Batteries, chargers and inverters...

[Mobius]

[quote]
Good lord..

[BFMF]

I've been watching this thread with some interest. I'm only in my second year of an electronic engineering tech course in school, so I wasn't going to try to argue with my limited knowledge...lol

But for what its worth, I think Brett is right, atleast some of the stuff that I understand...

[eno]

I feel a Mythbusters type challenge comming on here.

Why don't you both build one of each system and run them simultainiously using a small bulb as the device.

It'll save all the energy of constant typing

[Fozzer]

I feel a Myth-busters type challenge coming on here.

Why don't you both build one of each system and run them simultaneously using a small bulb as the device.

It'll save all the energy of constant typing

..... ....!

I have two Pencils on the Desk in front of my Computer.
On one Pencil, the lead is perfectly sharpened to a point.
On the other Pencil, the lead has broken off.

I tried both of them, to write on a piece of paper.

The Pencil with the point was definitely the preferred choice for the application.

Paul.... ... ... ...!

[H]

Why don't you both build one of each system...

That was the other part of our 'discussion'. Brett was having a difficult sell trying to "convince [me] that it won't work" while I had my A system operating on the floor.
There are other issues involved when operating inductive loads, not all inverters being of equal internal configurations, making sure the manufacturer has given the operating power out and not the 'peak' output, etc. The inverter can be as weak a link in the system as the battery. Although standard inverters put out a square wave (even modifieds aren't true sine wave) it works well enough with most household usage as long as the load is kept within the operating power range.

...run them simultaneously using a small bulb as the device.

A 60w incandescent lamp was plugged into the other outlet while the charger was operating.

8-)

[Brett_Henderson]

The inverter output wave type is mostly a non-issue. AC voltage is more about RMS, than peak-to-peak. However, a cheap invert's wave type could be too 'square'.. meaning that a needed, peak voltage is never achieved... OR, even too 'saw-thoothed'.. meaning that meeting an RMS rating would result in peak voltages that are too high, and that could end up damaging sensitive equipment... like a computer whose power-supply filters/regulators were substandard.

All of that gets into the inverter deficiencies that I mentioned.. and that that might be how your system appears like it's 'working'. Your inverter could be so mis-matched to the task at hand that you do indeed get more 'flushes' out of the system by introducing this electrical black-hole:




How it exists in your system..




The water analogy would be that your toilet leaks, and in order to get the maximum amount of flushes, you have to flush more often, else lose the leaking water. Of course this not only drains the system more quickly, you also get fewer useful flushes

[H]

Now you have another flaw in your diagram. No matter what type of inverter configuration, the charger's input (from the inverter) is run to a (step-down) transformer (you know, that long coil of wire, shorted across the supply line, that's wrapped around an insulated metal core; another, shorter but heavier, coil of wire is also wrapped around the metal core, shorted across the charger's rectifier input). That's why I have a problem with your 'charging a battery with a battery' statement: that is not a direct fact, since the charger output is rather isolated from the inverter via the transformer. The charger's rectifier is not directly working from the inverter's output but, rather, the magnetic-field-induced current from the secondary coil of the transformer. You are directing your flow in my diagram as if it's DC (and, yes, I know a half-wave of AC can be considered variable voltage DC); however, DC isn't going to pass across the transformer -- it's going to choose the most direct route, through the coil.
The charger's output capacity at max is 10a (the actual application is dependent upon how drained the battery is and reduces with the charge) versus a 3a input; we're not getting something for nothing because the input wattage is something under 400w while, at about 13v, the output max is @130w. That is why you must keep the operating/charging cycles short.

P.S. Not to confuse Mr. Esselbach, electrical engineering preceded electronic engineering (in practice). We later discovered that current flowed the other way, thus you'll find many electronic diagrams with the flow from negative to positive. As you can see, electrical engineering is still the wrong way.

8-)

[Brett_Henderson]

Ok..

[eno]

It would be so much easier to buy a battery charger and charge both batteries from the mains ...... PROBLEM SOLVED

[SubZer0]

The question that lies is, "Is it a rechargeable battery?"

[H]

It would be so much easier to buy a battery charger and charge both batteries from the mains ...

What "mains?" What do you think started this?

The output inductor of a transformer cannot decide how much current it draws from the input inductor.

::) The entire transformer is an inductor -- I must assume you mean its input and output coils, relating them to seperate induction coils?

Now since impedance is frequency dependent.. and we're talking about a fixed (60hz) frequency; the whole thing is a constant. The isolation is meaningless beyond the fact that even a short-circuit after the transformer will not alter what the transformer can deliver.

