Batteries Parallel Wiring

This is my third post in a series about RV electrical set-ups. Although the information is fairly basic it will help if you read the entire series.
Post #1 Deep cycle batteries
Post #2 Ratings and sizes

Batteries Parallel Wiring

There are two ways that batteries are typically wired, when there are multiple batteries being used for electrical power in your RV, that is either parallel or in a series. Parallel wiring is the most common. In this post I will describe parallel wiring. Parallel wiring does not increase the voltage, so when two 12 volt batteries are wired in this way it remains a 12 volt system. here is an example:

2 battery parallel wiring


the effects can be seen when jump starting a car. The battery in the dead car remains 12-volts, and will still turn the starter, but only very slowly. Parallel wire a charged up 12-volt battery to the weak battery, and the dead car turns the starter at the required speed and the car starts immediately. Parallel wiring the charged battery to the weak battery did not alter the voltage – it remained a 12-volt system. The car’s system is 12-volt, and running greater voltages through that system would be destructive to it. To avoid increasing the voltage and damaging the vehicle, the batteries are simply parallel wired.


Two 12 volt batteries wired in parallel means that the positive post of each battery is connected to each other, and the negative posts are also connected together. Connecting the lead of the positive side of one battery to the load, and the lead of the other battery’s negative side to the load is the best practice. In parallel the voltage remains the same, but the amount of current available increases. Batteries connected in parallel should be the same brand, type, size, and age. Otherwise long-term capacity could be reduced. It is possible to connect more than two batteries together in parallel, but space is a major hindrance in a RV setting.

It is recommended that if you are going to wire more than two batteries together in a parallel system that they share a common positive connection, and a common negative connection. This will best allow each battery to be charged correctly. Again using the same brand, type, size, and age are important factors for the life of the batteries.

How many batteries do you use in your set-up (motor home, or travel trailer)? How long are you off the grid usually?

Batteries-Ratings & Size

This is part two in my series on batteries. In part one I explored the different types of batteries used for RV’s. In this post I will do an overview of batteries-ratings and size.

Batteries are rated in one of two ways Amp Hours or Reserve Capacity. RC is the most common rating today.

  • Amp Hours (AH) .The amp hour rating is basically, how many amps the battery can deliver for how many hours before the battery is discharged. Amps times hours. 5 Amps X 20 Hours = 100Amp Hours or 20 Amps X 5 Hours = 100 Amp Hours.
  • Reserve Capacity (RC). Reserve Capacity rating is the number of minutes at 80 degrees F that the battery can deliver 25 amps until it drops below 10.5 volts. If you want to figure the amp hour rating you can multiply the RC rating by 60 percent. RC X 60 percent.

RC rating is established by the Battery Council International (BCI). Some manufacturers use a 15 or 22-amp discharge rate rather than 25-amp discharge. The lower discharge level allows a higher number of minutes to be displayed on the battery label which does not reflect the true RC minutes at a 25-amp discharge. According to interstate batteries


BATTERY CHART CHEAT SHEET The battery group size number listed for each battery in our chart represents the maximum dimensions of the battery and they are as follows: Maximum LENGTH x WIDTH x HEIGHT

  • Group 24: 10.75” x 6.82” x 9.4”
  • Group 27: 12.1” x 6.82” x 9.25”
  • Group 29: 13.2” x 6.75” x 9.2”
  • Group 30: 13.5” x 6.82” x 9.25”
  • Group 31: 13” x 6.82” x 9.44”
  • Group 34: 10.25” x 6.82” x 7.88”

Batteries Deep Cycle

I was talking with a friend about his RV set-up that allows him to go hunting and stay off the grid for weeks at a time. I thought this info might be helpful to RV’ers of all kinds so I’m going to do a series on batteries, which will lead into solar set-ups too. Just so you know I’ll be using references from the “RV Repair & Maintenance Manual” by Bob Livingston Trailer life books 1998.

The electrical system in your RV runs on two types of current; AC (alternating current) the same as your house, and DC (direct current) the same as your car. The stronger your DC system, the longer you can remain off the grid. The terms you need to understand are amps, watts, and volts. Most RV’s run on a 12 volt system, but did you know 2 – 6 volt batteries wired in a series will run your lights and appliances longer than 1 – 12 volt battery? Before you go and replace your batteries lets look at some basic information in this post, and the pros and cons along with the requirements of each set-up in posts to follow.

Batteries are not created equal

  • A car’s battery is designed to provide a very large amount of current for a short period of time. This surge of current is needed to turn the engine over during starting. Once the engine starts, the alternator provides all the power that the car needs, so a car battery may go through its entire life without ever being drained more than 20 percent of its total capacity.

