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Question of the Day: Have you ever ordered a product online and received a fake knock-off?
Wall Sockets/plate with Built in USB
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tRoN
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As long as it will charge my iPhone overnight I am happy with the neatness of it.
Good for iPhone (assuming it has Apple specific resistors network for 0.5A), not good enough for iPad.
anarchy2007
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The same goes for your devices' "original" charger. It also takes 220VAC and supplies 5VDC. This does not change just because the power supply is in a wall socket. 99.9% of all low voltage power supplies have some type of isolation. Isolation is usually achieved by some sort of optocoupler in smaller devices. Optocouplers are used since they are much cheaper than transformers.
anarchy2007
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It will eventually damage your battery charging it at such a low current. I speak under correction but believe that the iPhone's charger has a current rating of 1A. On the other hand it's better than charging it with a notebook's USB port.
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anarchy2007
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I read this over and over "Apple specific resistors network for 0.5A" and don't understand what you mean? Are you referring to the original lightning cable that has a special chip so that Apple can stop all 3rd party cables from working? If so that is in the cable not the PSU so it won't be a problem.
The reason I ask is that resistors or not rated according to current (Amp) or Voltage (V) but according to Watts (W) and resistance (Ohms). A resistor network is basically just a few resistors parallel to each other in the same package.
That is just wrong - this will be a switch mode power supply, not a "resistors network". But it will have resistors inside, just not in the way you are suggesting.
But you are correct, the iPad might show that it is not charging due to the low current.
Isolation can be achieved by means of opto-isolators, but for signals. Not for isolation of power lines. All traditional isolated switch mode power supplies will have transformers inside, albeit of the ferrite variety, with a higher switching frequency, you are able to reduce the size of a transformer drastically. Heavy traditional iron core transformers are used less frequently nowadays, due to production cost etc. A switch mode power supply, could incorporate opto-isolators in the design, but that is for isolation of either the feedback signal, or in some cases isolation of the switch signal to the switching device (igbt/mosfet).
As long as it gives a steady 5V and 500mA, it should work. It will be slower than the devices charger, but for instance Samsung phones assume it can not draw more than 450mA unless it detects an oem charger. It will not damage your battery if the current rating is too low.
Here is a 1A version:
http://www.livecopper.co.za/search/products?keywords=usb
But they are too expensive still IMO.
http://www.livecopper.co.za/search/products?keywords=usb
But they are too expensive still IMO.
tRoN
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What proof do you have it will damage the battery?
Not about lightning cable.
Resistors network is connected to D+ and D- (data) lines. Voltage created by this network is a signature about capabilities of the charger (0.5A, 1A or 2A). iPhone/iPad will draw maximum current not exceeding above, or will display message "incompatible charger" if voltage is out of range.
It is why I talk about Apple specific charger, it is different from USB charging standard and other brands proprietary solutions.
Re: Opto-coupler and isolation transformer: Both are present in typical switching mode power supply. Isolation transformer is for transfering power (at high frequency 20-250KHz, it is why it can be small) and opto-coupler for closed-loop regulation, but later one can be replaced by another isolation transformer.
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anarchy2007
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Sorry I should've put that differently. It will negatively effect the "performance" of the battery.
The industry standard is that Lithium-ion batteries can be charged at almost any current and that even at a much lower current the battery will simply take longer to charge but not have any I'll effect on the battery life and actually help maximize battery life (note this is not the time that the charge is held, but how many years the battery will last). The same does not go for the applied voltage as that should remain consistently with in the recommended charging levels at all times. The issue is that if more current is drawn than the PSU can supply, the voltage will drop. If the supply voltage drops to below the minimum needed voltage to charge the battery it may effect the life span of the battery.
Now the very big BUT. In today's society we rely more on performance than life span of batteries for portable devices. If you where given the choice between 2 day "talk time" with 2 years life span or 1 day "talk time" with 3 years life span. 90% of people would opt for performance over battery life. And this is exactly what the difference is between charging at the correct current or too low current. Please note that you cannot charge at a higher current even if you use a PSU with a higher current rating as this is not controlled by the PSU on portable devices that use USB power.
Also a very big influence on battery life and performance is the way it's charged and when charging stops. Luckily in most portable devices today the charging is controlled by a power controller chip on the device itself rather than the power supply or charger. What this means is that if you charge your battery with the correct voltage and current as recommended by the supplier (provided they don't manufacture "cheap" electronics) then you will get both maximum performance with maximum battery life. Charging with power supplies that supply to little current will effect the performance and the time that the charge last.
