Recommended, maximum and effective charge currentGeneral


  1. Thorsten

    Thorsten Well-Known Member

    I'm about to buy a 5000 mAh external battery pack and I'm wondering about the best output current. The products I've found and like offer either 700 or 1000 mA.

    Conventional wisdom seems to say that the stock charger delivers 1000 mA. However, on the plug itself, it clearly says,

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  2. AQAA

    AQAA Well-Known Member

  3. Thorsten

    Thorsten Well-Known Member

    What does
  4. AQAA

    AQAA Well-Known Member

  5. OverBoard

    OverBoard Well-Known Member

    I don't think the OV will draw more than .7Ah. If you plug it into a 1.0A charger, it will should still draw .7Ah max.
  6. K-L-M

    K-L-M Member

    Each battery has a controller chip built in and will limit the amount of current, independent of the power source capability. It also keeps track of charge cycles, can determine end of life and more. This chip is to prevent the self destruction that occurs with lithium.

    I have an Optimus V and made some current drain measurements during charging. The Optimus limits the current from an external power supply to no more than 400ma, whether the phone is on, off, charging, or full- 400mA is it's regulated limit.

    If you have a power source .7A, 1A, etc. it won't matter charging speed wise due to the 400mA regulation, But.....Assuming the manufacturer does not lie about the power supplies capabilities (use poor/under rated components), having a supply with higher ampacity over what the device actually can use, would put less stress on the charging components.

    Why is this forum killing my double spacing? I have not had this happen with any other forum. Sorry about all my text running together. Trying 'advanced mode', will see if that helps.
    Thorsten likes this.
  7. Thorsten

    Thorsten Well-Known Member

    Mind sharing how? ;)

    Interesting. This would suggest that charging from the wall adapter should be no faster than via USB. Did you compare the two methods?
  8. K-L-M

    K-L-M Member

    Hello Thorsten,

    More good questions there...

    You asked how did I measure current. In this case I wanted a quick idea of what to expect from this phone. So I used one of my bench supplies, in this case a 35 Amp linear regulated power supply adjusted down to 5 volts output, the same as the output of a USB port, car charger or the AC charger that came with the phone.

    I used a digtial DC ammeter in series with power going supplied to the phone. In this method I am measuring the total amount of current drawn by the phone as needed to recharge the battery and power the phone itself.

    And so I came up with the maximum current drain for my Optimus V at it's thirstiest under varoius conditions like dead battery charging while making a phone call...It still limited to limited to 400mA.

    I have details of other power drain measurements I took during this test, like roughly how much does current does a download on wifi pull, and what power is actually saved by dropping back to1xRTT, and so on, but, I did not want to appear to hijack the thread in some way, in posting all those measurements. Being you are the creator of this thread, you can determine if such info is appropriate of course :)

    You asked if I compared wall adapter versus USB. As you know there is a lot of talk about that here and there. I did not test with USB, as all USB ports are not created equal, and I was going for max current drain results. Going USB for a power source could affect those measurements as USB ports have their own current limits, some with steeper limits than others.

    But theoretically, if you know you have a hefty USB port, then yes, it should be just as good as a wall charger.

    Anyone can determine if a USB port is limiting the current by first using the wall charger, see how long it takes to charge, then on the next totally depleted battery, charge it up with the USB port if one must. If it takes longer than the wall charger, it's the USB port slowing things down.

    Also don't worry about running down a lithium totally dead as the rumors go. The chip in the battery never really lets it get to zip for saftey reasons. not even close. In this case we have a claimed 1500mAH battery, but about 1000mAH gets drawn before the phone claims it's exhausted. This is normal, for phones, lap-tops, and other lithium powered stuff ;) Same goes for full charge. It's never really full, for safety reasons. And yet phones and laptops melt down. Bad chip! Baaad chip!

    Personally,using a USB port as a power source makes me nervous. I've seen them burn often. If I blow up my USB port, it's a lot harder to replace than a wall charger, etc.

    Okay got the (forum) double space figured out. Have to go to advanced post mode. Been a reader for a while, but had not posted until I ran across a topic I have knowledge about an could contribute :)
    Thorsten, jj2me and Investor22 like this.
  9. AQAA

    AQAA Well-Known Member

    I agree with most everything you have posted.

    The equipment like laptops, phones etc that use lion batteries have safety measures built in to limit voltage drop beyond the limit required to keep a cell alive including protection and regulation from charge levels.