  • A deep cycle battery is designed to provide a steady amount of current over a long period of time. A deep cycle battery is also designed to be deeply discharged over and over again, something that would ruin a car battery very quickly. To accomplish this, a deep cycle battery uses fewer, but thicker lead plates often coated with antimony or calcium, which increases the hardness of the plate.

Deep cycle batteries tend to cost more than the average car battery, but buying a regular car battery for your RV will only save you a few dollars on the short run. It will wear out quicker making it necessary to replace sooner.



Saving with Credit Cards?

Saving with credit sounds like a contradiction, and is but read on. Saving money usually requires us to stop using credit, but there is one way that using credit can save your money. We all want to save money, right? I do. Recently my wife and I were pleased to pay off all our credit cards. In our excitement to be debt free my wife was only using her debit card, no credit cards, for purchases both local and online. When I realized that she was using our debit card online, I suggested she not do that.

If your debit account is compromised and money is stolen your bank will work with you to identify the fraud and recover the loss, but the money is gone until the dispute is resolved. Small amounts may not impact your checking account much, but what about a significant loss of funds?

Well, just like I warned her (this isn’t a I told you so, but advice for others who are trying to live within their means) I got a text from my bank about a large purchase (that wasn’t mine). When I called to talk to the fraud department there were several purchases. Someone got our debit number and went on a shopping spree. Our account was emptied, but we still have bills to pay, and are responsible to make sure our account doesn’t overdraw.

If you want to save your money use a credit card for online purchases. If your account is compromised, the bank will work with you to identify the fraud and resolve the issue. The difference is that your credit limit is reduced until there is resolution, rather than funds from your checking account being depleted.

Have you had your debit card stolen from online activity? How long did it take for the dispute to be resolved?

RV Surge Protector

Surge protectors seem to be a gimmick of the RV market right? Only if you’ve never experienced a surge while at a RV camp site. According to Decisive Magazine power surges are fairly common, and the results can be devastating. Personally I have never experienced a power surge or brownout while at a RV campground, but I have experienced both in a residential setting. All my expensive electronics at home and work are plugged into surge protectors. Why? Because a power surge fried a couple circuit boards. In fact at my work the fire department insists that all our electronics be plugged into surge protectors.

Pete Leighton the owner of Main Street RV, Mesa, AZ said, “We just repaired a RV that had it’s wiring burned by a power surge in a local camp ground.” He said, “The campground assured the RV owner that they hadn’t had power surges.” Pete said he loaned the RV owner his personal surge protector, and as soon as the protector was plugged in, it tripped, meaning there was either a power drop or power surge.

The wood and fabric in an RV make it a quick hot fire if one breaks out, RV.NET has a great post on fire safety worth reading. Make sure your fire extinguishers are working and you know how to operate them, but that’s a completely different blog post.. A simple addition of a surge protector can help reduce the risk of an electrical fire.

Do you have a power surge or brown out story? Has a surge protector saved your RV? I’d like to know.

Email Pete ( at Main Street RV tell him I promised a deal on a good quality surge protector.

Vintage DIY Help

May be you have a vintage trailer that has been sitting around your backyard, and unlike some very creative people, you can’t think of what to do with it. So it sits collecting dust (mold, mildew, and dry rot)

or may be you just have an older trailer that needs some repairs.

I found a resource, actually they found me first on Twitter, that has a collection of everything you might need to find parts, learn how to for some of the common repairs, or sell what you think is just junk in your backyard. It’s the Tin Can Tourists.

As I started to click through the pages I was impressed with the wealth of information and the amount of helpful links I found. It’s a great site if you’re looking for help with a vintage travel trailer.


Hail No

I was searching the RV forums and found one talking about a trailer that was hit by softball size hail. The question led to a discussion on the quality and craftsmanship of RV’s. The following comment gives some good advise that I felt was worth repeating.

“Looks to me like you have all the information to buy a unit that will satisfy your quality concerns.  Nothing like maintaining a vehicle for a period of time to point out poor design, or poor quality.  Looking at a new rig at the dealer (I always suggest a show where side-by-side comparisons are easier) and really inspecting it can give you the information on quality.

A few things I’ve learned to look at – Does the wiring look neat and organized, or are their bundles of wiring behind the sink or converter, wiring pulled across underside that should have been secured?  Are wood braces cracked by screws or staples?  Is there excessive caulk covering poor fitting trim.  Are their screw-heads dog-eared out from poor workmanship?  If you stand back and look at the rig, are lights, trim, windows in line and mounted straight?  Are the axles sized with enough extra capacity or are they the minimum for the weight of the trailer?  Are the axles provided with shock absorbers?

