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David 38

On site 12 v from car.

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If I make up a twin lead with 13 pin connectors  from the permanent 12 v (pin 9), I have failed to find a commercial made one, wound my caravan work off it in an emergency if my leisure battery became low?

I'm thinking the internal wiring in caravan might be ignoring it.

I'm aware of the other 12 V that only is live when engine running and it feeding then.

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Without the cars engine running, it would drain the car battery. This is all dependent on your IF so I suggest you just carry a spare leisure battery for the few occasions where it is possible that your existing leisure battery gets flat.

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25 years ago I toured for 7 weeks using just a plug into the back of the car. In our case it was just for the water pump and lighting and so during the summer not a lot of consumption. No LEDs then and general light was from car type bulbs. The car was used most days for at least 10 miles and we moved every 3 days. 

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if pin 9 is permanent live why do you need to make up a new plug? Cant you just plug the caravan directly into the car? 

you would need to be careful on how much you draw from the car as you could flatten the battery and disconnect the caravan before trying to start the car as a precaution.  Also disconnect when you don't want to draw power, again as a precaution.

 

 

 

macafee2

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Posted (edited)
11 minutes ago, macafee2 said:

if pin 9 is permanent live why do you need to make up a new plug? Cant you just plug the caravan directly into the car? 

Not sure what circuits pin 9 powers but it won't charge the battery in the caravan and don't most circuits work via this battery. The OP is talking of usage when leisure battery is low. If using the car battery to augment the system (and the car gets some daily use) I would want it connected most of the time during caravan battery usage rather than connecting to the caravan only when the leisure  battery is really low,

Edited by Easy T

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26 minutes ago, Easy T said:

25 years ago I toured for 7 weeks using just a plug into the back of the car. In our case it was just for the water pump and lighting and so during the summer not a lot of consumption. No LEDs then and general light was from car type bulbs. The car was used most days for at least 10 miles and we moved every 3 days. 

That is all our first caravan had. There was no onboard battery so a lead was run from the car when we returned to the caravan each evening, to power the single electric lamp and an (upgraded from manual) electric water pump. The other lighting was from a gas lamp and while we had an old Electrolux gas fridge, it did not require 12V to run!

We connected the caravan with a commercially available 12N extension lead with only two pins wired. Look closely and you can see it in use with the Astra (the red blob below the caravan hitch is the plastic cable reel for the lead.

Elddis Whirlwind & Vauxhall Astra 1600S.jpg

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Ah, back then in days of dumb fridges that worked well, gas lights, foot pumps for water and often added fluorescents everyone (mostly) ran off the car. 

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23 minutes ago, macafee2 said:

if pin 9 is permanent live why do you need to make up a new plug? Cant you just plug the caravan directly into the car? 

 

Yes might be possible but I was thinking flexibility of just where car next to caravan.

16 minutes ago, Easy T said:

. The OP is talking of usage when leisure battery is low. If using the car battery to augment the system (and the car gets some daily use) I would want it connected most of the time during caravan battery usage rather than connecting to the caravan only when the leisure  battery is really low,

No I do not want to connect at the same time, only either, when leisure battery low I do not want it to pull car battery down.

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If you have a car with a decent sized battery and it has a good alternator ( 150 amp) or more and you are only using a few lights for a sensible time each night and a water pump only , I would take a chance , I'm sure it would be OK. Make sure you have a good set of jumper leads so you can get a start from a friendly nearby camper if you need one.

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In the days of 7 pin plugs, all filament bulbs and CRT TVs this was common practice, with many caravans having a changeover switch on the control panel, rather than the now normal habitation relay. Ready made leads were available in most accessory shops.

Jump leads were a common sight in the morning for those who had flattened their car battery!

No reason it could not work with modern 13 pin plugs, but extra care would be needed with so many cars being almost impossible to unlock, to access the battery, once the battery is flat!

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Our 2018 lunar has the ability to switch between the leisure battery or the car battery when on site. 

I have used the feature on a previous van, when leisure battery died on the last night. 

The only potential issue is the new car has “smart” electronics, and it powers off pin 9 Shortly after locking the car

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Thanks for replies.

Have been in garage dug out two discarded  leisure battery's one is 10 volt the other 12.25 volt.

The 10 volt with smart charger on does nothing, assumed dead.

