That's a bit of a worry. I rely on full battery charging to my leisure battery en route as I don't use electric hookup.

I'm currently waiting for a new tow car which will have a factory fitted tow bar. Hopefully it will sense the caravan has been connected and put out the correct voltage to the leisure battery and fridge. Not sure how to test whether it works or not though.
The above video link seems to be targetted at after market installations so hopefully my new installation will be OK.

I would imagine that one simple and probably effective remedy would be to turn off the Stop/Go function when towing. I can see this latter function probably serving a purpose in and around town in daily use but when towing most of the time most of us are either getting from A > B via using motorways or 'A' roads and the like not pottering around through stop/go town traffic.
I personally ALWAYS turn off the stop/Go function each and every time I start the car but that's probably another topic altogether.

I believe that on my new car (Seat Ateca) with the factory fitted towbar, stop/start is automatically turned off when the trailer is detected, so that is not a problem.
The potential problem is whether the smart alternator runs conventionally when the trailer is detected or in smart mode which will quickly trash the leisure battery.
No good asking the dealer, they barely understood the requirement for full 13 pin wiring for fridge and battery charging any way :(

Is Rod still on this forum, I don't recall seeing any posts from him recently. Hooe he's ok?

Cheers Mark

Quote: Pepé Le Pew wrote in post #5

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Quote: Ray Lawrence wrote in post #4

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The potential problem is whether the smart alternator runs conventionally when the trailer is detected or in smart mode which will quickly trash the leisure battery.

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I don't really understand what you mean by that. What's 'smart mode'?

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Pretty much all new cars have this technology to improve fuel consumption and reduce CO2 emissions.

This technology came to light when caravanners started to report defrosting fridges and low batteries in transit.
The video shows an easy way to check if your car has this technology.

Quote: Pepé Le Pew wrote in post #11

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I don't understand what he's saying in that video.

He says to check to see if your car has 'regenerative braking' or a 'smart alternator' (and I don't think the alternator itself is smart per se; if there's any smartness going on, it's in the car's ECU) you should go for a tootle with a voltmeter plugged into the cigarette lighter and monitor the alternator output voltage as you drive.

He goes on to say if that voltage drops to 12.4V when you're on a dual carriageway or a long straight road (as opposed to somewhere else, when you'd expect to see 14-odd volts), then you've got 'regenerative braking' or a 'smart alternator'..

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Smart alternator = regenerative braking, as you say, the smartness is in the ECU.
When driving along a dual carriageway or motorway, the ECU reduces the voltage to the field windings of the alternator, thus reducing the load on the engine as the alternator is no longer working. Under braking or running downhill, the alternator effectively becomes a dynamo and puts a large current/voltage in to the car battery.
That's apparently fine for a car battery but not for a leisure battery.
This is what I have understood from one viewing of the video, I may have it wrong in some minor way but I believe this is the essence.

The problem will manifest itself if a tow bar is fitted by a 3rd party and doesn't connect properly to the car's electrical system. Many towbar fitters put in a voltage sensing relay which detects when the output from the alternator is above 13.5V or there abouts. The relay then connects the car battery to the caravan fridge and leisure battery.
With a smart alternator/regenerative braking system, the output from the alternator drops to 12.2V thus the relay will not operate so the fridge will not be powered and the leisure battery will not charge. On braking, anything up to 17V and 200amps will be shoved in to the car battery, the relay will open and that voltage/current will go the the fridge and leisure battery. The fridge might be able to cope but the leisure battery's life will be shortened apparently.

I am hoping that my factory fitted towbar will be fitted and the ECU re-programmed so that I don't have this problem. :)

Tomored,

I don't believe the stop/start feature has much to do with this issue.
In my handbook, it is recommended that the stop/start function is disabled when towing. If a towbar is factory fitted, the stop/start function is automatically disabled when the car senses that a trailer has been connected.

Have a look at this blog. Stop start issues are discussed a little further down under the title "other issues" A good simple explanation.

https://caravanchronicles.com/2017/02/15...and-motorhomes/