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Battery discharge


dawki

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Hi all

I was looking for some battery info if poss

Could somebody please tell me how long it should take fully charged leisure batteries to discharge

I have two nearly new 100ah batteries

If I have the van at home and fully charged by Hook up and then disconnect it roughly how long should it take to go from 12.6v to say 11.9v

My control panel normally says -0.1 or 0 when not on hook up

Many thanks

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Fully charged, your batteries should be around the 12.8 volt mark. At 12.2 volt they will be approximately 50% discharged. It's not advisable to let them go below 50%. Some people recommend they should not be allowed to fall below 12.4 volts.

 

When my van is layed-up, I normally charge the batteries up every 2 to 3 weeks.

 

My control panel shows me the voltage of the leisure batteries at all times (with the panel switched on), so when they get a bit low I give them a boost for 24 to 48 hours.

 

If your control panel doesn't display the voltage (when not being charged) you'll need to check them with a multimeter.

 

It's a good idea to check with a multimeter anyway because the control panel readout can be a bit inaccurate.

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Bit of a 'How long is a piece of string'

 

It will depend on make, model, type, temperature stored and a few more. ;-)

 

For an answer look up your particular battery specifications.

 

or

 

Simply check with an accurate multi-meter once a week and do not let them go below 12.2v with nothing connected, ie. charging or discharging.

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Note that 12.6v can be a fairly highly discharged battery, as much as 40% in the case of VRLA and some sealed batteries, etc. So when you say 'fully charged' it doesn't seem like yours are?

Also letting them drop as low as 11.9v could have a major impact on the batteries life.

 

 

The fact that your Control display is showing almost zero volts when off EHU, but presumably displays the correct voltage when connected to EHU?, suggests that maybe your Habitation batteries might not be 'in circuit' through some fault?

 

I assume you are asking because they run down more quickly than expected?

 

If you supply more info about the set-up you might get some help from the Forum as different vehicles may have different devices permanently connected and taking power like a Frost protection valve, Radio standby draw, etc?

Unless of course you mean the batteries are isolated by removing the battery Clamps once taken off EHU?

 

 

 

 

 

 

1757950748_BatterystateofChargeChart.jpg.3948943a8191c62a67d8c04e5ea97eb4.jpg

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Hi many thanks for your replies

 

some further info as suggested by aandcaravan

 

The batteries are conventional wet batteries and i have the sergant EC325 charger on a 2007 Auto trail

yes the control panel does change from a -0.1 draw to a 15.3 amp current when re- conected to EHU

 

and yes your right i am concerned that they run flat very quick

 

i disconected EHU last weekend after being on charge for at least 5 days and by yesterday the control panel display was down to 11.9v

 

i never leave it much more than a week without EHU and sometime i just leave on EHU for 2 or 3 weeks if not being used

many thanks for your interest

 

 

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Hi, Just back from holidays so brain is not up to speed yet, not that it ever is these days. Anyway, I suggest you fully charge the batteries and then disconnect them for a week and then see how much the voltage has dropped. If the 12.6 volts after charging is a clue to the batteries failing and having a high self discharge.rate. You may find a large drop in volts just after a day or two.
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dawki - 2016-08-14 10:15 AM

 

Hi many thanks for your replies

 

some further info as suggested by aandcaravan

 

The batteries are conventional wet batteries and i have the sergant EC325 charger on a 2007 Auto trail

yes the control panel does change from a -0.1 draw to a 15.3 amp current when re- conected to EHU

 

and yes your right i am concerned that they run flat very quick

 

i disconnected EHU last weekend after being on charge for at least 5 days and by yesterday the control panel display was down to 11.9v

 

i never leave it much more than a week without EHU and sometime i just leave on EHU for 2 or 3 weeks if not being used

many thanks for your interest

 

 

If nothing was left ON, discharging the battery, then it is knackered (technical term).

 

That 0.1amp draw, is not helping 0.1*24*7 =16.8 amp.hrs.

 

Assuming 100 amp.hr (20hr rate) battery that is 16.8% of the battery capacity but your battery is old and used so probably not now a 100amp.hr capacity, lets say it is now capable of 50% of its original.

 

That makes 16.8% amp.hrs now 33.6% of it capacity (50 amp.hrs)

 

A fully charged battery should last weeks not days, without a very large drop in voltage/charge with nothing connected.

 

There are lot of factors involved temperature for one but 'self-discharge' is typically 2 to 4% per month

 

Higher the temperature, higher the 'self-discharge'.

 

For a fully charge lead acid battery (at rest and surface charge dissipated) I would expect the voltage to be about 12.6v, a month later I would expect it to be roughly the same possibly down 0.2v

 

So from fully charged to 11.9v in a week implies that, that 0.1amp load is nearer 60% of your available capacity that makes 100 amp.hr battery a 40 amp.hr battery this assumes the load was left connected if no load connected then the battery is an even worse state.

 

In my opinion, time to buy a new battery and check that the charging system is working correctly and the battery is always fully charged when it is left for a period of time and if possible all loads disconnected.

