Powering up cellphone on USB power only without battery - Page 1
Forum section: electronics / beginners

author: edy
author_rank: Super Contributor
timestamp: September 21, 2023, 06:41:01 pm
content: Hi everyone,I have a question about powering up some old devices without the batteries installed (particularly cellphones). For example, I have some old Blackberry phones with removable batteries which have "bloated" (vented gas). I dare not risk puncturing these batteries... and I don't want to start buying replacements that will do this again and again. I simply want to power up these phones on a USB plugged in. However, most do not power up unless there is a battery installed. My laptops, on the other hand, don't even need a battery.... they will do just fine plugged into the mains supply and I use them as plug-in computers (like desktops).Is there some way to "trick" these older cellphones to run on USB power only without the battery? Or is there a "dummy" battery I can place or short some pins to make the phone believe there is a battery installed, even if it is charging nothing? The Blackberries I have usually have a 4-pin connection to the battery. The outer two are labelled "+" and "-" and the middle two I don't know what they do (sense battery voltage or temperature?). I want to have some old BLACKBERRY phones (Curve, Z10, Bold, etc) powered long-term for an installation that runs on mains power without having to worry about the battery bloating or exploding.I saw some "hacks" online using a voltage regulator/converter (Buck converter) and soldering directly to the pins on the back of the phone battery compartment. However, they also placed a resistor across one of the power pins and middle pin (where there was a 3-pin battery connection) I guess to trick the sense circuit. The BlackBerry phones have 4 pins, so I'm not sure what other stuff is needed to fool it into believing there is a battery there, which pins to use, and what voltage it expects to be supplied (the existing LS1 or C-S2 batteries both say 4.35VDC max charge voltage and nominal 3.7 or 3.8VDC).I'm assuming that some phones will NEVER allow direct power using USB only (software programmed not to), but it should be possible to supply the voltage through the battery compartment pins. As long as I'm not plugging the phone to a USB supply at the same time, the phone will not try to "charge" whatever I have attached to the battery terminals. I'm wondering if there was something used in those old fixed-stand store displays that inserted into the battery compartment to provide power for demonstration to customers without them having a cable sticking out the side.By the way I found this site meanwhile and wondering if anyone has tried this and if it works with BlackBerry (https://www.makeuseof.com/swollen-battery-replace-run-smartphone-without-battery/). Since the batteries have 4 pins also (although not in the same order, the outer 2 are "+" "-" on BlackBerry and in the tutorial is different), it's the middle pins that are the "sense" pins that I will need to somehow figure out how to trick the sense pins. It says in the above tutorial to measure the voltage on the battery sense pins. Do they mean the resistance? I am not getting infinite resistance value across the 2 middle pins. If I measure voltage on the LS1 battery, counting the 1st pin ("+") and the last pin 4 ("-").... I'm getting 4.5V from pin1-4 ("+" to "-"), 3.53V on pin1-2 and 4.31V on pin1-3, and 0V doing any other combination (pin 2-3, pin 2-4, pin 3-4). So I'm assuming that I would have to simulate whatever resistance is leading to a voltage drop to pin2 that gave it the 3.53V reading and that gave pin3 a 4.31V reading (considering the pin1-4 was 4.5V).Note my other battery (C-S2) I get 4.39V from pin1-4 ("+"/"-"), 4.04V pin1-2, and 4.21V pin1-3. So essentially similar kind of change in voltage, with pin1-2 the least, going up at pin1-3 and highest at pin1-4, and similarly no voltage across any other pin combination (pin2-3, pin2-4 or pin3-4). I do however get a resistance across pin2-3 on the C-S2 battery of about 126 Kohm, and 86 Kohm from pin2-4. and 39K ohm from pin3-4 (note that the LS1 also gives a 40 Kohm resistance measurement from pin 3-4, but not on any other pin combination do I get a resistance).Any help would be appreciated! Thanks!