    One caution though, and again I agree with you, "if" the control electronics should fail in any way, you are at the mercy of whatever current levels are available to the battery.

    Therefore staying within limits is generally a good idea.

    I have worked with the unprotected lipos for years in RC equipment and you better make sure you are well within the limits in all aspects.
    These batteries a able to cause nasty flame ups and burns should things go wrong.
  10. K-L-M

    K-L-M Member

    ^^ Yep. To that I add, you get into buying smart batteries on the ultra-cheap from countries unheard of are the ones that usually have sub-standard gas gauge tech in them, and so....'flame on!' (the battery).

    As you mentioned if the controlling circuit should fail and the battery is at the mercy of the source supply, it would just hasten the melt down if you used a supply of heavier current capability. :)

    If the chip in battery and the power FET they often drive all shorted out- even with the stock charger at .7A or even half that....would cook the battery quick and a 'reaction' would start.

    To that, I have long been an advocate for the need of a 'watch dog' circuit for these batteries. Manufacturers like Sony can't seem to rely on battery manufacturers to always make a good product all the time, thus the mass recalls we read about. But this adds to the cost of the battery circuit etc. Some times all we can do is keep our fingers crossed :D

    Yes, just the cells and no gas gauge IC to control them, as you pointed out, have to be monitored externally. Would not want a $7k R/C plane to suddenly go 'poof!' as it plummets to the ground.

    There are times when I have needed to extract or install solderable batteries, and had a few 'run away' on me in the process. By then, it's a case of get it out of the unit in a hurry and toss it some where safe to 'splode. Some times if I had no where to go with it in a hurry, I'd do a Fukushima cooling technique. (submerge the heat source)

    The chip that manages the batteries to keep them safe, can make small calculating errors, not enough to cause any harm or reduce battery life(by the math only not in actual health). But the problem with the small errors is one small error+another+another= battery believing end of life is nearing, so reduce amount of charge and output, as we have all seen over time.

    Some smart batteries (for all devices) seem to manage better than others over their lifetime. No way to tell until you use them unfortunately.

    Have a great day everyone :)
  11. benslgdroid

    benslgdroid rockstar Guide

    The only warning i can give is some ebay sellers will sell batteries manufactured from China where the safety chip has been removed in order to save on costs which is why they are so cheap. There has been reports of those exploding because they cannot regulate themselves.
  12. Thorsten

    Thorsten Well-Known Member

    By all means, hit us. ;) I can't see a problem with sharing extensive technical information here; nobody is forced to read it.

    Thanks for all the other useful info. :)
  13. K-L-M

    K-L-M Member

    Hello all, okay, and thanks for the approval. Here's my notes I made back in January regarding Optimus V power consumption.

    I have an Optimus V now. I just made some current drain measurements during charging. The Optimus limits the current from an external power supply to no more than 400ma. About half an hour into the recharge current consumption dropped back to 350ma and stayed there for most of the cycle.


    I found that if you turn the phone off, It will still draw the same current when charging. So if it is off, it will charge a little faster (compared to phone idling sipping juice) but not by much. Try not to use the phone so much while charging might be best if charging speed is important. And yeah using power from a USB/computer is not a good idea. Might wear out low tolerance parts in the machine.

    Other power drain notes (Battery fully charged, and using external linear regulated power source). Current is measured at the input of the phones USB connector:

    48mA- Phone off (note the 4 buttons are lit)

    31mA- Phone on standby mode, screen off

    69mA- At the 'home' screen

    123mA- Screen rolling a page

    75-85mA - Looking at the Settings> About Phone > Status screen (looking at signal strength change, etc.)

    165mA- WiFi turned on and using it to download 1MB file. Once done drops back to 69mA

    235mA- (WiFi off) Network data enabled (3G), downloading angry birds, 4 bars reception

    235mA- Using the maps app to show me where I am at. drops to 113mA when network data is idle, map on display.

    155-160mA Playing Angry Birds

    140mA- Phone call with 4 bars reception

    275mA- Phone call with speaker phone on, 4 bars reception

    Some folks wanted to see the difference in current drain between 3G and 1xRTT, and the general belief that 1xRTT is a big battery saver compared to using 3G. And some claim WiFi may be a better way to go. Let's see what I found...

    3G / 1xRTT / WiFi current drain comparison:

    (speed test performed, signal strength -85dbm (weakish), non stock apps stopped, background data/sync off)

    3G 250mA average Speed test complete in 9 seconds 284kbit/s

    1xRTT 210mA average Speed test complete in 25 seconds 132kbit/s

    WiFi 170mA average Speed test complete in blink of an eye. Router 25' and 1 wall away from phone.

