95Ah Oil Filled Battery Unit
The BEBS comprises a stainless steel enclosure that is mounted on the outside of the diving bell (or welding habitat). The enclosure contains an array of four 12V 55Ah lead-acid rechargeable batteries which are connected together to make a 110Ah nominal (95 Ah actual) 24V system.
The enclosure has two separate compartments and the batteries are housed in the lower, larger section. The battery compartment is oil-filled and the oil completely surrounds the batteries – including the areas inside the battery cases above the electrode plates. The type of oil used is conventional mineral hydraulic oil.
The upper, smaller compartment houses the diagnostic and power management circuit board for the system, and this is also oil-filled with the same type of hydraulic oil. The two compartments are, however, hydraulically isolated from each other (i.e. the oil in each is separate, allowing one compartment to be drained while the other is unaffected).
Both compartments have transparent plastic windows on the front face allowing a clear view of the inner components. This is useful: for the battery compartment, to monitor oil-level and the battery's physical condition; and for the diagnostic compartment, the diagnostic PCB LED displays and indicators can be clearly viewed.
When the bell is submerged during diving operations, the oil inside the two compartments is automatically pressurised to approximately the same pressure as the surrounding seawater – which allows the system to use a relatively thin-wall enclosure as the enclosure does not need to resist the external hydrostatic pressure.
This system is also suitable for use as a power supply for the Diver's Heated Suits.