Check mA of your Nexus charger

Hnk1 said:

Hello

I have a official nexus charger with ratings 2.0 A. My Phone was charging a bit slow so I tried different chargers with Nexus/phones to check the mA ratings with this application.

Current Widget : Battery Monitor

I am getting about 1000 mA from Nexus charger of 2 A while 750-770 mA from my phone charger which is 0.850 A.

Do you think I have a problem with my Nexus charger ?

Can anyone use the widget (drag from widgets to home while charging and set update interval at 1s) and share results what are you getting ?

I would be very thankful!

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Did you try your experiment with a dedicated charging cable?

If I understand the issue correctly, using a sync cable for charging redirects some of the charging current for other purposes.

Hnk1 said:

No, I havenot. Just the official Nexus cables and Xperia Cable. Xperia has built in fast charging as far as I know

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What those cords do is short pins 2 and 3 together allowing your tablet to command more current which will charge the battery faster if you have a charging brick with more Watts (power.) Bricks like the Asus and Amazon fast chargers for instance. More Watts means more current can be supplied at the same voltage. (P=I*V)

That said, you don't want to heat that battery to much. 700mA - 800mA is a great charge. I charge my tablet in 4 hours or less with that. You can also open your brick and short the pins but the cord is cheap enough.

Sent from my Nexus 7 Flo running CM 11 4.4.2 with ElementalX Kernel using XDA Premium 4 mobile app

LinearEquation said:

What those cords do is short pins 2 and 3 together allowing your tablet to command more current which will charge the battery faster if you have a charging brick with more Watts (power.) Bricks like the Asus and Amazon fast chargers for instance. More Watts means more current can be supplied at the same voltage. (P=I*V)

That said, you don't want to heat that battery to much. 700mA - 800mA is a great charge. I charge my tablet in 4 hours or less with that. You can also open your brick and short the pins but the cord is cheap enough.

Sent from my Nexus 7 Flo running CM 11 4.4.2 with ElementalX Kernel using XDA Premium 4 mobile app

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But try to charge N7 in car while using GPS with 700mA-800mA car adapter. You will get discharging, not charging, so you must use 2000mA. I recommend to use 2.1A for car(I am traveling a lot and never got disappointed), and normal 2.0 for AC charging.(5.0V)

Sent from my Nexus 7 using XDA Premium 4 mobile app

milleringer said:

But try to charge N7 in car while using GPS with 700mA-800mA car adapter. You will get discharging, not charging, so you must use 2000mA. I recommend to use 2.1A for car(I am traveling a lot and never got disappointed), and normal 2.0 for AC charging.(5.0V)

Sent from my Nexus 7 using XDA Premium 4 mobile app

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The OP did not specify with GPS in the car. But for that I use this in the car while storm chasing http://www.amazon.com/gp/product/B0088U4YAG/ref=oh_details_o04_s00_i00?ie=UTF8&psc=1 20 Watt 4.2 Amp. I use GPS all the time and the Asus and Amazon bricks charge just fine while using GPS.

Still the tablet has to command the Amps it wants. This is decided in part by the Watts in the charging adaptor/brick. You can have a power supply with all the current capabilities in the world and it won't mean a thing without Power, Voltage and demand for Amps from said tablet/phone.

Sent from my Nexus 7 Flo running CM 11 4.4.2 with ElementalX Kernel using XDA Premium 4 mobile app

LinearEquation said:

What those cords do is short pins 2 and 3 together allowing your tablet to command more current which will charge the battery faster if you have a charging brick with more Watts (power.) Bricks like the Asus and Amazon fast chargers for instance. More Watts means more current can be supplied at the same voltage. (P=I*V)

That said, you don't want to heat that battery to much. 700mA - 800mA is a great charge. I charge my tablet in 4 hours or less with that. You can also open your brick and short the pins but the cord is cheap enough.

Sent from my Nexus 7 Flo running CM 11 4.4.2 with ElementalX Kernel using XDA Premium 4 mobile app

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I don't believe that's possible. It's my understanding that charging circuits are "smart," in that they'll "take" a voltage and current that tends to maximize battery life and endurance, with thermal limiting to guard against overheating. I think the profile is for the current and voltage to taper off a bit as the battery reaches full charge. Some devices do this better than others, but that's the basic principle.

The charger itself is regulated. The regulator maintains a set voltage, in this case 5.0 VDC. As the device's power requirements increase, the decrease in voltage at the regulator allows an increase in current to maintain the set voltage. Once the device's draw reaches the capacity of the charger, the battery takes over, because the charger can no longer maintain the required voltage. In other words, a 2 amp charger isn't constantly shooting 2 amps to the device unless the device is demanding that much current.

