Current draw of things
I HATE camping, I really do.
But you can be comfortable,
and you can keep from "camping" by addressing consumption concerns.
solar cells or generator
batteries, q storage
Off the Grid
"Well... He should have armed himself."
Poochy, and my wife, and me like to go to state parks where there are no hookups.
In such situations, it is important to know the power
consumption of things.
The Power Budget...
Power from the solar cells leaves the solar cells in the form of current i.
This current changes all the time, from day to day and from minute to minute.
This current is subject to fog and clouds, and temperature, and the suns elevation.
During the day, the charge q is stored in the batteries, and is usually stated in the nomenclature of "Amp-Hours".
A few amps for many hours is the same as a huge amount of amps for a few minutes.
The batteries accept this energy at any rate and at any time.
The solar energy becomes stored energy.
Many devices such as refrigerators, lights, and TVs, pull the charge q back out of the batteries, each at their own rate.
Not long after that, the younger son got together all he had,
set off for a distant country
and there squandered his wealth in wild living.
The devices use up and "consume" the energy.
The energy is available from the batteries for consumption, day or night.
When you are far from home, the electricity can not be squandered.
The object with any RV, that is "off the grid", is to have more production of electricity than what electricity is used.
RV On-Demand Water Pump
The on-demand water pump starts out below 5 amps when the pressure is 25 lbs.
Then as the pressure builds in the accumulator, the load builds.
The pump labores more and more, and slows in the number of pulses per second.
And finally, at "cut off" the pressure is about 50lbs, and the current is 6.45 Amps (as shown).
The pump pulls slightly more current as the time increases between pulses which is the time that the solenoid is
At night, with the pump turned off, I can use the commode several times without the noise of the pump coming on
and awaking my wife, or even the dog. I built my own accumulator, which prevents blown water hoses, (which has happened to me) and reduces current draw.
I will have to show it in another section.
I should point out, that after this picture was taken, the pressure was reduced to 30 lbs.
The original hoses were bursting seals at 50 lbs. And to make matters worse, the
water pump is not adjustable, and under low battery conditions can no longer pump up to 50 lbs .
I had to go buy an external pressure switch, which was easy to do and install.
Otherwise, the pump would just hammer away at 49 lbs all day. Gaining nothing!
This would continue indefinitely untill the battery would be dead.
I never thought the RV industry would have overlooked this problem:
Two simultaneous conditions of Low voltage and too high of pressure.
There is no solution for ordinary RV life if the pump is not adjustable in pressure; You are screwed!
Eventually it WILL happen. You will have a dead battery for no apparent reason.
Also, for power consumption, a 30 lb setting consumes less current than a 50 lb setting.
5 amps verses 6.5 amps
I never listen to the radio. But here is the current with the audio turned down: about 400mA.
The current comes up slightly as you turn up the sound volume, maybe .5 amp.
This radio is a particularly bad one. It is complicated, and can not be figured out.
And it will turn on the alarm for no apparent reason. I hate this thing.
The alarm always comes on at midnight, and defaults to the outside speakers. And every time that it has
happened, it has defaulted to "loud" - really loud. After the damn thing woke all the peacefully sleeping neighbors
at midnight one night, I cut the wires to the outside speakers with a pair of dykes - twice. Both wires!
...Why? Because it felt good. The park's deer were running for cover, and every ones lights were coming on.
That will NEVER EVER happen again.
And why it is legal to sell a RV with outside speakers is beyond me!
It should be a criminal act to sell an RV, with outside speakers, in conjunction with a damn demon possessed radio.
These are the first and easist things to change in an RV.
10HiCluster .... 6HiCluster .... 14DescreteCluster .... Incandescent .... Single
Five kinds of lights:
Incandescent C921 1400mA 260 to 100 Lumens $ 2.00
14-Cluster- Descrete LEDs- 40mA 25 to 35 Lumens SkyBlue $ 8.95
06-Cluster- HyBright LEDs- 145mA- 120 Lumens PureWhite - $11.98
10-Cluster- HyBright LEDs- 230mA- 200 Lumens NaturalWhite- $12.98
These look like two single bulbs, but they actually are two 14-led clusters under the covers.
Almost 100mA for two. Luminosity depends on voltage: 13.99 volts is brighter than 12.60volts.
G-4 Bi-Pin LED Lamp
The cheapest way to go. If you can get the small flashlights for about $2 a piece...
Got these at Harbor Fright for two for $3.00.
Here are two flashlight assemblies installed in my 12 volt stove hood.
Go here to see how to wire these LEDs up...
LEDs have made this little RV Trailer the brightest thing in the RV park.
And it is not even connected to the Grid!
LapTop DC-DC Charger
Here is a charger just sitting on a table, plugged in to a cigaret lighter receptacle.
