Cable current rating advice

steve14:

Yes you are correct this is a charging circuit. Not fully understanding your post, are you saying all charging wiring needs to be twin sheathed. From the van we have the dealer has used single core cabling for teh charging circuit, this was also the same on the past three vans we have owned all from different dealers.


Also our battery in the leisure area is under he passenger seat and already has protection device fitted in this area. For the vehicle battery this is under the passenger foot well and has fuses directly attached to the batter. Are you saying you cannot have any protection (fuses or circuit breakers) under the passenger seat. This van does not really have a battery compartment for leisure battery as it is open space under the seat as all van builds are.


 

Not twin-core sheathed - as you'd have to removed the sheath before you got to the battery terminals and what you're trying to achieve is something akin to double/reinforced insulation between the two poles or anything they're connected to either of them (e.g. the chassis). When I re-did our caravan I just used a couple of lengths of heat-shrink sleeving individually over the single core battery cables - although it seems that just wrapping with tape is also considered sufficient.


As I see it, automotive fuses are at best semi-enclosed - at at their moment of operation will generate temperatures that will melt metal and likely produce an arc as well. Really not the best thing to have next to a rather temperature sensitive battery that can under certain conditions evolve flammable and potentiall explosive hydrogen gas (at least in the case of the various forms of lead-acid battery). The risks might well be tolerable in an engine compartment where you'd typically have good ventilation and a steel bulkhead between the battery and passenger compartments but perhaps the same approach isn't quite so comfortable inside a passenger compartment - especially one often used for sleeping.


I know what you mean about there often not being an obvious battery compartment especially in older vans (newer ones tend to have a battery box accessible from outside) - although (at least with lead-acid) batteries there's usually at least a plastic container with a loose fitting lid - to contain any escaped electrolyte - personally I'd like to see the battery fuse at least comfortably outside of that - but it's probably a bit of engineering judgement based on how close and how well ventilated.


I'd also beleive that that caravan industry doesn't seem very good at adhering to its own standards - our (second hand) van came with an apparently professionally fitted motor mover - where the installer seemed to think it adquate not only to use cables at least one size smaller than the manufacturer recommended (and the insulation was showing signs of discolouration and cracking by the time we got it) but to leave the entire system completely unfused - so nothing but a relay between a 100Ah leisure battery and thinwall singles tie-wrapped to the underside of the chassis (alongside the gas pipework of course),


As I understand it, (BS) EN 1648 (Leisure accommodation vehicles. 12 V direct current extra low voltage electrical installations) is the standard that should be followed (part 1 for caravans or part 2 for motor caravans) and BS 7671 section A721 seems to be lightly edited copy of the same. It's the BS 7671 version I'm most familiar with and it is possible that some details are different BS EN 1648. A lot of it does seem to have been written with lead-acid battery technology in mind, so it might be that some of the precautions aren't necessary with other battery chemistries - but others here will have a better idea of that than me.


    - Andy.

steve14:

This is a new van. Fiat ducato. The engine battery is under the passenger foot well same as most vans and the fuses are attached to the battery. 

the leisure battery is not in a seal box but under the passenger seat. It is a lead acid battery but a sealed one. No chance electrolyte spillage. They are designed to be installed like this. I will be changing this to lithium soon again sealed battery. 

The starter battery would be part of the basic vehicle so won't come under BS EN 1648 but under some automotive standard - which likely allows fuses next to the battery (and I might suspect is nominally outside of the passenger compartment and possibly ventilated to the outside, even if it's accessible from the passenger area). The leisure battery would come under BS EN 1648 - and I suspect even "sealed" lead acid types are usually valve regulated - i.e. can still emit hydrogen etc. under some fault conditions - so if in a passenger area it seems sensible to me to keep fuses etc a little away from the battery.


   - Andy.