Power usages

[jwcolby54]

Maybe we can start a "power usage" thread. I have a Kill-o-watt power meter which seems to be reasonably accurate. A few measurements I have taken in my TT:

1) ResMed s7 CPap: 12 watts
2) 32" samsung LED tv: 36 watts
3) Toshiba 2 year old AMD quad core laptop (charged state) 9 watts
4) 5 year old Dell Intel dual core laptop (charged state) 22 watts
5) Asus TF300 10" pad (charging) : 3 watts

[Bob Miller]

Just to ask: DO the numbers you got from the kill-o-watt match the numbers shown on the devices???

[Byron Kinnaman]

Originally Posted by jwcolby54

Maybe we can start a "power usage" thread. I have a Kill-o-watt power meter which seems to be reasonably accurate. A few measurements I have taken in my TT:

1) ResMed s7 CPap: 12 watts
2) 32" samsung LED tv: 36 watts
3) Toshiba 2 year old AMD quad core laptop (charged state) 9 watts
4) 5 year old Dell Intel dual core laptop (charged state) 22 watts
5) Asus TF300 10" pad (charging) : 3 watts

I believe the Kill-O-Watt meter measures 120 Volt AC power.
Now let's translate the Watts to amps for both 120 AC and 12 DC
1) 0.1 Amp 120 AC -- 1 Amp 12 DC.
2) .3 Amp 120 AC -- 3 Amp 12 DC
3) .075 Amp 120 AC -- .75 Amp 12 DC
4) .18 Amp 120 AC -- 1.8 Amp 12 DC
5) .025 Amp 120 AC -- .25 Amp 12 DC.

If you want to know how approximately much each of those will draw from your battery (12 DC) inverter or direct which ever is required multiply each by the estimated usage time.
Example 1) usage 8 hours x 1 amp = 8 amp hours.
Example 2) usage 4 hours x 3 amp = 12 amp hours.
Example 5) usage 6 hours x .25 amp = 1.5 amp hours.

That should give you some approximation of how long your battery power will last before needing to recharged.

I assumed the reason for the thread is to determine how long the house battery will last.
I did not take into account the efficiency of an inverter which would add 5% to 10%.

[jwcolby54]

Originally Posted by Bob Miller

Just to ask: DO the numbers you got from the kill-o-watt match the numbers shown on the devices???

Nope. The numbers on the device tend to be 'max' numbers, worst case so to speak. Real life are usually less.

My Samsung tv says 59w but then says 33w typical usage. I saw 36w.

[jwcolby54]

Yes, the point is to get a feeling for some 'typical' devices we might run on battery. The first thing they say when looking at solar is to figure out your usage, which drives your battery and panel requirements. I use the tv as a monitor for the toshiba laptop.

Right you are, the next part is an inverter to provide the ac used by the devices. The efficiency rating is typically 85-90% so watts + 15%. The total watts gives a picture of the size inverter required as well. I don't try to run any cooking or heating devices.

[Byron Kinnaman]

Originally Posted by jwcolby54

Yes, the point is to get a feeling for some 'typical' devices we might run on battery. The first thing they say when looking at solar is to figure out your usage, which drives your battery and panel requirements. I use the tv as a monitor for the toshiba laptop.

Right you are, the next part is an inverter to provide the ac used by the devices. The efficiency rating is typically 85-90% so watts + 15%. The total watts gives a picture of the size inverter required as well. I don't try to run any cooking or heating devices.

Watts (power) is a good measure when going from one voltage to another. But it's a good idea to change all to current for battery usage since batteries are rated in amp-hours. Also when dealing with solar, the measurement of interest is amps again, because batteries are rated in amp-hours. Most solar panels specifications will give you short circuit out in direct sun in amps. That's a good starting point. In fact in measurements it works out pretty close.
Also charge controllers are rated in amps, with a lot of confusion stuff. Many, if not all, have a "load" connection. That's to be ignored unless you like spending money. I would select a charge controller based on the maximum current from the solar panel.
Example... My case, I have a 65 Watt solar panel. Maximum current is about 4.1 amps. My charge is 6 amps and I power a ham radio with one of my batteries that draws 22.5 amps on voice peaks. If I used the "load" connection I would need at least 25 amp controller at about 3x the cost.

FYI, my solar system is about 5 years old now and we spend about 3 months at a time off the grid.

You're right about not powering heating devices from the batteries, they get very hungry in a hurry.

You're on the right track.

[hotfishtacos]

Originally Posted by Byron Kinnaman

... I would select a charge controller based on the maximum current from the solar panel.
E....

Byron, most people don't have an issue with incorrectly sizing the controller but I think the bigger issue is that many controllers don't charge efficiently (correctly) and put out far less voltage than required and some aren't very well staged in cycling design; watts (lots) of panel charging capacity going to waste.

