Calculator- Selection of starting accumulator batteries

Power of starter [kW] in range from 0 to 20 kW	Battery capacity [Ah]

Selection of cross-section of the cable supplying starter:
due to heating S₁= [mm²],	due to permissible voltage drop cable length l= , S₂=[mm²]
standarised cable: [mm²]

Rated voltage:	Type of accumulator battery:
24 V	Lead-acid with latticed structure plates
12 V	Alkaline cadmium-nickelic

Temperature of electrolyte:

25 °C, batteries placed on board of ships sailing in the tropical zone,

15 °C, batteries fitted on board of ships sailing in unrestricted zone,

5 °C, batteries fitted on board of ships sailing in unrestricted zone or operated in moderate zone and installed in the engine room or compartments to heated by adjacent rooms,

-15 °C, batteries fitted on board of ships sailing in unrestricted zone or operated in moderate zone and installed in non-heated rooms,

-25 °C, batteries fitted on open decks on ships other than sailing only in the tropical zone.

Temperature coefficient a= , assumed:

Battery capacity is rated at start of one combustion enegine for 6 starts-up taking 5 seconds each. In case when one battery is a source for more than one starter, the total capacity should be calculated as a sum of the required capacity of the greatest starter and a half of the required capacity for each of the remaining starters.

Calculations were carried out based on the Polish standard PN-W-89509:1997 Merchant ships, batteries, selection, in accordance with the following equations:

, where

Q_r - required of capacity of the starting battery,

C - capacity related to the starter power (curves are available in the standard),

a - temperature coefficient (curves are available in the standard) taking into account reduction of the capacity due to electrolyte temperature,

0,75 - undercharge coefficient,

, gdzie

S₁ - minimum cross-section of the feeding cable due to heating [mm²]

I_zw - short circuit current in the starter during start-up (curves available in the standard),

j - permissible current density shall not exceed 20 [A/mm²]

, where

S₂ - minimal cross-section of the cable due to voltage drop related to short-circuit current I_zw, [mm²]

l - lenght of the cable, [m],

U_n - rated voltage of starter, [V].