The other is charging at 13.2 V, so there is hope, will see how it progresses, might get me out of trouble if I over do my 2 or 3 nights out in a field with the one on caravan.

I've not used this caravan on battery only before and battery came out of my previous caravan and I can't recall when it was bought.  Its not been on hook up for 2 weeks and is reading 12.42 V so plugged it in for a few hours and will then let stand and see what I get.

My unknown is what the electronics do to it whilst stood and when I set off I have to use my mover and travelling well less than hour to get to field situation.  Thus I wanted back up if only to run water pump and lights, might be able to get a battery charge in a nearby building for main battery if I put this hopefully old one on.

Nothing is straight forward is it just discovered a spanner needed to get clamps off!

 

 

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32 minutes ago, David 38 said:

Thanks for replies.

Have been in garage dug out two discarded  leisure battery's one is 10 volt the other 12.25 volt.

The 10 volt with smart charger on does nothing, assumed dead.

 

 

Many smart chargers simply refuse to play when faced with a truly flat battery. Sometimes an old fashioned dumb charger will force some initial charge in and then a smart charger can be used.

Never any certainty though once it has stood flat for any length of time.

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52 minutes ago, Stevan said:

Many smart chargers simply refuse to play when faced with a truly flat battery. Sometimes an old fashioned dumb charger will force some initial charge in and then a smart charger can be used.

 

Will try that, thanks

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You have 2 batteries. Connect them in parallel then put on your charger. Remove the "better" battery after 10 minutes or so. Your charger will then charge your "worse" battery. 

 

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Stevans post seems to be working, Smart charger is now on it and working this time.

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5 hours ago, David 38 said:

No I do not want to connect at the same time, only either, when leisure battery low I do not want it to pull car battery down.

Fairy Nuff. That is why I said that I would wish to connect car to caravan each time so that the leisure battery was never that low to pull the car battery down

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Gents,

 

There have been a few comments along the lines of "this is what we used to do when everything was in black and white"

I thought that too.

 

Then I thought again.

 

Danger!!

 

Things aren't in black and white any more are they? 

I'm happy to be contradicted on this as I've never tried it on a modern van....

The only time the car battery is effectively connected to the van battery is when the engine is running and therefore (generally) charging. At this time, the habitation relay is open, isolating the van 12 volt consumers.

But if the habitation relay is closed, the van battery is connected to the consumers - but the car battery cannot be connected to the van battery as the engine is off. Having the consumers connected to the car battery directly means isolating the van battery from the consumers, which is counter intuitive.

I've looked at Flying Togs nice schematics and I'm confused.

I've seen a nice simple schematic fairly recently on here - can someone put me out of my misery as all this thinking is doing me no good!

 

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I've done this for years prior to solar panels. Left the onboard battery selected during the day too power the fridge (control system) when we are out and switched to the car on our return. That way we had a 2 week holiday running off the battery. Obviously the car battery is charged everyday. My new caravan doesn't have a selector switch but not a problem now we have the solar panel. Still carry my extension reel for emergencies though. 

I think you we find their are 2 feeds from the car. Low current feed for lighting pumps etc and a feed for the fridge/battery charger which is only available when the engine is running.

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49 minutes ago, CraigP2005 said:

I think you we find their are 2 feeds from the car. Low current feed for lighting pumps etc and a feed for the fridge/battery charger which is only available when the engine is running.

 

There are indeed two feeds from the car - one, when the engine is running, supplies the fridge and a supply to activate a relay that connects the car battery (and hence charging voltage) to the van battery. Note that the fridge supply does not directly supply charging voltage to the van battery.

The "permanent" supply from the car to caravan goes through this relay as well as supplying the ATC

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Needing a feeble excuse to take the car for a blast - it's a nice sunny day 😊, I went to our storage place and connected up.

Sure enough, the van habitation electrics worked fine with no van battery connected.

Or at least most of them.... The alarm and associated awning light switching didn't work, and, I think the fridge electrics didn't either - I couldn't see the light, but that may have been my eyes rather than the fridge. Note I mean the panel lights, not the fridge itself. 

 

 

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I still keep one of these leads as a backup,  it must be over 30 years old.

Originally it has the black 12N plug and socket, then when I got a newer caravan with 12N and 12S plugs, I changed the plug and socket for grey 12S ones.

A few years back, as the standard changed again,  I swapped them for 13pin plug and socket. 

