Should running the fridge from the leisure battery while traveling leave the battery flat?

[Grum]

We have a 2 year old Rimor Katamarano which we bought a couple of months back and one of the issues we have is that the leisure battery goes flat when used to cool the fridge while driving. We have been told that the engine battery needs replacing after it too went flat when we were listening to the van radio (engine off) for @ 20 minutes. Would this be taking the power needed to charge the leisure battery or is there something else I need to be looking at? Any help appreciated.

[Tracker]

Hi Graham and welcome to the forum.

 

Firstly if you bought from a dealer there should be a warranty to sort this issue out, either from the converter or dealer as two months is barely enough time to get to know your van let alaone suss out the complications of the electrics?

 

If not it would appear from what you have said that somebody has been messing about with the on board electrics because the fridge - assuming it is a Dometic 3 way type (gas/12vdc/230vac) - should only run on 12 v when the engine is running and at no other time on 12 v.

 

It should be supplied from the engine battery only which is kept topped up by the alternator and never from the leisure battery and the leisure batteries should have a relay to prevent cross discharging.

 

When stationary the fridge should offer you the alternatives of mains electic 230 v ac or onboard gas operation only.

 

It is possible that if both batteries have been allowed to go totally flat that they will not recover and if it were my van I would have both batteries preferably off and on the bench to be recharged with something like a multistage Ctek or similar charger asap.

 

If not at the very least disconnect the batteries or isolate the fridge to prevent further damage pending resolution, and beware of leaving any batteries in a heavily discharged condition as they do not like that sort of treatment and permanant damage thatwill shorten their life will occur.

 

Due to poor design of the conversion electronics and the resultant abuse they suffer it is not uncommon for two year old vans to need all new batteries which if they do not get looked after will also not last long. This is made worse by the base vehicles being designed for daily use with standard electronics that drain the engine battery when it is left standing for more than a couple of weeks.

 

But of course nobody tells you any of this when they take your money.

 

 

[Derek Uzzell]

Tracker - 2016-01-19 6:35 PM

 

...It should be supplied from the engine battery only which is kept topped up by the alternator and never from the leisure battery and the leisure batteries should have a relay to prevent cross discharging...

 

Historically that was true (as much as anything because motorhomes often did not have a leisure-battery as standard) but it’s no longer the case nowadays.

 

This has been discussed here before: example here:

 

http://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Running-Fridge-from-Leisure-Battery/17117/

 

[Grum]

Hello Tracker,

thank you for the welcome. Unfortunately I didn't buy the van from a dealer so have no comeback on that score. I guess that as you say, if one battery can need replacing then so can the other one too, after all I don't know how the van was kept before I got it...

Thank you for your answer. I have been sticking the mains power on every 7-10 days over night to keep the leisure battery charged but if here is already damage that won't help much will it? I'd best get down to my nearest electrical shop and get a tester.

[747]

If you can charge your Leisure battery (and van battery) off the mains but it is flat after driving, it sounds like your onboard charging system is faulty. It could be as simple as a blown fuse.

 

Put a multimeter across the Leisure battery to obtain the voltage. Switch the engine on and recheck the voltage. If it has not increased, you have a fault.

[Robinhood]

...well, the answer is, no it shouldn't.

 

I have, however, had the same problem in the past on an Auto-Sleeper, and whether the same issue applies will depend on the wiring that your converter used.

 

On my Auto-Sleeper (and I believe this method is still in use in some installations), the fridge 12V supply was wired across the leisure battery terminals. This is fine under normal circumstances, as these terminals are supplied from the alternator when the engine is running and the fridge supply circuit had a relay in it that was activated by the alternator "sense" supply, such that the fridge only drew power when the engine was running.

 

The arrangement being similar to the top half, here:

 

http://www.jktowers.fsnet.co.uk/motorhome/images_technical/split_charge_wiring.jpg

 

My problem arose from the fuse in the leisure battery (alternator) charging circuit having blown. Hence, on the road the leisure battery was not getting charged, but the fridge circuit was still completed by the relay, and thus the leisure battery was (fairly rapidly) depleted.

 

So, you may want to look for and check the fuse(s) protecting the charge circuit to the leisure battery.

 

Interestingly enough, though the offending fuse was blown by my "tinkering", I suspect that a very low engine battery and a well-charged leisure battery might just cause enough of an issue to blow such a fuse when demand was put on that engine battery.

 

I fixed another AS owner's issues with the self-same problem on a campsite in Ireland.

 

[Grum]

Thank you for the info 747, I will give this a try and see what happens. From what you say, if the voltage does go up then the problem would be a dud battery?

