Leisure battery discharge rate question

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Leisure battery discharge rate question

Post by CC on Wed Dec 11, 2013 10:28 pm

A few weeks ago I fitted a new Banner leisure / habitation battery in our Nuevo motorhome, but I'm finding it's not lasting that long compared to the previous battery it's replaced and wondering if I've bought a dud.

With the motorhome sitting on the drive with no drain ie nothing switched on how long should I realistically  expect the battery to last without the voltage dropping? 

Last week while away, after about 30 mins of having just the TV on and some lighting it had dropped enough for the CTEK indicator panel to show red and checking the onboard control panel fitted by Autosleepers it was showing something like 11.7v so immediately put it on charge.

Returning home Sunday and leaving the motorhome on the drive, checked this morning and the CTEK indicator panel was flashing red again and the onboard panel confirmed again it was under 12v within 2 days so it's back on charge.

How can I properly check the battery to be certain before contacting the company it was purchased from? They state they will only except returns (bought online) if it is accompanied by an alternator output report, but if it's not holding it's charge from being charged by either the onboard charger or the CTEK charger I don't really see the relevance of this although I could understand its importance if it were a starter battery.

Any tips would be helpful thanks

CC

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Re: Leisure battery discharge rate question

Post by roli on Wed Dec 11, 2013 10:54 pm

It is possible you have an iffy battery, but Banner have a good reputation and I havnt seen any complaints.
Being a leisure battery its not possible to do an alternator charge test and what I would do if I got a low OCV reading over the terminals with a multimeter is get a Load Discharge Test done on it.
Most battery suppliers, accessory shops,Halford etc have one of these testers which are more accurate for this test than a multimeter or voltage meter.
Was it fully charged before you took it out and did you have a hook up?

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Re: Leisure battery discharge rate question

Post by Paulmold on Thu Dec 12, 2013 5:59 am

You haven't left the radio over-ride switch on have you? If in the on position, it still draws power as if the radio was on apparently.

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Re: Leisure battery discharge rate question

Post by ubuntu1 on Thu Dec 12, 2013 8:11 am

Is the charger working?

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Re: Leisure battery discharge rate question

Post by Paulmold on Thu Dec 12, 2013 8:18 am

Paulmold wrote:You haven't left the radio over-ride switch on have you? If in the on position, it still draws power as if the radio was on apparently.

Ignore me - the radio is wired to the engine battery (unless you've had that changed) and won't affect the leisure battery.
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Re: Leisure battery discharge rate question

Post by Peter Brown on Thu Dec 12, 2013 9:40 am

Paulmold wrote:
Paulmold wrote:You haven't left the radio over-ride switch on have you? If in the on position, it still draws power as if the radio was on apparently.

Ignore me - the radio is wired to the engine battery (unless you've had that changed) and won't affect the leisure battery.

If you have a radio switch in the habitation area then the radio is connected to the leisure battery and if that switch is left on , the leisure battery will drain even though the radio is switched off. I suspect Paul had that switch but CC's newer van won't.

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Re: Leisure battery discharge rate question

Post by brodco on Thu Dec 12, 2013 10:05 am

Hi  wave
Paulmold wrote:You haven't left the radio over-ride switch on have you? If in the on position, it still draws power as if the radio was on apparently.
Interesting.  Any idea why? It sounds like a bit of duff design to me. shrugg 

Anyway, I’d test the battery off the van to eliminate any problem with the van’s electrical system.  You could take it to a garage and get them use a battery tester on it. They are quite good but from experience I can say that they are not 100% reliable. OK if the battery fails but I have seen one pass a duff battery.

Personally I prefer a functional test to prove is the battery is (or is not) up to spec.
Charge it up from a mains charger, measure the terminal voltage and make sure that it reads around 13.5 to 13.8V when the charger is still connected. If you have a smart charger such as the CTEK the voltage will go above this but you’ll  need to wait until it comes back down again.
Disconnect the charger and connect a known load. I’m a fan of headlight bulbs for this but anything that draws a few amps will do. Preferably measure the current as well.

Check the terminal voltage regularly and see how long it takes to discharge to say 10.5 to 11V. You then have a rough estimate of the capacity in AH for whatever current your load was drawing.

Battery capacities are usually quoted at a 20A discharge rate so you should get longer at anything less than 20A.  Armed with those figures (assuming they prove the battery is faulty) it’s hard you see how the suppler could argue.

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Re: Leisure battery discharge rate question

Post by Jaytee on Thu Dec 12, 2013 10:08 am

As Brod says and I have found that it takes a good 48 hrs on hook up to 'really' fully charge the battery after it has got really low. When fully charged the off charger no load voltage should stay around 12.7 with a new battery for quite a while then drop to about 12.5.
Your on board charger should take the voltage up to approx 14.3 and then drop back to a maintenance charge. If it is not making at least 14.2 then the battery is not getting fully charged.

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Re: Leisure battery discharge rate question

Post by Peter Brown on Thu Dec 12, 2013 10:21 am

With respect to checking the battery:

The only way to do this is to charge the battery and then disconnect it. Leave it to stand for an hour then measure the voltage, it should be 12.6v. Leave it stand another hour and it should be the same.

