Understanding Leisure Battery

[zaria123]

Sorry if this has (im sure it has), been covered before but I can't ever get the search facility to work for topics older than 'since last log-in'. Sorry also if this is long winded, and from a novice trying to learn as quickly as possible (Patience please :-)

 

Being new to this motorhome technology, this is simply to provide an understanding of what we are expecting to see on the control panel.

 

The question stems from our Gas Heating red light flashing intermittantly. Which we assume is a drop in leisure battery power as the system works 100% fine when on mains hook-up.

 

Our control panel is a fairly simple affair with an LED readout and a range of selection buttons e.g. Battery Voltage, Current, Internal Temp, External Temp etc.

 

Assuming all components are working efficiently:

 

1-What should the leisure battery voltage show to ensure all appliances operate properly (Or whats the minimum to keep the likes of the gas heating running).

 

2-How long would it take driving the vehicle to recharge the leisure battery fully?

 

3-Once the leisure battery is fully charged what is the expected (roughly) average lifespan of the charge if using Trumatic Gas Blow Heating (i.e. is this system hard on power)?

 

4-The Motorhome has a built in battery charger when connected to the main. How long would this system take to fully recharge the battery?

 

I appreciate these questions are all subject to a lot of other factors, but Im just looking for an average rule of thumb.

 

We have a new 110 deep charge battery fitted.

 

Thanks in advance

Alan

[spospe]

Alan

 

Roughly

 

1) Over 12.4 volts

 

2) It never will fully charge from the engine.

 

3) I don't know for sure, because I don't know what other 12-volt apparatus you are running. The heater on its own should run for over two days continuously.

 

4) The built-in battery charger, probably is not a battery charger at all, it will most likely be the 12 volt power unit and it will never fully charge the battery as it will be voltage limited to about 13.6 volts and you need 14.7 to fully charge a lead-acid battery.

 

I suggest reading Trackers current posting on a similar subject at:

 

http://www.outandaboutlive.co.uk/forums/forums/thread-view.asp?tid=18597&posts=55

 

[Brambles]

1-What should the leisure battery voltage show to ensure all appliances operate properly (Or whats the minimum to keep the likes of the gas heating running).

 

12.4 volts is the voltage a battery starts to sulphate and is equivalent to about 25% of capacity used.

A battery discharged about 50% will have a voltage of 12 to 12.2 volts. This is really the lowest you should discharge a battery. (hese are no load voltages)

But to answer the question equipment should work down to 11.5 volts or even less and I would still expect to work down to 10.8 volts.

 

Some heaters have seperate mains input and therfore it is possible the 12 volt connection is broken hence why ot does not work on battery and only hookup. What model heater is it you have?

[Derek Uzzell]

Alan

 

Those questions are rather like asking how rapidly a person can get drunk and how quickly he/she can then sober up - there are so many variables involved it's difficult to provide even ball-park answers.

 

If you start out with a fully-charged 110Ah battery and run just your blown-air heater, then how quickly the battery's charge will be 'drained' will depend on the heater's 12V requirements. A current model Truma E-2400 demands 0.6A-1.1A, while an E-4000 uses 1.0A-2.3A. So, if you ran an E-2400 continuously at maximum power it would (in VERY crude principle) take 100 hours to fully flatten the battery, while an E-4000 would drain the battery in about 48 hours. Anyway, you ought to be able to run your heater continuously for quite a long period of time.

 

I don't know what low battery-voltage threshold Truma sets for E-Series heaters, but it's 10.5V for C-Series appliances. Assuming your battery's charge-state is OK and there's nothing physically wrong with your heater, if the reason for your heater's red light flashing intermittently is indeed voltage-related, the culprit is likely to be the electrical cabling installation.

 

Truma's Installation Instructions for blown-air heating appliances normally emphasise the importance of using cables of adequate cross-section and recommend that the heater be connected directly to the battery - however, this advice is regularly ignored. Skinny cables linking heater and battery via a round-the-houses route can result in massive voltage drop at the heater end. I was going to suggest that you take voltage readings at the heater, but I remembered that you can't access it easily.

