Series: RV Electrical Upgrade
In this article...
- RV Electricity 101
In this article, the first in the series, I want to introduce to you what we're trying to achieve and why. We'll talk through our requirements, our constraints, and ultimately the design of our system. Although neither Diana nor I have a formal background in electrical engineering, my degree in Physics and my years of dabbling in micro-electronics makes me pretty comfortable working with the electrical systems in our RV. That being said, although I'll be sharing lots of advice for how to embark on something like this yourself, it's up to you to ensure it's done safely.
Disclaimer: Mistakes in the electrical system can cause fire, injury or even death. If you have any doubts about working with electricity in your RV, consult with a professional electrician.
As I write this article, we have already installed everything we're going to be talking through, so where appropriate I'll also highlight if something didn't work out as planned or we changed our approach.
As with most things in an RV, there is rarely a "best" solution and instead it comes down to tradeoffs - what's important to you and what are you prepared to forego. Ideally, you learn through experience what works for you, but in our case we were designing the system before we had even bought the RV, let alone lived in it - but we knew once we hit the road, we wanted to get traveling as soon as possible.
How long will we be off-grid?
We're on a journey to visit and explore all 400+ National Park Units in the US - these are often in remote areas that have limited RV campground options. Further, we want to live in the outdoors, so early on we decided that boondocking (camping in rural locations without electrical, water or sewer hookups - aka "dry camping") would feature heavily in our travel style. We also knew that we would be moving location quite often - rarely staying in any one place more than a couple of weeks. In fact, most Bureau of Land Management (BLM) land has a maximum stay of 14 days.
So early on in our RV selection process, we decided to optimize for up to 2 weeks of dry camping. This would govern how many clothes we would keep, how big our tanks would need to be, etc - but importantly for this article, it set a guideline for designing our electrical install.
What do we want to run?
Some people want their RV to function like a "normal" house - all sorts of kitchen appliances running, multiple TVs on in the background, etc. In our 25ft travel trailer, we're limited as to how many appliances we can store, and we only have a small 12V TV that gets used pretty infrequently (we cut the cord on our cable subscription in our house back in 2016). We're also happy to be conservative in our electrical consumption - turning off lights when not needed (yes, mom, I've learned at last!), etc.
Given our technophilic lifestyle, we have several laptops, phones, cameras and other electronic gadgets - all of which run on batteries that need charging. In the kitchen, we have an electric kettle (I'm British and I need tea to survive) although we can also boil water on the gas stove. We also have an Instant Pot (which we love!) and immersion blender that we use for making smoothies and soups.
Beyond that, the other big electrical consumers are the typical RV suspects - the Air Conditioning unit, the fan in the furnace (even though the furnace runs on propane, the fan is electrical), the fridge (can run on propane, but there's still a pump that needs electricity), water pump, our MaxxFan, and a few other small devices such as the radio, propane gas detector, etc.
For the devices that can operate off propane or electricity (fridge, water heater, etc) we can of course use electricity when shore power is available, and then when off-grid we can choose depending on how much electricity we have available.
How will we generate power / charge the batteries?
Most RVers typically power their RV or charge their batteries one of four ways:
- Shore power - plugging in the RV at a campground or similar
- Generator - usually runs on gasoline or propane and generates 120V AC power
- Tow vehicle - take power from the vehicle engine, usually via the 7-pin trailer connector
- Solar panels - roof-mounted or portable panels to generate free power from the sun
Given our desire to stay off-grid as much as possible, plugging into shore power would work to occasionally charge the batteries, but isn't something we could rely on day-to-day.
One of our most controversial decisions was to say we don't want a generator. In addition to being yet another large item to carry around (weight and space are both limited for us with our ½-ton truck and small travel trailer), another engine to fuel and maintain, they're also noisy. We want to enjoy the peace and quiet of the outdoors, not listen to the hum of a generator. Yes, I know that even if we don't have one, our neighbors likely will - maybe, but we can always move further away or find new neighbors in the great outdoors!
Since we'd be towing our trailer pretty often, charging the batteries from our tow vehicle seems like a good option. Our 2016 Ford F-150 has a 210 Amp alternator which means oodles of surplus power - the question is how to get that to the trailer. The 7-pin connector to the trailer on most vehicles is rated to, at most, 20 Amps - our F-150 has a so-called "smart alternator" that means in reality we're only likely to see ~5 Amps at most. Read more about how we plan to solve this later in the Design section of this article!
