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DC LV Battery Power Supply for Motorhome

TrigPoint
Hi everyone!


I've been asked to install some wiring in a van conversion and I need a bit of advice. The plan is a 110Ah 12V leisure battery, a SELV system and TT earthing (earth electrode from the body of the van.) 


I'm trying to work out the PSCC and PFC so I can choose the overcurrent and fault protection.


So,


a) Is measuring the impedance of the battery and using Uo Cmax / Zs 2R1 (with the measured battery impedance as Zs) acceptable to calculate PSCC


and,


b) Is Uo/Ze (with measured the battery impedance as Ze) acceptable to calculate PFC?


Many thanks in advance for your answers.


Trig


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  • 0
    With only a single 12 volt battery, I agree that vehicle fuses are the way to go, cheap and readily available.

    For a larger or more complex system that uses 24 volts, or multiple parallel 12 volt batteries, then I am not convinced that vehicle fuses have sufficient breaking capacity and would prefer BS88 fuses.

    But for a simple, single battery system, vehicle fuses should be fine.


    PSSC can be estimated by measuring the voltage drop under heavy load at the battery. A voltage drop of 1% under a 50amp load suggests a 5000 amp short circuit current. This is only an approximation and may subsequently vary if a different type of battery is fitted.


    It is common to "earth" the negative pole of the battery, but this usually means by connection to the vehicle chassis, and a not a true external earth connection.
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  • 0
    With only a single 12 volt battery, I agree that vehicle fuses are the way to go, cheap and readily available.

    For a larger or more complex system that uses 24 volts, or multiple parallel 12 volt batteries, then I am not convinced that vehicle fuses have sufficient breaking capacity and would prefer BS88 fuses.

    But for a simple, single battery system, vehicle fuses should be fine.


    PSSC can be estimated by measuring the voltage drop under heavy load at the battery. A voltage drop of 1% under a 50amp load suggests a 5000 amp short circuit current. This is only an approximation and may subsequently vary if a different type of battery is fitted.


    It is common to "earth" the negative pole of the battery, but this usually means by connection to the vehicle chassis, and a not a true external earth connection.
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