[Byron Kinnaman]

Originally Posted by hotfishtacos

Byron, most people don't have an issue with incorrectly sizing the controller but I think the bigger issue is that many controllers don't charge efficiently (correctly) and put out far less voltage than required and some aren't very well staged in cycling design; watts (lots) of panel charging capacity going to waste.

Oh? So you think it would be ok if used a 1 amp charge controller attached to my 4 amp solar panel?
I won't go into detail about your voltage concerns, most of the voltage requirements issues are myths and sales talk.

[Byron Kinnaman]

John,
If you have the same furnace that I have it's about 3.5 amps when running
The incandescent lights are about 1.5 amps each.
I don't know what the water pump if have an electric water you'll need to find out how much current that draws.

I switched LED lamps and they're about .1 amp each and installed a couple LED fixtures that I modified to have two levels of like, the low level is quite enough and that's about .05 Amps. each. The LED lights along save a whole lot of power.

[jwcolby54]

All my lights were switched to led by the po. Thanks for the furnace info. I also have a fantastic fan, three different speeds.

There really are two different issues, overall dc power draw affecting solar panel and charger selection and then ac draw affecting inverter selection.

[jwcolby54]

In 1969 I was in 9th grade. I was given a bunch of ARC5 and other tube based WW2 receivers and transmitters. These came out of airplanes. A 1955 radio amateur manual was included. By the end of the year i had read the book cover to cover several times and knew ac/dc theory, tuned circuits and filters, amplifiers, oscillators, etc. All tube based of course. With the help of a ham operator we got my stuff working and I listened to the lower ham bands for hours. I practiced morse but never quite got fast enough to get my license. I did get a late 60s arrl manual and learned transistor and fet stuff, phased lock loops and so forth.

In 1972 I joined the navy and went to 90 weeks of school to repair computer mainframe and peripherals, then spent several years on a carrier fixing their systems. So by then I was into digital which i continued to fix and build my own ucomputers until 1986 when i finally moved full time to programming. However ucontrollers continues to be a hobby. In the early 80 I studied op amps extensively. All during that time i built by own computers as well as audio gear.

I never did get back to amateur radio. But i do have the background to understand and analyze every aspect of solar systems, chargers, charging algorithms, inverters etc. I know down the circuit level the various functional blocks inside these components.

It is my educated opinion that most of the low end stuff is junk. The people specing the stuff in my scamp don't understand what they are buying and assembling. They don't have a clue about battery voltage levels, amps required, wire size and resistance per foot, voltage drops on those wires, etc. All i hear is 'use 10 ga' when that is just waaaaay small for battery to anything. My pd 'all in one' is located at the rear of my scamp with my batteries about 15 feet away as the cable runs. Yea the wires to the lights are fine, but to charge the battery? No remote sense that i can see. The pd power widget should have been placed under the front seat 3 feet from the battery. Moving it is a nonstarter, everything is wired to the back seat.

As someone trained to understand the ramifications, i am seriously annoyed with my electrical system!

[jwcolby54]

Here is a cool calculator for voltage drop. Somebody mentioned charging a battery from the alternator. Feed this to the calculator

Dc
10g
15v
20 ft.
50 amps

You end up with 13v at the battery. Hmmmmmm

Voltage Drop Calculator

[Bob Miller]

CAUTION... Verbal Prozac follows:

While not a highly trained computer technician, I can claim about 12 months Navy schooling on aircraft electrical systems, that is if any one really gives a rats patootie....
------------------------------------------------------------
That said.....

Fortunately some things work well in practice, if not on paper. I have used #10 & #8 wire for battery charging lines from vehicle alternators to coach battery's for about 40 years now without every finding that my coach battery wasn't being charged adequately.

Hopefully no one is going to move more than about 15 amps through that wire when charging, otherwise a boiled over battery or warped plates are almost a guarantee. Interstate Battery, for one, indicates that prolonged charging rates over 15 amps on a group 27 battery can damage the battery.

And, anyway, most automotive alternators sense voltage at the vehicle battery and start shutting down as it's fully charged state is reached, leaving the coach battery what technically might be called "Sucking Hind T!t" based on the averaging voltages between the two or more batteries in the circuit.

In the PD-4045, Progressive Dynamics has indicated that their smart charger circuit senses battery voltage during a null period in the charging cycle (when there is no voltage drop) and adjusts the charging mode/rate accordingly. Also note that the desulfating cycle is short in duration, again to prevent damage to the plates.

Just my somewhat sophomoric take on the issues.....

As the Other Bob said:
"Don't Worry, Be Happy"

[honda03842]

I'd be surprised if 10 gauge is even rated for 50 amps....

