Charging mobile phone battery without phone

Have you got any of these: an accurate voltmeter, a multimeter, a variable power supply?

Bill

I have a multimeter :)

At the risk of stating the bleeding obvious, does it power up when connected to a power supply? Firstly with the battery in place, then with the battery removed. I would be pretty confident that the board is protected from being fried by a 5 volt USB supply with the battery removed.

As you probably realise, the risk in messing around with the battery is that you overcharge it and it catches fire. In principle you should be relatively safe by feeding appropriate volts direct to the phone pins, but as Bill says it's safer to do that with a good quality variable voltage power supply and a meter where you are confident about at least the first decimal place.

get a single cell lithium or charge up the one you have

Actually its 3.7v medium 4.2v full and IIRC about 3.3 flat

Yes tried both and nothing. After posting this I thought I would check to see if the battery voltage increases with it in the phone on charge. It was reading 0v (or 0.3 on the 300mV setting - not sure what that means) and now after a couple of hours it is reading 0.2v (the 300mV setting is saying "overload"). So it seems like it might be charging albeit very slowly. Will leave it plugged in to see if it holds any charge.

Yes my multimeter is an old Fluke digital one so should be accurate. How best do I generate the voltage required?

Have you checked the charger? When this happened to me it was the charger that was knackered. It is unusual for a phone not to power up with a charger connected this has been the case going back years I believe. The only Samsung phone I owned was a Galaxy Ace and you could power from the charger and do all even though the battery was pancaked.

Richard

I could charge the one I have but not sure how to do that without the phone being able to do it?

Don?t mean to be rude but have you tried another charger and a new usb cable? Cables fail frequently, chargers less often but still do die occasionally.

When you?ve tried a new/different charger/cable combination will the phone power up when attached to the charger (with or without the battery installed)?

If none of that works then I guess trying to charge the existing battery out of the phone is worth a shot. I?m pretty sure all Li-ion phone batteries have built-in overcharge protection so I don?t think the explosion risk is high. ;-)

Tim

Have you tried simply plugging it into a PC via a USB port, using a suitable lead? The charger one may be power only.

You might find it sees the storage drive. That works with my S4.

What do you have?

For a crude charger, a 5V supply with a silicon diode in series will make

Now we need to limit the current to prevent it charging too fast. Let's say we'll limit the peak current to 200mA when it's dead flat (V across it is

So put diode-diode-18ohms in series across a 5V supply - you should see maximum 3.6V across the resistor. Due to the current limit, it's safe to keep it like this (assuming your resistor is at least 0.75W).

Now put the battery in series with this circuit and observe the voltage across it. If you see the voltage rising slowly, that's good. If it rises to 3.6v rapidly, the battery is knackered. If it stays at 0v it's shorted (knackered, and really you shouldn't leave it for a long period to prevent it cooking).

A 'proper' charger is constant-current/constant-voltage, so it does CC mode for bulk charging and CV mode at the top of charge. The diode+resistor is a very crude and slow approximation, but if the current is low enough it'll be safe.

Theo

The photos might even be on a removable memory card.

Agreed, it may also be a dodgy socket in the phone. You sometimes find they will work with some cables but not with others.

Surely the OP would have thought of that, but perhaps I should me a backup of the photos on my and swmbo's phones as the phones do not have have slots for memory cards.

Hi All,

Definitely a bit of an odd one this. The phone died last March (ish) with the symptom of not charging - left on for a few hours, no charging led and phone wouldn't turn on. Tried various chargers, leads, connecting it to a couple of PCs etc. nothing. Looking online there were a number of reset type fixes involving holding various button combinations, starting it with/ without battery etc. and no sign of life.

It was my wife's phone so she has been using an old iPhone 5 since which she hates. So... for Christmas I bought her a new Andorid phone. Yesterday I tried to get the photos off the old phone to put on the new one. No charging again so posted the above. After a couple of hours the charge in the phone went up very marginally but decided to leave it plugged in. All of a sudden, it seemed to suddenly charge (measured on MM to around 2v) and the led "I'm charging" lit up! Phone continued to charge as normal and now seems to work fine.

After all this there were only 2 (not interesting) photos which had not been copied to the server!.... I use an Android app which automatically copies all photos to my server via NFS for backup - it had been playing up resulting in you having to manually hit the upload button instead of doing it automatically. So given my wife rarely does it manually assumed there would be loads to do. Guess I should have tried to correlate the time stamps on the server with roughly when the phone died!

Anyway net result is she has a nice new phone and we have a spare if needed!

Anyone have any idea what suddenly spurred it into life? It was almost like it knew there was a new phone on the block :) Only thing I can thing of is that it has been in the cold utility room for the past few months - maybe this did something to the battery - like the "put it in the freezer" trick?

Thanks for all you help

Lee.

Simplest way might be to find someone else with a similar S5 phone and charge it in that (or buy a new battery for it and hope it comes with enough charge to do what you want). eg

I may have insight. I once flattened some LIPO flight batteries badly. (left em plugged in to a model for a week) The charge only recognised a three cell battery as one cell and refused to charge it over 4v.

Loathe to condemn the battery without at least a try to restore it I popped it on a nickel cell charger at low current - 100mA I think for a few minutes. Once it read over 8V I put it on the proper charger.

It did charge, but the capacity and internal resistance were pants.

So it was f***ed, but it did hold a bit of charge

To get a battery replaced in a phone is about £40 including labour and many little hole in the wall arcade shops will do it. I would get that phone a new battery. Chances are it will spring to life.

Lithium (all chemistries, like Cobalt or Iron Phosphate) apparently do not have good charge acceptance at 0C or lower.

Not all charging chips are pro-active about this. But this is some copied text from one chip that does care.

TEMP(Pin 1) :Temperature Sense Input Connecting TEMP pin to NTC thermistor?s output in Lithium ion battery pack. If TEMP pin?s voltage is below 45% or above 80% of supply voltage VIN for more than 0.15S, this means that battery?s temperature is too high or too low, charging is suspended. The temperature sense function can be disabled by grounding the TEMP pin.

Warming a Lithium pack up to room temperature before charging, is a good practice for them.

Paul

Ah interesting... I wonder if when I was taking the voltage of the battery I inadvertently grounded the temp pin then. The battery pads are about the same width as my probes so very likely I inadvertently shorted some of the pads

Could he simply use a torch bulb as a current limiter?

Bill