kelly58 Posted June 11, 2013 Share Posted June 11, 2013 Because the vehicle 12v sockets are only live when the ignition is switched on I am going to fit a 12v socket in the Habitation area direct to the leisure battery with an inline fuse on the live wire. What size fuse would be correct as I am going to use the socket for charging mobile phones / tablet and kindles also maybe a small inverter. Link to comment Share on other sites More sharing options...
sshortcircuit Posted June 11, 2013 Share Posted June 11, 2013 The fuse needs to be less than the current carrying capacity of the cable you are going to use which should be big enough for the load you are going to take. If we assume your load is 5 amps then the cable needs to be able to carry 5 amps, say 12 amps and the fuse would then be 10 amps. Link to comment Share on other sites More sharing options...
lennyhb Posted June 11, 2013 Share Posted June 11, 2013 Rather than wire direct to the battery would it not be better to wire into the vehicles distribution system, that's what I did. On my van there were spare outputs just had to buy the right connector & plug in. Link to comment Share on other sites More sharing options...
Brian Kirby Posted June 11, 2013 Share Posted June 11, 2013 I think you will find it easier, and probably cheaper, to charge all those appliances via an inverter. They will already have 230V chargers that give the correct charging current, whereas to charge them from 12V will probably require you to buy a 12V to whatever voltage converter for each, as their individual charge voltages will be liable to all be different. Your only question then is what size (output amperage) inverter you will need to cope. If you need to charge more than one appliance at a time, you will either need an inverter with more than one socket, or to size the inverter appropriately and use either a multi-socket extension lead, or hard wire in a twin socket outlet. You will need to fuse the 12V feed to the inverter, but you can't size either the fuse or the cable until you have decided what size inverter, and how far from the battery it will be mounted. You will need to be able to isolate the 12V feed to the inverter, because it will otherwise draw current from your battery whether or not you are using it. You may not need a pure sine wave inverter if the chargers you will be using are all switch-mode chargers. You will need to check this. If in doubt though, go for pure sine wave. Sterling Power quote about £50 for a 100W quasi sine wave model, and about £150 for a 200W pure sine wave model. Link to comment Share on other sites More sharing options...
kelly58 Posted June 11, 2013 Author Share Posted June 11, 2013 All the items I would need to charge have their own branded vehicle chargers that is why I am putting in the 12v socket . I have 2 110 amph leisure batteries and a 150w solar panel , so plenty of 12v power its just that I do not want to leave the ignition on so as to use the dash mounted 12v sockets whilst charging when not on the move. All my other motorhomes have had a 12v socket installed , but because I have a tv / satellite system installed Auto-Trail have unfortunately not fitted a 12v internal socket. Link to comment Share on other sites More sharing options...
Brian Kirby Posted June 11, 2013 Share Posted June 11, 2013 Then all you need to do is look at the chargers to see which takes the highest current, and size cable and fuse to the next logical capacity above that limit. Halfords, as well as other motor factors, sell automotive cables with amperage ratings clearly stated. The fuse can be lower rated, or the same rating as the cable, but should never be higher rated. As said above, the fuse is to protect the cable from overload, so should be sited as close to the battery as possible. Link to comment Share on other sites More sharing options...
Keithl Posted June 11, 2013 Share Posted June 11, 2013 Kelly, Most (bot not all) 12 v sockets like yours deliver 10 A of current so assuming this will meet your needs then use cable rated at say 20 A and fuse somewhere in-between, say 15 A. This will then hopefully meet any future needs or cater for when someone plugs something in with a moderately higher current draw without blowing your fuse. And don't forget the fuse needs to be as near to the battery as conveniently possible. Keith. Link to comment Share on other sites More sharing options...
Dr Dave Posted June 11, 2013 Share Posted June 11, 2013 Current capacity of cable is a bit misleading because it is not the current carrying capacity that is of most importance in this case rather the voltage drop of a 12 volt system due to relatively high current flow and low voltage. The length of the cable run and the cross sectional area of the cable are inextricably linked use this calculator to work out the CSA of the cable for a given length and allowable voltage drop of about 3 to 4% and fuse it at the next standard size up from the maximum load of the socket with the fuse being as near to the batteries as possible. Cable calculator. http://www.solar-wind.co.uk/cable-sizing-DC-cables.html Hope its useful Dave Link to comment Share on other sites More sharing options...
vindiboy Posted June 11, 2013 Share Posted June 11, 2013 The "small inverter " you spoke about is the key, whatever Wattage that is will most likely be the biggest current puller so you will need to ensure you look at the spec. of that and use cable, fuses and 12 volt socket compatible with that. Link to comment Share on other sites More sharing options...
