Electrical Systems, Batteries, and Power

Questions and answers on Power systems.

Questions about Gnome Homes Teardrop Trailers:

Can I …

Go off-the-grid?

Plug in at the campground?

Plug in at home?

Have 120 power?

Run everything off batteries?

Get all the electrical conveniences of a heavy trailer?

Charge my trailer from my car?

Charge my car from my trailer?

The answer is “yes.” We can provide for all of these options. We can set up your system. Custom design and install it. We’ll generate a drawing so that no matter where you are or who is looking at it, the system is laid out clear and simple.

Basic off-the-grid setup:

Gnome Homes are provided with a storage battery that runs cabin, galley, and porch lights as well as provides outlets for charging and powering 12 Volt devices. The battery is charged by the automobile [alternator] when the vehicle cable is plugged in and the engine is running. Many people like this very simple set up.

A solar panel can be added to charge the battery as well. It simply unfolds and plugs in.Solar Panel 90 Watts

A trickle charger can be used to charge the batter as well.

Basic on-the-grid setup:

On-the-grid includes all of the off-the-grid features as well as a converter. A Gnome Home with converter has AC power when plugged into shore power. While the trailer is plugged into AC, the converter charges the battery as well as provides AC power [120v AC] to any AC electrical outlets that were required and included in fabrication.

Power setup:

This power option includes the features of off-the-grid as well as an inverter. The inverter ensures that there is always AC power available. When unplugged from shore power the inverter uses the battery to produce AC power. When plugged into shore power, the inverter switches to charge mode and allows the shore power directly to the installed AC outlets. The battery is charged while AC is in use.

The inverter is intelligent, and will not trip shore power. When you’re at a campground, you should not suffer the embarrassment of overloading the circuits and seeking out the manager to turn your power back on. Will the manager want to turn the power back on?

[many converters are not intelligent and will trip shore power rather than regulate charging]

Other questions:

Q: How come you offer a 12 V TV? Why can’t I just use my 120V TV from home?

A: You can use your 120V TV; however it is not very efficient. Your 120V TV is just going to convert the 120V back down to lower voltage in order to run the internal circuitry. You’ll waste about 20% of your power by doing so. The Canadian Electric Code forbids us to install an inverter connected to a 120V device in this manner. Besides, the little 12V TVs are so cute!

Q: What the heck is an Isolator? And how come you like them so much? Is it cool or useful?

A: A battery isolator may be cool, but we like them because they are useful. As a kid, we always had to disconnect the trailer from the automobile so that we didn’t run the battery down. Now, isolators allow us to leave the vehicle plugged in without worry about running the battery down. Also, if someone borrows the trailer, you have the assurance of knowing it won’t happen to them. There’s more. Now we can safely charge the storage battery from the automobile; the isolator makes sure the automobile battery is charged first. In the rare instance that it may be required, the isolator also allows us to charge the automobile battery from the trailer power system. [ok, this last point is more cool than useful]

Q: How long will my battery last on a charge?

A: Have you seen our cute little Gnomes?

It’s just math. But some people don’t like math, so we have a table in our manual.

Using one of our typical batteries to power of all of your lamps for 6 hours a day, and charge up your smartphone for 2 hours a day, the battery will last for about 10 days before needing a recharge.

Or, you could fry about 5 lbs of bacon using a George Foreman grill.

When lit, all of the lights in the trailer combined will consume about 1 Amp of power. The battery will provide 104 Amp hours (Ahrs) before it needs to be charged. So you can run the lights for 104 hours. [This is why we use only LED lights. Incandescent lights will consume the battery in 10 hrs or less.]

When using the inverter, we need to look at watts. Let’s say you want to run a 1200 watt hair dryer for five minutes. We need 1200W/ 12V = 100 amps to run the hair dryer. Plus we consume energy doing the inversion work; so, 20% or 20 amps to run the inverter. Now 100 + 20 = 120 amps is needed to run the hair dryer on battery. Since it is only 1/12 of an hour, we need 10 Ahrs. We can dry our hair every day for 10 days. Or run the lights and the hair dryer for 5 days without a recharge.

Definitions

5 Volt/ USB outlet: typically used to plug in a charge cord for a device like your smartphone. Also called TypeA cable configuration . We also provide 1A USB for older devices like Garmin GPS.12V charging ports

12 Volt outlet: a receptacle in your vehicle to provide 12V power for operating or charging devices. Also known as a cigarette lighter socket; however, modern 12V outlets will not fit/ power a cigarette lighter. Meets SAE J563 specification.

AC: Alternating Current. The type of current that runs normal household appliances. When off grid, there is no AC unless you have an inverter.

