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Battery showing zero volts


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After I got back from my first trip away the battery condition is showing nothing. I've tried leaving the battery on charge for a few days but no luck. It appears as if there is no battery what so ever but all connections look ok.

 

Caravan: Lunar LX2000 1998 

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Have you tested the battery with a multimeter on the posts?

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I've not had a Lunar, but do you have a three way switch, like many older caravans, which was labelled, Car/Off/Van ?

 

If so, what position is it ?

 

As Ern says, your first test should be at the posts and expect around 12.5 volts, then at the battery terminals, make sure they are clean and tight, you should get the same as at the posts, then test on towards the PSU.

 

A few questions:

 

1)How  did you charge the battery, did the battery show fully charged, did you charge it on the van or out of the van.

 

2) Did the condition meter register OK when you were away on EHU and did all 12v items work OK.

 

3) Do any 12v items work now.

 

4) Can you plug it in to the mains at home, if so does it now read.

 

5) Has any work been done on the van, or did you just park up after getting home and it didn't work.

 

All caravans have a ' battery fuse ' somewhere in the +ve ( red cable ) between the battery post and the PSU, usually 20A  or 25A.

 

Some, rarely, are in the battery box in the red cable, most are inside the van, behind or around the back of the battery box, again in the red cable, then there are those that are hidden away ( under seats or wardrobe, cupboard bottoms ) and finding them means tracing the red cable all the way to the PSU, though they should be pretty near to the battery.

 

If you find it, change it if it has obviously blown, if it looks OK then either check it for continuity with a DVM or put a new one in, sometimes they can be open circuit but look OK and whilst you are at it check the fuse holder for signs of corrosion or overheating.

 

Let us know how you go on, someone on CT with the same or similar van may be along with more info.

 

 

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22 hours ago, Ern said:

Have you tested the battery with a multimeter on the posts?

Cheers for your reply currently the battery is only reading 4.7v 

21 hours ago, Silversurf said:

I've not had a Lunar, but do you have a three way switch, like many older caravans, which was labelled, Car/Off/Van ?

 

If so, what position is it ?

 

As Ern says, your first test should be at the posts and expect around 12.5 volts, then at the battery terminals, make sure they are clean and tight, you should get the same as at the posts, then test on towards the PSU.

 

A few questions:

 

1)How  did you charge the battery, did the battery show fully charged, did you charge it on the van or out of the van.

 

2) Did the condition meter register OK when you were away on EHU and did all 12v items work OK.

 

3) Do any 12v items work now.

 

4) Can you plug it in to the mains at home, if so does it now read.

 

5) Has any work been done on the van, or did you just park up after getting home and it didn't work.

 

All caravans have a ' battery fuse ' somewhere in the +ve ( red cable ) between the battery post and the PSU, usually 20A  or 25A.

 

Some, rarely, are in the battery box in the red cable, most are inside the van, behind or around the back of the battery box, again in the red cable, then there are those that are hidden away ( under seats or wardrobe, cupboard bottoms ) and finding them means tracing the red cable all the way to the PSU, though they should be pretty near to the battery.

 

If you find it, change it if it has obviously blown, if it looks OK then either check it for continuity with a DVM or put a new one in, sometimes they can be open circuit but look OK and whilst you are at it check the fuse holder for signs of corrosion or overheating.

 

Let us know how you go on, someone on CT with the same or similar van may be along with more info.

 

 

Thanks for your reply, during the holiday and before the battery was charged internally by the caravan itself.

 

Whilst away the condition meter was in the green all of the time.

 

The 12v operated devices don't seem to work and the ones that do such as lights are very dim and barely visible.

 

I've tried charging the battery in the both the central switch and the van switch and still no change on the meter ( I've tried both positions on charge for a few days)

 

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I think the battery has had it at that voltage. 

Graham

Unless otherwise stated all posts are my personal opinion 

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At 4.7V the battery is flat and liable to not hold its charge at all unless restored to 12V plus as quickly as possible and even then it may be too late to save it. 