The DC laptop charger uses 12 volts to obtain 18volts. And just sitting idle pulls about 100mA.
The digital meter reads 0.12 Amps for the DC charger.
That is not too much overhead, and 20mA of that is for the two LED indicators!
LapTop AC Charger
AC Laptop charger.
The inverter pulls about 400mA quiescent, no load, just sitting there.
If the load is too much, this inverter,
as well as all other inverters, will beep and shut down.
The ones that I have seen will shut down from two reasons: thermal heat, and instantaneous current.
For several years this inverter has been running even my power tools with no problems.
I do not know why I tried this, there is no rational reason...
Behold, he put no trust in his servants; and his angels he charged with folly:
Only a genuine nut would try this...
The hair dryer is a 1600 Watt unit. That is over a 100 Amps. And that is way more than 15 Amps.
Lucky that I did not burn up my meter!
Wife's curling iron is fine at about 7.4 Amps.
She does not know anything about amps.
Funny thing is that she does not even want to know anything about amps.
RV Air Heater
central air, runs under the floor in ductwork using return vents
Air Heater on the left.
Here is the heater blower in the still-running-cycle, but with the gas cycled off.
The air heating unit uses about 700mA for its solenoid, which is for the gas, and about 6.7 Amps for the blower,
as shown on the meter. The meter 6.7 amps shows the cool down cycle: blower with no solenoid.
With both the solenoid valve and the squirrel cage blower on, the heating unit pulls a little over 7.5 Amps.
There is also an igniter that consumes 100mA, but is only on for a few seconds.
Solenoid and Relay, Curtesy G4 Halogen 10W Lamp, and circuit board
Climate Control (Turned off, Heater that evaporates condensation. Use sparingly.)
RV Water Heater
Hot Water Heater on the right, and is incased in styrofoam.
Solenoid that turns on the gas pulls almost one amp.
The resistance is about the same as the Air Heater, at about 16 ohms.
This variable speed drill starts out at about 2 amps climbs to 10 amps with no load.
With load; 12 amps or more. Shown here is 12 amps drilling through wood.
If you look at the rating label, you will see 3 amps at 110vac.
So, under heavy load this thing can go 3 amps at 110 volts,
or aprox 30 amps at battery voltage.
30 amps is over 300 watts.
That is at the upper end of what the inverter, displayed above, will deliver continuously.
I am putting in a 600 watt inverter that should be able to handle almost a drill stall.
USB Power Supply
At only 14mA, You can leave this thing plugged in all the time.
variable speed SaberSaw: 8 amps, no load.
Weller Soldering Station
Max current 3.4Amps, (has not reached temperature). After it reaches temperature, the ONN light "flutters".
The inverter handles fast ONN and OFF current changes just fine.
Weller Soldering Gun
Weller Soldering Gun
Weller soldering Gun
New tip! And using the pure sine wave inverter, instead of the modified sine wave inverter.
Inverter fan comes on full force, instantly.
11 Amps (including the fan)
Range Hood Fan
Range Hood Fan
1.5 Amps for the Hood Fan.
This is one device that is not even close to what is printed: 3 amps.
I later put in a speed control that saved power and greatly reduced the loud noise.
For that kind of current, you might as well run the Furnace and heat the whole place!
An electric blanket is not a viable option for being Off-The-Grid.
I might also note that electric blankets DO NOT like square wave inverters!
The electric blanket control box began to smoke. Actually, I could not see any smoke,
but could smell it. The blanket was on for only a couple of minutes. It is the only device
that I have ever seen that did not like 120 volt AC power from square wave inverters.
It was reason enough to replace the inverter with a Sinewave Inverter.
Picked up this nice pump at Harbor Freight. Set all my tires to 42 lbs.
The current varies according to the air pressure:
At zero lbs the current is about 5 Amps.
At 42 lbs about 10Amps.
The literature warns to not turn on the pump "loaded", or the fuse will blow.
So I guess that you have to start it at zero lbs. Otherwise; Works fine.
Full load is already 10Amps, normal running at 42 lbs. Would not take to much more
to be at the max rated 15Amps - like in a starting "stall".
I have to feed out a window on both sides of the trailer to get to all four tires.
The window screens slide independently from the glass. Fortunately, I had previously wired
12 volt cigarette lighter receptacles on all four sides.
There is a law somewhere that states that you will always need more 12volt receptacles
and more 120 volt receptacles in any well planned installations.
Gota keep your lights going...
At midnight the cry rang out: Here's the bridegroom! Come out to meet him!
Then all the virgins woke up and trimmed their lamps.
The foolish ones said to the wise, Give us some of your oil; our lamps are going out.
4.5 Amps to 9.0 Amps
And according to the manufacturer can go to 10 Amps, or 120 Watts!
