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.


Reader comments

Accessory review: Seidio Innocell 3500mAh Extended Life Battery for HTC Evo 4G


There is one for the g2 as well. Where i would love to have this, it just takes away from my beautifully made phone. I feel like i would buy this, but only use for times where i am going to be out and a bout for a day into the next. Not for a daily driver.

The Stock Evo battery lasts sooo much longer than my Pre did. The thing that ruins it for me is that the stock HTC rubber bump case would need to be modified to work.

I got the 2 pack of 3000mAh batteries off ebay, and i'm very pleased with both the case and the battery. No funky geometry. Twice the normal battery level. Paid $23 shipped for 2 batteries, 2 cases, and a wall charger.

I have had this battery for a few months, and I agree with everything you said. The biggest complaint about this battery is the added bulk/thickness, which I agree kinda sucks, but it is not as bad in-person as it is in most photos you will see online.

I also didn't like the fact that there was no marking(s) on the back cover after adding this battery, so I added a small black decal and I think it looks pretty sweet.

My phone is an absolute beast, I love the power, my battery cannot be killed, I love this battery.

I've been using this extended battery for almost 5 months now and I absolutely love it. I agree that the phone is a bit thicker and heavier, but honestly I haven't noticed. It fits in my hand nicely and, as the review stated, it provides peace of mind to know that you can go hog-wild on your phone and not have to worry about losing battery power when you need to make an important phone call. I bought my smart phone to use as a smart phone, not turn down the brightness, restrict gps/bluetooth, and only turn on wifi only when I was absolutely sure I need it.

The only odd thing I noticed is that the battery quickly drops from 100% to 90% in a manner of minutes and then is very slow to drain after that. I assume this is due to the phone not tracking the battery's capacity well or something, but this isn't an issue after that first drop off.

I highly recommend getting this - really opens up a world of possibilities and allows you to use your phone as you wish.

It seems to me like they could have done a MUCH better job tapering the extended-battery door rather than leaving it looking like, well...whatever it is.
Battery life = total win.
Battery door = total ugly.
Surely they could have blended style and functionality better here.

This battery gets two thumbs up from me. I got it and the ruggedized extended case and am a happy camper. I don't play Angry birds, but my phone lasts all day with heavy use and lower than half screen brightness until I hit the pillow around 12:30am from 6am daily. Couldn't be happier. This battery totally ROCKS!!!!

Can't say I love the thickness (btw, I had no idea the G1 was that thick), but a positive side effect to it may be the ability to ditch my case. I use the case soley to protect the camera (and my AUX cable is too thick to fit through the hole to connect it to my car radio, so it comes off a lot anyway). With the added bulk, the camera lens is no longer sticking out so far.

I understand the price, and from what I've seen on other batteries, it doesn't seem to expensive, but its $70 I don't need to spend. Since I turn off auto-syncing and background sync when I'm at work, my battery lasts the whole day. Granted, I could avoid turning this off, but its not inconvienence. Just a tap of a widget, and I don't need to know I got an email when I working anyway. When I have free time, I force it to sync, and read everything then.

I have the Extended battery as well and can echo this review in its entirety. Great writeup.

One question though. How did you know the extended battery was exactly at 100%? My battery meter still thinks I'm on a stock battery when I charge and I rely on SystemPanel to judge, more or less, twice the charge time to know the battery is full. I really would love my battery meter to recognize the extended battery and reflect that.

Also, ever notice the mAh of the battery itself in SystemPanel? I've seen it read over 4000.

From my Evo. :)

I bought 2 3500mAh batteries for $16 from Ebay. They come with a nice battery door and a charger. They perform like the Seidio one but a lot cheaper. I can go for 33 hours of normal use (calls, texting, games, live wallpapers, etc). Go to Ebay and get those batteries instead. You'll be hapier.

Another con for me in addition to how ugly it makes the back look is the fact that you're not going to be able to use a case with your Evo if you've got this battery. I love my Otterbox, plus I wouldn't want to be carrying my Evo around naked. I get a day out of a charge anyway since I'm not a heavy user. A few texts, a few e-mails, some web surfing, gaming and videos and I'm at 10% by midnight when I hit the sack.

>"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."

It is called a "car charger" :)

Plus, I bought 2 new spare Evo standard batteries and an external charger from Ebay or Amazon or something for $30. Nice to have spares, although I almost never need them. Me happy.

One question... can you still use the desktop docking station with the built-in HDMI connector with the extended battery? Does the EVO fit into the slot??

Why are you people so defensive about your spare batteries, car chargers etc.?? Some people have enough things to worry about!!! If you think for a minute that I would rather walk around with an extra battery in my pocket for my phone than just have a battery twice the size in my phone all the time you are wrong.... to me that is just silly.

So when your battery dies, you have to pop the back cover off, turn your phone off, swap the batteries, put the cover back on, reboot, all just because you don't want a thicker battery cover? And what if you forget to charge your second battery one day? Can I live without my phone when the battery dies? Sure. Do I have to? No.

Get the sprint 2600 mah battery. Doesn't stick out as much and the lines are cleaner. Still gets twice the battery life. Oh and its cheaper and at the sprint store.

I'm suprised this took so long to be officially reviewed. As a long term user, I can't stress how important this battery is to my overall enjoyment.

There's nothing like using the Evo how it was designed to be used. Now I have to worry about the government tracking my every move bc I never turn GPS off.

I hope you never have a problem with the battery and need Seidio's help to make it right. They are TERRIBLE at customer service! Once they have your money they do not care about anything else. Sure they talk a good game, but when it matters that's all it

You couldn't GIVE me a Seidio product.

as much as I want this battery, the covers kills it for me! the battery should be a combination of a battery and a case! something that adds thickness to the phone but doesnt give that odd ugly shape in the back!

I got the 3500 battery for myself at Christmas. I've had marginally better performance, and curious if a battery charger would work better than the stock phone charger. Seidio also sells a protective case & holster combo that protects the phone well, even from my 4 year old twins!

Is anyone else having problems with the charger connecting to the device? I have two chargers, the first one only seems to charge at a certain angle. And my second one is starting to be stubborn about where i place it to charge?

Bulk vs Battery LIfe is always a trade off, something we have to live with. The problem I face is it takes so long for accessories to come out from Seidio that by the time they arrive you have already bought other versions.

The battery should be just fine for the ThunderBolt, but now we need a new battery door (or maybe not) and of course new cases so it will be 2 months or more until they get stuff ready. I just wish mfg's would work more closely with 3rd party companies to get accessories ready.

Like everyone, I've had this battery for at least 5 months and it's very well worth the $19.95 (for two batteries) that I spent on Ebay. You just have to wait a little longer since they come from Hong Kong - no big deal. Unfortunately, your case and dedicated HTC Evo Car Kit will no longer fit with this new battery. Have fun!

I bought the non-Seido extended battery off Amazon for $25 or so as well as the Seido rugged case/holster combo for use with extended battery. This is a really, REALLY great combo for the Evo.

Is it a little more bulk? Sure. But not only have I gotten used to it I actually love it now. It really lets me get a solid grip on the phone and make it a lot easier to use.

Install an Superior Battery Charging (SBC) kernel and you'll find that your extended battery finally gets a full charge. You should see another 20-30% higher battery life using a SBC kernel. I've been using SBC since it came out to make my Seidio battery have a full charge.