 

Whilst a battery is being charged the condition meter will show circa 13.8V and a sound, charged battery disconnected from the charger, should show something like 12.8V. It sounds like either the charger has failed or a fuse has blown. 

I've got nothing to do on this hot afternoon

but to settle down and write you a line.

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i believe that Lunar use the BCA power distribution and charging system.

First of all, check the battery voltage at its terminals without mains power connected to the van.

Then ensure the mains is connected and the charger is switched on and check the voltage at the battery terminals again.

 

If the charger is working then that voltage should be at least 13.8, probably 14.8 initially.

If the voltage does not change then the charger is faulty, which is a well known problem with the location of the charger being inside the main power distribution box.

It may just be the kettle plug to the charger has become loose , or the charger has failed internally and needs a replacement, but I would not recommend the same make of charger.

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22 hours ago, Brecon said:

i believe that Lunar use the BCA power distribution and charging system.

First of all, check the battery voltage at its terminals without mains power connected to the van.

Then ensure the mains is connected and the charger is switched on and check the voltage at the battery terminals again.

 

If the charger is working then that voltage should be at least 13.8, probably 14.8 initially.

If the voltage does not change then the charger is faulty, which is a well known problem with the location of the charger being inside the main power distribution box.

It may just be the kettle plug to the charger has become loose , or the charger has failed internally and needs a replacement, but I would not recommend the same make of charger.

 

23 hours ago, Steamdrivenandy said:

At 4.7V the battery is flat and liable to not hold its charge at all unless restored to 12V plus as quickly as possible and even then it may be too late to save it. 

 

Whilst a battery is being charged the condition meter will show circa 13.8V and a sound, charged battery disconnected from the charger, should show something like 12.8V. It sounds like either the charger has failed or a fuse has blown. 

 

23 hours ago, WispMan said:

I think the battery has had it at that voltage. 

Thanks again for your replies, I took apart the distribution box inside the caravan and got direct access to the battery charger. It turns out a fuse had blown inside it. Thanks for all your help.

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23 minutes ago, TaylorElton said:

 

 

Thanks again for your replies, I took apart the distribution box inside the caravan and got direct access to the battery charger. It turns out a fuse had blown inside it. Thanks for all your help.

Upon further inspection the new fuse I fitted has blown again. I replaced the existing fuse with another red 10amp fuse. Would a larger fuse be required?

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You need to look at the physical location of the fuse to get an idea of what it does. If it is a small 20x5mm glass or ceramic fuse and rated maybe rated 2-5A and that has blown then it is likely that the main switching transistor has gone short circuit (as they do when the box overheats) and a new power unit is required.

If the fuse is a blade fuse close to the 12V output connection then I would have expected a fuse rated at more than the power unit capability. If the unit is rated 20-24A (as is common) at 12V then I would have thought the fuse would be 25A or 30A: if yours is 10A unless the power unit is also rated 10A then it has the wrong fuse. The fuse rating in power units (technically known as a switched mode power supply or SMPS) is very often printed on the top of the printed circuit board close to or under the fuse.

 

BEWAREThe mains side of the unit converts the incoming 240Vac mains to d.c. at around 380V which is stored in a couple of capacitors. These capacitors can take anything up to 10-15 minutes or more to fully discharge once mains is removed. If not discharged they may not fully kill you but can give you one hell of a belt and likely a severe burn. Whichever will certainly not do you any good!

 

My advice would be to keep well away from the innards of the unit unless you really know what you are doing and the necessary safety measures to take. I spent 43 years in electronics and I would never even contemplate repairing a SMPS unless I had the full circuit diagram and component layout to hand. Ultimately which is more important, your life or your bank balance?

 

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I agree with Woodentop, forget trying a DIY repair on these units it is too risky, and just putting a bigger fuse in is just asking for trouble.

There must be a reason why the fuse has blown , twice now, so bin it and get something much more suitable for the van. 

 

I se this situation with BCA units far too frequently and have found that replacing the charger with a Sargent PX300 is the better option as it is a smart charger and power supply, and mounted outside the BCA box is well ventilated.

Edited by Brecon
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