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Smallest Ah Battery


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what is the smallest ah battery i could use in a caravan ? just wondered if there was a big saving in weight of them

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Two key questions, without knowing these it is impossible to even begin to answer your question.

 

1. Do you use a motor mover?

2. Do you always use ehu?

Edited by Stevan
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I have a pair of 7. 5Ah SLA batteries inside the caravan wired in parallel for when on EHU and the when without I add a 100Ah in the battery box. One 7. 5Ah would be fine to use when on EHU it's only needed to stabilise the voltage when under load. Of course this would never run a motor mover or inverter, however, I don't have a motor mover and only need the inverter off grid when the extra battery is connected

Edited by DeadMeatUK
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obviusly i would have to deactivte the charger then

I don't understand? I leave the charger on so soon as it's plugged in it starts charging

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I don't understand? I leave the charger on so soon as it's plugged in it starts charging

Would not the built in charger's current way exceed the level to satisfy the recommended 8 to 10 hour charge time for reasonable battery life? Most van chargers are far higher current output than 1. 5 Amps

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obviusly i would have to deactivte the charger then

If you deactivate the charger, you would be running all 12v circuits from the leisure battery!

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Would not the built in charger's current way exceed the level to satisfy the recommended 8 to 10 hour charge time for reasonable battery life? Most van chargers are far higher current output than 1. 5 Amps

Ah I see. .. That's a very good point. My charger/power supply is 10A which is above the recommended charge current, however, on a charged battery it will only be charging at a few amps at the most.

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I use a 44ah car battery that weighs 10kg and yes I do have a motor mover. It works fine for what I need.

We are always on EHU so a full size is not needed. I got it from battery megastore online for under 30'quid.

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i was looking at a 50-60ah battery to be honest

 

Since my 90Ah leisure battery packed in a year or two ago I use a 50Ah car battery from a Citroen C3. We don't have a mover, we're rarely off grid for more than a few days, we've no tungsten lights and we don't watch telly.

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The BS7671:2008 states:- A721. 55. 3. 2 Capacity An auxiliary battery should have a minimum capacity of 40 Ah at 20 h discharge rate. However it also says if a battery is fitted there are some caravans which don't have batteries.

 

I have used a 7 Ah battery to take surge when water pump used quite successfully, but the limit is really down to the charger fitted. Battery chargers and power supplies come in many different flavours and one of the versions is the so called stage charger. The stage charger recharges the battery far quicker than a float charger and monitors the charge rate to switch between stages. As a result they are matched to a range of battery sizes.

 

This http://www. amperorassociates. co. uk/c-battery_chargers/BatteryC-3_25A. html is a typical replacement for a caravan charger when they fail. You will note 60 Ah to 260 Ah range of batteries, but it also has a switch which can be used to make it only float charge for when it is being used as a power supply rather than a battery charger.

 

Set to float charger you would not need a battery at all, you could use a 7 Ah just to work lights before connecting the caravan to the EHU. The 7 Ah battery is what is called a valve regulated lead acid (VRLA) battery and should not be stage charged plus any over charging would soon destroy it. The 13. 8 volt stated on the linked battery charger is a bit on the high side for a VRLA battery normally they would be floated at 13. 4 volt.

 

My old caravan had a very simple battery charger around 4 amp not the 25 amp of the linked to charger. The lights used more than 4 amp and it relied on the fact it would be recharged over the day then discharged in the evening. Old caravans i. e. those with gas lights were fitted with 8A battery eliminators when always on EHU. Today we use more like 18 to 25 amp battery eliminators.

 

Of the three caravans I own I have not a clue what type or size the battery charger is, one built into the consumer unit, one is separate and the big caravan not even found it.

 

As to saving weight it is the design weight that matters not the actual weight of the caravan. The large caravan I own I can't tow because it's design weight is too high. The car has ample power to tow it the Kia has same engine as my son-in-laws Chrysler and same size engine as sons Jag, but the manufacturer "Kia" has stated the maximum tow weight for my car which is too low, so it does not matter how I alter the caravan unless I do something to down grade the chassis and take it to be re-classified nothing I can do.

 

There was a time when there was no towing limit, my Uncle towed a home made caravan with a motorcycle and side-car and I in early days made all my own tow bars, including one for Mini with tow ball at the front for launching a boat, but those days are gone. So there is really no need to try to save a few pounds of weight. Looking at spec for car and caravan your well within the limits unless I have selected wrong models.

 

I tried to look up charger all I found was it's a 15A switch mode and called a battery charger. It does not say if a stage charger or not. I would say safe limit in case it is a stage charger is about 40 Ah. If you can be sure it's not a stage charger then 14 Ah i. e. golfing trolley battery would be an option. In the main stage charging is started once the power is removed or the battery drops below 11. 5 volt. It is possible if the battery is left connected stage charging will never be started, so some people even with a stage charger may get away with a small battery. I have no idea why the IET states 40 Ah minimum, but it does seem likely they did not pull this figure out of the air, but put some thought into it. So I would recommend you don't go below 40 Ah unless you know exactly the type of charger being used.

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Would not the built in charger's current way exceed the level to satisfy the recommended 8 to 10 hour charge time for reasonable battery life? Most van chargers are far higher current output than 1. 5 Amps

 

Er, no. The 'charger' is usually a constant voltage power supply at around 13. 8V. The fact that it can output 20A does not mean it will push 20A into the battery. The internal resistance of the battery will limit the current - in other words the battery will take whatever current it needs and no more. If the batteries (assuming two in parallel) are only there for show (they will have little other use) and are well charged then they will probably only take a few hundred milliamps.

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  • 4 months later...

Some of the battery suppliers advertising on the net give whe weight of the battery and its dimensions as well as the Ampere Hour (AH) capacity

This is a sample supplier.

http://stores. ebay. co. uk/absbatteries?_trksid=p2047675. l2563

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what is the smallest ah battery i could use in a caravan ? just wondered if there was a big saving in weight of them

 

Pop into The Carpet & Vinyl Centre at Goldthorpe and ask Nigel, he sells batteries in all sizes, as well as making removable carpets for the caravan ;)

Paul B

. .......Mondeo Estate & Elddis Avanté 505 (Tobago)

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