 

I await aandn's thoughts.

 

 

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Dawki, you started the post with, "I have two nearly new 100ah batteries", but the last item talks about 2 year old Banner batteries, are these a different set?

 

If the Banner batteries are the ones that you are talking about, then you will most likely find they are shot as, in our experience, two years is well into their twilight years. We agree with KeithM but suggest you do Brambles test first?

 

If you open the tops, you are likely to find they will be bone dry of any Acid? In which case you can save yourself the trouble of any testing.

 

When you remove the Tops from the batteries there is the potential for an amount of dangerous Hydrogen and Oxygen to be released, especially if they have recently been on charge? Suggest you look at the Battery Explosions and Topping Up guide at the bottom of this page : http://www.aandncaravanservices.co.uk/battery-technology.php for advice on how to stay safe?

 

Back in the seventies, when I was on my first Car, everyone checked battery fluid levels once a month so the dangers were known by all, but with so many batteries now being Maintenance free that every day knowledge seems to have gone?

 

 

 

 

 

 

 

 

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Hi and sorry yes I am talking of the banner batteries I thought they was about a year old but they are nearly two years old

I will disconct and inspect tomorrow

I have topped them up every 6 months most recently about two months ago

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Hi all just a quick update

Charged the batteries up on the van and then disconnected EHU Monday evening

After a couple of hours the control showed12.8

I then removed them from the van the battery fluid level was fine

I also checked the batteries with multi meter and that displayed 13v for both batteries

The batteries are still off the van and I just checked again

Now showing 12.97v

I was going to leave them off the van for a few days and keep an eye on them before I go ordering any new ones?

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So now they are 'charged' but at what capacity?

 

Will they be able to run a load, for any period of time without failing.

 

If they are not completely knackered (that technical term again) they may well maintain that voltage for a few days but as above fail as soon as load is connected.

 

As before if they drop to 11.9v in a few days they are completely dead.

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Hi all and thanks for your input

Just to update

Batteries left off the van for about a week

I checked them on Saturday and both saying 12.8

I put one back on the van and left one off the van but decided to order new batteries

I have just fitted new batteries to the van

The old battery on the van was down to 12.1v in three days even thou there was nothing on in the van using power

The one that's off the van was still reading 12.7v

Does this sound right or could there be a problem with the van?

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dawki - 2016-08-23 6:45 PM

 

The old battery on the van was down to 12.1v in three days even thou there was nothing on in the van using power

The one that's off the van was still reading 12.7v

Does this sound right or could there be a problem with the van?

 

Yes!

 

You have a load on the battery even though you think everything is turned off.

 

You need to find this load before flattening your new batteries.

 

Keith.

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A quality battery like the Varta LFD90 will hold close on 13.0v for 4 months if isolated from the vehicle.

 

That yours have dropped to 12.7 in a few days suggests they should be sent for recycling?

 

It does sound like you also have a load on the battery, like when the control panel is left on?

 

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The fact that your connected leisure battery has lost voltage compared to the one not installed indicates there is some draw from the leisure battery.

 

My van has circuits which are always live, even with the 12v switched off at the control panel, ie. electric step, fridge control panel (when set to gas or 240v) and one circuit which gives minimal illumination when entering the MH.

 

Suggest you set your multimeter to DC amps mode and withdraw the fuses (one by one) in your 12v distribution box and see if any register a current draw.

 

My system always seem to register a small current draw from the fridge control panel even though I have the fridge switched to OFF at the energy selection switch ie. off/gas/240v/12v.

 

Probably the workaround in this situation is to remove the fridge fuse when the vehicle is not being used.

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Hi and thanks for your replies I have in fact just fitted a pair of those vatra batteries after reading your previous post

The van is EHU now and was going to leave it on over night and the un plug in the morning

Could you give me guidance where might be the the first place to look for any load that is on the battery?

Thanks again

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Dawki, Robbos advice is a good way to start.

 

In a standard installation, turning off the Control Panel will normally isolate most 'users' of power, aside from those listed above that need to stay on. Even with these 'essentials' active, a Habitation battery normally remains charged for several weeks

 

We normally find problems arise when something is changed, like a Car based Stereo used to replace the low power Motorhome one or an Inverter wired in (usually needs to be manually switched off at the Inverter as some draw quite a bit on standby, even when not being used), the installation of a different Television that has a standby power draw, etc

 

So if it has been ok in the past, maybe look more closely at something that has changed from standard?

I am sure you have probably already investigated these, but I have included these as it might be useful to other readers of the Post?

 

You might also consider isolating the batteries using something like in the photo, they are only a few pounds on eBay.

 

1995178839_BatteryClamp3.JPG.b8c31a42a71c43684dd6657bcec527be.JPG

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When I was a newbie, I often forgot to turn the power off to the fridge after a trip. The door was left ajar to stop the interior going musty. It was not until I went in one dark night that I realised the fridge light was still on.
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