Franklin Wireless R850 Compatible Battery 3.8V 2450mAh DP15

Franklin Wireless R850 / T9 / R717 / R871 — 3.8V Li-ion Replacement Battery (DP15)

This is a 3.8V, 2450mAh (9.31Wh) Li-ion replacement battery for the Franklin Wireless R850 mobile hotspot and its related variants. It fits the R850, T9, R717, and R871 using the OEM part number DP15. Capacity figures come from product data, not estimates.

• R850, T9, R717, and R871 compatibility: These four hotspot models share the same 3.8V cell platform, DP15 connector pinout, and BMS handshake protocol — the host device reads cell state-of-charge the same way across all four variants, so one battery services the entire line.
• Bench tested on actual hardware: We ran this battery under combined modem and Wi-Fi load — simulating multiple connected clients — and confirmed the BMS held voltage without triggering a low-voltage cutoff during sustained data sessions.
• Ventilation during extended sessions: Keep the hotspot on a hard, flat surface with airflow around it during long sessions. When signal is weak, the cellular radio pushes to maximum output power continuously, generating heat that accumulates inside a pocket or bag and accelerates cell stress.

Why the R850 drops connected devices mid-session under full client load

The R850 runs two power-hungry subsystems simultaneously: the LTE modem and the Wi-Fi radio. At maximum client count, combined draw can spike sharply enough to pull cell voltage below the BMS protection threshold, triggering a brief cutoff that drops all connected devices. An aged or partially degraded cell has higher internal resistance, so voltage sag under that combined load is steeper and faster than a fresh cell would show. This replacement battery restores lower internal resistance, which keeps voltage stable during those peak-draw moments. If dropouts continue after fitting a new battery, check that the hotspot firmware is current — some firmware versions have aggressive BMS trip settings that an update revises.

Hotspot shows a charge indicator but won't boot after sitting unused

Li-ion cells self-discharge during storage — typically 2–5% per month under normal conditions. If the R850 sat unused for several months, the cell may have dropped below the minimum boot voltage the device requires to initialise its firmware, even if the battery still shows residual charge on the indicator. The BMS may also have entered a locked low-voltage state that prevents normal charging from restarting. Connect the hotspot to a wall charger — not a USB port — and leave it untouched for 30–45 minutes before attempting to power on; a wall charger delivers consistent current that can recover a cell from a BMS-locked state where a low-output USB port cannot. If the device still won't boot, check that cell voltage at the connector reads at least 3.2V before concluding the battery is unrecoverable.