Below link is how lithium-ion batteries generally charge, but do keep in mind that the voltages, time, charging limits and current is controlled by the device and not the PSU. Unfortunately the quality of your PSU will directly effect the voltage drop due to too much current being drawn. If the voltage drop is too great and it's used as an every day charger then it will damaged the battery over a period of time.
http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries
***Edit***
Sorry completely forgot about the proof part.
We need to assume that the following is true. (Although the specs on PSUs is usually the total max that can be supplied and not what they run at at all times or what the device uses). Also this is not the exact voltage drops and there are much more accurate ways of proving voltage drop. But it's the simplest way to prove that voltage does drop.
iPhone draws 1.0A @ 5VDC
3RD party Charger as mentioned above supplies .75A @5VDC and does not limit the current when the voltage drops.
Using Ohms law
I (Current) = Voltage/Resistance, V = I x R and R = V/I
R = 5VDC/1AMP = 5 Ohm (iPhone)
V = .75AMP x 5Ohm = 3.75V (3rd party charger)
the above shows a voltage drop of 1.25V
Now referring back to the supplied link above we can see that at 3.75v the battery would only charge to 60% at full saturation, meaning that although it shows 100% on your screen it's only charged to 60% capacity.
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anarchy2007
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I wrote some much I forgot the actual reason I wanted to post. CABSTRUT in PTA also does the USB face plate. It's a modular design and unfortunately only fits their trunking, but what I liked about it is that it's only a fitting and not the PSU (if I understood correctly). That means that one can connect you own PSU in the wall box and not be limited to a 0.5A or 0.75A PSU. The only down side is that the face and one USB connector costs just over R400.00.
rubber_otter
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Subscribed to this thread. I would like one, too. But with at least 2.1A output.
anarchy2007
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Yes you are correct, in fact charging it at low currents and voltages will actual greatly increase the life cycle of the lithium-ion battery (not most others). What I actually meant is that the performance of the battery will be useless as the battery will never charge to full capacity, leading to shorter usages times. Obviously this is highly dependable on just how low the voltage or current is and also taking into account that too low current chargers may cause voltage drops unless they limit the current to avoid voltage drops. Effectively leading one to believe that the battery is in fact faulty as it does not last as long as it should, when in actual fact the problem lies with the charger or PSU.
P924 was right indeed. Your comment is not valid, as nobody charge lithium battery with 5V. Each device has its own regulator which controls voltage applied to to the battery, typically between 3.1 and 3.2V (with current limiter and temperature cut off), so external power supply voltage can drop quite low from nominal 5V and still it won't affect charging control.
In summary slower charging not only extend life cycle, but also allows to charge battery to the full capacity (in contrary to what you say).
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tRoN
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Now I'm really confused.
So contrary to anarchy, u are saying a slow overnight charge will improve BOTH battery life and performance.
I'm a layman buy I still can't understand how anarchy says that although the charge will show 100% but will only be 60% with a lower current despite being on the charger for the whole night.
I do confirm, that for lithium battery slow charging extend battery life. Fast charging increase temperature, which is a real battery killer. For some other chemistry fast charging can be a cure - for memory effect by example - but it doesn't apply here.
It was many wrong statements (or at least inaccurate) I just addressed a few, most critical one. Anarchy can be right on the 100%/60% issue observation, but not conclusion. Charging system might be fooled by wrongly estimating (not measuring) power taken by device during charging cycle and initiating timer based cut off, similar to temperature cut off (before battery voltage achieves desired level). Real charge = power delivered - power taken by device. Longer charging increase importance of second component. Therefore faster charging can show more realistic charging level than the slower one. It has nothing to do with battery life, just false indicator. It means that charging algorithm can be improved, or the charger is to weak (incompatible) for this device (see my first comment in this thread - 0.5 A charger is good for iPhone, but not good for iPad).
In summary, when I talk about slow charging to improve performance, I don't take into account under-spec charger nor a poor charging algorithm. There are graphs on the WEB showing charge capacity graph when lithium battery is charged to the same voltage at different current level. Taken from memory, difference is up to 20%; higher battery capacity is achieved when charged at lower current. There is no question about.
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