[Grum]

I shall also check my fuses as you say Robinhood, although it took me ages to find out where the leisure battery was stowed so a fuse box might be more of a challenge. Turns out the battery was hidden in behind panel where the drivers footwell is.

[Tracker]

Two of the most handy diagnostic tools in my toolbox are -

 

http://www.amazon.co.uk/Draper-60792-Digital-Multimeter-Backlight/dp/B0001K9XKW

 

and

 

http://www.amazon.co.uk/Battery-Electric-Cigarette-Lighter-Voltmeter/dp/B00B58VNZW/ref=sr_1_8?s=diy&ie=UTF8&qid=1453232271&sr=1-8&keywords=12+volt+car+digital+volt+meter

 

I have two of these - one in the cab to keep an eye on the engine charging and battery and one in the habitation area to keep an eye on the leisure battery!

Paranoid or what!! Or just fed up with iffy batteries and electronics over many years and many vans!!

 

 

 

[Tracker]

Derek Uzzell - 2016-01-19 6:50 PM

 

Tracker - 2016-01-19 6:35 PM

 

...It should be supplied from the engine battery only which is kept topped up by the alternator and never from the leisure battery and the leisure batteries should have a relay to prevent cross discharging...

 

Historically that was true (as much as anything because motorhomes often did not have a leisure-battery as standard) but it’s no longer the case nowadays.

 

This has been discussed here before: example here:

 

http://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Running-Fridge-from-Leisure-Battery/17117/

 

Thanks Derek - yet another complication that I did not know had happened.

You, and this forum never cease to amaze, entertain and inform me!

Why did it change I wonder and what are the advantages of using the leisure battery?

[aandncaravan]

The way RobinHood describes the operation is spot on, in that many Fridges are actually wired from the Habitation area battery.

When the control box/relay gets the Alternator D+ signal to say the Alternator is spinning it connects the Fridge to the battery, which should now be receiving 14v from the Alternator. So it should effectively run using power from the Alternator via the Starter battery.

 

Easy to check if this is happening correctly :

With the Fridge off, you should be seeing 14+v at the habitation battery on the display unit when the engine is started.

If the voltage at the Hab battery does not rise when the engine is started, there is an issue with power getting through from the Alternator.

If you then watch the display while someone turns the Fridge to 12v, you might see the Habitation voltage drop from say 12.8v to 12.1v. Indicating the D+ circuit is working and bringing in the load of the Fridge, but Alternator power not getting through.

 

The most likely cause is a fuse in the Starter battery to habitation battery feed as stated above. However, we have also seen issues with bad Earths on some vehicles, especially if the batteries are below par.

The Alternator works so hard overcoming the poor connection that little charge gets through to the Habitation battery.

Usually enough to top up the Habitation battery in isolation, but a poor connection (like Earth strap) might mean there is not enough to replenish a dying Starter battery, poor Habitation battery and supply 12amps to the Fridge.

 

 

Poor Earth/connections:

The display unit should show 14.4v at the Habitation battery with the Engine running and Fridge off, but if this drops to say 13.1v (so still enough to show voltage/current is getting through from the Alternator) when the Fridge is switched to 12v, then that suggests a poor connection somewhere. Like a poor Earth.

 

There will be some voltage drop at the habitation battery when the Fridge is switched to 12v, but it should still be up near/above 13.8v'ish if the connections, batteries, etc are all good.

 

Some Hymer Motorhomes with an AES Fridge option, have the ability, if the AES fuse slot is populated, to run directly off the habitation battery even when the engine is not running.

This allows short term use when travel stops are made at services that don't allow a naked flame for gas operation. But it is for very short term operation only.

 

Some Hymer vehicles will only switch in the Fridge if both the 12v 'alternator' main supply and the Alternator D+ are present.

 

Sorry, not very good at writing these explanations. This is where I appreciate someones help in re-phrasing it so it is understandable!!

 

 

 

[747]

Grum - 2016-01-19 7:11 PM

 

Thank you for the info 747, I will give this a try and see what happens. From what you say, if the voltage does go up then the problem would be a dud battery?

 

Yes, that could be the problem. Especially if your van was not used for a while before you bought it. If the Leisure battery was allowed to go flat and left flat for a while. A quick way to check the battery would be to charge it up (in situ) and switch your Hab lights on to give a small drain on the battery (aim for about 5 amps, which would equate to about 5 small Halogen lights). Leave them on for about 4 hours, switch them off, wait half an hour and then recheck the voltage. 20 Amps should not have a big impact on the voltage, unless your battery is U/S.

 

There may be 2 fuses near your Leisure battery. Often they are a big one (40 or 50 amp) and a small one (2 amp). It is worth checking both of them as if either one is blown, it will give you a problem.

