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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
    Yeah I'm a bit confused too.


    On my side the issue is simple, I have a number of items requiring grounding to the van body itself, plus an unlikely but not impossible breakdown in insulation to the van from the 12V circuits. I expect that any problem from the 12V circuits will dissipate through the metal of the van and also any fault current will blow the fuses. But, the batteries themselves seem to require earthing to the metalwork and there's a solar panel which seems also to earth through contact with the roof. The regs for caravans and mobile transportable units say to earth/bond exposed conductive parts via the MET however I don't have a 240V system and therefore no MET. Providing an earth electrode seemed the best answer.


    I also thought RCD's would probably be the best bet for detecting anything going wrong with the batteries and earth faults on the body of the van. It might also serve to protect the electrical SELV system from outside faults. So connecting these batteries to a small DB which had Positive, Negative and Earth might actually facilitate this. However I'm extremely sketchy on whether this will actually work the way I intend, or whether it will introduce problems to the SELV circuits.


    Hence trying to work out the PSCC and PFC.


    Trig
Reply
  • 0
    Yeah I'm a bit confused too.


    On my side the issue is simple, I have a number of items requiring grounding to the van body itself, plus an unlikely but not impossible breakdown in insulation to the van from the 12V circuits. I expect that any problem from the 12V circuits will dissipate through the metal of the van and also any fault current will blow the fuses. But, the batteries themselves seem to require earthing to the metalwork and there's a solar panel which seems also to earth through contact with the roof. The regs for caravans and mobile transportable units say to earth/bond exposed conductive parts via the MET however I don't have a 240V system and therefore no MET. Providing an earth electrode seemed the best answer.


    I also thought RCD's would probably be the best bet for detecting anything going wrong with the batteries and earth faults on the body of the van. It might also serve to protect the electrical SELV system from outside faults. So connecting these batteries to a small DB which had Positive, Negative and Earth might actually facilitate this. However I'm extremely sketchy on whether this will actually work the way I intend, or whether it will introduce problems to the SELV circuits.


    Hence trying to work out the PSCC and PFC.


    Trig
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