I’m a professional QA/QC person, and travel the country (and a few places outside the US) to buy transit vehicles, commuter rail cars, locomotives, and subway cars.  My experience is that if it “doesn’t look right” it most likely isn’t.  Finally, it is possible to make and sell a perfect RV.  Problem is no one can afford it.  Quality is what we, as consumers are willing to accept.  You may want a Lexus, I may think a Ford is fine, both of us will be happy if our expectations of quality are met, neither if the vehicle is a lemon.

No travel trailer is made to withstand softball sized hail. Your best plan for that is store it under cover, and make sure you have insurance coverage.  How often does hail like that appear anyway? I’ve never seen or heard of it in the West.

There is wisdom in knowing what you are buying and a quick look for quality control will give you a pretty good idea of what you are getting into.


DIY: Replace a RV Marker Light

As I have mentioned before my Trailer is a 1986 model. UV rays and temperature changes take their toll on plastic over time, and marker light lenses are no exception. The lenses on my trailer are cracked, faded, and letting water inside the housing.

I picked up some new marker lights at Walmart for less than $3 ea. I will walk you through the process of changing the entire marker light. It’s pretty simple. First remove the 2 screws, and then the red lens should pop off.

The only thing holding the housing to the trailer at this point is some plumbers puddy. Gently pull on the housing and it should pull away from the trailer, be careful the wires in the back should have room to pull out, but could catch. You don’t want to break a wire and have it stuck inside the wall where you can’t reach it.

I’m not sure if all trailers use the same color coding for their wires, but on mine green is for the power side of the marker light and white is the ground. If you are not sure you can pull off a taillight and see what colors are connected to the bulb and what color is grounded to the trailer body.

I replaced the yellow wire nuts with new ones because the old ones were rusty inside. I also put some electrical tape on the wires to keep them together (RV’s bounce and rattle going down the road). I placed some plumbers puddy on the upper edge of the marker light, this lets water run down if it gets inside, but makes a nice seal on top. It is also being used to keep the housing mounted even and tight.

I screwed in the new marker light housing, and put a liberal amount of caulking around the housing. I did leave weep holes on the bottom side to allow for water drainage.

I snapped the new lens on and it’s good as new. The entire process took about 20 min. It’s as easy as that.

Inexpensive Update For Old Trailer Flooring

My trailer is a 1986, it’s old but it’s paid for. The floor itself was in good shape, but the floor covering was not great (honestly half of it was really bad – the carpeting). We decided the carpeting had to go, and the linoleum could use an update. I know how to lay down sheet flooring, but the thought of working around all the corners and cabinets seemed challenging. We thought we would try stick on tiles. We found the cheapest tile @ $.29 a square and it had a 80’s look too. I wasn’t sure if the sick on tile would stay stuck with the temperature changes. It’s stayed in place for over a year now.

Here’s what you need to do:
1. Remove the carpeting (linoleum is installed the entire length even under the carpeting, do not remove)
2. Make sure there are no staples or tacks. I pulled most but had to pound a few down and grind a few.
3. Remove items that you can like the toilet or tables.
4. Use a product like TSP to clean the linoleum. It gets rid of wax and dirt.
5. If you have any tears in the old linoleum you can use a skim coat to level out the flooring. Any bump or dirt will show up with the shine of the new linoleum.
6. I started my first row at the door way. Remember you need to keep tiles square (a little bit off shows up way off on a long run) existing cabinets & walls should be square.
7. Slide the tile close to the wall leave about a 1/8″ gap. I found these tiles need a little room for expanding and contracting.
8. Slide the next tile snug against the previous tile. Start with that edge pressing down working your way to the next edge.
9. You can cut the tile with the protective paper still on as you perfect the fit around items like cabinets. Remember to leave a little room for the tiles to expand.

Here’s my final product.

Sealing Tape

Have a leak in a seam, a rip or a tear in the roof or side of your trailer? I did. I had a dent in the roof of my trailer that is right on a seam. It allowed water to pool, and eventually leak. The best fix I found was 10’x6″ white  sealing patch tape (Di-seal I think).  The white tape was the closest match to the color of my trailer. What I did was apply the tape the entire length of the seam to make sure it was completely sealed. You need to Clean the area well. Make sure it is dry and free of debris. Apply the tape on a warm day it makes the adhesive stick better, and makes the tape more pliable. My trailer is aluminum with ridges, and the tape adhered well. I put the tape on two year’s ago and the leak is still sealed. You can see in the picture it goes completely across the width of the trailer.