I've probably used it once, but it's always worth keeping it for piece of mind. 

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On 29/08/2019 at 10:26, David 38 said:

Thanks for replies.

Have been in garage dug out two discarded  leisure battery's one is 10 volt the other 12.25 volt.

The 10 volt with smart charger on does nothing, assumed dead.

The other is charging at 13.2 V, so there is hope, will see how it progresses, might get me out of trouble if I over do my 2 or 3 nights out in a field with the one on caravan.

I've not used this caravan on battery only before and battery came out of my previous caravan and I can't recall when it was bought.  Its not been on hook up for 2 weeks and is reading 12.42 V so plugged it in for a few hours and will then let stand and see what I get.

My unknown is what the electronics do to it whilst stood and when I set off I have to use my mover and travelling well less than hour to get to field situation.  Thus I wanted back up if only to run water pump and lights, might be able to get a battery charge in a nearby building for main battery if I put this hopefully old one on.

Nothing is straight forward is it just discovered a spanner needed to get clamps off!

 

 

I have an energy monitor, so I tried charging some sulphated batteries while monitoring the input to charger, it sat there for 10 days doing as it seemed nothing, then as if a switch had been flicked over an hour it went to full charge rate for that charger, OK only 0.8 amp, it continued to charge for Ah/charge rate, then ramped down again, and the battery seemed to be fully charged.

 

This was unexpected, did not expect after 10 days it would do anything,  but repeated this with other batteries 3 times, 4th however failed, it seemed to be following same pattern then voltage dropped and in the end it went to skip site.

 

When I bought the last caravan it had a fault, so I had to work out how it was wired, and I used a small 7 Ah battery to test with, I found there are from memory 5 relays, and it seems the ignition live works a relay so permanent live is connected to an output, can't remember of hand exactly which way around, however BS7671 says same supply should not be used to charge battery and run fridge, so relay gives one a second ignition supply from permanent live supply.

 

However today things are changing, the problem of cars switching off the charger means the simple split charging no longer works, so the inverter charger is slowing getting more and more popular, this lifts the voltage from car and so charges the caravan battery a lot faster then ever before, however with a 10 amp version 110 Ah battery still needs 11 hours and we don't normally tow for that long.

 

So I use a starting pack, a 150 watt inverter charges the pack at quite a low rate, but it's being charged every time I use the car, and also useful for pumping up push bike tyres. And if we have drained caravan battery too much, it will give us an extra 20 Ah. Not best idea, but already have it all so cost nothing.

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6 hours ago, ericmark said:

 

However today things are changing, the problem of cars switching off the charger means the simple split charging no longer works, so the inverter charger is slowing getting more and more popular, this lifts the voltage from car and so charges the caravan battery a lot faster then ever before, however with a 10 amp version 110 Ah battery still needs 11 hours and we don't normally tow for that long.

 

 

 

Hopefully, none of us would ever allow the battery to become so utterly depleted, at worse approaching 50% SOC?

 

Our van's Schaudt controller/charger unit features this inverter based technology that took even a low voltage reaching the van from the towing vehicle and lifts it to achieve a very effective charging voltage. It is rated at 8amps but as I doubt our 90 Ah battery ever drops below 75% SOC it achieves a worthwhile, health improving level of recovery on route.

 

 

Re on site car battery to caravan battery transfer there used to be a neat Welsh made unit called a "Uni Charger", This did this same trick of lifting the low voltage of the car's off charge battery to supply to the van's battery a level of voltage to effect a recharge. It had an important additional clever trick of only doing so whist the charge state of the car's battery was left adequate for an engine start. It worked very well in practice. These days with the modern caravan wiring I would couple this directly to the van's battery, though now with solar our need for these things has effectively waned. Our TV needs if likely to be heavy I address by taking a portable 60 Ah extra battery uniquely for that job. That then being recharged via a DUO solar controller as a secondary battery, so not risking the "life" supporting duties asked of the van's battery.

 

I played around with a quality little pure sine wave inverter driving a 3.6 Amp CTEK smart charger, that worked as a test, but of course never had that car battery level protection feature so whilst an experiment I have never done this in a time of need. These days also, at least in my case the capacity of the tow car's battery is smaller than the brute of the ones I had in my Defenders of that period.

 

 

 

Edited by JTQ

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