Samsung Galaxy A7 Sm-T500

caffeine

[2025-04-20 Sun] tried without success enable wakelock, https://f-droid.org/fr/packages/com.github.muellerma.coffee/ (2.24), https://f-droid.org/fr/packages/com.hifnawy.caffeinate/ (2.1.0) but https://lab.zhs.moe/caffeine/ (2.0.8), from https://moe-zhs-caffeine.en.uptodown.com/android/download worked

root

upgraded the firmware from the tablet, got T500XXS8CXG1 in the build version

power off -> Vol Down+vol up + plug on the computer -> download mode long press vol up vol up

don’t enable the wifi connection (to be able to mess with the date later), make sure the date is at least 7 days in the past

following https://topjohnwu.github.io/Magisk/install.html#samsung-devices

using odin4 from https://xdaforums.com/t/official-samsung-odin-v4-1-2-1-dc05e3ea-for-linux.4453423/

odin4

using that version of magisk -> app-release.apk

got this version of the firmware (from https://samfw.com/firmware/SM-T500/EUX/T500XXS8CXG1) -> –progress SAMFW.COM_SM-T500_EUX_T500XXS8CXG1_fac.zip

adb -s R9TR3087Z2J push AP_T500XXS8CXG1_T500XXS8CXG1_MQB82507325_REV00_user_low_ship_MULTI_CERT_meta_RKEY_OS12.tar.md5 /sdcard/Download/

adb -s R9TR3087Z2J install app-release.apk

in the device, install, select file, use that file

adb -s R9TR3087Z2J shell ls /sdcard/Download/|grep patched

magisk_patched-28100_tELz5.tar

adb -s R9TR3087Z2J pull /sdcard/Download/magisk_patched-28100_tELz5.tar magisk_patched.tar

power off -> Vol Down+vol up + plug on the computer -> download mode check the OEM value -> OEM LOCK : OFF (U) -> OK check the KG status -> PRENORMAL -> need to wait for 168h

Prenormal: your device is temporarily locked, reaching 168h of uptime should trigger unlock

— https://topjohnwu.github.io/Magisk/install.html#samsung-devices ([2025-04-19 Sat])

boot on the device again -> enable the wifi and automatic date to get the date to today (hence more than 168h after the time the bootloader was unlocked from the point of view of the tablet).

odin4 -b BL_T500XXS8CXG1_T500XXS8CXG1_MQB82507325_REV00_user_low_ship_MULTI_CERT.tar.md5 -a magisk_patched.tar -s CSC_OXM_T500OXM8CXG1_MQB82507325_REV00_user_low_ship_MULTI_CERT.tar.md5

You get into the recovery mode, wipe user data wipe cache

reboot

I get into the “security error only official released binaries are allowed oto be flashed (vbmeta)”

In the download mode, I can see it is back in prenormal state

I put back the stock image with

odin4 -b BL_T500XXS8CXG1_T500XXS8CXG1_MQB82507325_REV00_user_low_ship_MULTI_CERT.tar.md5 -a AP_T500XXS8CXG1_T500XXS8CXG1_MQB82507325_REV00_user_low_ship_MULTI_CERT_meta_RKEY_OS12.tar.md5 -s CSC_OXM_T500OXM8CXG1_MQB82507325_REV00_user_low_ship_MULTI_CERT.tar.md5

following https://wiki.lineageos.org/devices/gta4lwifi/install/#pre-install-instructions, I can see that vbmeta can be flashed separately.

vbmeta.img is part of Android Verified Boot (AVB) — a security feature that ensures the integrity of your device’s boot process. It’s like the bouncer at the club: if something sketchy (like a tampered kernel or system image) tries to get in, vbmeta will shut it down.

— chatgpt ([2025-04-19 Sat])

following lineage os instructions

Get vbmeta from https://download.lineageos.org/devices/gta4lwifi/builds (https://ipfs.konubinix.eu/p/bafkreicsqdvj3kfdqrfzojtabvskuygvnnfspdjhkbe2okhgxylsojuun4?filename=vbmeta.img)

tar --format=ustar -cvf vbmeta.tar vbmeta.img

Do the same stuff to get the time to today and therefore get out of the prenormal state

odin4 -a vbmeta.tar

It asks to do factory reset in a recovery mode ish.

reboot

doing again the magisk steps, making sure to set the date to today again

adb -s R9TR3087Z2J push AP_T500XXS8CXG1_T500XXS8CXG1_MQB82507325_REV00_user_low_ship_MULTI_CERT_meta_RKEY_OS12.tar.md5 /sdcard/Download/a

adb -s R9TR3087Z2J install app-release.apk

in the device, install, select file, use that file

adb -s R9TR3087Z2J shell ls /sdcard/Download/|grep patched

magisk_patched-28100_wapre.tar

adb -s R9TR3087Z2J pull /sdcard/Download/magisk_patched-28100_wapre.tar magisk_patched.tar

odin4 -b BL_T500XXS8CXG1_T500XXS8CXG1_MQB82507325_REV00_user_low_ship_MULTI_CERT.tar.md5 -a magisk_patched.tar -s CSC_OXM_T500OXM8CXG1_MQB82507325_REV00_user_low_ship_MULTI_CERT.tar.md5

factory data reset

reboot

Now, that’s ok

[2026-08-24 Mon] dealing with a spicy pillow

remove the battery

check whether I need a new battery

why

I can work with a tablet running only from an external source of power

note

Most phones and tablets cannot even be started without a battery, because the charger does not have enough power to meet the device’s peak demand.[1]

