
4 x 3.2v 100ah LiFePo4

Will the current 1000w inverter work with Lithium? Also, any other things that I'm forgetting?

Thank you,

Ray

[LolaT]

Bump

[alano]

Ray,

I went with the standard Renology 100 W panels for the following reasons... panel efficiency is affected by temperature. The higher the temperature, the lower the efficiency. The flexible panels are nice from an aesthetic point of view, however when you mount them to the skin of the airstream, the panels will not have airflow behind the panels for cooling, so the net result is that the flexible panels run hotter and less efficient that the standard frame-style panels. They also cost $70+ more per panel.

Your inverter (12 VDC to 120 VAC) will work fine with lead-acid/AGM/Lithium cells. The converter (120 VAC to 12 VDC) is another story. Since you're planning on going forward with a solar installation, in my opinion you don't need to rush out and buy a new converter. Simply make sure the batteries are in the "Store" position when connected to shore power so that your converter is disconnected from the batteries. This will avoid the converter from charging the batteries.

It's recommended to wire the solar charger directly to the batteries, and make sure you fuse the positive connection. It's also a good idea to add a disconnect switch between the solar cells and the solar charger. Typically the switch is located right next to the solar charger.

I'm a big fan of reusing the existing #10 gauge wiring since the losses in the solar pre-wiring can be less than 1% with your configuration if you series connect them and less than 2% if you parallel connect them. The Blue Sky MPPT controllers with the IPN pro remote are nice and you also get to leverage using the pre-existing CAT5 wiring which is another plus. I think it's important to have a good battery monitor and the Blue Sky setup does a nice job of integrating both the remote battery monitor and solar controller monitor together in one, nice package.

Good luck with your installation!

[RaymondFitz]

Hi Al,

Thanks for your response. In a different thread you recommended the Solar Boost 3024iL MPPT to me, would the Solar Boost 2512iX-HV MPPT be a good fit for the system? The 3024 and 2512 appear to be the same except one is a 40 amp and the other is a 25 Amp. Since we can only get about 200 to 250watts from our system, do to the limited roof space on the 23D? How about the Shunt controller or series controller, I guess I'm not getting what that is for? I like the idea of using the pre-wire too, with that low % of loss, I'm assuming that there isn't any danger of the wires over heating since our system wattage is so small, correct?

Ray

[ghaynes755]

Don't forget that with a lithium setup you should also install a Battery Monitor System. That tightly controls each of the cells within the overall battery pack. With your setup you would have 4 sensors, one on each cell, and the control unit. Without it you have a risk of damaging cells either through over charging or excessive discharge. In the scheme of things relatively inexpensive items to save an expensive battery.

[RaymondFitz]

You are correct, I would get the BMS with the purchase of the batteries.

Ray

[Al and Missy]

Shunt controllers are largely used with water or wind generators so they don't spin up with no load. For solar a series controller is recommended. At least that is what I think I know from a couple of years ago.

Al

[alano]

Ray,

The Solar Boost 2512iX-HV but you cannot wire your panels in series with this controller. The maximum input voltage is specified as 35 V and your panels are rated at a Voc (open circuit voltage) of 21.7 V. So if you place two panels in series you'll have a Voc of 2 * 21.7 V = 43.4 V.

So if you want to go with this controller, you'll need to wire your panels in parallel. With that said, in your configuration the optimal current of both panels in parallel will be only 5.7 A * 2 = 11.4 A, and the optimal voltage will be 17.7 V (from the datasheet). So let's assume your pre-wiring length is 16 feet in one direction. We'll double it since you have two wires and therefore you're losses in the pre-wiring will be 32' * .001 ohm = .032 ohm. At 11.4 A this will result in a voltage drop of 11.4 A * .032 ohm = .365 V. So your loss is .365/17.7 = 2%. If you went with the larger solar controller you could wire your panels in series and your loss would be 1%. In my opinion it's not worth it to pay the extra dollars to save 1% so I'd stay with 2512.

Not sure about your series or shunt question. Go for a MPPT controller and a battery monitor. Included with the battery monitory is a shunt resistor. This is a very low resistor that you mount near the battery and is used measure the current flowing into and out of the battery.

The Blue Sky chargers are programmable, so you can always adjust them when you fit your system with lithium cells. Personally I'm waiting for a lithum battery that can replace my existing batteries in the outside box. Since the cells need a BMS (battery monitoring system), some of the systems coming on the market are not yet recommended for mounting in the outside battery box so I'm going to see how the market develops in the next year or so.