 

Does the heater actually shut down when the light starts to flash? If it doesn't, then try experimenting to see if the light only flashes when a significant extra load is suddenly placed on the 12V system (eg. when the water pump begins to run).

 

The 'light-flashing' may be a characteristic of your motorhome that you may be able to ignore. Having a word with the previous owner could be useful, as there's little point concerning yourself over the flashing light if it's been doing this for years.

[Brambles]

2-How long would it take driving the vehicle to recharge the leisure battery fully?

- 5 to 8 hours should give a reasonable charge to 80% capacity, but all depends on type of battery, flooded, gel or AGM. The last 15% of charge to get fully charged takes longest as current falls right off to just an amp or less. So could take another 12 hours or even days of driving.

 

 

3-Once the leisure battery is fully charged what is the expected (roughly) average lifespan of the charge if using Trumatic Gas Blow Heating (i.e. is this system hard on power)?

- Yes they are hard on power and you need to look at the curremt or power it requires, the duty cycle and the work it out from this. Everyone has different requirements for warmth and if on 24 hours and blasting away heat all day you will only last one day, but if you just like the chill taken off in evenings, then maybe 4 days is no problem.

(Edit --- Derek's reply is much more informatve than mine.)

 

 

4-The Motorhome has a built in battery charger when connected to the mains. How long would this system take to fully recharge the battery?

 

- You have said charger so assume it is dual function power supply and charger and would exoect the ouput to be 14.4 or 14.8 volts before cutting back to 13.8 volts. This will charge your batteries in 5 to 8 hours from 50% depth of discharge to fairly full but to really get fully charged

should be left 12 to 24 hours. Again an awful lot depends on type of batteries and specification of the charger.

 

[Guest Tracker]

So much depends on how good or not your leisure battery (ies) is/are and given how unreliable and of such poor durability that so so many of them are these days I would test or get them tested as a matter of course so that you do at least know where you are starting from.

 

If you have space for a second battery I would recommend it but it would be better to have two identical batteries of the same age as a pair so that the best one does not get dragged down to the same level by the worst one.

 

[Brambles]

Hi,

Tracker, Alan has a new 110Ah battery, said at end of his initial post.

There is no point in fitting two if not needed. So as I have often said the details and parameters are needed to be known, how much power is used for how long etc.

 

[Guest Tracker]

Sorry - I mis read it - nevertheless we all know how good many alleged new batteries really are!

 

What we often don't know is just how long they have been in storage and the voltage allowed to drop below sulphation level before being shipped out or topped up for resale!

[zaria123]

Hi Guys thanks for all the info and replies.

 

The leisure battery was fitted new 3 months ago, but the motorhome wasn't used at all during this time until we bought it.

 

The control panel was and is reading about 10.5 volts (it went up to 11.1 after we drove the 400 miles back home).

 

We've plugged it in to the mains now and its reading 13 volts, so we going to leave it for a couple of days and see what it does.

 

The Truma Heating seems to work down to 10.5 volts, but if it drops to 10.4 volts it doesn't switch on. The heating works perfectly fine until the voltage drops below 10.5 / and when hooked up to the mains.

 

Thanks again, I'll report back what happens after its been hooked up, and then maybe do a test to see how long the battery last with equipment being used.

 

Cheers

Alan

[Guest Tracker]

The mains charger in the van will only charge at 13.8 maximum volts and you will need a charge of around 14.4 volts to get it fully charged.

 

I wonder who put the new battery on and why? Might be hiding a different fault? Is the engine battery charging OK?

 

If the vehicle alternator failed to charge fully over 400 miles the chances are you either have a duff battery or there is something with a heavy power drain on all the time?

 

Duff new batteries are not unusual - it took one dealer three goes to give a decent battery - and that bugger only lasted 16 months!

 

Grasping at straws now but maybe the fridge is wired to the wrong battery - unusal but not unknown?

 

Do you have a digital multimeter that shows amps? If so you could disconnect one of the battery terminals and connect it in series between one of the battery posts and the lead and measure any drain. Start at 10 or 20 amps and work down to avoid nasty fizzing sounds or loud bands and showers of sparks!

