Seidio Innocell 3500 mAh extended life battery for HTC Evo 4G review.

The stock battery on the HTC EVO 4G leaves much to be desired, and many of us with an EVO 4G can't go a whole day on one charge.  The Seidio Innocell 3500mAh extended life battery just might be the solution.  Checking in at a massive 3500mAh (more than double the capacity of the stock battery), this extended life battery by Seidio met and exceeded my expectations right from the get-go, which is good, as it's priced at $64.95.

You'll never read a review about the HTC EVO 4G that doesn't mention its battery life.  It's a lot of phone, and it needs a lot of power.  I've been using this battery exclusively since I got it last week, and to say I'm impressed with its performance is an understatement.  Right from day one, I couldn't believe how well it was holding up.  I really want to break it down for you, so join me after the break for some pictures, additional thoughts, and most importantly -- benchmark results.

I live in Maine, and our winters are anything but pleasant.  It gets dark around 4 p.m., deer and moose litter the roadways, and driving on icy highways in a blinding snowstorm is second nature.  For these reasons alone, I like to make sure there's plenty of juice left in my EVO's battery.  A cellphone is invaluable in an emergency, so I always like to make sure I'm covered in that regard.

Seidio Innocell 3500 mAh extended life battery for HTC Evo 4G review - battery door thickness comparison. Seidio Innocell 3500 mAh extended life battery for HTC Evo 4G review - battery thickness comparison.

I've hacked my EVO to run CyanogenMod 6.1, keep GPS on, and my screen is set at maximum brightness.  I don't live in a 4G market, and I don't do anything special to try to conserve battery -- I let Android be Android.  I also like to use my EVO 4G.  A normal day for me consists of heavy text messaging, 40 to 50 e-mails coming in on three Gmail accounts, 3G web browsing, a bit of Angry Birds, and some Wi-Fi around the house.  Toss in some widgets, Facebook, Twitter and the like, and I probably use my EVO just like you use yours.

My daily usage always varies slightly, a typical day for me ends with ~40% battery remaining on the stock battery.  However, after a full day with the Seidio Innocell 3500mAh battery, I was pleasantly surprised to come home with 79% still in the tank.  Even on days that involved a solid hour of Angry Birds (at max screen brightness) on top of my regular daily use, I've never seen this battery fall below 50%.  It holds up insanely well to a hard day's work.


Battery life is (almost) everything when it comes to your phone.  Your phone is useless with a dead battery, so it's important to know what you can expect out of its battery.  For the purposes of this review, I setup a little benchmark.  I put both batteries through the same exact stress test, and the results are impressive -- exactly what you'd expect from an extended battery boasting more than double the capacity of its stock counterpart.

Seidio Innocell 3500 mAh extended life battery for HTC Evo 4G review - added funky geometry.  Makes the Evo look kind of awkward. Seidio Innocell 3500 mAh extended life battery for HTC Evo 4G review - kick stand feels more stable.

Battery benchmark settings:  Bluetooth on. Twitter syncs every five minutes.  Facebook syncs every 30 minutes.  Snowstorm every one minute.  Screen on maximum brightness.  System Panel running in background to log battery and CPU.  Wifi on and connected.  GPS enabled but not on. Three Gmail accounts with mail and contacts syncing.  SMS2PC pushing all text messages to my PC via Wi-Fi.  Angry Birds running on the screen.

For this test, I let my EVO sit on my desk with Angry Birds on up the screen, and that's it.  I just let it sit there and drain.  I also want to note that each battery was pulled off the charger right as it reached 100 percent, ensuring a genuine 100 percent charge.  

Stock battery:

  • Off the charger at 12:29 P.M.
  • 15 percent low battery alert at 3:01 P.M.
  • Shut off at 3:33 P.M.
  • Battery lasted 3 hours, 4 minutes.

Seidio Innocell 3500 mAh Extended Life Battery:

  • Off the charger at 10:37 P.M. 
  • 15% low battery alert at 4:08 A.M.
  • Shut off at 4:52 A.M.
  • Battery lasted 6 hours, 15 minutes.

I just want to insert a quick note here that says even though three hours, or six hours isn't that long, this is under 100 percent CPU load, with LOTS of Twitter/Facebook/Email syncing going on, text messages coming in, and screen at maximum brightness.  I wanted to stress these batteries to the max in order to drain them as quickly as possible.  I don't reckon your daily usage habits will be as taxing on the battery as this stress test.  If it is, well ... wow.

Seidio Innocell 3500mAh Extended Life Battery Benchark.

What are you looking at here?  This is a screen grab of System Panel -- an app that will monitor your device's battery charge in relation to device/CPU usage.  The top chart is the battery charge, middle row (blue) is device usage, and the bottom graph is CPU usage.  The graph tells the whole story.  As you can tell from my notations, on the left we have the Seidio Innocell 3500mAh battery.  You can see its gradual discharge over time, while CPU and device usage stay maxed out.  Once it died, I plugged it back in, and went to sleep.  You can see it charging up until I pulled it off the charger for about ten minutes -- only to briefly plug it back in to give it a full 100% charge before disconnecting it for its turn in the gauntlet.


  • Huge gains in battery life.  In my testing, the Seidio Innocell 3500mAh Extended Life Battery lasted over twice as long as the stock battery.
  • Allows for robust EVO usage.  Don't have to carefully watch your radios, screen brightness, running services, or app/widget synchronization.
  • The added thickness makes the kickstand more sturdy.
  • Don't have to bring your charger with you if you're going somewhere over night.
  • Thick battery props the EVO up nice and high -- don't have to worry about scratching the camera lens when it's on your desk.

Seidio Innocell 3500 mAh extended life battery for HTC Evo 4G review - G1 on the left.  Evo with Seidio battery on the right. Seidio Innocell 3500 mAh extended life battery for HTC Evo 4G review - G1 on the left.  Evo with stock battery on the right.


  • Nobody likes added thickness, but it's not that bad.  When the EVO is equipped with this Seidio battery, it's just a tad thicker than a G1.
  • I don't really like the funky geometry the battery adds.  Adds a lot of odd looking angles and edges to the back.  Though it does provide a little more to hold onto.
  • Not a big deal, but I was rather partial to the metallic red ring around the camera, and the 'htc' logo that was embedded into the battery door.  Both are gone with the Seidio battery door.
  • The battery door comes off REALLY HARD.  I like that it's nice and secure, but man, is it hard to get this thing off.  Every time I pull it off, I feel like I'm just a few angel hairs away from snapping it in half.  Don't cut your fingernails too short -- you'll need them for as much leverage as possible.

Other thoughts:

I love this battery.  I've been an EVO owner since it launched, and now that I have a substantial amount of battery power, I find myself using more and more features that I never cared much about before.  More syncing, longer screen timeout, more gaming, more mobile hotspot, more everything.  Whatever you get for usage now from the stock battery -- expect this monster to double it, and then some.  It really is that good.

It's worth mentioning that despite the added thickness this battery provides, your EVO will still fit in this Mobi Products charging cradle.

If you're an EVO owner -- or shopping for somebody who is -- you absolutely cannot go wrong with the Seidio Innocell 3500mAh extended battery.  It adds a bit of thickness, and funky geometry to the otherwise beautiful EVO, but it's worth it.  Very, very worth it.  It's available for $64.95 in the Android Central Store.

Seidio Innocell 3500 mAh extended life battery for HTC Evo 4G review - double the capacity = double the thickness. Seidio Innocell 3500 mAh extended life battery for HTC Evo 4G review - not quite as pretty.