USB Chargers and the Nexus 5

[coppcar]

You might be wondering the same thing I was, "Can my variety of USB charging devices be used to charge the Nexus 5?"

I have several of these things. Some plug into the wall, others to the 12 volt socket in the car. The output voltage ranges between 5.4 to 5.5 volts. In an attempt to answer this question, I did some studying of the Nexus 5 service manual (kindly supplied by an unknown person prior to the release of the N5).

Here are my findings. Use with caution! Although I have reason to believe this manual is accurate, it may not be. Furthermore, I'm not an engineer, just a curious and resourceful techie.

There are two integrated circuits between the voltage sources (wireless charging chip and micro USB cable) and the battery. The first integrated circuit (chip) is called an over voltage chip, the second is the battery charging chip, which charges the battery.

Over Voltage Chip - Each voltage source (micro USB connector and wireless charging IC) has an over voltage chip between it and the battery charging chip. These protect the battery charging chip from over voltage or reverse polarity situations. The part number for this over voltage chip is MAX14670E.

Battery Charging Chip - This chip is made by Texas Instrument and the part number is BQ24192. It has a "Volts In" spec of 3.9 to 17 vdc, and an "adjustable" "Volts Out" spec of 3.5 to 4.4. This output voltage charges the battery. The "adjustment" is designed into the device by the manufacturer and never changes. The "Volts Out" remains constant, regardless of the
input voltage.

From what I can tell, I will be able to use my USB chargers which I got with my Dell Axim X51 years ago. The Nexus 5 is replacing that Dell PDA. You can imagine my amazement of what these devices have become. I don't use the N5 as a phone, I have a $7/mo pay as you go dumb phone.

Hopefully this information will help others.

 

[Rukbat]

I'm not an engineer

I am, but I will say this with a note of caution.

As long as the output VOLTAGE rating of the charger (it's on the label) is in the 5.2 volt range, there should be no problem charging almost any phone or tablet made in the past few years. They all use 3.8 volt lithium batteries, and the circuits in the chargers and the phones/tablets are set up to charge them properly with about 5-5.3 volts.

The current rating (Amps or ma) is a different matter. Each battery is designed to be most efficient (as far as total lifespan goes) when charged at a certain rate. As long as the charger you're using can supply AS MUCH current as the one that came with the device (note of caution here) you should be fine. The battery will draw as much current as the circuitry was designed to allow it to draw. So if the battery is supposed to be charged at a 1,000 mA rate (that's 1 Amp) and your charger can put out 3 Amps, the battery will charge at 1 Amp and be happy.

If the charger can't put out as much current as the original one did, the problem is that the battery will take longer to reach full charge, given the same starting condition. This will reduce the total lifespan of the battery. By how much? I doubt that 10% of the people who buy cell phones condition their batteries, and that shortens the lifespan of the battery A LOT MORE than undercharging it does. So you'll probably never notice that your battery lasted only 734 days and not 736 days.

What you will notice is if you properly condition your battery. Now I know that various sites, which I respect, claim that conditioning has very little to do with battery life, but my current "go to if the daily driver goes bad" phone was made in 2002, and still gets the same amount of life out of the original battery that's still in it as when it was new. Tell me that something that I can see working doesn't work and I tend to doubt you a little bit.

Whenever I get a new cellphone battery (and that includes when I buy a new cellphone), the first thing I do is fully charge the battery. If it takes 2 hours or 24 hours, it stays off, on the charger, until the phone tells me to disconnect the charger. Then I use the phone normally, playing games, making calls, using the Nav app, whatever I need to do. Until the phone tells me to plug the charger in. I WILL NOT charge it again until then. (I'll turn it off if I'm going to sleep and it'll probably need charging before I wake up.)

I do this 3 times - 3 full charges, 3 "discharges until the phone 'wants to be' charged". And my batteries last a long time. (If some certain female employee of Best Buy is reading this, and she remembers setting a Note 3 up on the charger, not on the battery, she know who I am. Turn the new phone on using my new battery and it becomes your battery. I don't want it any more.) The battery could have been charged yesterday, and it could be used now with no problem, or it could have been sitting in a warehouse for the last 10 months and be just about dead. I don't know, so I assume the latter. (Assuming the former with a dead battery will give it a VERY short ifespan.)

LiIon batteries are supposed to be good for about 500-1,000 charges. I don't know exactly how many times I've charged the battery in my old Motorola V551, but it's been a lot more than that. Maybe my team just happens to win every time I wear my "lucky" bowling shirt, or maybe the shirt makes the ball go into the pocket, but I always condition my batteries and they always last a long time.

 

[coppcar]

I am, but I will say this with a note of caution....and they always last a long time.

Excellent!