Lastly, an increasingly popular option is solar panels - either permanently installed (with optional tilt-adjustment) on the roof, or deployed as portable panels on the ground. This is definitely something we want to integrate - the question is how much. Although we'd be trying to follow relatively good weather as we travel (stay South in Winter and move North for the Summer), we would have no guarantees of clear sunny skies. Additionally, from time-to-time we want to go skiing, stay in forests, and generally put ourselves in places where clear skies are less likely. So solar is a great option, but not something we can always rely on.
So in summary, we're looking to design an electrical system for our RV that lets us:
- Camp comfortably off-grid with no electrical hookups for up to 2 weeks at a time;
- Charge all our laptops, phones, cameras, etc;
- Use a few heavy electrical appliances (e.g. Instant Pot, immersion blender) which can't operate off propane;
- Recharge our batteries from our truck or solar between shore power hookups so we don't need a generator.
We spent a long time coming up with that list - yours may look totally different. It's absolutely fine if you are happy to run a generator, or only plan on being off-grid for the odd night here or there (if at all). The most important thing is that you spend the time deciding what you want to get out of the system.
Now we're clear on what the system should do, let's discuss the constraints - these are self-imposed limits that we feel strongly about. As with the requirements above, these are personal decisions and yours may be different - I'll talk you through our thought process.
Unfortunately, the RV industry lags behind those such as the auto industry or marine industry when it comes to electrical codes. In fact, as we worked through the install itself, we found lots of opportunities to improve the existing wiring - redoing loose butt splices, re-crimping loose connections and replacing broken breakers. From everything we've heard, it sounds like most RV manufacturers have similar build quality - one of the best things about doing this install ourselves was being able to define our own (much higher) safety bar.
Our RV is our home, and being safe in our home is of paramount importance to us. In lieu of any electrical codes for RVs, we relied heavily on guidance from the National Electrical Code (NEC), and most usefully, the American Boat and Yacht Council Standards (AYBC Standards). These standards cover a wide variety of topics, including appropriate wire sizing, fuse locations and connector types. Since this was a DIY install, we chose to hold ourselves accountable to these standards - and having now completed (most of) the install, I feel very good about the end result.
In addition to safe techniques for designing and building the system, the quality and type of components can also have an impact on safety. We said from the outset that we would buy the best quality components we could, and bias towards over-speccing the system where necessary. The impact of this decision was we ended up buying a lot of marine-grade components which are more expensive, but the quality is undeniable.
Space & Weight
If you live in a huge Class A motorhome or a giant 5th wheel trailer, then this section may not be that relevant for you. But for us, in a 25ft travel trailer with limited space and cargo weight, keeping the system small was very important. Batteries in particular can be incredibly heavy. For example, the 80 Amp-hour (Ah) Flooed Lead Acid (FLA) deep-cycle battery that came with our RV (a fairly typical standard battery for an RV from the dealer) weighed ~50lbs - and a Flooded Lead Acid battery can only be discharged to 50% State of Charge (SoC) without damaging it, so that's 50lbs for 40Ah, or 9.6Wh/lb.
We'll discuss what all these numbers mean later, but to put it in simple terms, our 6qt Instant Pot uses about 1,000W (or 1kW) when running in Sauté mode - the standard 50lb battery would be able to power the Instant Pot for less than half an hour before damaging the battery!
For us, adding more batteries at this kind of weight was not an option, so we'd have to find something different.
Spoiler Alert: Lithium batteries have an energy density more than 4 times higher than Flooded Lead Acid batteries, at a whopping 40Wh/lb!
Whatever our end design, there will inevitably be an upfront cost - both financial, and in terms of our time to actually install everything. But once it's installed, we really want a system we can forget about.
It's important to periodically check electrical connections in your RV (remember, your "home" experiences an earthquake every time you tow), but this meant staying away from batteries that require regular maintenance to top up water, or anything similar.
Although Diana and I are both former engineers and happy dealing with technical systems, neither of us wanted to have to navigate some complex technical process every time we wanted to make some soup. Similarly, if I'm making hot soup it's probably cold outside, so we didn't want a system that would require us to go outside to a storage bay or battery box to change settings either!
On a more serious point, there's an almost infinite amount of complexity you can add to the electrical system in your RV - our requirements are simple, and we wanted the system to be correspondingly straightforward to use. Specifically, this meant being able to quickly and easily see the current state of our batteries and electrical system, with a simple interface for changing settings as required, and this interface should be readily accessible to us inside the trailer.
OK, the big one: cost. Although keeping cost manageable is always important to us, this constraint ranked lower than the others we've mentioned already. In reality, this meant we would be buying high quality parts, building safely and spending the extra where necessary to improve ease-of-use of the system. We kept a comprehensive breakdown of everything we spent on this project - we'll include this information in future posts.