[RaymondFitz]

Al,

So you currently don't have a shunt of any kind on your system now?

From a really high level the only things I need right now to work with my current setup is as follows:

2x100w solar panels and necessary connectors.
Combiner box with dicor
Solar Boost 2512iX-HV (As long as I don't want to run my panels in series) plus this will support future Lithium batteries.
IPN PRO Remote Meter to monitor the system, this has the built in battery monitor.


Would that cover a bare bones system?
How about a Temperature Compensation Sensor?

Ray

[alano]

I would get the temp compensation sensor. Don't forget a disconnect switch in between the solar panels and charger and a 30 A fuse in the positive line connecting the solar charger to the batteries.

The only shunt that I have is to measure current. This is sold as part of the battery monitor.

[BigAl]

Has anyone done a test to see what the difference is between a flex panel glued to the roof and a similar panel that is in a frame above the roof.
I ask because I have flexible amorphous panels on my roof. They are not as efficient as the monocrystaline panels (per square foot) but are not as adversely affected by heat or shade.
Al

[lewster]

Big Al,

I have!

I had 500 watts of hard panels raised 2" from the roof of my Sprinter service van for 3 years. Connected to a 300 amp/hour Lifeline golf cart battery bank with a Magnum 2800 watt sine wave inverter and Blue Sky 3024iL controller with iPN PRO remote.

Regularly saw 30-35 amps to the batteries. Changed to lithiums (version 1) last year and still saw the same amperage to the batteries when required, although they re-charged in about 1/3 the time as the Lifelines.

Swapped out the hard panels late last year for 500 watts of Grape Solar's PhotoFlex panels. They are bonded to a sheet of .090 aluminum, which was bonded to the raised ribs on the van.

They gave no where near the power of the old panels! I never see over 25 amps now to the batteries. This is due to a couple of probable causes.

1. Being bonded to the aluminum, the panels get really hot and have no free air under them for cooling.

2. The surface is a glossy plastic (which is HIGHLY susceptible to scratching) and does not allow the same amount of solar radiance to strike the cells.

This combination, along with their decreased sensitivity to low light conditions ls readily shown by the results that I am getting.

Of course, the point is a bit moot in my situation as I have quite a bit of over capacity in my solar array and as a result, never have a charging problem. If you spec. close to a 1:1 ratio of watts to amp/hours, you might not be recharging your batteries every day with flex panels.

Even though I am using them, I don't install them on any of the rigs I work on.




Lew Farber
RVIA/RVDA Nationally Certified Master Tech
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center
Lifeline Batteries**Magnum Inverters
541-490-6357

[Siegmann]

I would reinforce the recommendation for a Blue Sky MPPT controller with the IPN pro remote. Mine has performed flawlessly for 7 years in an off-the-grid cabin.

[RaymondFitz]

Quick question, we bought the Roof C-combiner box from AMSolar, it's the big black box, should we just tape and Dicor it down and not use screws? Or, should we tape, dicor and screw it down?

[lewster]

If you mean VHB tape, that's all you need with a bit of sealant around the edge.

You can simply run a generous bead of SikaFlex on the bottom and press to the roof. No need for screws and more holes.


Lew Farber
RVIA/RVDA Nationally Certified Master Tech
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center
Lifeline Batteries**Magnum Inverters
541-490-6357

[RaymondFitz]

Thanks Lew,

Yes, I did get the 3M VHB tape and I also got DiCor from you guys too. The DiCor should work correct, that is what the Tech told me to use on the controller box and on the perimeter of Flexible Solar panels. I'll be using the VHB tape on the flexible solar panels to hold them down.

Ray

[lewster]

I know AM Solar uses Dicor, but I don't. SikaFlex has superior bonding properties and does not eventually dry and crack like Dicor, which has a high VOC content.

Just my preference.


Lew Farber
RVIA/RVDA Nationally Certified Master Tech
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center
Lifeline Batteries**Magnum Inverters
541-490-6357

[RaymondFitz]

So would the Homedepot Silkaflex work? I've included the link:
Sikaflex 10.1 fl. oz. White Construction Sealant-90618 - The Home Depot Just want to make sure I'm using the right stuff.

Ray

[lewster]

You want SikaFlex 221, not the construction grade.


Lew Farber
RVIA/RVDA Nationally Certified Master Tech
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center
Lifeline Batteries**Magnum Inverters
541-490-6357

[RaymondFitz]

So we can't find anyone locally that has SikaFlex 221 and we are in the middle of installing the panels right now. The only thing we can find is SikaFlex 715. Will that work???

Ray