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BATTERY CHARGING:
The RV battery bank can be charged from multiple sources:
• Solar charger/controller
• 120V battery charger (normally active when you have shore power)
• Front system Alternator (tow vehicule) (through a dc-dc charger activated with vehicule ignition.
Having multiple charging sources all connected to the battery bank bus bar is not a problem.
Chargers, solar controller have their own protections and the total charge current is splited to the battery without interferences.
TYPICAL SETUP
SPLIT CHARGING
A split charging simultaneously charges both the vehicle starter battery and the leisure battery from a common charging source, such as the vehicle alternator.
A split charging includes a device (relay or manual switch) to ensure that leisure and starter batteries are only connected while a charging source is operating and above +13V is obtained.(engine/alternator)
The reason is when you are off grid, and the engine is OFF you want those batteries to be isolated ,
and you don’t want to depleet the starter battery and be stranded !
See here the basics.
BATTERY TO BATTERY CHARGER (B2B)
The other solution (more costly) is to install a B2B (Bat to Bat) charger.
(also commonly known as DC-DC chargers) it allow you to charge an auxiliary / leisure battery from your alternator while the engine is running.
Take note the output rating (amps) of your alternator need to be verified to be able to feed both systems : the Starter battery ( with all vehicule electricals) and the B2B charging your leisure battery.
On a camper van this is a straight forward install, but for a travel trailer involving a tow vehicle other factor need to be considered.
TRAILER 7-PIN CONNECTOR : THE VOLTAGE DROP !
The 7 pins Connector: pin 4 of this connector provides +12VDC and is generally used for camping trailer to charge and maintain a typically a lead acid battery.
But his Is mostly limited to 10A and DOES NOT PROVIDE the correct charge capacity because of the vehicle AWG14 /AWG16 conductor, and the wire length which results in a large voltage drop.
A simple calculation shows with a length of 15ft with a copper conductor AWG16 and a load of 10A a voltage drop of 1.2V, and with an AWG14 conductor a voltage drop of .774v.
This voltage drop is also higher than the suggested 3% (.36v)
This voltage drop DOES NOT allow for a 100% charge of the leisure battery (VR).
It Is then strongly suggested to install a dedicated +12VDC AWG-4 conductor to a quick 60A disconnect at the tow vehicle and the same on the camping trailer to have minimum voltage drop at the B2B, and to be able to charge even up to 40A.
Typical B2B in this installation are Victron and Renogy.
See here typical installation:
https://youtu.be/gWvITGmj3pY
https://youtu.be/7NDnZsouUyY
Ref: https://climbingvan.co.uk/van-conversion/how-to-choose-the-right-battery-to-battery-charger/
TYPICAL B2B
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INVERTERS:
An Inverter is used to convert +12VDC to usable 120V-60HZ- AC to power appliances. (typically 2 to 3KW)
or 230V -50HZ in the UK.
The inverter can be connected to a set of dedicated 120V outlets,
or
can feed ALL outlets and 120V appliances in your RV. In this scenario , you cannot
use all appliance at the same
time unless
you install a very powerfull Inverter.
Also in this case a transfer switch (typical: Go Power TS-30 for 30A ) is required to auto- select shore power(grid)
or Inverter power (from batteries).
Normally on travel trailers this switch is grid dominant to get the shore power priority,
But, on most Class-A-B-C RV's this switch is GEN dominnat.
Also the 120V battery charger is ONLY active when shore power is available.
PURE SINE:
Modified Sine wave and Pure Sine wave inverters:
A modified Sine wave inverter outputs a shopped sine wave form and can be used ONLY with basic loads
( ie: incandescent lights, heaters)
Since your RV will probably be equipped with Expensive equipment, like Laptop, Connectivity router/charger,
TV/ Sound system
that are sensitive to quality 120V-60Hz service, a Pure Sine wave inverter is the solution.
Pure sine wave inverters output a lower frequency and smother current and a real sine wave form than modified
sine wave inverters. The output wave can be as smooth or better as the current from the grid .
If you are planning on setting up a system to use expensive audio/connectivity equipment or medical equipment
a pure sine option is a must.
