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Old 01-03-2015, 10:55 PM   #1
Sro
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About to install Solar...what mistakes am I going to make?

Okay, after a decent amount of research, this is my planned setup on my 16' Bambi:

NEEDS

I'm hoping to boondock indefinitely with light electrical loads or up to 3 days in 20 degree weather (main concern there is the power draw of the furnace).

EQUIPMENT

- 2 AGM batteries 12V deep-cycle batteries (going to install these underneath the couch by the door - where the sub is - they should just fit there.

- 2 50AMP "switchable" fuses (to switch the system between my 2-battery setup and the one stock battery that's on the hitch tongue). This will allow me to run on / or charge either battery system individually (since they're different types of batteries - they're not supposed to be hooked up together).

- 1 100W Renogy flexible panel (purchased on amazon)

- There's already a 15W panel on the roof from the PO...I plan on using it as well

- MPPT Tracer 2210RN Solar Charge Controller (purchased on amazon)

- I plan on using the factory pre-wire

INSTALLATION

- 100W and 15W panels wired in parallel. I plan on using 3M 4941 VHB tape and Sikaflex lap sealant to keep out the water. I also might use some 3M 5900 on the corners for extra strength. They're both 12V panels but I'm not sure about the exact specs of the 15W panel since it was already there...

- Use factory solar pre-wire. I'll drill a hole in the roof and use the West Marine 2-hole wire caps with 3M 5900 sealant.

- Connect to MPPT charge controller.

- Charge controller will be connected to the batters (one on tongue and the set of two inside) through two 50AMP switch/fuses. Only one set of batteries will be connected at a time. The two interior batteries will be in parallel.

QUESTIONS

What am I missing here? What are the thoughts about the 100W and 15W panels run in parallel?

Also, is there an easy way to add a second 100W panel to this setup - so 200W panels and one 15W panel? Not sure how that can be done...
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Old 01-03-2015, 11:44 PM   #2
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You are probably a bit under paneled and over done with batteries. I would suggest about 200 watts of panel capacity. The little 15 watt panel will do almost nothing, use it if you want or use the space for a larger panel.

You can get a 100 watt Grape Solar panel at Costco.com for $140 delivered to your door. Panels are inexpensive these days.

Panels can be wired in parallel assuming they have approximately the same open circuit voltage.
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Old 01-04-2015, 12:19 AM   #3
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I agree with more panel capacity. Using your furnace in cold weather will really drain your batteries. I would carry a Honda 2000 for insurance. On bad days when you really need your furnace, the panels may not bring your batteries up to where they should be.
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Old 01-04-2015, 04:40 PM   #4
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Thanks guys. Here's the final schematic: https://www.circuitlab.com/circuit/r...shot/1024x768/ - I bumped up the system capacity to 220W.

I'm now most concerned about:

- Mixing several different panels together (100W panel, 2 50W panels, and a 20W panel)

- No fuses between the solar panel and the charge controller (lightning strikes?)

- Two different sets of batteries of different types (AGM vs flooded) - I probably can't charge them together.

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Old 01-04-2015, 05:28 PM   #5
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Suggestion - if you are 'set' on using the flooded battery as a spare, isolate it and use the 15W and a seperate charge controller on it. Mount a pair of the 100W panels in series with a blue sky 2512ix-hv controller (series lets you use smaller wire) for the main batteries.

A single 100W panel will leave you short after a couple of cloudy days and running the furnace.
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Old 01-04-2015, 05:34 PM   #6
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You have LOTS of potential issues here......

First, unless ALL of your assorted solar panels are of almost the exact same specifications with respect to voltage output, you will have serious issues with the MPPT feature of your solar controller. Varying voltages (more that 0.2 VDC between panels) will confuse the MPPT and negatively effect it's viability, turning the controller into a basic PWM unit with no solar boost.

Second, any quality solar charge controller should be programmable for type of battery and size of battery bank, and many use a temperature compensation sensor placed on a non-primary negative battery terminal. Flooded liquid lead acid batteries have very different charging requirements from AGMs, and attempting to charge both banks using the same parameters will cause problems with BOTH battery banks.

You would be far better off buying a pair of matching 100 watt panels and ditching the rest, unless their specifications are almost identical to the 100s, and deciding on ONE battery bank. Keep it simple and make it more efficient!
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Old 01-04-2015, 05:39 PM   #7
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Some simple answers for you to consider. There are lots and lots and lots of if's and's and but's and without a 3 or 4 credit class in solar and professional studies, these are workable in most cases.


Fuses are generally not installed on small panel capacity solar systems. Panels are self limiting, that is they cannot produce more than their rated current. They can be shorted with no adverse effects. So, once you have enough wire capacity a fuse becomes just more resistance in the circuit. The charge controller prevents back flow from the batteries to the panels and panel wiring. Some panels have diodes included in them to keep reverse current from flowing.

Panels of different outputs will generally play together OK as long as their open circuit voltage is similar.

Different types/sizes/ages of batteries should probably be charged and discharged independently. Batteries don't play well together.
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Old 01-04-2015, 06:37 PM   #8
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Is factory wire 10 awg?
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Old 01-04-2015, 07:00 PM   #9
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do not connect agm and flooded batteries together.
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Old 01-05-2015, 11:52 AM   #10
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Quote:
Originally Posted by idroba View Post
Panels can be wired in parallel assuming they have approximately the same open circuit voltage.
Thanks, I'll measure the open circuit voltage - how close does it have to be? Like +- 1v?
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Old 01-05-2015, 12:04 PM   #11
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I wouldn't use 5900 for sealing off the outside. Tremco Trempro 635 is very de rigueur around here.

Also, if you use solid wire, and need to add terminals to the ends, pop for the expensive terminals. I use the Anchor brand, available from West Marine. I had too many problems with the ^%$#^$% cheapos from the auto parts store popping off! The Anchors have never budged on me, so it isn't poor technique on my part!

I'm also enjoying my Blue Sea panels and meters for monitoring my power. Very yachty!

You don't mention anything about an inverter or charger. If you don't have a smart charger, you could fry your batteries if you get a bunch of sunny days with the trailer not in use. I like my Xantrex, which auto-senses where power is coming in and deals with it without me having to think about it.

I like HiHoAgRV's idea about separating the small panel from the rest. Maybe use that just as a trickle charger only when the trailer is connected to shore power or just sitting unused.
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Old 01-05-2015, 01:12 PM   #12
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Is there an issue with ventilation for the interior batteries? I can't even imagine attempting this sort of thing, myself. You guys are "brilliant.!"
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Old 01-05-2015, 01:54 PM   #13
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Quote:
Originally Posted by Sro View Post
Thanks, I'll measure the open circuit voltage - how close does it have to be? Like +- 1v?
I honestly have never seen any figures on it. Usually panels with an equal number of cells have the same open circuit voltage in full sunlight. My gut feeling or what I would do with my own system is to look for open circuit voltages within half a volt or less.
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Old 01-05-2015, 02:10 PM   #14
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Lew answer the voltage question up above.

Varying voltages (more that 0.2 VDC between panels) will confuse the MPPT and negatively effect it's viability, turning the controller into a basic PWM unit with no solar boost.
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