The voltage when the battery is fully discharged will be 11.7v open circuit or 10.5v when on load.

Connect 3 21w 12v bulbs in parallel. When connected to the battery they will draw about 5 amps.

Connect the bulbs to the battery and measure the voltage. Subtract 10.5 from that reading and the result is the voltage drop from fully charged to fully discharged.

If your battery is 100AH, the 5 amp load will take 20 hrs to discharge it. after 5 hrs you should read a voltage that is 10.5 plus 75% of the voltage drop. After 10 hrs you should read a voltage of 10.5 plus 50% of the voltage drop, etc.

You should really be relating these readings to the specific gravity of the electrolyte and the temperature so they are only a guide. If the trend is something like my description then your battery is probably ok.

The voltage monitor in your van psu is designed to monitor voltage on load and I suspect the CTEK monitor you have added is designed to do the same. Neither expects the other to be connected so their is a slight possibility they are confusing each other. I suggest you disconnect the CTEK monitor until your are happy with your battery and sure there is nothing else draining current.

I have recently come across some interesting and inexpensive devices designed to measure DC current to high levels in model aeroplanes and helicopters. See example below that measure up to 100A. I have not had an excuse to buy one yet but one of them would be perfect for independently checking current output from a leisure battery.

Hope this helps.

Peter


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Re: Leisure battery discharge rate question

Post by CC on Thu Dec 12, 2013 10:37 am

Thanks for all the replies everyone, the battery has been fully charged using both the onboard charger and the CTEK charger. Not together though as i always switch off the onboard charger on the PDU before connecting the CTEK 

As pointed out the battery only seems to be going a couple of days before the red light on my indicator panel flash red indicating the battery is low and needs charging at first I thought it was the panel being over sensitive but the low readings are confirmed by the onboard control panel too.

There is nothing switched on in the van and the control panel is showing no drain, and our previous battery which we replaced went 3 or 4 days when away in France watching TV, lights on, water pump, awning light etc no problems so bit shocked the Banner battery is only going a couple of days without actually being used or any load coming off it.

Will check it when I go out to the van in a short while and check the readings and report back, most of the technical responses have gone straight over my head & I'm a bit overwhelmed as I'm not great at troubleshooting these kind of things, in my mind a battery either works or it doesn't so your help is appreciated...

Thanks

CC

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Re: Leisure battery discharge rate question

Post by mikethebike on Thu Dec 12, 2013 1:53 pm

Keeping this simple  as you want. You have a duff battery,tell Banner you want a replacement.
If you still have the fault after fitting, i do not expect you will , offer to pay them for the new battery.

Or if you have time, swap battery for known good one, maybe your engine one, to see what happens.

best regards

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Re: Leisure battery discharge rate question

Post by brodco on Thu Dec 12, 2013 10:42 pm

hI  wave

brodco wrote:Battery capacities are usually quoted at a 20A discharge rate
Firstly can I retract that statement because modern deep discharge batteries are quoted using a 20Hr rate rather than a 20A rate.
mikethebike wrote:Or if you have time, swap battery for known good one, maybe your engine one, to see what happens.
Good idea!  I’ll go along with that. Assuming the engine battery is OK I suppose the next step depends on what the battery supplier says. If they agree to replace the faulty battery fine, if not it will probably be necessary to supply more evidence that they have supplied a faulty battery.

It may be worth popping in to a local halfords to see if they would test the battery for a small fee.

Peter Brown wrote:Connect 3 21w 12v bulbs in parallel.  When connected to the battery they will draw about 5 amps.
Or 1 standard H4 60W headlight bulb (saves a bit of messing around).
Peter Brown wrote:With respect to checking the battery:
The only way to do this is to charge the battery and then disconnect it.   Leave it to stand for an hour then measure the voltage, it should be 12.6v.  Leave it stand another hour and it should be the same.
The voltage when the battery is fully discharged will be 11.7v open circuit or 10.5v when on load.
Connect the bulbs to the battery and measure the voltage.  Subtract 10.5 from that reading and the result is the voltage drop from fully charged to fully discharged.
If your battery is 100AH, the 5 amp load will take 20 hrs to discharge it.  after 5 hrs you should read a voltage that is 10.5 plus 75% of the voltage drop.  After 10 hrs you should read a voltage of 10.5 plus 50% of the voltage drop, etc.
I have to say I think that’s over complicating things a bit.

My justification for that statement is:

It’s not necessary to fully characterize the battery as you would if you were asked for a full report on its condition.  It’s only necessary to show that it doesn’t meet its specification. By measuring the voltage against time during the discharge you’re measuring the discharge curve and you wouldn’t need that to claim that a battery was faulty. Off course you would need to keep an eye on the voltage to make sure it doesn't fall below 10.5V.

The battery specification will quote something like:

20Hr  to 10.5V at 5A

If the battery hits 10.5V in well under 20 hours it isn’t up to spec. If it's very close to spec you may need a more comprehensive test but then again if it was very close to spec there probably wouldn't be a problem. From CC’s description the battery capacity is well down so the problem shouldn’t be hard to detect.