Due to its lower levels of harmonic distortion these types of inverters will be less stressful on your equipment.
* SETUP REVIEW: with Ross Likeman
* How inverters works:
TRANSFER SWITCH:
A transfer switch is really a 3 way switch to select : source-A or source-B. Typically Shore power or a Generator,
if your RV is equiped with an Inverter this SW may select: Shore power or the Inverter AC power.
see here Transfer SW. description:
Typical TX SW Go-Power 30A:
TYPICAL INSTALLATION
TYPICAL INVERTER
TYPICAL TX SWITCH
TYPICAL ROOF PANELS
COMBO :CHARGER+inverter
12V VS 24V SYSTEM
Most cars, RVs, and boats utilize a 12-volt electrical system, although there are some exceptions and 24V systems are used in semi-trailer trucks and busses due to the vehicle’s higher power needs and long cable runs.
You can also see 24V used in larger boats and some RVs with elaborate solar systems.
When looking at 12V vs. 24V systems, there are some pros and cons to each system type.
PLUS SIDES:
12V:
• 12V systems are relatively common. Most vehicles use 12V systems as components used in vehicles are designed to operate on 12V. The alternators generate 12V(14v) to charge the starter battery.
• When it comes to RVs, most appliances such as RV refrigerators, heater control, and the lighting work on 12V as well. 12V systems only require one battery and work well for low-power applications and short wire runs.
24V:
• 24V systems are beneficial because you can use smaller diameter wire and reduce amperage by two times. Using smaller diameter wire can reduce wiring costs and decrease the space needed to run wiring.
This is especially important where long wire runs are required.
This is because the higher voltage requires less current to produce the same power.
(This is the same reason power is transmitted on power lines at very high voltages. (typ 320Kv, 730Kv) The wires can be much, much smaller and carry lots more power!)
• When building out larger portable solar systems using higher voltages like 24 volts or 48 volts is very beneficial.
• SOLAR:
When using a 50 amp rated charge controller on a 12V battery bank, you can use the controller with 700 watts of solar. If you use that same charge controller on a 24V battery system, it can connect to 1400 watts of solar panels. This means that half the number of solar charge controllers is needed.
They will also operate more efficiently at 24 volts.
• Inverters: if you need more than 2KW of AC power 24V DC would be more efficient and wiring size is half of the 12v equivalent.
DOWN SIDES:
12V:
• 12V systems require massive wires when pulling large loads because the current (amps) are higher.
• Because 12V batteries use two times the amperage at a given power draw, they are less efficient than a 24V battery due to resistive and heat losses.
24V:
• If you are using a 24V system in an application with 12V appliances, you will need a converter to reduce the voltage down to 12V. While this works very well to provide stable voltage, it is an extra component , extra cost and incurs a 4% energy loss.
• 24V system operating with 6V batteries and having to remove 4 batteries when 1 battery fails, as apposed to 2 batteries with a 12V system.
Now: 12v vs 24v:
If your requirements are below 2000W, you can generally get- by with a 12V system. It isn’t always a clear-cut decision. There are many variables to consider when determining which one is the best choice. But this now becomes a personal decision !
As a general rule of thumb, you’ll want an inverter to match the watts and voltage of your solar panel installation.
What is crucial is making sure you properly size your system to determine what voltage and wattage is best for you.
Don’t be fooled thinking 48 volt is best just because it is a higher rating.
Like everything else in a solar installation, you need to consider your specific needs, the existing components, existing RV system, wiring length, and the system at large.
here
SAFETY:
Lithium batteries contains a lot of energy.
Making a wiring error or a short circuit can blow fuses,
burn wiring
and start a fire !.
If you are not familiar with low voltage wiring standard practice and safety
get your installation done by a professional .
RV’s are wired as per NFPA 1192/70 and the NEC therefore
DO NOT change the original power distribution wiring
unless you know what your are doing and the implication.
If you are starting a RV’s rebuilt project from scratch get a course on power distribution for RV;’s. and email me for advice.
SOLAR ENERGY CALCULATOR
If you plan a trip OFF-Grid you may need to evaluate your
total energy consumption. A basic Ah- Wh calculator will provide a good evaluation.
Basic Calculator:
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