Won't alter anything! Many convicts would have prefered you set up the electric chair; you cooked the transformer -- it won't deliver anything!

And.. if the frequency is constant, the impedance of all frequency dependent devices makes them effectively fixed resistors

Only if everything else remains constant, which it doesn't, anymore than you're getting Direct Current to jump through the transformer without a much higher voltage potential, Mr. Tesla.

and the whole circuit can be analyzed as though it were DC.

Now this sheds some light on the problem... it's been turned over to the government in DC for long debates that go nowhere.

This circuit (which is not a flaw on my part, it's simply representaion of what IS in your system)...

And yours -- there's no difference between our supply systems: there's a recepticle between the inverter and the charger to plug something into. If you're not plugging something into your recepticle, your battery will mainly die of old, old age since your system is sitting there useless.

Whatever it is that gets, salvaged, scavanged, recycled, or whatever term you choose, and ends up stored in the recipient battery; will have taken MORE than that FROM THE DONOR BATTERY to get it there.

[color=#003300]Which has no significance unless you're going to run your system with the same battery until it can't power the load on the supply system anymore. As I've said, durations are the main importance:
1. a. You run the system for 30 minutes on the first battery --

[Brett_Henderson]

Let's try going through this in reverse... maybe it will help illustrate that with no outside power source, the battery charger has no place in this system...



1) To end up with 1AH of stored energy in a battery; the battery charger has to run more than 1AH through the battery.

2) In order for the battery charger to supply 1AH; its step-down transformer and rectifier circuits will consume more than 1AH.

3) In order for an inverter to supply 1AH of power to the battery charger; its oscillator and step-up transformer will consume more than 1AH.


Even if we assume a ridiculousy high efficiency of 90%, to each of those steps (likely closer to 70%) ... it will require 1.4AH for every 1AH that ends up in the battery. At a more realistic 70% efficiency.. it would take 2.9AH to net 1AH stored. This is why I refer to it as an electrical, black-hole.

So.. as our system is chugging along; in addition to the power that is consumed by our, light-bulb, refigerator, or whatever it is that we're running, we've spent upwards of an additional 2AH of stored engery, to end up with 1AH of stored energy

[H]

[color=#003300]OK, we'll try this one more time so, first, I understand your "charging a battery with a battery" analogy. It is as wrong to me, however, as saying you "slept with someone" -- when sleeping wasn't what you did at all! I once used a 9v battery to charge a more needed 1

[Brett_Henderson]

Our problem here, to my view, is your formulated values per the real batteries and that the charging time for my batteries has barely differed, meaning your 2ah/1ah ratio (to say nothing of the 'more like' values) just doesn't entirely equate

Charging time (or discharge time) has nothing to do with it. 1AH can occur over 100 hours, or over one nanosecond. It's just a unit of energy, as gallons are to water. I'm pointing out that it takes MUCH more energy to charge a battery, than ends up stored in it.. doesn't matter if we're talking about a partial charge after a partial discharge.. or a full charge after complete depletion. Putting energy into a battery is a losing proposition. Doing it through a charger/inverter is even more a losing proposition.

if there were no other load on the supply, both batteries recouperate during that time.

For some reason, you keep disregarding the power wasted by the inverter and charger

[H]

if there were no other load on the supply, both batteries recouperate during that time.

For some reason, you keep disregarding the power wasted by the inverter and charger.

What energy... the inverter and charger are both (essentially) off during that time! They won't be 'wasting' energy until the charger initiates again... then it will cycle off again, etc. It does matter how drained a battery is -- your dead batteries will immediately result in two (essentially) dead batteries. Their usage time is important because, in practice, the charging qualities for a well-drained battery are substantially different -- a much heavier load -- than when that battery charging begins much closer to its full potential; its self-charging qualities reduce, as well.

We're taking about how to get the most life out of a finite amount of stored energy. It doesn't matter how carefully you monitor your system.. or how often you throw the switch.. You are STILL talking about taking energy from one storage device, and putting it into another storage device, via devices that consume MORE power than they transfer. There's no getting around that fact. How does that reality keep getting lost in this discussion?

It's not but that's not what you're doing -- you're trying to have the devices consume power sourced from where there is none while ignore the inherent power on the recieving end -- it's definitely not infinite but my batteries aren't dead, the intent being to prolong that event as long as possible. You're trying to prove the existance of the devine, or equivelent, as my batteries have 'magically' recharged on the floor.

8-)