Leisure batteries [voltage] dangerously low (1 Viewer)

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Dec 23, 2014
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It has done it again.

Autotrail 740SE with EC325 PSU, two 110 amp batteries and 100w SP. When not in use the vehicle sits on the drive with EHU connected but PSU charging switched off. Sargent control unit switched off also, i.e. in theory nothing using 12v. The batteries are normally easily kept up by the SP.

Went to the van this a.m. to do a small job. Outside air temperature about 3 deg C. Activated the 12v with the intention of firing up the heating but was met with the unit flashing the message leisure battery voltage dangerously low”. According to the Sargent book this message only appears if the leisure battery(s) gets to 6v or below. Vehicle battery okay and showing 12.4v. Fired up the PSU charger and the batteries seem to be taking a charge.

This is the second time this has happened and I cannot find a reason; so over to the brains of the motorhoming world. Any suggestions?
 
Feb 9, 2008
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Hi, I too have an Autotrail with the Sargent intelligent system and hooked up on the driveway and like you 2 x 110 amp Bat. and a Solar Panel. I suggest you do as I do and switch your PSU on so the intelligent charger can do the job it's designed to do. It will monitor both your leisure and cab batteries and keep them topped up (Solar panel will function but charge will not reach batteries for obvious reasons). I suspect you battery has run low because there has been a steady drain on it from one of your appliances and the Solar Panel might have been switched to keep the Cab battery charged and as a result no charge going to Leisure batteries. (Not sure what regulator you have fitted ! On mine I have an intelligent regulator that will divert power to lowest batters set reading). Leaving your Motorhome on permanent hook up with the PSU switched on will not cause any harm to your appliances or batteries. Just make sure your appliances are switched off and the Sargent will do the rest. Pop in every few days and check your battery readouts for peace of mind if you need to.
 

magicsurfbus

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Oct 11, 2010
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i.e. in theory nothing using 12v.

You're assuming everything 12v goes through the control panel. In my (CI) MH the blown air heater fan is completely independent of the control panel. I left it on once and it drained the leisure battery, which is why I fitted an isolator switch for the habitation area circuit when it's in storage.
 
OP
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Dec 23, 2014
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A lot of good points Phillippfit thank you, but a couple of things I do not understand.

Both house batteries are a good quality pair and less than a year old.

As far as I am aware when only the SP is being used to maintain the batteries the controller maintains both the house and vehicle batteries without human intervention. I also understand that when the EHU is connected and the charger is on, the default is to the house batteries; to charge the vehicle battery I have to manually switch it over. I also suspect that the battery has run low because there has been a steady drain on it but from where is a mystery. My heater fan will not run unless the 12v is switched on at the control panel and this has been switched off. I agree about keeping it on mains but it should also be okay without otherwise it will be useless when wild camping. I had a similar hiccup some months ago and it went away without me finding the problem. Any other thought will be much appreciated.
 

Wickolad

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Sep 10, 2013
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I have experienced similar situations with my Autotrail and discovered that the cab radio which is linked into the media system of the motorhome appears to remain in a live state even when turned off. This is evident as the power light remains illuminated red. Apparently the cab radio is powered from the habitation batteries in some Autotrails but not all. I started removing the pop off front display panel off the radio/ CD /DVD player as a precaution. It may be worth you checking if there is current draw on your radio media system even when power is off. Its just a thought, i wouldn't want to be pointing you in the wrong direction but if it sorts things, it will be worth the 5 minutes it takes to remove the fuse and put your meter across. :)

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Jul 5, 2013
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Activated the 12v with the intention of firing up the heating but was met with the unit flashing the message “leisure battery voltage dangerously low”. According to the Sargent book this message only appears if the leisure battery(s) gets to 6v or below.
Are you sure it says that?????? Long before the battery gets to that voltage level it will be completely knackered and will never re-charge again.
 
OP
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Dec 23, 2014
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100% Peterc10. The EC325 book is on line on the Sargent website.

2009 Philippft.

I'm charging the batteries for about 24 hours then I will check each separately whilst on the van and see if I can find what is causing the drain.
 

dave newell

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Oct 31, 2008
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Are you sure it says that?????? Long before the battery gets to that voltage level it will be completely knackered and will never re-charge again.

This is not strictly true, I have a van in at the moment being converted and when it was delivered the engine battery read 0.8 volts (zero point eight). I expected it to be knackered but recharged it on a recondition cycle with my CTEK 25 Amp charger and so far it has held charge since late August and only needed recharging once since. It has happily sat for up to two weeks without turning the engine over but will then start it when you need it to.

D.

