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Fitting a leisure battery to trailer tentViews : 2644 Replies : 10Users Viewing This Thread : |
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Feb 23rd, 2019, 14:16 | #1 |
Premier Member
Last Online: Yesterday 19:56
Join Date: Feb 2012
Location: Preston
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Fitting a leisure battery to trailer tent
Not having much idea on towing electrics, I thought I'd ask here:
I'm thinking of fitting a small leisure battery to my trailer tent, mainly to charge ipads/phones etc, and possibly run LED lights and the tap for the sink. We don't tend to use EHU when camping. The trailer is currently fitted with a 7 pin plug, but it needs replacing as it is falling apart, is this just a case of fitting a 13 pin plug and running the relevant cables to the battery terminals to charge it? My car has a 13 pin socket which currently has an adapter to 7pin on it. Cheers |
Feb 23rd, 2019, 16:12 | #2 |
XC70 SE lux D5
Last Online: Feb 25th, 2024 14:34
Join Date: Jan 2011
Location: Mansfield, notts
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Most caravans and probably trailer tents with leisure batteries fitted will have what's called a habitation relay fitted it connects the leisure battery to the charging circuit on the car only when the car is running/charging, and at all other times it connects the battery to the devices requiring power.
This is a typical diagram of the circuits using the fridge supply circuit from the car side to switch the relay. |
Feb 23rd, 2019, 21:44 | #3 |
Bungling Amateur
Last Online: Today 19:42
Join Date: Aug 2014
Location: Beverley, East Yorks
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.....aka split charge relay.
If you are just charging phones, led lights etc a decent battery should last a few weeks.
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2011 XC90 D5 Executive 2003 C70 T5 GT 2012 Ford Ranger XL SC 1977 Triumph Spitfire 1500 1976 Massey Ferguson 135 |
Feb 25th, 2019, 19:29 | #4 |
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Last Online: Feb 15th, 2022 07:50
Join Date: Dec 2001
Location: Back home in 'Norn Iron'
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The logic behind a habitation relay is that it only comes into operation to provide charge to the battery once the engine is running and the alternator is charging. The relay is activated by pin 10 becoming live and the relay then connects the permanent live pin 9 to the battery for charging. However, having researched this in some detail for my V50 it is apparent that most current Volvos simply provide switched power to pin 10, i.e. it becomes live as soon as the ignition is switched on and not just when the engine is running. This 'could' result in the starter motor in the tow car drawing on the auxiliary battery in the trailer. The solution would seem to be to install a voltage sensitive relay on pin 10 that will only operate once the alternator is producing somewhere around 14 volts, i.e. the engine is running.
Whether or not it is a problem in practice is another matter and as I said, as far as I can tell this is the way all current Volvos operate so it’s perhaps more a theoretical problem than a practical one. A split charge relay is a different thing altogether. Its purpose is, as its name suggests, to split the charge from the main battery, once it’s fully charged, to a second battery, and back again if the main battery gets depleted. This dates from the days when dynamos would have struggled to charge two batteries but modern alternators can cope with ease. With a regular trailer/caravan setup, the auxiliary battery is charged together with the tow car battery - it’s not an either/or situation.
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Simon J Last edited by Simon J; Feb 25th, 2019 at 19:35. |
Feb 26th, 2019, 12:36 | #5 | |
Bungling Amateur
Last Online: Today 19:42
Join Date: Aug 2014
Location: Beverley, East Yorks
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Quote:
This explains the systems well: https://www.12voltplanet.co.uk/split-charging.html
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2011 XC90 D5 Executive 2003 C70 T5 GT 2012 Ford Ranger XL SC 1977 Triumph Spitfire 1500 1976 Massey Ferguson 135 |
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Feb 26th, 2019, 12:52 | #6 | |
Premier Member
Last Online: Feb 15th, 2022 07:50
Join Date: Dec 2001
Location: Back home in 'Norn Iron'
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Quote:
What is being described on the page you linked to is in effect the use of a voltage sensitive relay to avoid drawing on the auxiliary battery when starting. That is often referred to erroneously as split charging but the term originally derived from the need to split the relatively modest output of a dynamo between two batteries - a main and an auxiliary. If the load on the main battery increases, say, because the headlights are switched on, then the charging switches back to it. But this doesn’t mean that current is also drawn from the auxiliary battery along the light gauge charging circuit. The circuits are ‘split’. Split charging is more usually found in motor homes with two or more batteries rather than in caravan/trailer combinations.
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Simon J |
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