author: SeanB
author_rank: Super Contributor
timestamp: September 21, 2023, 08:23:16 pm
content: Simplest is to remove the protection board from the battery, leaving a swollen pouch cell behind, and a thermistor and 2 tabs. Note which was positive and which was negative, and simply attach a 3V7 lithium cylindrical cell there, and attach the board back in the phone to contact the regular area of contact, and lead the wires to the 18650 cell out. That way you have a larger working cell that will not bloat, and still can run the phone off battery.

author: RoGeorge
author_rank: Super Contributor
timestamp: September 22, 2023, 06:53:45 am
content: Some phones would just work with the charger attached and no battery, most won't start. Nothing should go wrong if you try. Other times, you'll have to trick the phone into thinking it has a battery. Depends of the phone and its firmware.Read the battery model then search its pinout. Most often there are 3-4 pins.For 3 pins, there are +, - and another for a resistor or a thermistor (usually the other terminal is tied to -/GND). If it's just a resistor, the value of that resistors usually tells the phone which battery model it is and its capacity (e.g. old Nokia batteries). If it's a thermistor, it's for measuring the temperature during fast charging.The ones with 4 pins varies, can have a GND twice, or may have a near-field antenna on the inside (a wire loop under the plastic cover, if you look carefully it should be visible some deformation that encircles the surface of only one side of the battery, e.g. Samsung phones batteries).You can discover the battery pinout with a DMM, but just to be sure, search online for exact battery model and the word "pinout". Battery model is usually written on the battery body, if not, look in the phone specs/user manual or search for replacement battery of the particular model of phone you have.I've punctured a few swollen batteries (with a seringe needle, very carefully, so to puncture only the cover, not the core of the battery) and keep using the deflated batteries in a place where is only cement around, and nothing else to ignite other than the battery itself and a $2 sensor. The idea is to only squeeze out the gases without letting the air enter in the battery. Once squeezed, seal back the puncture. Vent them outdoors, the gasses are nasty.Of course, it is not safe, don't do any of that. The proper fix is to buy a new battery.Some phones might check for the battery model and refuze to start if they can not read the resistor pin, that's why the extra resistor added to the power supply that was meant to replace a battery. Even if you use a power supply instead of a battery, you'll need to keep the wires and/or add a capacitor near the connecting point.The voltage for a source destined to replace the dead batt is not critical. A normal Li-Ion battery will vary between 3.0-4.2V, but the phone won't suddenly explode if you apply 5V instead (directly from a USB charger or PC cable. Those voltage margins are critical for the battery only, not for the phone. Add the extra resistor and an electrolytic at the phone side, and it should work just fine from 5V instead of 4.2V, but I didn't try that with a Blackberry.Any electrical device may become a fire hazard for many reasons, particularly when it is modified. Don't improvise unless you are 100% confident with what you do.

author: u666sa
author_rank: Frequent Contributor
timestamp: September 22, 2023, 07:25:00 am
content: Oh mother of Jesus! So much memories with those old phones!Yes, some might power without battery, some won't.But what you can do is attach your lab power supply with some crocodiles to positive and negative of your phone's battery terminals, and power it like that. This is almost always true with old phones which have removable batteries. Even with some newish smart phones. But for the newest you'd need boot cables.Those old phones are highly sought after, because when the power is off, they don't transmit. You remove the battery and no one can listen in on your conversation. With new smartphones even if the phone is off, you can be listened to, your geolocation and sim data can be sent, so turning off your iPhone 14 and going to an area means your SIm information is registered in database and if needed that device can be dialed and listed to. Then if so for reason law enforcement says you was in the area at this particular time, there is no denying.Batteries can be bought on aliexpress, I bet you can still get them.

author: Peabody
author_rank: Super Contributor
timestamp: September 22, 2023, 03:18:28 pm
content: Quote from: u666sa on July 16, 1970, 05:21:15 amReally? Then my phone's battery should continue to discharge when the phone is powered off. But mine doesn't. Is there any evidence that a phone is still transmitting after it is powered down?

