HTC Legend battery indicator underreads

Thu, 2011-12-22 17:55 by admin · Forum/category:


I am talking about the problem where the HTC Legend does not, or does only after special measures, charge up to 100%, then too rapidly discharges down to some 3%, then continues to run for hours through these last three percent until the battery runs empty.

In fact, the phone and its charging behavior is mostly or wholly normal, but the displayed battery charge level is wrong and usually too low. You also get low-battery warnings long before the accumulator actually shuts off. This may be caused by an underreading voltage sensor.

Apparently the amount of underreading differs from phone to phone, but read on—we will solve this problem.

There are two solutions.

  1. If the phone is still under warranty, send it in and have it repaired or replaced. Insist that this is not a battery problem and that your battery is just fine, otherwise they may keep telling you to buy a new battery.
  2. If the phone is out of warranty, install Battery Monitor and switch it to voltage-based operation.

I have tested a few promising battery monitor programs and found only Battery Monitor by Simmo useful for this particular purpose. Be careful, there are a few programs with similar names.

The latest version requires Android 4, and the author has renamed himself to Sim2k. The older version 9.4 appears to work on Android 2.2 and up. It is still available from:

The easiest way to install it is:

  1. Make sure you have Menu, Applications, Unknown sources checked.
  2. Open this web page on your phone.
  3. Tap the above Dropbox link.
  4. Install Battery Monitor 9.4.
  5. You can now uncheck Menu, Applications, Unknown sources again, if you want to stay on the very safe side. Or leave it checked and just be careful what you install.

Thanks, Simmo, aka Sim2k, for providing this very useful program! Thanks also to jon_kennedy, who kicked in with the information on version 9.4.

Voltage measurement

  1. Power down your phone and connect it to the charger.
  2. After at least 6 hours start your phone. Leave the charger connected.
  3. Pull down the notification bar and check the Battery Monitor notification. Make a note of the voltage. This is your high voltage.

If your high voltage is around 4.1 V, the phone will likely be almost perfectly usable. If it is around 4.0 V, you will lose some battery capacity, because the phone will not fully discharge the battery. It will instead perform an emergency shutdown too early, before the battery is nearly empty. But you will not lose all that much, as the voltage only goes further down when the battery is already mostly empty.

If your high voltage is around 3.9 V, it may be better to discard the phone and get another one, because too much of the battery capacity will remain unused. The phone may only use 60% of the total battery capacity. At 3.8 V it may only use less than half, rendering the phone impracticable to use.

Tap the notification to open Battery Monitor.


  1. Make sure "Disable Notification" is not selected.
  2. Set the text color to your liking. Example: White + Orange / Red at 30%
  3. Tap the "Main Menu" button at the bottom. You may have to scroll down a bit.


  1. Select "Voltage Based".
  2. Set the Max voltage to the voltage you have measured with Android System Info.
  3. Set the Min voltage to 3450 mV. You can later adjust this voltage as described below.
  4. Disable "Display Both Levels", as the system level percentage is useless.
  5. Set "Other Options" to your liking. I do not yet know whether they pertain to the widget or to the icon or to both.

You can later fine-tune these voltages to make sure the percentages are most useful.

You should measure the minimal voltage by letting your battery run down until the phone shuts off on its own. For convenience you can do this on a day when your battery is near-empty anyway.

Then connect the charger, charge one minute, disconnect the charger, start the phone, and check the voltage again. This is your more precise Min voltage. Reconnect the charger and set this voltage in Battery Monitor as the Min voltage.

You can also adjust the Min voltage such that you see the percentage run down to 01% a short time before the phone shuts down on its own.

If the phone shuts down while you still see a higher percentage value than 01%, raise the min voltage a bit. If you see 01% for too long, lower it a bit.

Other settings

I do not recommend to put the widget on one of the desktop screens. I think the widget is useless and the icon in the notification bar is all that is needed.

If you use a ROM like CyanogenMod that allows you to display a percentage figure in the notification bar in the place of the battery icon, disable that (wrong) number as well, as it is just as useless and only confusing.

That's it. Your Legend is as good as new. (:-)

OK, not quite. You still get some battery-low warnings too early, and the orange low-battery light will be on after that. Just ignore them and trust the new indicator instead.

Also repeat the above procedures after a while. Your voltage sensor may have deteriorated again.

Unfortunately there will be a few cases in which the sensor is too far off or there is a more severe defect. So test your phone thoroughly to see whether it is indeed well usable. If not—sorry, bad luck.

One final hint: Charging the battery higher than 4.1 V (true voltage, not the voltage displayed by Battery Monitor), i.e. higher than approx. 90%, strains and thus ages it somewhat. Unless you really need a full charge, you may as well disconnect the charger around 85% to 90% (according to Battery Monitor), if you happen to spot that condition. Your battery will live a little bit longer that way. Just don't get neurotic about this. A new battery is not that expensive either.