Mugs & Plugs

A beginners guide to 12 volt camping

You want to join the world of 12 volt camping?
Can’t quite get your head around all the jargon and requirements?
This is what I’ve learnt in transitioning from almost 20 years of camping with a generator to using 12 volt solar. I’m no tech expert so this is aimed at the beginner/novice and hopefully will serve as a guide and a starting point for you. Six months ago I bought a new camper trailer and thought it time to move to generator-free camping where I didn’t have to worry about the “generators not allowed” signs and the need to cart fuel and oil.

Basic Lingo
Amps = current flow
Amp hours = current flow in one hour. The amount of energy stored in a battery, and it is calculated by multiplying the current (in amps) by the time (in hours) that the current is flowing.
Watts = a unit of power which measures the rate at which energy is being used or produced. It is calculated by multiplying the voltage (in volts) by the current (in amps) in a circuit.
For example, if you have a 12-volt solar panel that is producing 5 amps of current, the panel is producing 60 watts of power (12 volts x 5 amps = 60 watts).
Volts = electrical pressure (the ability to push current through a circuit enabling it to do work).

A 100 Amp hour battery (100AH) contains enough electrical energy to run 100 amps of current for one hour or 20 amps of current for 5 hours or 4 amps of current for 25 hours (bear in mind that batteries can be damaged by frequently running them flat).

A 200 watt camping solar panel might produce between 10 and 15 amps of current under ideal conditions. Over 6 hours of usable good sunshine conditions this will equate to 10 x 6 = 60 to 90 amp hours worth of energy put into your system.

A solar panel that produces 10 amps of current when exposed to full sunlight can recharge a 100 amp-hour battery in 10 hours (100 amp-hours / 10 amps = 10 hours).
It’s also important to note that the amount of power that a solar panel generates is measured in watts, and a watt is a product of volts and amps (Watts = Volts x Amps).

Battery Facts From Jason Gillies
ALL batteries can be discharged to 100% depth of discharge (DoD) however the deeper you discharge a lead acid battery, the less cycles it gives you. Some batteries will have a short lifespan if you frequently discharge them all the time. To improve their lifespan, it is recommended people only discharge Lead Acid to around 50% DoD or AGMs to 80% DoD. This creates a dilemma as you need to buy a bigger battery up front (more $$$) to provide the reserve time you want but you won’t have to replace it as often (less $$$). I’ll let you work out what works for you. For Lithium, Jason designed his system to assume capacity is available down to 80% DoD (20% remaining). Again, this is a personal choice. You need to work out what % you are happy with.

How Do I calculate What Size Battery and Solar Panel I Need?
In setting yourself up for 12 volt camping, you need to ascertain the following BEFORE making your purchases:

1. What appliances do I wish to run?
2. What is each appliance’s current draw per hour?
3. How many hours will each appliance be running in a typical day?
4. Using your answers to 1-3 above, calculate your daily power use in amp hours
5. How many consecutive days will I be “off-grid”?

Example 1:
• Fridge uses 2 amps and runs for an estimated 16 hours per day = 32 amp hours
• LED lights use 1.5 amps and run for an estimated 4 hours per day = 6 amp hours
• Phone charger uses 2 amps and runs for 2 hours. Two phones = 8 amp hours
• Total = 32 + 6 + 8 = 46 amp hours per day
• Thus after 2 full days a 100 amp hour battery would be drained

OR – To simplify: See Colin’s Rule of Thumb:

1. Get your load in Ah/Day
2. Double it to get your Battery Capacity
3. Double the Battery Capacity to get minimum Solar Power

Applying What I Have Learnt
In setting up my new camper trailer, I have the following considerations:
Running a 95l Dometic fridge with a consumption of 3.6 amps per hour, I will assume it runs 14 hours per day. Sometimes a mate may want to plug in his 40l Engel at 1.8 amps per hour. I also run some LED lights using 1.5 amps per hour and my water pump uses 17 amps per hour (but runs for a minimal time).
I mustn’t forget my electronics. Phone takes 2 hours to recharge at 2 amps and recharging my laptop will use around 4 amps for 2 hours.
This is where Excel comes in handy:

Notes:

• Unable to locate power usage of phone and laptop chargers using 12 Volt. Estimate has been used.
• Dometic fridge specified power usage (3.57 amp) is for one side on fridge and one side on Freezer. Setting both sides to fridge would lower power usage.
• Fridge power usage is dependent on ambient temperature, how frequently it is opened and ventilation
• Number of hours running time for fridges is an estimate.
• In a test I ran with the Dometic fridge for 24 hours with both sides on fridge not freeze, the actual power consumption was about 38 amps for the day – much lower than expected.