    Short answer: After a number of tests between the two, and a signal of -85dbm (not the best reception, but good for testing as the transmitter runs longer) the average current drain is only 40mA greater when using 3G as opposed to 1xRTT.

    * Note: Because the transmitter had to remain active longer in 1xRTT mode to complete the same test, the phone actually drew 0.85mA more over the length of the test than it did in 3G. So if phones are saving power in 1XRTT, there is another factor some where not supported here. You could say this was a lab test condition with lab tests results, but as we all know, things are always different in the real world right?

    Another way to look at it...If the 3G was transmitting for an hour I figure it used about 4% more battery life over 1xRTT. (Again in a lab test, and calculator isn't real world heh heh)

    Other tests I've done a few times now, show that to recharge a claimed dead battery, the phone drew right at 1000mA (phone off) total before charge was complete. But, how much of that 1000 went to circuitry, even though turned off at the time, and not to the battery? Well, best not ot pick it to death. I just wanted to point out that the battery says 1500mAH, but charges to 1000, it's normal, don't panic. This is where I usually talk about how if the the chip that manages the battery is well designed (and some are not), you generally don't have to worry about over charging, or running the battery down dead and causing shortened life, because the technology won't let you cycle the battery at full capacity anyway.

    More tests...

    Airplane mode ON / OFF- Some say the receiver is also turned off when airplane mode is enabled. I don't see a change in current drain in either state. Of course airplane mode does inhibit the transmitter.

    Charging time
    I found that I really needed to update my findings on this matter. Previous data no longer valid. Charging tests have been updated, and this time it includes fast charge rates. Scroll down a few posts and I will explain :)

    Hope this helps in realizing what the demands are that we put on the phone under typical conditions. I'm delightfully surprised.

    K-L-M
    LoneSnark and Thorsten like this.
  14. OverBoard

    OverBoard Well-Known Member

    RE: AC Charging vs USB Charging

    Modern smartphones need the data pins (D+ and D-) on the USB cable to be shorted together for fast charging (high current). This lets the smartphone know that it is connected to AC power (that can supply more than 500mAh, the USB limit).

    Using a DMM on my OEM LG AC .7Ah adapter, it says there is ~1 Ohm between Pin 2 & 3 (Data+ & Data-).

    In the android world, most phones will sense three conditions:
    a) No cable attached
    b) USB power attached -- phone will draw max 500mAh
    c) AC power attached (D+ and D- shorted) -- phone will know it can draw over 500mAh

    In the Fall of 2009, all of the major cell manufacturers and governing bodies agreed to standardize on the MicroUSB plug to charge cell phones. The standard also specified the shorting of the USB data pins to let devices know they are attached to a high power USB port (AC).

    Also see:
    Universal Serial Bus - Wikipedia, the free encyclopedia

    [FONT=&quot]When you were taking these measurements, what did your phone detect your power supply as, AC or USB? I suspect it is probably USB.[/FONT]
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  15. K-L-M

    K-L-M Member

    Great question. Regarding the test results I posted earlier, Yes I intentionally set D- and D+ high (not floating or low) so that the phone would 'detect' as you put it as a USB type power source and not AC type power.

    Quick test time

    Test 1
    I just took a moment to pull D- and D+ low So that it would reflect a higher current capable source. External power supply was regulated down to 5 Volts, 35+ amp capable. In this configuration The phone was drawing about 680mA.

    Test 2
    After that brief test, I let D- D+ float (like a PC USB port) and the charging current was approximately 380mA.

    Okay, now that's established.....Does shorting D0- and D+ make a difference?

    As per my notes in an earlier post, it takes 3+ hours to charge a dead battery if the phone was charged by a PC USB port type source.

    How long does it take to charge a dead battery phone using the supplied .7A charger that has D- and D+ shorted to signal higher charge current capable as OverBoard pointed out? I forget actually. **Update I'm back. It took 3 hours and 5 minutes.

    Woah! something is wrong here. Standard and fast rate take 3 hours?

    Need more testing to clear this up....See my next post....
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  16. OverBoard

    OverBoard Well-Known Member

    Your experiments are interesting to read, looking forward to the results!

