RV Solar Part II - The Equipment

So, following on from my gripping introduction to solar yesterday it’s time, with fanfare and fireworks (it IS almost New Year’s Eve after all), to reveal our choice of equipment. Every RV is different, so what we chose may not be right for your rig or your needs. Always, always take the time to figure out what’s right for you (true in life, love and general happiness, is it not?). So,  feel free to take our example as input, but definitely not as gospel

Going With 24V Panels

Our 100 Watt 24V Panels

I should start by saying that we decided to go with higher-voltage panels up-front and this, in turn, affected all our other equipment choices. The benefits of 24V panels are less loss through the system (using the water-hose analogy it’s like starting with a higher-pressure hose up-front) plus we liked the easier wiring and the current boosting capabilities it gave us (see below). It’s a slightly unusual choice and it is more costly. Most RVers choose 12V panels which require thicker wiring, but also give more open choice in controllers and panels. It’s a cost-benefit analysis and I would say you can get a solid solar system either way. In our case we’re geeks, and hubby had a decent year in the market so 24V was the way we decided to go…

Once we decided on 24V that immediately narrowed down our choice of vendors since not too many people offer a 24V panel that’ll fit comfortably on an RV roof. After much research we ended up going with a set of products from AM Solar, with an upgrade on wire-size and batteries. These guys only do RV solar (nothing else), have a good reputation, are all RVers themselves, are nice folks and above all were able to answer all our nit-picky questions. The final installation met our loss goals so we’re happy with the results. Here’s the full list:

1. 600Watts of 24Volt Solar Panels - We decided we wanted a pretty liberal power supply with 600 Watts of 24V panels, which led us in turn to 6 of the AM Solar RV100 series panels. We like the specs, warranty and format.
(Oct 2012 Update -> AM Solar has updated their line-up and now offer a  100W panel which is slightly shorter than the old RV100, plus some newer/niftier larger sizes. They no longer offer our exact 24V system, but all their panels are still “high voltage” so you’ll get the benefits. Check out their website for more info)

The Tristar Controller

2. Tristar MPPT 45 Controller (TS-MPPT-45) - Given our up-front choice for higher voltage panels, we needed a good controller that could handle the higher voltage input. MPPT controllers fit the bill and the Tristar 45 has good specs. It has all the charging profiles, including a custom setting, does temperature control and will actually sense and charge to the right voltage at the battery terminals using an external voltage sensor. This last feature is rather nifty since it makes sure you really get the right voltage exactly where you need it (= at the batteries) -> good stuff. Another nice feature of this controller is that if you generate more voltage than you need, it’ll convert that extra power into additional current going into your batteries (= a little boost for faster charging). Since we’re using higher voltage panels we should (hopefully) be able to take advantage of the boosting feature on a fairly regular basis.
(Oct 2012 Update – This is still one of the best controllers out there and has worked perfectly for our 600 Watt system. However, if we were to do it over we would probably choose the bigger Tristar 60 so we have space to expand our system size in the future)

3. AM Solar Tilt Mounts – We went ahead and chose the tilt mounts from AM Solar. We like the fact that they provide space under the panels and allow us to tilt when we need to.
(Oct 2012 Update – We love these mounts and would recommend them even if you decide to use a different company/installer. They make tilting super-easy)

4. Combiner Box – We decided to use a combiner box on the roof. So, each panel is wired individually on the roof, then they’re combined together in the box and a bigger wire goes from there to the controller. The bonus of this set-up is that you can use smaller wires on the roof, the wiring is easier/cleaner, plus you can easily add another panel down the line (if you ever need it).

Marine-grade wiring for the roof

4. Wire Upgrade - The standard system from AM Solar for the 24V panels use #10 marine-grade 90˚C wiring on the roof  and #8 wiring internally. Now, that may seem waaay too thin given what I wrote yesterday, but remember that 24V can run twice as long as 12V on the same wire for the same loss, plus we’re using a combiner box. We wanted to target ~2% voltage drop from panels to controller and ~1% drop from controller to batteries. So, we crunched the numbers using the wire tables I gave you yesterday and decided #10 was OK on the roof, but we needed to upgrade to the #6 wiring internally. That combo ended up working for the amount of wire we used in our install. For a home needing more wire you might need #8 externally and #4 internally and for a 12V system wired in series you might decide to use #4 everywhere -> it all depends on voltage, current and how far you’re running the wire. If I were doing this over for someone else I’d crunch the numbers specifically for their home.
(Oct 2012 Update -> AM Solar now offers #6,#4 and even #2 wiring for their systems and if we were to do it over we’d go with one of the bigger wire sizes, simply for the extra leeway. Bottom line is you can never go wrong w/ thicker wiring)

5. Lifeline AGM Batteries - We decided to upgrade our batteries to a bank of 4 Lifeline AGM 6V 220AH batteries (GPL-4CT). The AGMs will charge faster, and since they’re sealed there’s the bonus of no more maintenance. Lastly, since AGMs have really low internal resistance you can pile a lot more current into them -> that meshes nicely with the current boosting feature of our controller.
(Oct 2012 Update – Fabulous batteries! These have served us perfectly and we’d choose the same again)

Xantrex battery monitor

6. Xantrex LinkLIKTE Battery Monitor - This monitor hooks onto the batteries and tells you exactly how much power is either going either in or out of your battery bank. It’s definitely a geek-device and allows us to monitor exact usage from the batteries, something none of the other monitors we already have will do. If you’re just starting out on your solar quest and are looking for a device to tell you how much you’re using out in the boonies, this is the device that will do it for you.
(Oct 2012 Update – This is a great battery monitor and has served us well. We’d choose the same again)

Looking for another panel supplier? Here are some good, additional links on panel costs and suppliers around the US:

• Solar Panel Comparison Shopping – http://www.solardesigntool.com/compare-solar-panels-modules.html
• Solar Panel Prices – http://www.ecobusinesslinks.com/solar_panels.htm

The final installation and measurement info comes next…..don’t go away…

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