Why do I need a Controller?
A controller is an electronic device that regulates and manages the flow of electrical energy in a system. In a solar camping system, a controller acts as a middleman between the solar panels and the battery, controlling the flow of electricity from the panels to the battery for storage. They are also called a Charger or Regulator.
The primary role of a solar controller is to protect the battery from overcharging, which can damage the battery and reduce its overall life. Additionally, the controller (If it has a Low Volt Disconnect) prevents the battery from discharging too much, which can cause permanent damage. The controller also regulates the voltage and current levels from the solar panels to the battery, optimizing the overall performance of the system.
In short, a controller is a crucial component in a solar camping system, helping to ensure the safe and efficient use of the solar panels and battery.

There are several types of controllers used in solar camping systems, including:

1. PWM (Pulse Width Modulation) controllers: These are the most common type of controllers and are widely used in small-scale solar systems. They work by regulating the amount of energy that is sent from the solar panels to the battery.
2. MPPT (Maximum Power Point Tracking) controllers: These controllers are more efficient than PWM controllers and are often used in larger solar systems. They work by optimizing the voltage and current from the solar panels to the battery, ensuring that the maximum amount of power is delivered to the battery.
   Each type of controller has its own advantages

Do I need an inverter for 12 volt camping?
An inverter is a device that converts DC (direct current) power, such as that produced by a solar panel or a 12-volt battery, into AC (alternating current) power, which is the type of power that is typically used by most household appliances and devices.
If all of the devices you plan to use while camping run on 12 volts DC, then you don’t need an inverter. However, if you plan to use devices that require 240-volt AC power, such as a laptop or a portable air conditioner, induction cooktop or electric toaster you will need an inverter to convert the 12-volt DC power to 240-volt AC power.
An inverter is not necessarily required for 12-volt camping, but it can be useful in certain situations. For me it seems like over-kill and an unwarranted additional expense.
Also, keep in mind that inverters are not 100% efficient, and some power is lost during the conversion process. So, it’s important to choose an inverter with high efficiency and a power rating that matches your needs.
In summary, whether you need an inverter for 12-volt camping depends on the types of devices you will be using and whether they run on DC or AC power. If you have devices that require AC power, an inverter is necessary, otherwise it may not be necessary.

Lithium vs AGM
Lithium and AGM (Absorbed Glass Mat) batteries are both types of rechargeable batteries, but they have some key differences in terms of performance, cost, and maintenance.
• Lithium batteries have a higher energy density, meaning they can store more energy in a smaller and lighter package. They are also more efficient and have a longer lifespan (typically around 10-15 years) than AGM batteries. They also have a much lower self-discharge rate, meaning they lose less charge when not in use.
• AGM batteries, on the other hand, are sealed, maintenance-free batteries that can be installed in any position. They are widely used in off-grid solar power systems, recreational vehicles and boats, and backup power systems. They are more affordable than Lithium batteries, but they also have a shorter lifespan (around 5-7 years) and they can be damaged by overcharging or deep discharge.
• In terms of performance, Lithium batteries have a much higher discharge rate and can be discharged to a greater degree without damaging the battery. AGM batteries have a lower discharge rate and can be damaged if discharged too deeply.
• Lithium batteries are more expensive than AGM batteries, but they can be more cost-effective in the long run due to their longer lifespan and increased efficiency.
In summary – Lithium batteries are more expensive, but this is balanced out by their longer life-span. Additional pros for Lithium include: they tolerate a larger Depth of Discharge, are significantly lighter and more efficient. Also -if you want to run a +1kW inverter, you need Lithium.

Acknowledgements:
Zane Deering and Jason Gillies of the DIY 12/24v camping 4wd set-ups Facebook Group

Links:
https://www.redarc.com.au/total-vehicle-management-system

https://www.coulombiq.com.au

https://www.facebook.com/groups/340809173669763/announcements