[Derek Uzzell]

Tracker - 2016-01-19 8:02 PM

 

Thanks Derek - yet another complication that I did not know had happened.

You, and this forum never cease to amaze, entertain and inform me!

Why did it change I wonder and what are the advantages of using the leisure battery?

 

When I started motorcaravanning in 1998 there were still instances (at least with UK-built ‘entry-level’ motorhomes) where a leisure-battery was an option. In such cases it was clearly necessary for all 12V habitatiion equipment to be powered from the vehicle’s starter-battery.

 

When fitting a leisure-battery to a motorhome became the norm, there was no particular incentive (at least for UK-built motorhome manufacturers) to alter the historic fridge-wiring arrangement from connecting the fridge to the starter-battery to connecting it to the leisure-battery. After all, a battery is just a battery and, as long as the battery providing 12V cooling power to the fridge was being adequately charged when the motorhome was being driven, it didn’t really matter which battery was providing power for the fridge’s cooling function. And, when a motorhome was on 230V electric hook-up (EHU) or operating from LPG, there was no unavoidable need for the fridge to have a 12V power-supply.

 

Then along came ‘smart’ fridges that required a continuous 12V supply to power their control-electronics. But it didn’t really matter which battery provided that supply as long as the charge the fridge was taking from the battery was replenished. Replenishment would occur when the motorhome was being driven or when the motorhome’s on-board battery-charger was charging the leisure- and starter-battery when the vehicle was on EHU. However, quite a few motohomes’ battery-charging systems did not have (and still do not have) a facility to charge the vehicle’s starter-battery when the vehicle is on hook-up.

 

I remember reading that (having overlooked Dometic’s installation advice) one major UK motorhome manufacturer originally wired ‘smart’ fridges in the time-honoured manner so that they took their control-electronics 12V power from the starter-battery. This was fine except for owners of motorhomes not having a ‘via EHU' starter-battery charging capability (and perhaps not even being aware of that capability not being present in their vehicle) who chose to stay long-term-static on a campsite. With the fridge continuously draining 12V power from the starter-battery and that loss not being replenished, when the time came for these people to move on their motorhome’s starter-battery had mysteriously gone flat.

 

Regarding “advantages"’, it would be logical for all of a motorhome’s ‘habitation’ equipment requiring 12V power (fridge, heater, reading-lights, etc.) to obtain that power from the leisure-battery, as the normal expectation today is that the leisure-battery will be recharged when the vehicle is being driven and can be recharged when the vehicle is on EHU. In fact, it’s difficult to identify disadvantages in that approach, and I can’t see what advantages there would be in using the starter-battery to power a fridge instead.

 

As Allan said in his posting of 19 January 2016 8:28 PM, many leisure-vehicle fridges are cabled to the leisure-battery. It may well be that most (all?) new motorhomes marketed nowadays have that arrangement.

 

 

 

 

[Tracker]

Cor Derek - you've had it easy man!

 

When I started you were lucky to get one working battery - and if you were very lucky - a starting handle!

 

Morris J2, Commer PA (I think?) can't remember with Bedford CA, Austin J4, Ford Thames!!!

 

And a fridge in a van was still a dream - and when it did come it only worked on gas and only then when you were perfectly level!

[PJay]

Derek

1998, I thought you must have been a Mh owner MUCH longer than that. Your knowledge (which you kindly impart, on forum) is SO helpful to all .I guess you have a technical background.

Do please keep on helping , as we have lost some very useful posters, in the past.

PJay

[Tracker]

PJay - 2016-01-20 9:06 AM

 

Derek

1998, I thought you must have been a Mh owner MUCH longer than that. Your knowledge (which you kindly impart, on forum) is SO helpful to all .I guess you have a technical background.

Do please keep on helping , as we have lost some very useful posters, in the past.

PJay

 

I will heartily second that expression of gratitude and respect for Derek's invaluable input.

 

[Alanb]

PJay - 2016-01-20 9:06 AM

 

Derek

1998, I thought you must have been a Mh owner MUCH longer than that. Your knowledge (which you kindly impart, on forum) is SO helpful to all .I guess you have a technical background.

Do please keep on helping , as we have lost some very useful posters, in the past.

PJay

 

May I start by endorsing PJay's accolade. We are approaching our motor-homing silver jubilee, but I am always impressed by Derek;s breadth and depth of knowledge.

 

May I now refer back to Robin Hood's statement.

 

"On my Auto-Sleeper (and I believe this method is still in use in some installations), the fridge 12V supply was wired across the leisure battery terminals. This is fine under normal circumstances, as these terminals are supplied from the alternator when the engine is running and the fridge supply circuit had a relay in it that was activated by the alternator "sense" supply, such that the fridge only drew power when the engine was running. "

 

It may be of interest to note that this is similar to what happens in a "cbe" 12V distribution board.