note

When the charger is fooled into “battery idle” mode, the device draws power from the external supply alone while the battery is not used.[2]

note

A factory cable supplies power to the device entirely bypassing the battery.[3]

note

A Samsung Galaxy J7, which uses a 4-pin battery connector (the author thinks the two middle pins carry data to the battery), stays on only a few seconds when an external supply is wired to the + and − pins, then shows “battery low” and shuts down.[4]

note

It is possible to “cheat” such a device into thinking a battery is connected while it is actually on external power, but this is a non-standard hobbyist method and a safety hazard.[5]

note

A search of Android Enthusiasts for “galaxy tab a7 without battery” returns 0 results, so no source on that site specific to the SM-T500 confirms that it boots or runs with no battery installed.[6]

hacks to run an Android device without a battery

why

After I plugged the tablet in it will not boot, so I am looking for a way to run it without a replacement battery.

note

Phone batteries commonly use a 4-pin connector; a Samsung battery is labeled −, T, + with T a thermistor and the fourth pin a 1-wire bus.[7]

note

On the Galaxy Nexus the fourth battery pin carries the battery’s NFC antenna to the motherboard’s NFC circuitry, so the 4th pin is often an NFC connection rather than power or data.[8]

note

A circuit that simulates a battery “in all respects (including the battery health pin which is usually the third pin on battery)” is technically possible, but the device’s SMBus may reject it as a non-genuine source.[9]

note

A published hack feeds a device through the battery pins from an external supply and shorts one pin (the third, per a Samsung account) with an 82 kΩ resistor; the primary write-up salvages connector pins from an SD-card adapter.[10][13]

note

A single-account report boots a phone without a battery by drawing a pencil trace on the motherboard from the GND pin to the − pin.[11]

note

Soldering a USB cable directly to the battery ports and using a supply of at least 2 A worked for a Moto G, but the phone then does not boot automatically after a power outage.[12]

note

A commenter reports running a Samsung GT-S5310L from a cell charger with a diode in series and the middle terminal left unconnected.[14]

note

A commenter attempting an LG V909 3D tablet with the same method reports it works while plugged in but switches off from time to time.[15]

note

A Galaxy View tablet owner reports the tablet switches off automatically when the battery is broken even with the AC adaptor connected, and suspects Android shuts down at 0%.[16]

note

A high-rep commenter notes a rooted device can disable charging to stop the battery from draining, pointing to the “Disable USB charging” thread.[17]

note

On a rooted Nexus 4, writing 0 to /sys/class/power_supply/usb/device/charge disables charging; a commenter notes the /sys interface is virtual and does not survive reboots.[18]

note

For a dead or dummy battery, one reporter finds Android will not boot even rooted, because it uses Vbus during boot; the only fixes are bootloader hacking or a charging-circuit modification, and on a Galaxy S3 the 5V bus was required to enable data.[19]

note

A user asks whether a Chinese tablet (“xpad xpod 7”) can be operated without a battery simply by plugging in the power adapter, and one answer claims most Chinese tablets can do that with no negative effect though the tablet might overheat.[20]

note

A method to “fake” a battery being connected by connecting crocodile clips to the battery terminals and supplying 3.7 V electricity is reported, though it requires special equipment, so buying a new battery is advised if possible.[21]

note

A high-rep commenter counters that even with a broken battery most phones work when connected to a charger with enough power, e.g. 5 V 3 A.[22]

note

An experimenter removes the battery from a Huawei Honor 9, connects the charging cable, and finds the boot logo appears but lasts much longer than normal, then services (Google, Huawei, UI) fail to launch and the notification bar shows 2% battery with no app able to launch.[23]

note

Two answers to a Galaxy Tab 10.1 “refuses to power on” question bear on a tablet’s power-on behavior with the battery altered: one (2,270 rep) says some devices can power up with the battery disconnected and only wall power, unsure if this model does, while another (1,094 rep) reports that holding the power button about 4 s then plugging the charger in while still holding powered the tab on — though that tab was 100% charged, so its battery was present.[24]

note

No source in this note confirms the SM-T500 specifically; a search of Android Enthusiasts for “galaxy tab a7 without battery” returns 0 results, and the hacks above are documented on phones, with one commenter’s intermittent attempt on an LG tablet, one tablet owner reporting a broken-battery tablet that shuts off even on AC, and one 1-rep tablet owner plus a 1-rep answer claiming a Chinese tablet can run without a battery (both accounts 1 rep).[5][6][15][16][20]

note

A broader “galaxy tab without battery” search (16 results) is otherwise off-topic, but two Galaxy Tab 10.1 answers describe powering on with the battery disconnected or by holding the power button while plugging the charger — still nothing SM-T500-specific, and both are revival tricks rather than confirming sustained batteryless operation.[24]

note

iFixit’s SM-T500 Answers enumerates 7 questions[25]; of the battery/charging-related ones — 800916 (replacing a swollen battery), 880136 (a charging port “still wont charge” after replacement), and 906270 (a tablet that “Will not boot after replacing charging port”) — each is about replacement or repair, none about running the tablet without a battery or simulating one; two further Android Enthusiasts searches, “SM-T500 battery” and “Galaxy Tab A7 battery connector,” each return 0 results.[25]

note

A rooted software workaround that disables charging does not make a batteryless or dead-battery device boot, because Android uses Vbus during boot; only a bootloader or charging-circuit modification can, per one reporter — so it does not address the user’s “won’t boot” symptom either.[19]

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