It can be reasonably safe to leave an old phone plugged in all the time if the battery is healthy, the phone has airflow, and you stop it from sitting at 100% by cycling the power with a smart plug. A swollen battery is the one thing you must never ignore: if the back cover bulges, unplug the phone and recycle it.
This guide covers how to check the battery, why 100% all day wears it out, how to set up smart-plug battery cycling, which Android settings keep the app alive, and how to make a phone camera survive months of continuous duty.
Key takeaways
- Check the battery first. A bulging case, a gap at the screen edge or a phone that rocks on a table means stop and recycle it.
- Lithium batteries age faster when held at 100% and warm. Cycling the charge between roughly 20% and 80% slows that.
- AndrIoT supports smart-plug battery cycling to do this automatically.
- Exempt the app from battery saver, or Android will stop it overnight.
- Use a decent charger, give the phone airflow and keep it out of direct sun.
Is it safe to leave a phone plugged in all the time?
Modern phones stop charging when the battery is full, so overcharging in the strict sense does not happen. The real issues are heat and time spent at a high charge. A battery that sits at 100% while warm ages faster and, in a worn battery, can swell. Most people who run an old phone as a camera on a charger for years have no problem, but those who do have a problem tend to find it late.
Treat this as a maintenance task, not a set-and-forget one. A short monthly check and one change (cycling the power) cover nearly all of the risk.
Battery swelling: signs and what to do
A swollen lithium battery is a fire risk. These are the signs.
- The back cover bulges or does not sit flat.
- The screen lifts away from the frame or shows a gap.
- The phone rocks when lying face-up on a table.
- The case feels hot to the touch even when idle.
- There is a chemical smell, or a visible leak or discolouration.
If you see any of these signs, unplug the phone, do not use it, do not puncture it, and take it to a battery or electronics recycling point. Do not put it in household waste.
Check on the first of each month, and after any heatwave. A phone that is in a case should come out of the case for the check.
Why 100% all day is not ideal
Lithium-ion cells are happiest in the middle of their range. Holding them at 100% keeps the cell at maximum voltage, which speeds up wear, and heat from the charger and the processor adds to that. Cycling between about 20% and 80% reduces both stress and time spent at the highest voltage.
Set up smart-plug battery cycling
AndrIoT can switch a smart plug according to the phone battery level, which keeps the phone between a low and a high threshold. You need a smart plug that AndrIoT can control.
- Pick a smart plug that works with your Wi-Fi and a charger that fits it. Any basic plug works as long as it can be switched from software.
- Plug the charger into the smart plug and the phone into the charger. Confirm the plug turns the charger on and off.
- Pair the phone and open its settings in the dashboard at app.andriot.net.
- Turn on smart battery. Set the lower and upper levels, for example 20% and 80%. Start with those and adjust after a week.
- Watch one full cycle. Check that the plug turns off near 80% and on near 20%, and that the phone never drops below the lower level.
- Check the phone does not die on a power cut. The power-outage alarm tells you when the phone stops charging.
Smart battery is a Standard and Pro feature. If you run a phone for months, it is the single most useful setting here.
Android settings for a phone that never sleeps
| Setting | Recommended | Why |
|---|---|---|
| Battery saver or optimization for AndrIoT | Exempt | Stops Android from killing the app |
| Adaptive battery or app standby | Off for AndrIoT if possible | Prevents background throttling |
| Screen timeout | Short, or off when not needed | Saves the display and heat |
| Screen brightness | Low | Less heat and ageing |
| Wi-Fi sleep policy | Keep Wi-Fi on while charging | Keeps the stream alive |
| Automatic updates | Pause large ones | Avoids a restart you did not plan |
| Do not disturb | On | Stops unwanted pop-ups on the screen |
Names vary by phone maker. Search the settings for battery, and look for a list of apps with an option such as Unrestricted or Do not optimize.
Heat, charger and placement
- Use the original charger or a reputable one with a proper cable. Cheap chargers run hotter.
- Give the phone airflow and avoid covering it. Remove a thick case.
- Do not put it in direct sun, behind a window in summer or next to a radiator.
- Place it on a hard, non-flammable surface, not on a bed or sofa.
- Do not leave a hot phone in a closed drawer or box.
If the phone ever feels too hot to hold comfortably, unplug it and let it cool down. A phone that does that regularly should be retired.
When to retire the phone
A phone camera should have an end date. If the battery drains from 80% to 20% in an hour or two on its own, the battery is worn. If the phone restarts by itself, swells, or the charging port is loose, replace it. You can buy a new battery for some models, or move the app to another spare phone and recycle the old one. Take the worn-out phone to an electronics recycling point, and use the setup guide to move the camera to the next spare phone.
Pros and limits
Pros
- Cycling between about 20% and 80% reduces time spent at full charge.
- Power-outage and tamper alarms warn you when the phone stops charging.
- Cheap to do: one smart plug and a few settings.
- Keeps the phone useful for months or years of camera duty.
Limits
- Not risk-free: a swollen battery must be taken out of service.
- Smart battery needs a controllable smart plug and a Standard or Pro plan.
- Old batteries still wear out and need replacing or retiring.
- Setting names differ by phone maker.
FAQ
Is it bad to leave a phone plugged in all the time?
It is not dangerous in itself, but a battery held at 100% and warm wears out faster. Cycling between about 20% and 80% with a smart plug reduces that wear. Always check for swelling.
How do I know if my phone battery is swollen?
Look for a bulging back cover, a screen lifting from the frame, or a phone that rocks on a table. If you see any of these, unplug it and take it to a recycling point.
Can I remove the battery and run the phone on power only?
Only on models designed for it, and many are not. Do not try to run a sealed phone without its battery.
What levels should I set for smart battery?
A common starting point is 20% for the lower level and 80% for the upper level. Watch a full cycle and adjust.
Will the app stay running overnight?
It will if you exempt it from battery saver and keep the phone on a charger. The setup wizard has a step for this.