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A possible power supply solution

I just won an action for a Chromebook 11-1101us and noticed the power supply wasn't coming with it. Everything I read states that it needs a micro B 5.25v 3A charger.

I was thinking... I have a PC power supply sitting around that states on it's side that the 5V line supplies up to 23A. For purely charging purposes, if I splice in a cable to the 5v line, will this be a good way to charge the laptop until I get replacement adapter?

UPDATE: 4/27/16

A lot of good answers and a lot to think about...

I initially used my PS to USB cable and it was charging my battery. The battery didn't get hot, just barely warm but I decided it's too much of a risk after reading that it might blow up my battery. I ended up using a 2.1 amp ipad charger and it worked good... except it took over 24 hours to fully charge from a dead battery.

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The HP charger that is recommended is about $23 which is actually more than I paid for the laptop.

I ended up using a 2.1 amp ipad charger and it worked good... except it took over 24 hours to fully charge from a dead battery.

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Dragon, happy that it worked for you and you can use the charger while using the computer near an AC outlet to extend battery time. Here is a fast charger that might provide the 3A. Also, can you change the chosen solution so others will go the correct route?

http://www.amazon.com/dp/B01CSCALOM?psc=...

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Hi,

Given that the adapter specs state 5.25V and you are supplying +5VDC the charging difference will be minimal. As it is a 3 cell battery that you are charging, this equates to 1.75V per cell with the correct adapter and 1.66V per cell with your supply. Obviously not the optimal charging voltage but it will suffice until you get the correct adapter.

A battery will only take as much current as it needs to, to charge. The only way you can put more current into it (overcharging) is to increase the voltage.

As long as you do not reverse the +ve and -ve connections on the charging cable that you are making there should be no problem

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I would not recommend doing this. First, the cell voltage for Li ion is around 4.0V/cell. Li ion batteries require specific charging levels and currents and if the battery is low you might greatly exceed the charge rate. As you probably know, these batteries can catch fire so over stressing them is a hazard. Wait and get a correct charger. If you have a USB charger rated for 2.1 amps that should work to charge it if the computer is shut down.

Check here if you want to know more about charging Li Ion batteries: http://batteryuniversity.com/learn/artic...

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Hi, How does this equate with the manufacturer's supplied power adapter having an output of 5.25V 3A and the specifications for the Chromebook stating that it has a 3 cell battery?

The OP didn't say that he was going to charge the battery 'out of circuit', so the Chromebook's battery management circuitry is being applied to the input voltage provided by the supply. Also his power supply is not a constant current source but is a constant voltage source. The amount of current that is supplied varies as to what is required.

If anything applying only 5V is undercharging it. You need voltage to drive the current into a battery so applying a constant 5V (which is less than the recommended adapter output) until the battery reaches 5V will not stress the battery, as the current will reduce as the battery charges, (battery voltage opposing supply voltage - Ohm's Law I=E/R where E = Esupply minus Ebattery).

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Battery chemistry only allows for a certain voltage and for NiMH it is 1.25V while for Li-ion it is a nominal 4.0V. Instead of 3 cells in series as you guess, they are likely in parallel. Electronics in notebooks and tablets should all run on 3.3VDC or less, so a buck converter would be used to lower the voltage from 4V to the required voltage. This is efficient and is not wasteful like linear regulators. If a higher voltage is required then a boost converter would be used.

Li-ion batteries are charged using constant current so a lower rated charger would still work but charge a bit slower if the device was off/asleep. Chargers usually have enough current to run the device while still providing a small charge to the batteries, hence the 3 A rating of the proper charger. Batteries are rated for charging at a 1C rate of current.

Power supplies and systems can be quite complex. Companies like Dell, HP and others have power engineers to specifically handle these issues. Hope this helps.

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Hi, I must be missing the point. The OP's charger option has nearly the same voltage specifications as the manufacturer's charger. His power supply can provide 'up to' 23A but this doesn't mean that it is going to supply that much.

Surely the Chromebooks battery management circuitry will ensure that as long as the input voltage is correct (or nearly, 5V as opposed to 5.25V) that the maximum current that is allowed will also be controlled and will not be exceeded simply by having the charger having the capability of supplying more.

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The current is based on the (input voltage - the battery voltage )/the parallel cell resistance in normal circuits. If the Chromebook has the charging circuit internal to it, then you would be correct and the rating of the power supply current would not matter. I don't have a schematic so I don't know that it has those circuits. Space is at a premium in devices so offloading charging would be expected. Normally, I would expect the charger to have the control circuits which includes several charge controls. If that is true, and you replace it with a straight supply with a high current rating then you have the ability to force many amps of current into the batteries depending on the battery voltage and resistance.

One example, if a cell shorts, a proper charger will either shut down or limit the current to 3A. A 5V, 23A power supply would not. BTW, its 5V +/- 5%

http://powerelectronics.com/mobile/multi...

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Hi, Thank you. Penny finally dropped. Given the replacement cost of a charger it doesn't seem that it would be too sophisticated but as technology improves and prices come down, cost may no longer be a consideration in regard to capability. Thanks again for your responses.

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Dragon940 Carp will be eternally grateful.
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