It's worth nothing that we saved a LOT of money by designing and installing the entire system ourselves. I don't know how much a professional installer would have charged, but I would estimate that even for someone who does this for a living, it would have taken them a couple days or more on the build phase alone - let alone planning, designing, consulting, etc.
Could it be done cheaper? Absolutely - there are countless examples of people building amazing systems for less money than we spent. However, as I look back on what we've built, had we elected to save money at some of the stages we would have risked compromising on our requirements or other constraints - or we'd have spent a longer time trying to source parts, something we weren't really in a position to do.
As I said at the start of this section, your constraints are personal decisions you need to make. Maybe cost is a higher priority for you, or you have existing components you want to reuse - whatever they are, write them down and prioritize them clearly.
To summarize ours, we said our system should be:
- Safe - high quality components, built well according to the highest safety standards we could find;
- Compact & lightweight - insofar as is possible, take up as little space and be as light as possible;
- Low maintenance - no regular battery maintenance or other distractions from our adventure;
- Simple to use - I shouldn't need my degree in Physics to make some soup;
- Good value for money - we'll spend money where we need to, but not waste it.
RV Electricity 101
Before we dig into the design of the system, let's cover a little bit of background about RV electricity. This won't make you an expert electrician, but will help familiarize you with the key concepts.
Your RV's 3 Electrical Circuits
Most RVs have 3 distinct electrical circuits:
- Vehicle lights & brakes
- 12V Direct Current (DC)
- 120V Alternating Current (AC)
Let's deal with each of these in turn - I'll be describing these in a travel trailer for simplicity, but the concepts are the same on 5th wheels and, largely, for motorhomes too.
Regardless of whether you're driving an motorhome, towing a travel trailer / 5th wheel, or just a utility trailer, any vehicle on the road needs lights and brakes. When you plug in the 7-pin cable from your trailer to the back of your tow vehicle, you are powering up the vehicle lights & brakes on your trailer by connecting them to the corresponding circuits on your tow vehicle. Typically, we never want to change anything with this circuit - it has a job to do, it works, and it doesn't need messing with. It's usually almost completely isolated from the rest of your trailer's electrical system (except a shared, common ground) - so even if you disconnect your battery, the lights and brakes will continue to work. Phew!
Next is the 12V DC circuit in your trailer, sometimes called the low power circuit. This draws power from the battery for low-power components such as interior lights, fans, USB sockets. Assuming you don't have an inverter (if you don't know, then you probably don't - if you do have one, then turn it off for this test), you can tell if something is running off the 12V DC circuit by disconnecting from shore power or your generator and seeing if the device still works. If yes, then it's running off the 12V circuit. The battery is typically recharged when you're hooked up to shore power (or a generator) by a converter-charger.
Safety Tip: Just because 12V is considered low power, doesn't mean it's not dangerous. Touching negative and positive wires together will "short" them, hopefully blowing a fuse but potentially melting wires or damaging components. If you happen to connect the positive and negative terminals on the battery with, say, a metal wrench, in a fraction of a second the wrench will weld itself to the terminals, destroying the battery and probably setting it on fire. Be careful!
Lastly is the 120V AC circuit. This is the same as the AC circuits in a house, and powers all the big or "residential" appliances - think Air Conditioning, fridge, coffee maker, etc. If it plugs in with a 2-prong or 3-prong plug, then it's powered by 120V AC. These devices usually only work when you're connected up to shore power or a generator. The exception is if you have an inverter - this is the opposite of the converter-charger (hence the name, inverter) as it inverts 12V DC power to 120V AC power. This lets you power your AC appliances from your batteries.
Volts, Amps & Watts
Now you have a little more knowledge about the 3 circuits in your RV, let's establish some simple definitions that are useful to understand. I'm not going to try to explain what each of these are, rather just how to use them to design our electrical system.
The most important thing to understand is the relationship between Voltage (measured in Volts), Current (measured in Amps, short for Amperes) and Power (measured in Watts):
Power = Current x Voltage
or to use the units:
Watts = Amps x Volts
This is really useful when it comes to designing the system, because it lets us equate power consumption between devices.
Sometimes, we know how much power a device draws - for example, microwaves typically specify their power consumption as something like 1,300 Watts (written as 1,300W or 1.3kW).
Other devices, typically chargers for things like laptops will have details written on them. For example, my laptop charger says "Output 19V ⎓ 6.32A". Using the formula above, we can multiply the Volts (19V) and Amps (6.32A) to calculate the power - or 120W in this case. These are usually the maximum power draw of the appliance, but can be useful to help get a good upper bound on the consumption.