    BTW, the market app Quick Battery shows the Optimus charging plug type: (AC or USB). Its a very small memory widget.
  17. K-L-M

    K-L-M Member

    Test results for standard (USB Port like) and fast charging (AC charger)

    I’m back, with a round of battery charging tests involving standard and fast rate charging times for the Optimus V.

    But first- data error! Or needs an update at least....
    According to my notes from 6 months ago, the standard charge rate (USB pin 2 and 3 not shorted) took 3 hours and 15 minutes.

    Yesterday, I just tested the fast charge rate (USB pins 2 and 3 shorted) and it took 3 hours and 5 minutes.

    This can’t be right that the standard and fast rates are about the same. So I performed a fresh standard charge rate test. This time it took 6 hours. Okay, that’s more like it.

    The test I did 6 months ago was done twice on a new Optimus V fully cycled 6 times prior to testing. Apparently the smart battery was not done calibrating itself or the like.

    With this discovery, I find that this battery is allowed to run down deeper, and charge more fully than I observed 6 months ago, and unlike other batteries I have observed. For those expressing concern about running down the battery too far and shortening life, you might be right. But as for me, I always fully cycle batteries to keep with consistency of ongoing tests. By the time this battery goes bad I may have another phone.

    Onto the test results for Fast and standard rate charge…

    Fast Rate Charging test 'a'
    a.) The supplied A/C charger does charge at fast rate. The Phone is turned off for test.

    - USB pins 2 and 3 are shorted up in the power supply to signal fast charge capable.

    - Charging current at the connector of the Optimus V was 680mA until it very slowly tapers off over the last 1 hour of charge.

    - Charging time took 3 hours 5 minutes.

    - Total current flow until phone off/battery screen animation stopped: 1,713mA.

    Fast rate charging test 'b'
    b.) Power source other than a computer or supplied AC charger that has a much higher current capability than the supplied AC charger. Phone is off for test. The purpose for this second test is to see if the supplied AC charger is limiting the charge rate. Can the phone be charged faster with something else?

    - USB pins 2 and 3 are shorted to signal this is a fast charge rate capable power source.

    - The charging current and charging time was the same as the supplied AC charger.

    So 680mAH charging current and 3 hours charging time for a dead battery seem to be the ‘fast charge rate’ limit as determined by the phone. The supplied AC charger is not hindering charging performance when the phone is turned off.

    If the phone is on (standby) or in use while the AC charger is plugged in the current draw from the charger will remain exactly the same, meaning some of that power is being diverted for the phones other needs. By example, you can expect a reduced fast charging rate by about 23% if you are playing Angry Birds. A standard (USB port) charging rate would be reduced by about double that.

    Standard Rate Charging
    Power source emulating a computer USB port or possibly a cheap car charger.

    - USB pins 2 and 3 are not shorted to signal a standard charge rate capable power source.

    - Charging current at the connector of the Optimus V was 380mA until it very slowly tapers off over the last 1 hour of charge.

    - Charging time took 6 hours.

    - Total current flow until phone off/battery screen animation stopped: 2,070mA.

    As you will note the current consumption for recharge with the phone off was in excess of the battery rating 1,500mA. A portion of the excess current can be explained away as being used by the phone in some way and a little bit of waste for the actual charging circuit.

    What about a high current car charger to charge the phone faster?

    We see this come up often don’t we? To be sure there are a lot of terrible car chargers out there. In my little collection of car chargers for various phones, I found that all of them did not have D- D+ pins of the USB connector shorted. So they are all the reduced/standard charge rate type.

    I do have one that has a higher output rating than the ones you can find at a dollar store. A Motorola SPN5400A ‘Rapid Vehicle Power Adapter’. The output current is claimed to be 750mA. (Update: There was an issue with the charger and has since been repaired and it does deliver on it's claims!)

    That’s lovely but guess what, D- D+ USB pins are not shorted. And so my Optimus V only draws 380mA maximum from it. (Update: The D- D+ pins are shorted, I measured wrong pin)

    So who makes a genuine rapid vehicle charger? Beats me. Update: The SPN5400A is solid charger after new findings, and a tear down analysis- which I will share with you, pictures and all. just scroll down a few posts where it starts out saying: 'Motorola SPN5400A - A quality car Charger'

    Hope this helps some one, and thanks for the input OverBoard which made me check things out again.
    K-L-M
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  18. K-L-M

    K-L-M Member

    ^ ^ Okay.....Now I got all that out of my system, I can get back to answering post #1 by Thorsten!

