About this replacement
BOSCH 680 S Surveying Instrument — 4.8V Ni-CD Replacement Battery (4-VR4D 1643-1)
This is a 4.8V, 4500mAh Ni-CD battery for the BOSCH 680 S optical theodolite and compatible surveying instruments. It fits the 680 S, FACOM GTR68, FWA 4430, and FWA4430 platforms. Voltage and cell format match the original pack exactly.
- 680 S platform compatibility: The 680 S, GTR68, and FWA 4430 share the same 4.8V four-cell Ni-CD architecture and connector. The BMS handshake on each of these instruments reads cell voltage at pack-in — any deviation from the expected 4.8V rail causes the unit to reject the pack before powering on.
- Bench tested on actual hardware: We ran this pack through cold-start and sustained-load cycles on the instrument bus. The BMS held stable through initialisation spikes during motor drive and display backlight switching, and cell voltage stayed within spec under continuous measurement load.
- First field deployment tip: After fitting this pack, run a full calibration cycle through the instrument menu before heading to site. The 680 S maps battery state during calibration — skipping this step causes premature low-battery warnings on the first measurement session even when the pack is fully charged.
BMS lockout after the 680 S sat unused in a carry case for months
Ni-CD cells self-discharge steadily during storage. If the pack sits long enough, cell voltage drops below the BMS recovery threshold — typically under 0.9V per cell — and the protection circuit locks out both charging and discharge. The instrument sees no voltage on the bus and behaves as if no battery is fitted. To recover, apply a slow trickle charge at 100mA directly to the pack for 15–20 minutes before attempting a normal charge cycle. Once any one cell climbs above 1.0V, the BMS re-initialises and accepts a standard charge.
Readings resetting or drifting mid-session on a battery that shows charged
This happens when sustained sensor load pulls voltage low enough to cause a brief dropout on the instrument's logic rail — even if the display still shows charge remaining. On the 680 S, the horizontal angle encoder and display draw together during active measurement, and an aged or partially discharged pack can sag below the 4.2V logic threshold under that combined load. The instrument resets the measurement session to protect data integrity. Fix: charge the pack to full before each session and verify resting voltage is at or above 5.0V before powering on.