An LCD is NOT a good choice for an RV. Instead, inside an RV use a LED tv.
The LCD uses a mercury lamp for the back light; and more importantly, is lit
ALL the time. It waists energy ALL the time.
I use this monitor for my computer room in my house. And I carry it out to the RV
when we go on a trip.
The current consumption for an LCD is totally dependent upon the "blacklight"
adjustment. With backlight adjusted to minimum, the current for my tv is 4.5 Amps, no matter the
screen content. With the backlight adjusted to maximum, the current is more than 9 Amps.
At night, I have found that there is only marginal detrimental effect from the backlight being
all the way down. Four hours of viewing at 4.9 Amps results in a battery voltage of 12.450 volts.
That is 4.9 Amps times 4 hours. Or 19.6 Amp-Hours of TV viewing.
According to a chart for flooded batteries, 12.45 volts is approximately 84% of full capacity.
Therefore, full capacity (=19.6/(1-.84))of my two batteries seems to be about 123 Amp Hours.
Rather disappointing. I was hoping for more.
But getting back to the TV.
You get what you pay for. Don't ever buy a cheap LCD for a RV. This one has a sticker on the
back that warns the set can pull 120watts. That is about 10amps with the black level turned up.
I can not afford that kind of waist! And it gets warm at the top.
On the other hand, an LED of the same size may only pull 2 amps, and it is lighter too. Now that is sweet!
But LEDs do not come cheap; I can not afford one at this time.
Also, don't ever buy a computer monitor: they can not be viewed from all angles.
Laptop screens can not be viewed from all angles either!
Therefore, DO buy a TV, and make it a LED TV.
A friend GAVE this nice LED TV to me.
Great friend! His name is Dan...
Don't mount flush with the wall. Leave space in the back for cables.
This thing is so cool!
It uses 2.6 amps. This is in contrast to the old LCD which uses 5 amps for the same brightness.
With a setting in the menu for BackLight at "5".
Uses 2.4A Current
With a setting in the menu for BackLight at "93".
Uses 4.8A Current
The conclusion is that LCD TVs and/or monitors are not RV fiendly.
Only LED TVs and monitors should be used in a RV.
LCDs will work OK in a house or mobile home with full hookups.
Plasmas are not even a consideration; Much worse.
The screen of the LED TV can be "shared" with a laptop in several configurations:
Laptop uses 3A with its LCD screen brightly lit. (6A when charging)
5.5A: Laptop and TV both on with both screens lit. Therefor, Individually 3A Laptop plus 2.5A TV
4.7A: No Laptop screen. Therefor, Laptop screen is 0.8A, during one test.
4.5A: No Laptop screen. Therefor, Laptop screen is 1.0A, during another test.
2.5A TV screen on
5.2A: Laptop LCD screen on black, TV LED screen on (black). Therefor, TV screen is 2.2A.
2.5A: Laptop and its LCD screen on black (was 3.0A in white)
Therefor, the individual pieces can be deduced...
Laptop Body 1.5A, Laptop Screen 1.0A
TV Body 0.3A, TV Screen 2.2A
In the prefered configuration of the laptop driving the TV monitor:
is from 4.5A to 5.5A, depending on picture content.
The rate of solar charging can be from 9 amps down to 1 amp, depending on fog and rain.
Over the period of six good hours from 09:00 to 15:00, an average of 5 amps might be typical.
That constitutes a budget of 5 times 6, or 30 amp-hours.
What ever amp-hours I use, those same amp-hours must be replaced.
Coincidently, my computer work uses 5 amps too, as outlined above.
I can not use more than the 30 amp-hour budget.
Therefor, I can not work more than 6 hours on the computer per day,
and still hope for any type of permanent sustainability.
Power Module Electronics Board 0.4 amps
Pizo Electric starter 0.05 amps, drops out after start
Solenoid for gas 0.25 amps, 49 ohms
(Total for normal running is 0.65 amps)
Inside Courtesy light, old: 0.8 amps, New LED:
(Total for running and door open is 1.45 amps)
Climate control 0.5 amp, 24 Ohms
Installing Chimney Fan 0.16 amps
Stated on label 1.3 Amps total.
Shut off is 9.6 volts
The Tail Lights are not part of the RV current draw. The draw is from the towing vehicle.
The Stop/Turn Filaments as well as the Tail/Running Filaments derive their power DIRECTLY from the tow vehicle.
The original Bulb on the RV is a 2057, and is not as bright as the Tow Vehicle's 1157.
The smaller and finer, or "lesser", filament is on for the Running lights. With the LED, the lesser intensity setting is on, characteristic of the Running lights.
The voltage is way down to 9.4 volts by the time wiring reaches the end of the RV.
This was measured with the engine off, and all side and tail lights on.
