Original post by: spacecow123 ,
Yes error 21 means there is a problem with the battery, in this case the connector is ripped of the logicboard. There is unfortunaly no way to boot without the battery or battery connector. The bootloop you're in is because an iPhone cannot boot from the charger only, and can also not restored without a battery After you resoldered the connector to the logicboard and it is soldered good enough, then your iPhone will normally boot from its battery and then you will be able to restore it. Watch out if your solderpads are still intact! If you need any more help you can always ask.