Advertisement
Message Forums |
|
 Topic: New tow car, what do I need?
|
  |
22/8/2018 at 11:37am
Location: North Wales
Outfit: Elddis
View Profile
Reply
Quote
|
Joined: 22/8/2018 Standard Member
Forum Posts: 55
| Site Reviews Total: | 0 |
|
| Site Reviews 2024: | 0  |
| Site Reviews 2023: | 0 |
| Site Reviews 2022: | 0 |
| Site Reviews 2021: | 0 |
| Site Reviews 2020: | 0 |
| Site Reviews 2019: | 0 |
| Site Reviews 2018: | 0 |
|
| Site Nights 2024: | 0 |
| Site Nights 2023: | 0 |
| Site Nights 2022: | 0 |
| Site Nights 2021: | 0 |
| Site Nights 2020: | 0 |
| Site Nights 2019: | 0 |
| Site Nights 2018: | 0 |
|
We have a Kia Carens 2.0 CRDi and before buying caravan we looked up the tow weight, except for automatic and EX and LX models it showed 1500 or 1600 Kg so we got a caravan unladen 1250 laden 1350 kg well within limits and it tows it fine, even on relatively steep hills.
However went to change address on the log book and find that states max tow weight 1250 kg hunted for a plate on car and could not find one giving weights, I think error on log book, however this has prompted us to look for new tow car.
My wife wants one which does well to gallon, so looking at newer models, seems 2013 there was a law change which has resulted in many cars becoming more efficient after that date.
However one of the ways to make them more efficient was to change how the alternator is controlled. To date we have not connected either ignition or non ignition supply to caravan. However it seems prudent to start using the fridge power from car, and maybe charging.
However it seems rather expensive! A Ring RSCDC DC to DC charger will set me back around £175 it will take a solar panel as well, but once fitted to the caravan it will remove the need for a blocking diode on the car, or a voltage dependent relay, however may need a relay for fridge, I seem to remember they draw around 8A which should be OK. And the caravan relay means the inverter is connected to non ignition supply once ignition is switched on, so two inline fuses is really all that is required.
However the Ring does switch off when donor supply drops to 12.6 and needs 13.1 volts to restart, there is clearly some volt drop to caravan and to be able to connect solar panels clearly it has to be fitted to caravan not car. 30A is a fair charging rate, so big question is with alternators controlled by engine management will the voltage drop to a point where the charger cuts out?
It is designed for the job, but so were split charging diodes and voltage dependent relays, both which were useless.
So is it worth it, and do I go for a car where alternator is not controlled by engine management as they make better tow cars.
As yet tow car not bought, so I can reject cars if they are a problem.
|
24/8/2018 at 6:35pm
Location: North Wales
Outfit: Elddis
View Profile
Reply
Quote
|
Joined: 22/8/2018 Standard Member
Forum Posts: 55
| Site Reviews Total: | 0 |
|
| Site Reviews 2024: | 0 |
| Site Reviews 2023: | 0 |
| Site Reviews 2022: | 0 |
| Site Reviews 2021: | 0 |
| Site Reviews 2020: | 0 |
| Site Reviews 2019: | 0 |
| Site Reviews 2018: | 0 |
|
| Site Nights 2024: | 0 |
| Site Nights 2023: | 0 |
| Site Nights 2022: | 0 |
| Site Nights 2021: | 0 |
| Site Nights 2020: | 0 |
| Site Nights 2019: | 0 |
| Site Nights 2018: | 0 |
|
Moved to KIA Sorento so no problem with smart alternators, it is only one year younger than old car, but has a 3000 kg towing capacity.
It only has one socket, so I will fit a second socket, not sure as yet what to do about charging? I could simply not bother, still need second socket for reversing light and fridge, but latter only draws 8A so simply connect to boot cig lighter supply.
It is the non ignition supply which is more important to consider, there are a lot of lights in the caravan so the draw could be quite high, and if I do fit a DC to DC inverter then it could draw 40 plus amps.
Clearly this will need a fuse to stop over loading the cable. Although BS7671:2008 stipulates 2.5 mm sq for most cores, and really I could do with 4 mm sq, I am having problems finding any for sale.
It is made Batt cables part number 37794 is 5 core flexible cable 4 mm sq there is also 7 core but only need 5 core. However finding some one who will sell 2 meters of the cable is something else.
Minimum cross sectional area for the BS AU 149a socket is 1.5 mm² except for earth which is 2.5 mm² but for the BS AU 177a socket it is 2.5 mm² for 4 of the cores and 1.5mm² for reversing light.
