Trick the hotspot/phone to run without battery, directly wired to PSU? - Page 1
Forum section: electronics / repair

author: nardev
author_rank: Unknown
timestamp: October 26, 2020, 03:19:50 am
content: Unfortunately i had to permanently position Alcatel y900 4G hotpot on the charger, however, after a month the battery bloated and i’m afraid to leave it like that any more.However, i don’t need the battery at the location at all but replacing the battery with just a power cable was not possible. The device doesn’t even turn on.The battery is TLi036A1 with 4 pins.pin 1. Vcc +pin 2. (not marked) BSI or BTEMPpin 3. GNDpin 4. (not marked) BSI or BTEMPI remember that there were some “hacks” to emulate nokia batteries, which made it possible to use direct power at the phone battery pins.So i tried that, i measured resistances:pin2 - GND => ~8kpin4 - GND => ~21k(btw the pin2 - pin4 resistance was => ~29k)Than i hooked the appropriate resistor, replacing the resistance of 8k and also tried adding 21k at the appropriate pins but it got the device to turn on, even expose the wifi, indicate 3G/4G connection and than RESTART. That way, the device was just in a loop, restarting.Everything was powered with appropriate 3.8V as marked on the battery.So, i believe this is pretty common issue for mobile repair shop, i was wondering if anyone have any suggestion how to trick the device (as it is essentially the mobile phone without physical interface) to turn on and stay like that.Anyone have any suggestion/idea what to try? How to make this hotspot to run of the direct power?thnx

author: lordium
author_rank: Regular Contributor
timestamp: October 26, 2020, 08:15:44 am
content: What kind of power supply was used for the 3.8V? The 3G/4G connection can peak quite high currents so maybe your supply is to slow (or cables to long). Could also try adding some capacitors in the now free battery spot to help with the current peaks.

author: nardev
author_rank: Unknown
timestamp: October 26, 2020, 05:03:37 pm
content: I used bent ch supply, limitation was much higher than the device consumed, so i'm pretty sure it's not about that.I think it was limited to 3.8V 1Amax and the peek was about 0.4A-0.6A

author: nardev
author_rank: Unknown
timestamp: October 27, 2020, 11:13:57 am
content: @lordiumI must apologize to you, when i turned the bentch PSU again i realizet it was not 1A but 0.5A set there.You were right.I eventually designed the plastic block and put the buck converter to regulate the voltage for the device, it runs for a while and than, of course, the buck converter get so hot it couldn't run any more. I replaced with another one, same thing.I also tried cutting the voltage with the diode that i had, similar story. I got the voltage down to 4-4.2V, which was ok for a while, but again the diode gets hot so much. Also, it seems that no USB charger is able to provided enough current for the direct running of this shitI don't know what to dop.s. i liked the battery replacement plastic box, printed on a 3D printerfastest speed mode it could, modeling and print done in an hour or bit more

author: sandalcandal
author_rank: Unknown
timestamp: October 27, 2020, 11:21:39 am
content: Neat 3D printed case/cover but I don't think embedding your buck converter like that is going to help with your thermal issues...Maybe find decent 4V wall wart or get a better efficiency buck converter that doesn't overheat...

author: nardev
author_rank: Unknown
timestamp: October 27, 2020, 11:24:04 am
content: I didn't check in details the buck capabilities, just directly plugged it inI realized that quickly, the PLA would have been melted all around the device pretty soonThnx

author: perieanuo
author_rank: Frequent Contributor
timestamp: October 27, 2020, 05:27:43 pm
content: hi,you can feed 4-4.2V with no problems. of course from a good psregards, pierre

author: nardev
author_rank: Unknown
timestamp: October 27, 2020, 05:29:44 pm
content: Quote from: perieanuo on October 27, 2020, 05:27:43 pmThnx guys. Well, the "good supply" seems to be pretty hard to find. It requires some kind of regulation and that's kind of a bottleneck : )