[Byron Kinnaman]

Furthermore the PO that put the converter/charger under the left rear dinette seat is named SCAMP. Wonder how many 1000s of trailers are built like that.... Hmmmm.


FYI. If anybody cares.
I entered the wonderful world of electronics in about 1954 working alongside my father in his radio and TV repair shop. Then off the military (AF) and electronics school, ground radio maintenance, then off to business and college (EE). Until retirement about 4 years ago. Lots of fun designing stuff.

[hotfishtacos]

Originally Posted by Byron Kinnaman

Oh? So you think it would be ok if used a 1 amp charge controller attached to my 4 amp solar panel?
...

Byron, read again what I stated, "most people don't have an issue with incorrectly sizing the controller." ..however, for you a 1 amp controller for your 4 amp panel would be perfect!...trust me!...

[jwcolby54]

LOL, Norm, no it is not going to handle 50 amps very well. Can you say smoke?

My point is that I never said that, however someone else in one of the threads said their alternator was going to recharge the battery in 15 minutes. 10 ga is common for these lines. To recharge a battery in 15 minutes is going to take HUGE currents.

This is a different kind of smoke as in "and mirrors". However I would bet my PD charger in the Scamp does use 10 Ga wire and I would bet money that there is at LEAST 15 feet between the PD charger and the battery. As the current goes up, so goes the voltage drop.

The battery manufacturer whose link I provided says they recommend 14.8 volts for the bulk charge, There is just no way that the PD will deliver anything close to that to my battery, EVEN WITH your wizard.

[jwcolby54]

Originally Posted by Byron Kinnaman

Furthermore the PO that put the converter/charger under the left rear dinette seat is named SCAMP. Wonder how many 1000s of trailers are built like that.... Hmmmm.

Thousands. Which doesn't mean it is done right.

How many Ford Explorers were built that rolled over and killed people. Just because something is done, doesn't make it right.

I get that no one here cares.

[Bob Miller]

"I get that no one here cares."
and
"Thousands. Which doesn't mean it is done right."

Cares about what?????
Is there something about power chassis being installed under dinette seats that is going to have even a minor impact on our lives or pocketbooks ????

And while some may argue that it's not the most optimal location, that doesn't mean that it was done wrong either.

If FGRV's was only built the "right" way I doubt if most of us could afford one..... Witness several recent makes that tried and are no longer with us..... vs. those that have been doing it "wrong" and have been her for 40+ years.

[jwcolby54]

Originally Posted by Bob Miller

CAUTION... Verbal Prozac follows:

Fortunately some things work well in practice, if not on paper. I have used #10 & #8 wire for battery charging lines from vehicle alternators to coach battery's for about 40 years now without every finding that my coach battery wasn't being charged adequately.

"Don't Worry, Be Happy"

Bob, here is what Trojan says about the subject:

Table 2. Charger Voltage Settings for Flooded Batteries


System Voltage
Charger Voltage Setting
12V
Daily Charge
14.8
Float
13.2
Equalize
15.5

As for "moving X amps through the wire" that is determined by three things:

1) The battery (dis) charge state
2) The charger capability
3) The size of the wire

So if a battery is entirely discharged then it is going to accept far more current than it would if it were fully charged.

If the battery charger is capable, it will source far more current than if it is not capable.

If the wire gauge is too small, then the voltage drop will be large, in and of itself limiting (to some extent) the actual power delivered into the battery because a bunch of power is being radiated off the wire in heat (and smoke).

And you can talk till the cows come home about "adequately charging" the battery but those words are simply meaningless, or at the very least only contextually significant.

Adequately charged to you could mean it will deliver enough power to get you through the night. To me it means delivering 110 AH from the time I start using the (fully charged) battery until the time I start charging it back up.

I am simply not interested in "adequately charged" I am interested in "correctly charged". Correctly charged is NOT contextual, it has a specific meaning for a specific battery. FOR MY BATTERIES, CORRECTLY charged means that when fully charged they will deliver 110 AH to the halfway point where I must stop using them or begin to damage them. FOR ME, CORRECTLY CHARGED means that the charger is CAPABLE of fully charging my battery.

I want MY batteries CORRECTLY charged. I don't give a rat's patuty about your batteries.

I can guarantee that a 10 gauge wire will NEVER CORRECTLY charge my battery (or yours) although it does apparently "adequately" charge your batteries.

I can also guarantee you that the PD charger (even with the wizard) will NEVER fully charge anyone's batteries. Trojan tells you what you need to deliver to FULLY charge their batteries and PD tells you that they do not deliver that. PD tells you that right in their Wizard literature!

And I get that no one here cares.

For most it seems "adequate" is good enough.