    Really I'm just posting this for readers following along and just like the summary :D

    - The best (charger) output current will depend on if the USB data pins are tied together (logic LO) to signal high current capable as OverBoard pointed out. I'd be concerned that a charger manufacturer just has two wires for the power and that is it. We tend to 'hear about those' from time to time.

    - We now know that the supplied AC charger is capable of charging the Optimus V as fast as the phone itself will allow, 680mAH plus or minus.

    Referring to post 1, you could use a 1000mA charger. The phone will self regulate and draw no more than about 680mA if it's the right charger. Also, if you use a charger with a current rating higher than the supplied AC charger, the phone will not get hotter due to self regulation. Numerous times I have used a power source that had 50+ times the Ampacity over the stock charger.

    Now I feel on topic :D

    Have a great night everybody- K-L-M
    Thorsten likes this.
  19. OverBoard

    OverBoard Well-Known Member

  20. K-L-M

    K-L-M Member

    Motorola SP5400A - A quality car Charger

    OverBoard
    - You are good to go on the Motorola SPN5400A for rapid charge. Mine is genuine Motorola, bulk item (non-retail). Unfortunate me this one had a minor problem (a solder ball) thus the current output was reduced as mentioned earlier. The cure was all to easy and...

    ...Mine will produce 880mA :eek: driven to near saturation. After that, it folds back as it should. For our readers, this means that this charger can deliver as much current as the Optimus V can take on which is approximately 700mA in fast charge rate mode.

    There are only two wires running down the cord. Pins 2 and 3 of the micro USB are shorted together in the connector itself. Earlier I measured the wrong pin so I thought they were open. The Micro USB has not 4 but 5 pins you know :)

    I decided to make a document with internal pictures about car chargers, and what I found with the SPN5400A and what I would like to point out to folks about the design of these chargers in general. Being everyone including me can't tell if a car charger is any good just from the packaging. I think this will help.

    Update: Here's the 2.2mb .PDF I made about the Motorola SPN5400A and compare it to some really cheap chargers. The document has a number of internal pictures, and some explanations as to what you are seeing, along with test results. Hope it comes out okay on your screen. http://www.mediafire.com/?33nf3356vnz4ocb

    K-L-M
  21. ariksa

    ariksa New Member

    Guys, what about the charging voltage?
    I've bought USB power adapter (220V to 5V) so I just plug my USB cable and charge. While charging my Nexus S, it stops responding but shows that it charges. I have measured - the adapter outputs 5.31V, while USB on PC outputs 5.11V.
    Do you think it can harm my phone\battery?
    What's the output voltage on your chargers?
  22. K-L-M

    K-L-M Member

    ariksa, Your output voltage measurements of 5.31 and 5.11 is okay. I'd say if you are within about 10 percent of 5 volts on the high side (5.5) you're probably okay.

    If you were to place various loads on your 5 volt power supplies, you'll see a small change in voltage. It's just the nature of 'switch-mode' supplies.

    For example, in a recent test I had a 5 volt charger running at 5.3 Volts at 670mA load. I increased the load on the same charger to 880mA and the voltage was 5.39.

    I did not quite understand the part where you mentioned 'While charging my Nexus S, it stops responding but shows that it charges'. Stops responding as in the phone is not operational yet it definitely charges?

    Have you tried another power source and it still stops responding?

    I should add that I'm not familiar with the Nexus S at all, but perhaps some one else on here is?
  23. ariksa

    ariksa New Member

    K-L-M, thanks for your reply.
    Stops responding:
    if the phone is locked and I slide the screen - nothing happens, the green Unlock icon doesn't slide to the right as it should.
    If the the phone is unlocked, it behaves strange - some icons start shaking, and again the screen doesn't respond to any of my gesticulation.
    While reading your answer, I though that perhaps the problem is that the charger has voltage on the 2 data pins... I'll check this out.
  24. OverBoard

    OverBoard Well-Known Member

    Symptoms like you describe can be the result from cheap non-OEM power adapters. A cheap cable and/or loose connection can cause problems. Try using a high quality OEM wall charger and known good cable and report back with results. OEM wall/car chargers are soooo cheap on Amazon there is almost no reason not to use a quality adapter if you can wait for Amazon to deliver it.
  25. Whyzor

    Whyzor Well-Known Member

    I also noticed some odd touchscreen sensitivity issues when connected to my laptop USB port today. In a program called multisensor visual test, the touchpoints jiggle more when my phone is connected to charger, wall charger has less noise than USB, and no charger has the most stable readings. Anyone else notice this?

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