author: u666sa
author_rank: Frequent Contributor
timestamp: September 22, 2023, 04:21:30 pm
content: Quote from: Peabody on September 22, 2023, 03:18:28 pmYou can't bring one with you to front lines, doesn't matter if it's stays off the whole time, enemy will know your positions.I wonder how you measured current of your phone? It should be done using power supply and boot cables, either DT880 or other.

author: AndyBeez
author_rank: Frequent Contributor
timestamp: September 22, 2023, 04:52:39 pm
content: As@u666sasays, use jumper leads to the bench PSU [or even to a cell rescued from a street vape.] Normally, the 5V USB supply powers the battery charger, the charged battery powers the phone. So no battery, no phone - and no phantom transmission.Jury rigged to an external supply, the phones should boot - these are not iphones that expect some Eeprom foo embedded into the battery. But given their vintage, they might not connect to a network due to their outdated frequency bands and protocols - even with a new SIM.

author: RoGeorge
author_rank: Super Contributor
timestamp: September 22, 2023, 06:29:32 pm
content: Quote from: Peabody on September 22, 2023, 03:18:28 pmShort answer, not really, but don't count on that.Long answer, normally a phone will not transmit after the operating system is shutdown. However, if there is any backdoor, either as a hack or by design, it is technically possible to turn somebody else's phone into a spying device, such that the phone will silently transmit audio and/or video, while the phone appears to be off.Also, when switching to Airplane mode, not all radio is turned off. Wi-Fi, Bluetooth, IR etc. are still on by design, no secrecy.Another thing less known is that the service provider can triangulate at any moment the location of a powered phone, even when your GPS is off, by using the info from their own towers on the land, can be done land only, without the need of satellites data. Usually this is allowed only by a surveillance order, by court. But in general, once a technical possibility for spying exists, somebody else might use that possibility, too, maleficent or not.Another even less known thing, is that the service provider can install and run proprietary software inside the sim card. This is independent of your phone model, or of your operating system, and without informing the end user. Or at least that's what I've understood after reading some technical documentation about 3G many years ago.Then, any phone can be eventually hacked. The only way to be sure there is no electronic leak, is to incapacitate the phone by physically removing it's energy source, the battery.Then. there is yet another security flaw in all the proprietary bloatware/spyware software installed by phone manufacturers and/or by mobile services providers. These are the worst in terms of security, and usually they can not be uninstalled without rooting the phone. Rooting the phone means trusting anonymous software "from the Internet", downloaded for free, and without any traceability. Behind it might be a white hack, or might be a black hat hack. So yeah, tough life.As a general rule, never assume you are un-hackable. All the encryption in the world won't keep you 100% unhackable either. Encryption only works if everything else around it is pristine and uncompromized, which is impossible to achieve in practice.Also, encryption does not mean unhackable, it only means harder to hack. If one is lucky, it might guess the encryption keys from the very first try.Or it can be a backdoor by design. Keep in mind that even the most rigorous mathematical proof are made starting from thousand of tacit assumptions. Mathematically-tight security is good to have, though that won't protect you against a drunk operator.Always assume your device has been hacked already. Make backups, and have a backup plan for the actions you must take, in case a device is compromised.Remember Enigma? The encryption machine used in WWII? Hacked. Remember diplomatic/embassy encryption machines from the Swiss? Backdoor by design. Remember the story when a court ordered Apple to unlock a seized iPhone? Apple honestly replied that it would be a technical impossibility to decrypt the phone, even for Apple. Big media scandal. A couple of weeks later and for a good pay, some private company unlocked that iPhone. Remember Aussie encryption laws, mandating gov backdoors by design? Impossible by math, though the law passed. Or that's how I understood from the news.When I was in the army, on each radio station, and on each landline telephone, it was written: "Beware, the enemy is always listening!". That quote still stands true no mater how many codes, and no matter what encryption scheme one uses. Even quantum encryption has flaws. There are public research papers published about various quantum encryption vulnerabilities.Always keep backups. Always have a backup plan against device hacking, or against device theft.