 

If not or you do not have the confidence or knowledge than maybe a local auto electrician could sort it out for you?

 

Do you have the name of the last owner? If so you could ask him for a clue - whilst stressing that you are not blaming or chasing him of course!

 

That should keep you busy!

[Brambles]

Oh Tracker I am imnpressed :-)

 

I can see you have learned a lot from your own battery problems.

Sorry Alan could not resist cmmenting.

 

I would check what your onboard charger supplies, not all are just 13.8 volts and many will be 3 stage chargers and charge to a higher voltage before droppng back and and acting like a power supply.

 

Totally agree, if your altenator is supplying the leisure battery OK, then the new battery is duff. If it was left flat in storage for a few months then it will have suphated badly, and may even have been subected to frost damage. If a battery is flat it can freeze. ( A totally flat battery has very low speific gravity and is almost pure water).

 

See how you get on with hook up, but just a few hours should see a good battery showing a over 12 volts.

 

[zaria123]

Had the battery hooked up on the mains for just under two hours, and the battery voltage is reading 12.1 after disconnecting.

 

Im hoping it was just lack of use, but bets are its not that easy lol. I know the motorhome had been unused for a few months, and it was parked outside in the freeing weather so the battery might have been affected.

 

To answer some of the questions, yes the engine battery is being charged and always starts with full life even after being left.

 

I have a meter and i'll have a play in daylight.

 

I don't imagine there are any heavy drains on the battery, as presumably the voltage would get gradually lower if there were. But the voltage reading hasn't dropped below 10.4.

 

Perhaps the 400 miles of driving didn;t pump much power in to the leisure battery as we were driving, through freezing weather and snow, with driving full lights, cab heater on full blast, CD Player going?

 

Not related, but ref my previous posts asking about driving with the trumatic heating going, I have discovered it actually isn't possible as the habitation electrics are automatically switched off as soon as the engine is started.

 

If the voltage on the leisure battery hold up to the charge I'm going to test it to see how easy / hard it is to drain with using the equipment.

 

Once again thanks for the time answering my questions.

 

Elddis owners manuals aren't exactly informative, or offer any great detail, so I appreciate the time given in your replies :-D :-D :-D :-D

[Brambles]

Your comment the battery has never dropped below 10,4 volts has confirmed you have a duff cell. 10.4 + 2.1 = 12.5 volts which is abuot right after you have drained some power. So there you go.

If you can get hold of the original receipt from previous owner you might be able to claim under warranty as could be a manufacturing defect.

Even without, if you have an stockist or agent for the brand near you they might replace without a receipt.

Jon.

[Derek Uzzell]

Alan

 

A couple of comments...

 

1. It would be a good idea for you to obtain John Wickersham's publication "The Motorcaravan Manual" (Haynes Publishing) if you anticipate involving yourself much in future in motorhome DIY maintenance and trouble-shooting. While the book won't cover everything you'll want to know, it does deal with the basics (like 12V batteries) very well.

 

2. Isolating the motorhome's living-area 12V system when the vehicle's ignition is switched on was a tactic introduced by UK manufacturers in the mid-1990s. The ploy was said to address concerns regarding electro-magnetic compatibility (EMC) between the vehicle's electrical safety systems (eg. antilock braking) and motorhome 'domestic' 12V accessories like lights, fans, or gas-burner igniters.

 

To the best of my knowledge the method is peculiar to UK motorhome constructors - Continental converters have never adopted '12V isolation' - and past discussion on the forum (and approaches to the UK converters themselves) strongly suggested that there were no regulations demanding 'isolation' and that the practice was habitual rather than reasoned and had little genuine benefit. It's certainly a damn nuisance if there's a wish to use 12V-powered motorhome accessories (blown-air heaters, reading lights, etc.) while travelling and plenty of motorcaravanners have chosen to disable the feature by simply disconnecting the isolation-relay.

 

(A question for forum members - do UK converters still 'isolate'? With safe (or at least "safe-ish") en-route gas heating becoming increasingly commonplace and modern fridges demanding a continuous 12V supply, is 12V isolation in motorhomes actually practicable nowadays?)