But I can't find it for sale as a 2 meter length, 30 meters is a bit of over kill when I only want 2 meters.
|
05/9/2018 at 10:23am
Location: North Wales
Outfit: Elddis
View Profile
Reply
Quote
|
Joined: 22/8/2018 Standard Member
Forum Posts: 55
| Site Reviews Total: | 0 |
|
| Site Reviews 2024: | 0 |
| Site Reviews 2023: | 0 |
| Site Reviews 2022: | 0 |
| Site Reviews 2021: | 0 |
| Site Reviews 2020: | 0 |
| Site Reviews 2019: | 0 |
| Site Reviews 2018: | 0 |
|
| Site Nights 2024: | 0 |
| Site Nights 2023: | 0 |
| Site Nights 2022: | 0 |
| Site Nights 2021: | 0 |
| Site Nights 2020: | 0 |
| Site Nights 2019: | 0 |
| Site Nights 2018: | 0 |
|
It took me some time to reverse engineer what the caravan does. However no electronics so relays are not voltage activated, other than the point where they would drop out as not enough volts to coil, there is nothing in the caravan to prevent power being supplied to the car on pins 3 and 4 of the BS AU 177a 7 pin plug where there is power to pins 6 and 7. I have tested this using small 7 Ah batteries.
It is clearly designed so that power on 6 and 7 (ignition supply) will power the fridge and a relay which in turn connected pins 3 and 4 to battery.
Without power to pins 6 and 7 but with power to pins 3 and 4 (i.e. ignition turned off) then the caravans internal lights work from pins 3 and 4.
There were normally relays or diodes fitted to the car to stop caravan powering car, but not in the caravan. How it was done in the car depends on the car.
The blocking diode will always work, however the volt drop means battery charging is nearly non existent in most cases.
The relay connected to alternator warning light was the next.
Then the voltage dependent relay.
However some cars have a aux on the ignition and no relays are required.
Today the problem is with a DC to DC inverter in the caravan you don't need anything in the car, in fact with modern cars switching off alternators it could be dangerous to have a voltage activated relay in the car, as it could stop the supply to the anti snake device. I don't know what is done in the car today? I would guess normally closed contacts which open when starter is engaged? or return to blocking diodes which would seem best option.
The problem is trying to match every car to every caravan, and this is nothing new. In the early days of the 7 pin plug pin 2 was for the vacuum warning light, since caravans did not have vacuum brakes, it was common to use pin 2 for a live supply to caravan.
Then we got caravans with an electric reversing hitch, so pin two was connected to the reversing light so it disengaged brakes when cars were put into reverse. Then the law on rear guard fog warning lights came in, so yet again pin 2 use changed to rear guard fog warning.
So we got the second 7 pin socket, reverse went onto pin 1 and we used the rest for power, often two ignition feeds and one non ignition, however there are still the odd trailers found which still need vacuum or air warning lights. So official pin 2 is classed "Coding for coupled trailer" which reduces the power supply to two, rules also state fridge and battery charging should not come from same supply, so to comply we got the relays in the caravan.
So the rules only state Continuous power supply and Power supply controlled by ignition switch it does not say any diode or relay is required, in the old days it would be down to the auto electrician to decide what to do. However today we are often forced to use manufacturers harnesses and relays in the car, no longer is it left to the electrician.
I have not fitted a manufacturers harness, it hardly needs an auto electrician to do that, it is plug and play, and I stopped working as an auto electrician around 1994 and even then I was working on the big stuff, like straddle carriers which lifted and carried 200 ton, not cars and caravans.
So I need to update my skills to work with modern car, it not how to make something work, I can do that, it is how to make it interchangeable which is the problem. If I wire my Kia Sorento then I can tow my caravan without a problem, but what happens when some one says "Can you move my caravan for me please, my cars in garage." If I plug in the S socket which if there is an anti snake device fitted I must, what then stops my car drawing from the caravan battery?
Again we have the situation where there is no standard wiring, and if I am going to wire the tow car, I want it as standard as I can make it. The annoying thing is 2.5 mm 7 core cable is not easy to find, so will need to wire using twin core, that's not so much of a problem as I can then use 4 mm up to engine compartment.
The next is rear view camera, what plug is used for them? I can clearly use any plug in stock and likely a coax plug as used for ham radio aerials would be good enough. But what is the standard?
|
|
|
7682 Visitors online !
Free UKCampsite.co.uk Window Sticker - Recommend to Friend - Add a Missing Campsite
[Message Forums]
[Caravan Sites & Camping]
[Company Listings]
[Features / Advice]
[Virtual Brochure]
[Shop!]
[Reception]
[Competitions]
[Caravans & Motorhomes For Sale]
[Event Diary]
[Contact Us]
[Tent Reviews]
Please note we are not responsible for the content of external sites & any reviews represent the author's personal view only. Please report any error here. You may view our privacy and cookie policy and terms and conditions here. All copyrights & other intellectual property rights in the design and content of this web site are reserved to the UKCampsite.co.uk © 1999 - 2024 |
Advertisement
|
|
|