You can apply the same calculation to batteries too - but since we're talking about storage of energy not usage of energy, everything gets multiplied by Time (that's measured in hours, but you knew that, right?). So rather than Amps, we talk about Amp-hours (Ah). 1Ah is 1 Amp being used for 1 hour. The same works for power too, so if I charged my laptop for 2 hours, it would use 120W x 2 hours = 240Wh.
A typical Flooded Lead Acid battery with 40Ah (i.e. theoretically, it can provide 40Amps for 1 hour) of usable capacity at 12V has a power capacity of 40Ah x 12V = 480Wh. In other words, it would consume half of the battery's usable capacity to charge my laptop for 2 hours!
We were able to go through all our devices and work out how much power we would be drawing in different situations - small devices like phone chargers are dwarfed by appliances like an Air Conditioning unit, but doing an electrical audit to find out how much power you need is an important step.
All that being said, there can be huge variation in the amount of power you actually use on a given day, and no device is 100% efficient - so it's worth adding some buffer once you've done the math.
Having been through the exercise above, we came to the conclusion (as I suspect most people do), that more batteries is better! Our real world experience shows us that we use about 75Ah per day when we're boondocking (assuming we're in the RV, working on our laptops, using lights, etc).
We didn't know this when we were planning, but after consideration we had settled aiming for 200-400Ah of usable capacity in our batteries. Based on what we had calculated, we felt this would give us enough usable power to boondock - the less capacity we had, the more often we would need to charge.
So how many batteries does that take? Let's do the math with Flooded Lead Acid batteries. Our dealer-supplied Group 29 80Ah battery with a usable capacity of 40Ah weighed ~50lbs. So to achieve 200-400Ah of usable capacity would have meant 5-10x Flooded Lead Acid batteries, weighing 250-500lbs! Erm, nope.
Enter, Lithium batteries. With a much higher energy density than Flooded Lead Acid batteries, Lithium batteries looked to hold the solution to our problem. Many in the RV community are moving towards Lithium batteries, recognizing their advantages. The LiFePO4 chemistry is incredibly safe (unlike older Lithium battery technologies, these are safe when exposed to heat, cold, shock or puncture!), and their entire capacity is usable, right down to 0% State of Charge.
Our first design of the system used raw Lithium cells - they need building into a battery pack, and combining with a Battery Monitoring System (BMS) to prevent under-charging, over-charging, etc. However, we later discovered a company called Battle Born, and were impressed by their 12V drop-in replacement batteries which weigh just 29lbs each. Note, we're not sponsored by them or affiliated with them in any way - we ended up purchasing their batteries at full retail price, but have been very impressed by their components and service since. They stand behind their product with a 10 year warranty too - it was 5 years when we bought our batteries but they have since increased it, including for retrospective purchases!
Creating 200-400Ah of usable capacity with Battle Born's batteries would need 2-4x Lithium batteries, with a total weight of 58-116lbs - much more reasonable!
Other than the batteries, there are 4 other major components in our electrical system design:
- Inverter - for powering 120V AC devices from our batteries;
- DC-DC Charger - for maximizing the charging power from our truck;
- Electrical Management System (EMS) - for protecting our system from unsafe electrical sources;
- Solar System - solar panels and a charge controller for free power from the sun.
In later posts in this series, we'll go through each of these components in detail, discussing why we chose them and the installation procedure.
One of the most controversial decisions we made in this process was the location of the install. For most, one of the external storage bays is the chosen location, but we decided to install all of this...under our bed. Are we crazy? Almost certainly, yes, but not because of this decision - we installed it under the bed for a few reasons:
- Safety - yes, it's perfectly safe. Nothing is going to explode, and we've taken all precautions against sparks. We sleep soundly at night!
- Temperature - Lithium batteries can't be charged if their temperature drops too low (although they can still be discharged), so keeping them in an interior space would ensure their temperature remains well within operating limits.
- Usable Space - since we full-time in our RV, we actually really need our (only) outside storage bay for, well, outside items. We store our outdoor chairs, table, hookup items, camping accessories and even our skis / snowboard in there!
- Safety - didn't I already say that? I mean the other kind, protection against theft. A lot of this equipment is expensive, and having it locked securely inside our trailer keeps it safer from would-be thieves.
So there you have it - our plans to upgrade the electrical system on our RV. We've talked through what our requirements are, the constraints that mattered to us, and a sneak preview of our system design.
In Part 3 I'll be showing you how we supplement the 7-pin connector and run a high-power charger directly from the truck alternator to pull 40 Amps whenever we're towing!
And in Part 4, we'll be installing the EMS, and connecting our AC and DC circuits to the existing RV electrical system. In future blog posts, we'll also look at adding some 12V fuse blocks to the RV, installing solar, and much more!
Stay tuned for full details, and if you haven't already done so, make sure to subscribe to our newsletter!