Rechargeable Lithium-Ion Batteries¶

Procedures for charging and querying the Teledyne Webb Research (TWR) rechargeable lithium-ion smart battery packs used in Slocum G3 gliders.

Hardware Overview¶

The rechargeable packs are smart batteries: each communicates over a set of channels, addressed as $R,0 through $R,3.

Charging Equipment¶

Charging Procedure — Batteries Installed in a G3 Glider¶

1. Remove the aft tail cowling.
2. Remove the LPIL-5 dummy plug from the charging port and set it aside.
3. Connect the battery charger (P/N 305839) to the charging port using the LPIL-5.
4. Plug the charger into a 110 V AC outlet.
5. Turn the charger on with the rocker switch above the AC power cord.

The batteries will begin charging.

Charging Procedure — Batteries Removed from the Glider¶

1. Remove the batteries from the glider. For pitch and energy-bay batteries, disconnect the pitch battery cable from the battery and leave the cable in the glider.
2. Connect the charging adapter to the battery. The adapter can charge one aft battery and two pitch batteries simultaneously — the connections are keyed.
3. Confirm the battery charger is off.
4. Connect the battery charger to the charging adapter.
5. Plug the charger into a 110 V AC outlet.
6. Turn the charger on with the rocker switch above the AC power cord.

Charge-current behavior is the same as the installed procedure above (~1 A rising to 12 A / 17 A, settling near 0.5 A when complete).

Querying the Batteries — Installed, via SFMC¶

1. Power on the glider and connect to it via Freewave on a mobile dockserver running SFMC.
2. Put the glider into Shell.
3. From GliderShell, type talk battery and press enter.
4. In SFMC, switch to the serial perspective terminal (different from the normal SFMC communication path):
   • Click the Configuration tab → System Status.
   • Under Dock Server Ports, find the green square for the USB port the glider is on, then click the terminal (>_) icon next to it to open the serial perspective.
5. Query the packs with the commands below, pressing enter after each.

Querying the Batteries — Direct Connection¶

1. Remove the batteries from the glider.
2. Connect the charging adapter (305879) to your computer via USB.
3. Open a terminal emulator such as TeraTerm or Procomm.

4. Connect to the USB serial port with these settings:

   Setting	Value
   Baud rate	115200
   Data	8 bit
   Parity	none
   Stop	1 bit
   Flow control	none

5. Query the packs with $R,0 … $R,3 (case-sensitive), as in the SFMC method. The channel a pitch/extended pack answers on (2 or 3) depends on the cable it is connected to.

Reading the Query Output¶

A single cell of a pack returns a block like this:

Batt #: 0
Status: 0xcc50
LTCO: 0x202
Voltage: 14551 mV
Current: 756 mA
Temperature: 298.101562 K
Serial: 1533
Remaining Capacity: 3685 mAh
Full Charge Capacity: 9876 mAh
Time to full charge: 508 min
Cycle Count: 4
Thermistor (raw): 32512
Thermistor (V): 2.480528
Manufacturer Name: INSPIREDE
Device Name: NL2054HD34
Device Chemistry: LION

Decoding the Status word¶

Status is a 16-bit value reported in hexadecimal. To interpret it, convert the four hex digits after 0x to 16 binary bits (e.g. with the Windows Calculator in Programmer mode, or an online hex-to-binary converter).

Example: 0xcc50 → 1100 1100 0101 0000. Reading the bits left to right as positions 1–16, the bits that are on are 4, 6, 10, 11, 14, 15.

Battery Life, Warranty & Shelf Life¶

Field Notes: Capacity, Discharge & Checkout¶

Discharge behaviour¶

• Recommended config is roughly f_coulomb_battery_capacity 215 Ah (standard) / 300 Ah (extended), with an undervolts abort around 12–12.8 V.
• Unlike lithium primary packs, the rechargeables have little or no real "shelf." Voltage falls fairly linearly toward ~12.2 V, then drops steeply, with the electronics shutting off near 10 V. Set undervolts conservatively and don't count on a shelf to fly home.

• Discharge rate matters. Usable capacity depends heavily on how hard you pull the pack — bench-testing an extended pack to a 12 V cutoff at a continuous 6.7 A (≈1000 m pumping draw) yielded ~309 Ah, versus ~285 Ah when the same pack hit the 12 V undervolts on a real mission; dropping to 2 A and a 10 V cutoff squeezed out ~326 Ah. Test at realistic mission rates, ideally after a mission to find the true endpoint.
• Real-world reference: three consecutive 30-day missions (recharged overnight between) each drew ~140 Ah, starting near 16.2 V and ending 14.0–14.4 V.

Pre-deployment checkout¶

• Always verify communication with every pack as part of checkout — query via talk battery (see above) and confirm all cells respond.
• The aft pack's aft connector latch tends to come loose or break during assembly — a frequent cause of a pack that won't talk or that drops voltage early.
• The energy-bay and pitch battery wiring harnesses look identical but are not — a swapped harness has caused garbled/absent pack output and unexplained capacity loss. Confirm the right harness on the right pack.
• As with primary packs, re-check the compass (four-point check) after installing batteries.

G2 vs. G3 wiring¶

• On a G3, rechargeable packs connect to the lithium circuit — the glider powers on as soon as the battery is connected.
• On a G2, rechargeables typically connect to the alkaline circuit instead. The Li-ion pitch pack also sits further forward of the ACME nut, so the pitch-motor calibration may need adjusting.

See Lithium safety on vessels for charging, fire, and transport precautions that apply to these packs.