 

A fused (50A) power connection is taken from the starter battery (B1), A second low current connection is taken from an ignition key controlled source and passed through an integral voltage controlled relay to provide a simulated D+ signal. I deduce from the small amount of published info pertaining to the "cbe" board that the simulated D+ signal is used to operate the coupling and fridge relays, but this may be one relay with two separate output contacts.

 

The main 50A fuse carries both charging and fridge heater current, the latter being sub-fused at the distribution board fridge connection. (50A is the cbe recommendation. My PVC was originally supplied with a 40A blade fuse.)

 

If this fuse were to blow, the coupling and fridge relays would still operate when the alternator ouput was high enough, and connect the fridge element to the leisure battery, which would start to discharge.

 

With the above arrangement the main charging fuses needs to be rated high enough to support the prospective leisure battery charging current plus the fridge heater. However the rating should also be low enough to protect the connecting cables.

 

I have not experienced any problems with a 40A fuse in this position, even though we have drawn heavily on the leisure batteries on a few occasions.

 

Alan

 

[veletron]

The 'average' dumb 'van leisure battery charging system will put maybe 15-25A in the leisure battery when the leisure battery demands it. I have generally found that the wiring is pretty wimpy, and could not cope with any more than around 30A without creating a significant voltage drop over the cable run.

 

A large double-door fridge freezer will have a 12V element rated at around 180W@12V == 15A == around 0.8Ohms. At a higher voltage say the 14.4V that your alternator runs at, this element will be running at a considerably higher wattage 14.4Vx18A = 260W approx. In reality it is not as simple as this as this current draw over the generally wimpy cable used in motorhomes causes a voltage drop. On my old Tribute 650, 14V+ was measured at the 12V element feed with the element disconnected, but this dropped to 12V when the element was connected. This is a 2A drop over the cable length == ~24W of wasted energy!

 

If the converter has run a power feed for the fridge from the leisure battery, and triggered the 12V fridge/AES relay from the alternator D+ output (rather than running the elements 12V feed directly from the alternators D+) then this might be your issue. There are three possibilities:

 

1) The fridge is consuming all the current than would have charged the batteries

2) The fridge 12V element load coupled with that from the leisure battery(s) has created a voltage drop over the cabling pulling the voltage down to below the voltage that would otherwise efficiently charge the leisure batteries. @13V, your leisure batteries will not charge - and your fridge would cause a net discharge in them.

3) A combination of 1) and 2) !! --> the most likely result

 

If you have a multimeter, diagnosing the fault is easy.

 

1) With engine off, fridge off, no load, measure leisure battery voltage and engine battery voltage, both should read 12.4V+

 

2) With fridge off, start engine, measure voltages again, both should be ~13.4V-14.4V if batteries are discharged they will be at lower end of this scale as they will be applying a load on the alternator dragging it down. With both batteries 'fully charged' one would expect habitation battery to be lower than van battery due to cable runs

 

3) Switch fridge to 12V operation and measure voltage at leisure battery once more - voltage should not really be effected by turning on the fridge maybe 0.2V max change. If voltage drops dramatically, you have found your problem.

 

Nigel

 

 

[aandncaravan]

Derek, Your are right, but some of the German built vehicles still have a separate, direct feed from the Starter battery for the Fridge. It is usually a 20A fused supply.

Next to the Starter battery on a Hymer you will usually find 3 fuses together, a 2a (D+), a 20A (fridge supply) and 50A (main charge lead to Habitation battery).

 

The advantage of the system is potentially lower voltage drop via a dedicated cable and less reliance on the main Charger feed cable.

 

The 20a Fridge feed from the Starter battery goes into the Schaudt box through a D+ operated relay, then out to the Fridge.

 

It is only ever live if the D+ is 'active'. So you can't run the Fridge off the starter battery without the Alternator also running.

 

Along with the live 20a feed from the Starter battery, there is also a separate, neutral connection directly from the Starter battery to the Fridge. This neutral is not shared with anything else.

 

It does give a better power supply to the Fridge because of this direct +/- connection, as it tends to not to suffer the Earth issues and main power issues that sometimes afflict the Habitation battery cabling. Voltage drop tends to be lower, and with the current draw of a Fridge element, a few points difference has quite an effect on the current.

 

It is obviously a more expensive solution because of the extra cable runs but we think it is more reliable. We like the system a lot : Firstly it is easier to diagnose Fridge issues. Secondly you have a separate power path into the van from the Alternator to help fault find issues on the main Charge/D+ circuit.