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Feb 9, 2008
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OK Thanks for that. Mine is the 2011 model and fitted with the EC500. The P.S.U. came with the Solar Panel regulator already fitted as standard, All I needed to do was buy the connecting cables from Sargent and drill one hole in the roof, make the connections and job done. With my set up both the S.P. regulator and Intelligent battery charger monitor battery condition and switch the charging supply to which ever battery needs it. When a 240 volt supply is hooked up the S.P. regulator still monitors battery condition but stops the charge going beyond this point. (You can see the Ampere reading from the S.P. regulator flickering on the display and this is a pulse signal send to the batteries from the regulator to check the charge state. (as confirmed to me in conversation with Sargent)). I suspect on your version you may have to manually select the set of batteries being charged and if this is the case it will go part way to explain why one set has been discharged. I do not think you have a significant problem here. I think it's a straight forward case of one or more appliances taking a small charge from the battery, It's just a case of establishing where this drain on the leisure batteries is when everything appears to be switched off. One way to establish if anything is taking power out of your leisure batteries is to start pulling fuses whilst measuring out put from your batteries. This should point you in the right direction. In the meantime keep your MH on hook up with the pSU switched on so your batteries are kept topped up, when on the drive way.
I suggest you check your battery condition once there fully charged, just because they read full when on charge does not indicate they are OK. You need to discharge them a little and see how well they recover after the load is taken off (without hook up being connected).
Please find attached a document on Leisure batteries you may find useful. At the bottom of the page there is a further link to another document which should be of value.
Broken Link Removed
 
Jul 5, 2013
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This is not strictly true, I have a van in at the moment being converted and when it was delivered the engine battery read 0.8 volts (zero point eight). I expected it to be knackered but recharged it on a recondition cycle with my CTEK 25 Amp charger and so far it has held charge since late August and only needed recharging once since. It has happily sat for up to two weeks without turning the engine over but will then start it when you need it to.

D.
Dave, I am not an expert but I have read regularly on this forum that I should not allow my batteries to drop below 50% capacity, which is well above 6V as I understand it. Is that information not correct or do you think you were lucky in managing to rescue that battery? I am surprised that the Sargeant unit regularly allows the batteries to drop as low as 6V before any warning comes up. My Schaudt unit for example switches everything except the frost protection valve off when the batteries drop to 10.5V, which, they say, shows that the batteries are "totally discharged"
 
Apr 29, 2012
312
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Holmfirth
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20,777
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1990 Gulfstream RV
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30yrs
your leisure batteries are classed as discharged when they get below 12.4v. They will survive getting lower for a few occasions though. Many appliances will not work on less than 12v, especially some LED TVs. Your engine battery will also have its life shortened by keep getting low, but may still start your engine at just over 12v. All the batteries should be showing 12.8 to be healthy.
 
Feb 9, 2008
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Dave, I am not an expert but I have read regularly on this forum that I should not allow my batteries to drop below 50% capacity, which is well above 6V as I understand it. Is that information not correct or do you think you were lucky in managing to rescue that battery? I am surprised that the Sargeant unit regularly allows the batteries to drop as low as 6V before any warning comes up. My Schaudt unit for example switches everything except the frost protection valve off when the batteries drop to 10.5V, which, they say, shows that the batteries are "totally discharged"
You are correct ! (trust you are OK with me replying to a question directed at you Dave!). If you read the technical paper linked in my post your theory will be confirmed. (Actually, I've read don't let them go below 80%). I suspect any battery that is allowed to fully discharge and then be fully re charged will not have as much life left compared to a leisure battery that has never been allowed to discharge more than 80/50%. My reasoning is that Leisure battery life is determined by the number of Cycles they can perform. (the higher the number of cycles the better the battery) Whilst the above battery may appear to be fully recovered I suspect (though have no proof or knowledge otherwise) that the number of remaining cycles will be adversely affected.
 
Feb 9, 2008
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your leisure batteries are classed as discharged when they get below 12.4v.
I thought I would quantify your quote. At 12.4 V a battery is 50% discharged.
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Jul 5, 2013
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I thought I would quantify your quote. At 12.4 V a battery is 50% discharged.
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My Schaudt instructions for the display give slightly different figures. More than 12.8V = full, 12.5V = 75%, 12.3V = 50%, 12.2V = 25%, 12.0V = 0%, and less than 10.5V = totally discharged. Cleverer people than I can attempt to explain the difference between "0%" and "totally discharged". Mind you they say those figures apply to a lead gel battery.
 
OP
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Dec 23, 2014
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Hello all,

Thanks for all you suggestion and info. Here is an update so any further suggestions will be welcome.

Charged overnight the batteries were back to full strength this morning (0830) and with the sun out, although not really up, the control panel was still showing around 13.5v about 30 minutes after the charger was switched off; some of which would have been due to the SP. Left them off charge for the day and have just checked again this p.m. Both batteries metered individually are still showing 13.4v to 13.6v with the assistance of the SP. I have also pulled every fuse and metered draw amperage on each circuit with all the switches off. Every circuit showed zero except the 5a permanent connection circuit which showed a 0.002 amp draw; hardly enough to drag down two 110amp batteries that are being topped off by the SP each day. I will keep looking but for the moment it is still a mystery.
 
Feb 9, 2008
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Just to make sure !!! You are aware of course if the batteries are still receiving a charge you will be reading the amount of voltage going in ! To measure the battery true state disconnect power and wait for battery to settle before measuring condition.
I agree with you about the draw, I have this too on mine and it's the alarm system. The SP should compensate for this, so I too am at a bit of a loss as to why your Leisure batteries are flat.
 
