"iPads have a fault that sometimes puts them into a boot loop (dead battery logo, then apple logo, and repeats over and over when on a charger). This is caused by a completely dead battery on an ipad that was not powered off properly. The ipad thinks it is suppose to stay on, but the battery is dead. So when you plug in the charger the ipad immediately tries to turn on but is so dead it shuts back off and repeats.. There are a couple of fixes for this, but this is the easiest one that I have found.
All apple devices have a temperature protection circuit that will turn off the device if the temperature gets either too hot or too cold. If you put the device in the freezer for about 45 minutes and immediately put it on a charger when you take it out it will allow the device to get enough charge to properly boot up.
Note: If you have already tried to restore the device you will need to hook it up to itunes and complete the restore after the device has a decent charge (10% or greater).
"What do you mean by boot loop? What exactly is happening? If it shows the red low battery symbol then goes to the Apple logo and repeats the problem is that the iPad wasn't properly shut down and the new battery has too little charge to start it up so it goes through that loop. A different charger capable of delivering more current may allow you to charge enough to boot then shut down properly. Otherwise you can try plugging in the charger, unplug as soon as the Apple logo appears, and when the home/login screen comes on very very quickly plug the charger back in. iOS should shut the iPad down and allow it to charge. The power/home button reboot thing you mentioned is another way to address this, but realize it takes like a gazillion tries to get it to add 1% to the battery, and if you take a break you're back to square one.
One other solution, the one that I'd use in my shop as I don't want techs sitting around holding buttons all day :) , is to open the iPad again, remove the battery, and charge the battery directly by applying ~4.2VDC directly to the battery + and - terminals using a DC power supply."
"I changed the rear housing on an iPad 2, which requires you to remove the battery and upon completion I powered it on and as soon as it made it to the lock screen I slid to unlock and 2-5 seconds after seeing the home screen it would go blank and the apple screen would come up and repeat (loop) and if I did not unlock it, the same thing would happen within 5 seconds. The battery was not in the red.
My fix was to go back in and disconnect the battery and clean the contacts with alcohol, air dry and reassemble. I don't seal the screen in until all systems are go.
"A new shipped battery should have a 40% charge ideally. In this case the battery had none, boot loops most often occur because of battery issues and incorrect shut down. As the charge is applied Ipad starts to boot, this creates boot current draw that the usb charging circuit cannot provide (normally this comes from the battery!) Triggering temp sensors can allow a boot charge to gather giving the battery enough energy to meet the boot current demand, then be shut down properly then of course charged in the normal way.
However if this happens with a new battery I would strongly suspect the battery, you should never seal a case after changing a battery, until the Ipad has been booted and all functions checked!
I have observed a number of cases where a battery low signal has been shown when plugged in, applying moderate heat to the rear casing has within a minute allowed the ipad to boot and show a good charge level, in all these cases a malfunctioning Li battery pack was identified as the cause and changing them resolved the issue. (these cases typically presented as ""I put it on charge last night and it was stone dead this morning!"".
If plugging in your charge cable triggers any life then it is not your charger, port or charging circuit almost certainly battery. If you have a boot loop apple logo restarts and you do not have jailbreaks installed it is almost certainly battery charge condition < the real question here is why on earth these devices are not setup to shut down automatically at 4% or so charge level to prevent such a scenario!! Maybe Appleinc could chime in and explain it to me, especially when a device absolutely must have minimal input froma battery to boot or it will enter an almost inescapable fault state to the end user!!!