No need (in my view) to wait an hour before starting the test. The terminal voltage /discharge curve will be nonlinear, particularly at the start end of the cycle. The initial voltage drop will be rapid, so whether the start voltage is 12.6V or 13.5V will have little effect in terms of a test that should last for up to 20 hours.

As I understand it CC is using a CTEK charger which will analyse the voltage drop after the charge cycle has finished before going into maintenance mode.  Modern CTEK chargers really are remarkably good.

In any case I wouldn’t worry about testing for self-discharge unless the 5A  discharge test showed no problem.


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Re: Leisure battery discharge rate question

Post by Dutto on Thu Dec 12, 2013 11:20 pm

Hi there CC,

I suggest that you have a quick read of this:

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It will provide excellent ammo if you get into an "I want a replacement battery." argument.

Hope this helps. allthumbz 

Best regards,
 drinksallround

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Re: Leisure battery discharge rate question

Post by CC on Fri Dec 20, 2013 12:49 pm

Just an update on my battery situation... Thanks for everyone who replied and some useful information. I took the motorhome to our local ATS at Holt in Norfolk (very helpful & friendly if ever in the area) told them of my problems and they did a drop test on the battery and said its fine, the guy pointed out that contact with the earth terminal caused a slight spark and this could indicate a short? 

I explained to him that I had fitted the CTEK comfort indicator panel shortly after fitting the battery, his advise was to disconnect it and see how it goes... So disconnected from the battery and gave battery a full charge overnight with the standard CTEK croc connectors so I new for certain battery was fully charged. Reading was 15.3v on the control panel when the CTEK charger had reached stage 6 (recondition) then reduced to 13.3v at stage 7 (float charge) after a few hours it settled at around 12.7v

The van has been standing on the driveway since last Saturday and this morning I've just been out to check and the control panel is reading 12.3v so it's dropped a bit but this is more in line with our previous battery, so with this in mind it looks 'ironically' that the CTEK indicator panel I fitted is / was the cause of the drain? 

When fitting the panel the diagram showed the positive and negative wires going directly to the battery terminals, but reading through some bumph it advised you to only fit the positive wire to the battery and the negative wire to an earth point on the vehicle, does anyone have any thoughts on this please? It would be a bit of a bummer if I've fitted the CTEK panel for nothing, so would like to retain it providing it works as intended.

CC

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Re: Leisure battery discharge rate question

Post by Peter Brown on Fri Dec 20, 2013 1:13 pm

The simplest way is to put a 'push to connect' switch in one of the wires from the indicator to the battery and install it next to the indicator.

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Re: Leisure battery discharge rate question

Post by Backtrax on Fri Dec 20, 2013 3:53 pm

Must confess I dont see the difference between the negative terminal being connected to the negative side of the battery or to the vehicle chassis.
Unless your Leisure battery and its charging device is free floating from the vehicle battery then there should be virtuallu zero resistance between the Leisure battery negative and the vehicle chassis.
Indeed if there is an appreciable resistance then you have other problems and need to sort out why.

You mentioned a slight spark when contacting something with the earth terminal.
The root cause of that is something I would explore.
Could be just a high current surge if you are conecting a 12v source to a flat battery for example, but check that out first.

It could be that your CTEK panel is faulty as you say.

Peter's suggestion of an in-line momentary switch is a good solution to treat the symptom but does not solve the cause.
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Re: Leisure battery discharge rate question

Post by mikethebike on Fri Dec 20, 2013 4:24 pm

Going back to CC original question.
I have just done a 7 week check on my leisure battery. disconnected  its 12.71v.
I have left my car with alarm etc on for 7 weeks and still over 12 v
I often leave batteries for 6 months disconnected and have no problems.
A good battery will be ok .

regards
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Re: Leisure battery discharge rate question

Post by CC on Tue Jan 28, 2014 4:40 pm

Sorry I've not come back to thank you all for your replies... I've left the battery to check it before coming back for further advise. I've left the CTEK comfort control panel disconnected which is rather annoying after buying it but the battery seems to hold it's charge as before. I intend to contact CTEK to get their advise as to the comfort panel draining the battery as I don't understand why it should do that.

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Re: Leisure battery discharge rate question

Post by ourwanderer on Tue Jan 20, 2015 4:39 pm

Hi CC, I have connected my CTEK as permanent fitting, like you have found my battery will only last 12 hours, without using any 12 volt fittings. Could this be my problem also. Perhaps the CTEK is only supposed to be a attached to the battery when a charge is required.
I must get my meter out and check the current in no charge/standby mode!
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Re: Leisure battery discharge rate question

Post by ourwanderer on Tue Jan 20, 2015 4:48 pm

Hi Peter,
With respect to checking the battery:
Brilliant instruction regarding checking the leisure battery.
Will purchase one of those checkers, so cheap for the multifunction properties.
Advice please, would the device be placed in series, or across the battery.
Brian
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