Feb 9, 2008
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As an after thought ! I would be a little surprised if 2 flat 110 AH batteries were fully charged overnight. Do you know what the output is from your charger. ?
 
OP
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Dec 23, 2014
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In fact they were on for about 15-16 hours and are on again tonight. In fact they can now stay connect unless I have aspecific reason to switch off.
 

dave newell

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Dave, I am not an expert but I have read regularly on this forum that I should not allow my batteries to drop below 50% capacity, which is well above 6V as I understand it. Is that information not correct or do you think you were lucky in managing to rescue that battery? I am surprised that the Sargeant unit regularly allows the batteries to drop as low as 6V before any warning comes up. My Schaudt unit for example switches everything except the frost protection valve off when the batteries drop to 10.5V, which, they say, shows that the batteries are "totally discharged"

I don't claim to be an expert either but I have worked with 12 volt lead acid batteries and their charging for over 30 years so I claim experience which is what I base my comments on. I was taught (rightly or wrongly) that fully charged voltage would be 12.8-12.9 (13.8 is float charging voltage). totally discharged is 10.00 and 11.9-12.1 is 50% aproximately. To discharge a standard lead acid battery below 50% occasionally will PROBABLY cause minor damage and reduce its capacity, to discharge to 10.00 volts will DEFINITELY cause some damage and reduce its capacity. Not fully recharging the battery from either condition at the earliest opportunity will CERTAINLY aggravate any damage already caused.

I was also taught that voltage reading alone is about the most inaccurate way to establish a battery's state of charge, other than dipping a finger into the electrolyte and tasting it!

My point was simply that assuming a battery to be fubar simply because it has been excessivley discharged once or even twice is a good way to dispose of workable batteries.

I too am surprised thr Sargent unit will allow the batteries to go so low but I'm equally surprised that the OP leaves the van on EHU at home but with the charger switched off, that makes no sense to me what so ever.

D.
 
Aug 30, 2012
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It's the luck of the draw some you win and some you don't
We have left plant for months with flat batterys and got away with it and sometimes we don't
I do think with fresher newer batterys your more likely to get away with it rather than old ones
 

Don Quixote

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Not long enough, but a little common sense helps..........
Hi Philippft,

Up to 25 amp.

Not possible that a 25amp charger will FULLY 100% charge 2 x 110 amp batteries. 220 amp divided by 25 is 8.8 hours at 25 amps per hour without dropping 25amps and at 14.4 volts ish. Most "on board" chargers will start of at 25 amps for maybe 1 hour then drop down to 2,3,5 amps per hour as does the voltage from starting at 14.4 to 13.0 or less. Therefore 3 amps ish per hour - in reality 74 hours of charging without drawing power from batteries before your 2x 110 amp batteries are fully charged. All that is happening really is your batteries are being "topped up" a little.

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Glandwr

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I like Dave Newall managed to revive a starter battery that barely had a positive voltage with a CTEC intelligent charger. Reason it was flat was another story.

Beware! It performed as normal for 3 months easily going up to max charge and holding it for weeks at a time. Van always starts first crank. Then in an Auchan car park in France it totally collapsed! Wouldn't even light a warning light on the dashboard. No warning at all. Now it might have been a coincidence, but I believe that the total discharge was ultimately to blame.

Dick
 
OP
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I too am surprised thr Sargent unit will allow the batteries to go so low but I'm equally surprised that the OP leaves the van on EHU at home but with the charger switched off, that makes no sense to me what so ever.

D.

A certain, possible faulty, logic here. About 6-8 weeks ago we went camping. The van was off EHU for about seven days being used normally and relying on the SP for charge as it had done whilst parked up for a month or more prior to the trip. When we got home I wanted to vac inside so plugged in the EHU but did not switch on the charger. I was in and out of the MH quite frequently and at each visit I checked the batteries and until I found the problem they had been fine. Why the sudden change I do not know. However, I am now not certain that we can camp off EHU as we have previously.

I have wondered if the fact that the EHU is connected affects how the batteries are charged by the SP. Any thoughts?
 

dave newell

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Being plugged into EHU will not affect solar panel charging unless the mains charger is switched on in which case the solar reg will "see" the higher battery voltage as being fully charged and will shut down the solar supply to the batteries. At this time of year in the UK solar is of little use other than maintaining batteries when in storage, there simply is not enough sunlight falling onto the panel to produce any meaningful charge. To my mind it makes no sense whatsoever to have a perfectly good and functioning mains charging system, keep the van on EHU but leave the charger switched off.

D.
 
Apr 18, 2009
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As Dave says at this time of the year (and unless you have a very very good expensive solar regulator, even in the summer) your Solar panels will NOT FULLY charge your Batterys, you need to put your van on EU (with the charger on:xdoh:) for a few days now and again to give them a boost and again if you are going on a trip. I am NOT an expert but this much I have gleaned on Fun:xThumb: it may be your charger needs checking:xdoh:

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