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Scotty V3 24/48V DC-DC Converter

  • Type: Bidirectional or unidirectional DC-DC converter (Scotty V3)
  • Use: Step-up/step-down between 24V and 48V systems

Installed

  • Quantity: 2 units installed
  • Role: Bridge between 24V GEL bank and 48V Meteor bank

Configuration Notes

  • Document input/output voltage configuration and current limits.
  • Note enable/ignition wiring, protections, and thermal derating.
  • Record any CAN/serial settings and firmware versions.

Context: Bridge a 48V LiFePO4 bank (Safiery Meteor, 1S16P) to a 24V GEL bank (Victron 12-165, 2S2P).

  • Mode
  • Direction: 48V → 24V (buck) enabled
  • Reverse (24V → 48V): disabled (avoid charging LFP from GEL)

  • Parallel units: 2 identical units sharing load (set same targets)

  • 24V Output (GEL charging targets at 25°C)

  • Absorption voltage: 28.2–28.8 V
    • 28.2 V for long life (≈14.1 V × 2)
    • 28.8 V for cyclic use (≈14.4 V × 2)
  • Float voltage: 27.6 V (≈13.8 V × 2)
  • Absorption end: tail current ≈ 4% of C or time cap 2 h
    • Tail current basis: 330 Ah bank → 0.04 × 330 ≈ 13 A
    • If tail-current not supported, use time cap only

  • Temperature compensation (if supported): −48 mV/°C from 25°C

    • (−24 mV/°C per 12 V block × 2 in series)

  • Current Limits

  • 24V charge current (total for both Scottys): ≤ 66 A (≈0.2 C of 330 Ah GEL bank)
  • Per-unit limit: ≤ 33 A each (or below unit’s continuous rating and wiring/fuse limits)

  • Suggested initial setting: 25–30 A per unit for cooler operation

  • 48V Input (LFP source safeguards)

  • Start charge threshold: ≥ 52.5 V
  • Stop/hysteresis: ≤ 51.5 V (resume when above start threshold)
  • Low-voltage hard stop: 50.0 V
  • High-voltage limit: 58.4 V max (16S LiFePO4 full)

  • Note: With 2 units @ 30 A each on 24V side, input current ≈ 30 A × 24 V × 2 / (48 V × η) ≈ 30 A at 48 V (η≈0.95)

  • Protections & Control

  • Enable/Ignition: wire to enable only when system is on and cooling available
  • Thermal: ensure airflow; derate current above 40°C as per manual
  • Fault actions: latch-off on OVP/UVP/OTP; require manual reset

Rationale: Voltages reflect Victron GEL datasheet targets and common LFP limits; current limited to ≈0.2 C for GEL longevity. Adjust per temperature and duty cycle.

Manuals

Wiring

Maintenance

  • Inspect connectors, fusing, and ventilation path.
  • Verify mounting hardware torque and check for thermal events.