More Power! Tim’s bonus battery bonanza, Part II

~ A special, highly technical, data-driven guest series written by Tim ~

Did you know February 18th is National Battery Day? The history of this auspicious day must be electrifying, right? We’ll never know as my Internet search for this was a bust, but celebration of this day is a good backdrop to part II of our 2008 Heartland Bighorn electrical system upgrade (please read part I first). This second installment discusses equipment research, costs, and selections of the new components.

Costs and Suppliers

Gratefully, a budget wasn’t a limiter for this project; that said, I did not simply buy name-brand items or potentially overpriced packaged kits. Using a mix of online and local sources (to save time), I researched the best specifications for our requirements, and sought out the least expensive sources. My pre-tax and shipping & handling expenses were just over $2,900.

Many suppliers in the solar and renewable energy industries carry the necessary parts, most of which I found on the websites previously mentioned in Part I, or through my own searches. I was generally happy with all of them: Factory Motor Parts, solarseller.com, altestore.com, and the lowest price providers I was able to find on amazon.com.

 

RV Batteries 

The RV dealer where we purchased our used Heartland Bighorn had installed the typical underwhelming RV/Marine 12V battery that barely provided enough juice get us through half a night of parking without hookups, especially if operating the furnace. True deep cycle batteries are the best for RV coach applications. Please search the Internet or ask in the comments below if you do not understand why.

Our requirements, discussed in Part I, showed we needed a battery bank capable of at least 400 amp-hours of energy (capacity), but I still had to decide on the type, voltage and manufacturer. Being a systems engineer, I identified important factors, and gathered data.

Weight (capacity per pound) was an initial focus. Lithium batteries (superb weight per amp-hr ratio) are an option, but I could not justify the cost. I also initially considered Absorbent Glass Mat (AGM) batteries, and would have gladly spent the extra money for them if warranted. The main benefits of AGMs include being able to use them in/near living spaces, operating them in extreme temperatures, and not having to do routine maintenance. The first two were not relevant in our application, and I personally prefer to put my hands on such a critical system component once a month. Combine this with the cost savings benefit of flooded lead batteries, and they became the obvious choice.

Two common approaches to provide 12V battery power in an RV are to use 12V batteries, or to combine two 6V batteries in series. However, a single 12V battery, or a single pair of 6V batteries, will leave you “dead in the water” if just one battery fails. Solutions with multiple 12V, or four or more 6V batteries provide important redundancy and capacity. Deep cycle 12V batteries exist, but their limited capacity means more are required. I opted for 6V golf cart batteries.

Trojan Battery Company’s T-105 6V batteries are a popular choice for RVers. I found Factory Motor Parts has FVP-labeled batteries they stated are made at the Trojan plant in California. The warranty isn’t quite as long, but at 75% of the cost, it was worth the gamble. The design and specifications match the T-105s.

Inverter/Charger

Inverters apparently don’t rate their own day of celebration, but they’re important for RVers who want to boondock (dry camp) and be able to use their household-like appliances. An inverter changes 12V into 120V electricity — or as my wife says, “It performs magic!”

This purchase required the most research time after the battery decision.  The analysis in Part I of this series sized our inverter in the 2,000 to 3,000 watt range. I knew the 2,000W model would be sufficient if we managed the electrical load properly. To better protect my plethora of computers and electronics, I chose a pure sine wave inverter vice a modified sine variant. In most cases, using a combined inverter/charger (to keep those special batteries running) makes sense.

My research confirmed why many choose Magnum Energy products, but I selected a different brand for two reasons. First, most larger coaches take two 50A live wires (i.e., legs) from shore power, routing it to the inside circuit panel. This panel is designed to handle these currents, whereas not all inline inverters are. I only found one inverter I was confident could handle two full 50A legs. According to Jack Mayer, others existed previously, but most manufacturers now expect installation of a dedicated sub-panel for use by inverted loads. I felt the extra cost, work and weight outweighed the benefits. Please note my approach requires more personal discipline with load management.

The second reason was value. The option I chose doesn’t require the extra sub-panel and it meets or exceeds the specifications of comparable Magnum inverters at a fraction of the cost. The IC-2000-12 is a new product by GoPower (gpelectric.com), a reputable company involved with inverters and solar technologies for many years. On Amazon, I was able to get the IC-2000-12 with the remote controller for several hundred dollars less than a comparable Magnum product.

Electrical Management System (EMS/Surge Protection)

Most long-time RVers I’ve spoken with can confirm that they’ve parked at locations with poor electrical shore power. Our older Bighorn came with a simple electrical setup that brought the shore power straight to the circuit panel. There was no convenient and simple way to ensure there was quality electricity feeding my sensitive computers and other appliances. The project already called for shore power service to be re-routed through the inverter, so the timing was right. This was one situation where I skipped independent research and trusted recommendations for the Progressive Industries EMS-HW50C, a box that is hardwired in the service line before the inverter.

System Monitoring & Control

The inverter and the EMS came with remote monitors/controllers, but I didn’t have anything to monitor my new battery bank, and I neeeeded that. Really. Seriously.

Do-it-yourself designers often look to Bogart Engineering’s Trimetric for their battery monitors. Thirty seconds on their website was all it took for me to realize that wouldn’t be sufficient. Remember when I said I was a geek? Get ready to get it on, because Bogart Engineering has the PentaMetric for us misfits — two more better than the Trimetric! The PentaMetric allows a computer to program and control the battery monitor, and capture bunches of data on the battery bank’s state, even every minute. Overkill? Perhaps for mere mortals.

Kidding aside, the former owner of Bogart Engineering stated that the PentaMetric is a superb tool to see the performance of your system over time, and to identify problems before they get worse and potentially cause damage. Right up my alley.

Other Stuff

Our beloved batteries and other equipment form the core of an upgraded RV electrical system. Cabling/wires, connectors, fuses, switches and shunts tie the components into a usable system. These need to be sized properly for safety and performance. An inverter’s installation manual may include cable size requirements, but they are likely to be the minimum. Connectors get sized based on the cable’s size and the size and type of the terminal.

In the final installment of this series, I’ll cover more about cable and connector sizing while showing the steps taken to complete our installation. And no project of this magnitude is going to be completed without learning some lessons. Stay tuned!

Disclaimer: Electricity and electrical systems can be dangerous to living things and electrical equipment if not handled properly. What I write will convey my own experiences. If you or anyone else should choose to use any of the information in this post, you do so at your own risk. If you’re not comfortable handling electrical circuits or equipment, find someone who is knowledgeable about such things to help you.

(Author’s note:  a version of this post appears at Heartland RVs. It is printed here with permission.)