Editing Oberon-class submarine (section)

===Propulsion systems===
The class used [[diesel-electric]] propulsion, with [[Lead-acid battery|lead-acid batteries]] to provide power when the engines cannot be used. Each vessel has two Admiralty-pattern V-16 [[diesel engine]]s (ASR1 16VMS), each driving one 1280-kW 880-V [[Electric generator|generator]]. These can provide power directly to the two {{convert|3000|bhp|lk=in|adj=on}} [[electric motor]]s, one directly connected to each [[propeller]], or for charging batteries. The diesel engines can only be operated with external ventilation, but this can be obtained either while on the surface or when shallowly submerged by use of two [[Submarine snorkel|snorkels]] which can be raised from the fin. One snorkel brings in new air to the boat, while the other takes exhaust fumes from the engines. The ventilation system is designed so the fresh air spreads through the boat.<ref name=SFMNPA>{{cite web |title=C.F. 'O' Class Submarines - Electrical Systems |url=https://maritime.org/doc/oberon/electrical/index.php#toc |website=San Francisco Maritime Nation Park Association |access-date=10 June 2024}}</ref>

[[File:HMS Otus - Sassnitz - inside 10.jpg|thumb|right|Engine compartment on {{HMS|Otus|S18|6}}, twin V16 diesel engines]]
The generators are cooled by an internal fan on the shaft which circulates air through a filter and water-cooled heat exchanger within the casing. A grill allows pressure equalisation inside and out. The generator has one pedestal bearing fed with oil from the diesel engine lubrication supply and is fitted with an internal heater to prevent condensation when not running.

The submarine has two batteries, each comprising 224 2V cells (type D7420) giving  a nominal 440&nbsp;V output. One battery is located underneath the crew accommodation compartment, and the other under the control compartment. Each battery has a switch circuit in the middle so it can be split into two banks of 112 cells.  The cells are designed to deliver 7420&nbsp;[[Ampere hour|Ah]] at the five hour discharge rate. All steelwork within the battery compartments is lined with rubber to protect the metal from attack by acid, and also all conducting material is insulated to prevent risks of electric shock. Waxed timber is used to make framing and crawlways to access the batteries and support them because of its resistance to acid. The battery compartment has a [[sump]] to collect any spilled liquids.  Each cell weighs {{convert|1,120|lb|abbr=on}} and contains 18.5&nbsp;gallons of electrolyte. Cells are held tightly in place with wooden wedges to prevent movement with the boat. Each cell has four connector bolts to each electrode and an agitator pipe which bubbles air through the cell to ensure the electrolyte remains mixed and uniform. Cooling water is fed through pipes attached to the electrode connectors to  prevent overheating and the battery temperature is monitored.<ref name=SFMNPA />

In operation, each battery is charged until the voltage reaches 560&nbsp;V, then allowed a further hour's charging. Fortnightly, it should be allowed 5 hours' charging after reaching 560&nbsp;V to ensure a maximum charge is reached. Every two months, the battery should be given an equalising charge of eight hours to ensure all cells have reached their maximum.  The battery is designed to operate with a [[specific gravity]] of the electrolyte between 1.080 and 1.280. Initial charging current should be around 1650&nbsp;amps for s.g. below 1.180, 1250&nbsp;A above 1.180, falling to 280&nbsp;A when charging is complete. At a voltage around 538&nbsp;V, the cells begin to give off explosive [[hydrogen]] gas, so the applied power is reduced during charging to keep voltage below this value until current falls to 280&nbsp;A, which is then maintained while voltage is allowed to rise until  the requisite voltage and charge time are reached. In an emergency, the charging current can be raised to 2000&nbsp;A. To maintain overall capacity, batteries need to be completely discharged over a five-hour period once every four months and then completely recharged. The battery compartments are sealed to prevent gases escaping into the submarine, or salt water entering, which inside a battery would cause the release of poisonous [[chlorine]] gas.  Ventilation fans are used to extract hydrogen released by the cells and catalytic converters are placed strategically through the submarine to remove hydrogen from the air by recombining it with oxygen to form water.<ref name=SFMNPA />

[[File:HMS Ocelot 1962 propellor motor control panel.JPG|thumb|right|Propeller motor control panel: The panel telegraph (top and left) showed instructions issued from the motor telegraph position beside the helm station in the control room which were to be carried out.]]
Each of the two propellers on the submarine is connected to a 3000&nbsp;bhp DC electric motor. Each motor is designed with two separate [[Armature (electrical engineering)|armatures]], in effect two motors in the same unit. Speed of the submarine can be varied by connecting the batteries and armatures in different series and parallel combinations. Slowest speed is obtained by connecting both batteries in parallel, thus supplying 440 V, across all four motor armatures in series, thus applying 110&nbsp;V to each ('shafts in series').  Next, the batteries in parallel may be applied across the two motors in parallel, with their armatures in series ('group down'). This applies 220&nbsp;V across each armature. Third, both batteries are applied in parallel across all four armatures applying 440&nbsp;V to each ('group up'). Finally, the batteries can be arranged in series so as to apply 880&nbsp;V across all four armatures in parallel ('batteries in series'). Each armature also has an associated field winding which is separately supplied with current which may be varied resistively, providing further speed control (maximum 35&nbsp;A).<ref name=SFMNPA />

The motors are designed with a sealed oil [[sump]] from which oil is pumped continuously to lubricate the bearings. A fan draws air from the engine room through the motor to cool it and returns the exhaust air to the engine room through a water-cooled heat exchanger. This arrangement reduces the possibility of water being drawn into the motor should there be a leak in the cooler. The motor is also fitted with a heater to keep it warm when not running so as to prevent condensation internally. Temperature and revolution speed are monitored and displayed on the control panel.<ref name=SFMNPA />