Absorption:  the state of charge used when the battery is almost at full charge. The voltage is held at a constant value and the current is adjusted for optimal charge. Good control allows the battery to last longer.

Automatic Transfer Switch: is an important safety device that must be included when there are multiple sources of AC power. Transfer switches keep the shore lines from being energized from the RV.

Bulk (Rapid) charge: when the batteries are run down the charge controller will give them a boost to quickly bring them up to near fully charged. The current is held constant to increase the voltage gradually. The controller then goes into absorption mode to fully charge the battery.

Charge Controller: Charge Controller: a controller that regulates the charging power to the storage battery. The controller ensures correct charge is used for the battery State of Charge and number of charging cycles (or hours). Typical charge states are Bulk (rapid), Absorption, Float (idle), and Equalization. With a proper charge controller deep cycle batteries can last up to 4 times longer.

Converter: a device (aka transformer) that converts 120 Volt power to 12 Volt power. Some converters have an integrated charge controller. We will limit our information to converters with integrated controller.

DC: Direct Current. The kind of current produced by batteries. The RV uses direct current to run the lights and power devices.

Equalization: a charging cycle where the electrolyte is activated to de-sulfate the plates and eliminate stratification. Deep cycle batteries require equalization.

Flanged Plug: is just a fancy name for a plug that is mounted in the wall. Our inverters and charge controllers need to plug into AC power, and we use a flanged plug for convenience.Flanged plug

Float (Idle) charge: deep cycle batteries last longer if the charge goes to “idle” once the battery is fully charged. Idle lessens gassing and water loss. The battery lasts longer.

Inverter: Converts power from your battery to 120V power for those things that you just can’t do without. Some inverters have an integrated charge controller as well as an automatic transfer switch. Since it is quite a space saving option to combine these three items into one, we will only comment on integrated units here.

The inverter will not exceed the specified current draw, and trip the shore power.

It seems that the hair dryer is the most popular item. Be aware that many hair dryers draw 1600 or 1800 Watts of power, which is too much for most inverters. It’s a good idea to find a small 1000 watt dryer to keep in the trailer.

Off-the-grid: not connected to utility power.

Shore power/ on-the-grid: connected to utility power.

State of Charge: is the level of charge of a battery. Storage batteries generally have a full charge of about 12.7 Volts so at 12.7 Volts the SoC is 100%. Also from the battery manufacturer SoC sheet we would find 20% charged is 11.7 V. We would set up our system to never go below 11.7V or potentially damage our battery.

Solar Controller: a controller that receives power from the solar panel and converts it to regulated 12 volt power.

Solar Panel: is a bank of photovoltaic cells that produce electricity from sunlight. The solar panel needs a solar controller to make the power useful for RVs. Our discussions will include only solar panels with an integrated solar controller. In most RVs these items are two separate pieces of equipment.

Starter battery: battery used by a vehicle to start an engine and has to be maintained at a high level of charge e.g. over 60%. Has less storage, thinner plates, and less electrolyte than storage batteries. These batteries are small and light.

Storage battery: battery that stores a lot of energy and can be discharged to 20% of capacity. Has thick plates and large amounts of electrolyte. Also called deep cycle. These batteries are large and heavy.

Stratification: the electrolyte in deep cycle batteries can stratify when sitting for a long time. Equalization fixes this problem.

Sulfation: build up of sulfur on the battery plate, which is normal for deep cycle batteries. The batteries become less efficient. Equalization fixes this problem.

Trickle charger: a 12 V DC charger designed to charge automobile batteries. These devices are acceptable to charge a storage battery. Every so often, say 10 charges, the battery should be equalized to extend battery lifecyle. Most trickle chargers cannot perform equalization or idle.

USB/ 5 Volt outlet: typically used to charge a device like a smartphone.  Also called a Type A cable configuration. We also provide 1A USB for older devices like Garman GPS.

Typical RV power system:

    • Transfer switch

Converter/ charge controller

Inverter

Battery

Solar panel

Solar controller.

 

Gnome Homes:

    • Inverter

Battery

Solar panel

50% of the components. The same power in a small package

Additional considerations.

  1. When the trailer is connected to the automobile, the trailer is going to be able to draw energy from the automobile battery, potentially draining the battery. If the connection is “keyed” i.e. connection is only made when the ignition is turned on, the trailer cannot run down the automobile battery inadvertently.

If the system is not keyed, simply unplug whenever you’re parked. Campers have been doing this for many years.

Alternatively, if the trailer is pulled by several different automobiles, it is advisable to use a battery isolator.