The voltage would be even less, if RVs used the customary automotive 1157 bulb.
Also, theoretically, there could be a legal problem:
When you step on the brake,
the extra wiring losses would prevent the brake filament from fully lighting as designed.
The result is that there is little difference between running lights and brake lights.
This may be an issue with DOT, where brake/turn must be much brighter.
I am eliminating ALL those problems; I am going LED.
The 1157 is a 26.9 watt bulb (at 12.8 volts). Amp draw is 2.1 amps
1157 is 3 cp candle power for running lights. And 32 cp for brake/turn.
1157 is rated at 1200 Hours.
The 2057 stop/turn is the same as 1157 stop/turn,
but the RV 2057 Running lights are dimmer.
2057 is 2 cp candle power and 32 cp for brake/turn.
Before buying LED, you should consider one more thing.
Do not be forced into buying a White LED
because you have to simultaneously light your licence plate on the left side with a single bulb.
You will have an efficiency problem of pushing white light through a red lense.
Just as with the incandescent bulbs; You are going to lose light.
When I took the cover off, this was indeed my case.
I simply installed a second dedicated LED bulb for the license plate,
and I was able to keep my RED LEDs. You can only use white on the plate, as police need the true
color to help identify the state.
Used in the left Tail Light.
A white wedge directed down towards the licence plate.
Also, some Red LEDs have a label saying for "off road only".
Meaning the color has not been formally approved, but in practice is accepted on road.
Others dispense with the label.
Many styles and intensities to choose from.
Stop/Turn intensity: 270 lm = 270/(4*pi) = 21.4 candle
1157 LED Bulb - Dual Function 18 SMD LED Tower - BAY15D Retrofit
So, I got two stones with one bird. I dramatically reduced the electrical work load of my tow vehicle,
and also have brighter tail lights.
An Oscilloscope is one of my engineering instruments. It gives me pretty pictures of electrical voltages anywhere in the RV.
The Oscilloscope pulls 3.7 amps. I thought it would pull more because it is an old CRT (Cathode Ray Tube) scope.
With this low current, I can even work at night in the RV with little concern.
In the day there is no concern at all, and can run as long as I want, as the solar panels more than make up for it.
When I first bought the RV, I was NOT comfortable. It was like "camping", and not
fun. I HATE camping, I really do. With modifications my RV has become very comfortable.
It is now without compromise and a modern pleasure.
On this page I have shown gobs of consumption stuff.
Your RV will be different, but you
get the idea. With planning, you can have-it-all too.
One more thing; Standards.
I have been an Engineer all my life.
Before I was in kindergarten I was an engineer, and I rode a tricycle.
I had a coffee can on the back step.
I remember that the stupid can would not stay, and I could not tie a string.
I always had to ran in the house and have Mom secure the coffee can with a string.
I punched a small hole in the side of the can, down near the bottom.
This was my gas tank and I filled it with water. Before I could go anywhere I had to have gas.
As a child, I knew that I had limited range before my fuel ran out.
I loved to peddle the dusty paths, and watch my little trail of water,
as it marked everywhere that I had been. The gas station was the spigot of the well,
located on a well worn path, which was a main road that went a long way to the west of the house.
Later, I added a second hole that I left plugged with a nail until I needed more power.
But all this extra power came with a price. There was a tradeoff: my gas consumption would increase.
I have been an Engineer all my life, and I loved it, and I could handle it well.
Solar Panels and Batteries are much like gas cans of two different colors.
Solar Panels and batteries are measured in different units. They need not be.
Solar Panels are measured in Watts, and batteries are measured in Amp Hours.
This is how you buy them, one in Watts, and one in Amp-Hours.
But both are containers of Energy, and this is the common ground.
First; for batteries:
Amp Hours are very convenient, and refect indirectly the real measurement of energy.
The real measurement of energy is Volts x Amps x Time.
I will continue to use Hours for time, as it is convenient.
And if so, the Units are Watthours.
A 100 Amp-Hour Lead Acid battery is equivalent to 1200 Watthours.
(12.0 volts is a mean point between 12.6 and 11.0. Lithiums have flatter decay slopes and voltages.)
For Solar Panels:
The energy of a solar panel is its Watts x time. Again we will use Hours.
But there is a problem: We must assume a standard length of time in a day.
For example: What is an appropriate average, considering cloudiness and latitude?
Of course, there is no standard, so you must create one for your own unique situation.
For me: "Five hours".
If so, then a 100 Watt solar panel is equivalent to 500 Watthours.
One more consideration if you are matching solar panels to batteries.
Lead Acids, unlike Lithiums, are not designed to be taken down below 12.0 volts.
Therefor, the useful, or available, energy is only half of the above calculations.
So now, batteries and panels can be compared, side by side.