lennyhb Posted June 12, 2013 Share Posted June 12, 2013 Keithl - 2013-06-11 5:40 PM Kelly, Most (bot not all) 12 v sockets like yours deliver 10 A of current so assuming this will meet your needs then use cable rated at say 20 A and fuse somewhere in-between, say 15 A. This will then hopefully meet any future needs or cater for when someone plugs something in with a moderately higher current draw without blowing your fuse. And don't forget the fuse needs to be as near to the battery as conveniently possible. Keith. Not good advice Keith you are suggesting a 10 A rated socket is fused at 15 A, the absolute max rating of the fuse should be no more than the socket rating. Link to comment Share on other sites More sharing options...
sshortcircuit Posted June 12, 2013 Share Posted June 12, 2013 Wrong advice. The maximum rating of a fuse should be less than the rating of the cable used and at the rating of the socket. Link to comment Share on other sites More sharing options...
bolero boy Posted August 25, 2014 Share Posted August 25, 2014 sorry to revive this, but might be relevant....i have one habitation 12v socket which charges my HTC phone , kindle etc no problem, but wont charge my ipads, one a mini. I have tried two different adaptors, one rated at 5w output which is more than the ipad requirement of 2.5w according to our apple mains adaptor. the same cigar lighter adapter(s) fitted into the dash socket (with ignition on) will charge the ipads successfully...... i also have two inverters, (150w, i think, and 500w) and these will also charge ipads. could it be that the habitation socket is just not supplying sufficient amperage for the iPads? Link to comment Share on other sites More sharing options...
StuartO Posted August 25, 2014 Share Posted August 25, 2014 bolero boy - 2014-08-25 9:15 AM sorry to revive this, but might be relevant....i have one habitation 12v socket which charges my HTC phone , kindle etc no problem, but wont charge my ipads, one a mini. I have tried two different adaptors, one rated at 5w output which is more than the ipad requirement of 2.5w according to our apple mains adaptor. the same cigar lighter adapter(s) fitted into the dash socket (with ignition on) will charge the ipads successfully...... i also have two inverters, (150w, i think, and 500w) and these will also charge ipads. could it be that the habitation socket is just not supplying sufficient amperage for the iPads? It could be that the adpater for your IPads is faulty or isn't making effective contact in the 12v socket you are using. I bought a cheap 12v plug/adaptor as an extra for our set of Apple stuff and it turned out to be a duff one. Link to comment Share on other sites More sharing options...
bolero boy Posted August 25, 2014 Share Posted August 25, 2014 ho Stuart. I have two such adaptors....they both work in the rear bedroom socket when charging other items like phones and kindles, just not either ipads. in the front, the same adaptors both work with all items including the iPads....conclusion, the socket in the rear isnt delivering sufficient to power the ipad, which needs 2.5 amp....that my guess, looking for any technical confirmation re the spec of the rear socket. have posted same query on swift talk so might get some feedback there. rgds. chris. Link to comment Share on other sites More sharing options...
Brambles Posted August 25, 2014 Share Posted August 25, 2014 The sockets may have a much longer wiring loom and so is a larger volt drop when current flows. Especially if the wiring is shared to power other items such as lights etc. Try the sockets again with mains hook up or engine running so the voltage is slightly higher, you may find they then work indicating volt drop in the wiring is indeed the problem. It could also be the inductance of the wring though as the adapters may be switch mode supplies drawing short large spikes of current. During the short spikes of current the volt drop is just too large due to the inductance as well as resistance of the wiring. In layman's terms the long length of wiring acts like a filter to block pulses of current. You could maybe fix this issue by putting a supressor capacitor across the socket but will have to be quite a large one which will act more like a tiny battery. Link to comment Share on other sites More sharing options...
bolero boy Posted August 25, 2014 Share Posted August 25, 2014 Jon, thanks. on our van, I am fairly sure the habitation 12v socket will turn off when the engine starts.....will check later. not too much of an issue, just curious, will try next time on EHU. as a PS to you, i used something you posted a while back re running ebike chargers, assessing the impact or not on leisure batteries, with or without daytime solar.....i have done some testing and the effect on leisure batteries was negligible, following the recharging of a half discharged ebike battery via an inverter. thank you. Link to comment Share on other sites More sharing options...
Brambles Posted August 25, 2014 Share Posted August 25, 2014 Hi, You have indeed highlighted a point I overlooked on UK vehicles where the habitation electrics are isolated when the engine runs. Darn!!! So just leaves hook up to try and boost the voltage and see if it make a difference. Forgotten what was said about the cycle chargers. Probably somethng like not taking much from the leisure batteries. say 12AH at 36 volts half discharged = 6Ah at 36 volts. That would be 18Ah at 12 volts so two batteries at total 200Ah is only 10% of the capacity ...... neglible impact. Sounds about right to me and hope that matches roughly what I said previously. Link to comment Share on other sites More sharing options...
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