PEGATRON LITHIUM ION BACK UP BATTERY MODEL: PB013 FOR: MODEM/GATEWAY DPC3939 DPQ3925 DPQ3212 ONLY* 10.8V---2600mAh For CISCO and Motorola Modems UPTO 8 HOUR BACKUP BATTERY FOR CABLE MODEM FOR DPC3939 DPQ3925 DPQ3212 MODELS ONLY Battery requires 12-17 Hours Prior to use. Backup Battery only supports the Phone service in case of electrical outage. Battery Port on your Modem needs to be active by the activated on your modem by your service provider. MAKE SURE YOU PLUG THE MODEM DIRECTLY INTO ELECTRICAL SOCKET AS THE BATTERY MAY NOT CHARGE IF PLUGGED INTO APS OR POWER SURGE PROTECTORS OR SO ON.