On the subject of chargers, we're not talking about laboratory grade here. Your 2 amp charger may or may not be able to actually produce 2 amps, much as the actual output voltage may not be exactly five volts. It's also important to note in the discussion that device batteries aren't rated at five volts, but something less. 4.5-4.7 is a common range.

Hnk1 said:

Hello

I have a official nexus charger with ratings 2.0 A. My Phone was charging a bit slow so I tried different chargers with Nexus/phones to check the mA ratings with this application.

Current Widget : Battery Monitor

I am getting about 1000 mA from Nexus charger of 2 A while 750-770 mA from my phone charger which is 0.850 A.

Click to expand...

Click to collapse

Are you sure your Nexus charger is 2.0A? I think the 2012 charger was rated for 2A out, but my Nex7 (2013) charger lists 1.35A output on its nameplate.

Either way, could be that the 2013 Nex7 is configured not to draw a lot of current, generally this is for thermal management.

Hnk1 said:

First of all,I didn't realise I was using new nexus charger (1.35A) and I thought it was the old charger (2.1A). So that cleared the doubts if my chargers were faulty.

Using a 2A charger would charge the battery more quicker, about 2x but it would reduce the life span of battery as well and may damage the device.

As more battery is being charged, more amounts of electrons would be present inside battery so the flow of current would start to decrease slowly . (So it would take more time to charge in the end.)

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Glad we got to the root of your issue.

There are a couple of misconceptions though:
All things being equal, you are correct that charging at higher current will produce more heat and will generally reduce battery lifespan. It is not likely that you will damage the device by using a higher-capacity charger (unless it is some cheap knock-off charger, but those are dangerous regardless of capacity). The charger is not "constant current", meaning it does not always supply the full current, only what the device requests. Some of the supply current gets used to power the device, and some goes to the charging circuit.

The charging circuit limits the amount of current going to the battery based on how full the battery is (fast charge up to a certain charge % or cell voltage, then slow charge to ~100%), the battery temperature (if temperature is too high, reduce charge rate), and some maximum current (depending on the charge circuitry, battery ratings, design decisions, etc). edit: If you use a (quality) 2A charger, one of two things will happen: either your device will charge faster and you may reduce your battery lifespan, or the charging circuit will still limit the current to some lower limit (like 1.35A), and nothing will change. You are not really at any risk of causing device failure.

Also, there are not "more electrons" in the battery. The number of electrons stays the same, since current must flow in a loop. What changes is the energy state of those electrons. When slow-charging (constant voltage charging), as the battery is charged its voltage rises towards the constant charging voltage. The difference between the charging voltage and the battery voltage drives the amount of current, so as that difference gets smaller the amount of current decreases towards zero per ohm's law.

Hnk1 said:

First of all,I didn't realise I was using new nexus charger (1.35A) and I thought it was the old charger (2.1A). So that cleared the doubts if my chargers were faulty.

I did few tests, asked my dad who is an Electrical Engineer and came to the following conclusions.

When I'm charging my phone/tablet ; say I'm using 1A, the power given would be around 850-900mA . The power be always less than rated.

If I'm using my phone and charging with same 1A charger, and the power used by my phone is 500mA, I would only see 350-400mA power given to battery as net because the power given would be subtracted from power being used.

Using a 2A charger would charge the battery more quicker, about 2x but it would reduce the life span of battery as well and may damage the device.

As more battery is being charged, more amounts of electrons would be present inside battery so the flow of current would start to decrease slowly . (So it would take more time to charge in the end.)

If charge power is less than usage of device, you would see discharge of device. In this case using a high power charger would charge the device but still it would damage the battery.

Basically, there is a safety factor of a device/battery. So if more current flows into it, lets say it can withstand 1.2 A and came with 1A charger. Using 1.3A or higher would damage the device/battery nonetheless.

I hope this helps and thank you for all your opinions and suggestions

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I think that would be true... if there weren't a charging profile built into the unit. That profile has the most "juice" going to the battery below a certain charge state. It tapers off as the battery reaches the fully charged state. On some newer devices the batteries contain electronics that help things along. There is certainly thermal limits built in, and at any rate, on higher quality devices at least, only so much current is used for charging. It'll charge at whatever current level the manufacturer has designed and no more, even if more current is available.

And you're correct in that while the device is charging, some current is used for charging while surplus current, if available goes to the running device. Once the device's battery reaches a full charge, the full charger current is available to run the device. If the charger is capable of providing the current needed to serve the device's needs, life is good. Otherwise, the cycle begins again.

Generally speaking, so long as you're not flogging your device by taxing the CPU and or GPU, a 2 amp charger should be sufficient to run say, a music program and a nav program using the GPS. Plug an OTG cable in and start hanging peripherals off of the dongle and all bets are off.