# Alternator, Charging and Fridge....



## Eisbaer (May 1, 2005)

I have recently decided to tackle a leisure battery charging issue that has been nagging at me for years. Namely, our motorhome is not wired up to charge the leisure batteries while driving. It can be a problem is our case when on longer journeys in Europe. For example, the fridge will only run on 12v and unless we turn it off (and have stuff in the freezer semi-thawed by the end of the day) the leisure batteries will be drained after a day's driving. Is it as simple as running an extra charging cable from the alternator - via a relay - to the leisure batteries to fix this issue? Or would the extra load put too much duty on the alternator? If yes, is it advisable to upgrade to a higher output alternator? We have two 100ah leisure batteries. I believe the alternator fitted at the moment is rated at 150A output.
Even with a higher output alternator, would the system be able to cope with the high current draw of a fridge/freezer?

Any advice would be appreciated. Cheers.


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## WildThingsKev (Dec 29, 2009)

I think the fridge only takes about 10A.


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## Penquin (Oct 15, 2007)

Our MH has a relay to protect the battery so that the fridge can only operate when the engine is running - the current from the alternator closes the relay and allows 12v to flow to the fridge - my first thought would be to fit a relay like that to protect your leisure batteries.

Once that protection is fitted, is there a wire from the alternator to take current to the leisure batteries? If there is, that should be charging them, but of course, if the fridge is draining them at about 8a they will not keep charged for long.....

I am sure others will be along to give specific advice but my order would be;

1. fit relay to protect batteries from draining to run fridge when engine not running,

2. fit wire (if not already fitted to charge leisure batteries - probably with a Battery Master to ensure the vehicle battery is also charged).

How do you currently charge your leisure batteries? Presumably via an EHU system?

The alternator would be OK AFAIK but there needs to be that facility, generally the more that is needed from an alternator the more it will give...

Dave


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## Stanner (Aug 17, 2006)

Your fridge should not be running off the leisure battery when on 12v, it should run direct off the alternator via a relay.

The same relay should also supply a feed to the leisure battery as well.

How old is the van? As it sounds as if someone has messed about with the electrics.


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## blackbirdbiker (Mar 12, 2007)

Typically the heating element on a fridge is approx 140 watts. therefore current drawn is approx 11.5 amps, no problem for your altenator.

Keith


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## rayc (Jun 3, 2008)

It is worth mentioning that if a 'split charging' system is installed that when the engine is running that the cab and leisure batteries are paralleled together. The fridge is then connected to both the leisure and cab batteries and to the alternator.


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## Eisbaer (May 1, 2005)

Thanks all for swift replies!
Wild Things Kev & Blackbird Biker - I went and RT'd the FM - my fridge (it's a big one) uses 175w = 14.5 A.....
Penquin - I can't run my fridge on 12v when stationary.
Stanner - you're right on the money there! It's a 2000 Due Erre and wired like a 1962 Fiat 850. Not a split charge relay in sight.
Ray C - do you mean that the cab battery is then compromised?


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## Stanner (Aug 17, 2006)

Eisbaer said:


> Stanner - you're right on the money there! It's a 2000 Due Erre and wired like a 1962 Fiat 850.


You need to get a good motorhome electrician to have a look at it and put it back as it should be.


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## rayc (Jun 3, 2008)

Eisbaer said:


> Ray C - do you mean that the cab battery is then compromised?


I am not sure what you mean by compromised. It is 'normal' for both the cab and leisure batteries to be 'joined together' and both charged by the alternator when the engine is running. The fridge is obviously powered from somewhere and as both batteries are paralleled together and being charged by the alternator then it must be to all three.
This is what has been happening since the early days of motorhomes and caravans for that matter. Then there were two separate relays, one for the leisure battery charging and one for the fridge. These days the relays are normally part of the DC control system.
Under non engine running conditions the batteries are not paralleled and the fridge is isolated from the batteries.

Going back to your original question "Is it as simple as running an extra charging cable from the alternator - via a relay - to the leisure batteries to fix this issue?" then the short answer is yes. You want to connect the leisure battery to the cab battery via the relay and the relay to operate only when the engine is running. The way this is normally done is to use a voltage sensing relay that operates when it senses the rise in voltage when the alternator is running.
Something like this:
http://www.altecautomotive.co.uk/70amp-split-charge-relay-kitbr-2392-p.asp

The problem as I see it is that when the engine is not running you still want the leisure battery to supply the fridge. I have never done this but it would be simple via a switch and fuse but how long it would take to discharge the leisure battery is the question.


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## teemyob (Nov 22, 2005)

*12v*



Stanner said:


> Your fridge should not be running off the leisure battery when on 12v, it should run direct off the alternator via a relay.
> 
> The same relay should also supply a feed to the leisure battery as well.
> 
> How old is the van? As it sounds as if someone has messed about with the electrics.


Just to clarify.

Seems the poster has an issue with the wiring or lack of it.

If the Fridge is a compressor fridge, it will have to run off battery when stationery if no EHU is available.

If 2 or 3 way. Can run off battery if you have the capacity.


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## WildThingsKev (Dec 29, 2009)

rayc said:


> Eisbaer said:
> 
> 
> > Ray C - do you mean that the cab battery is then compromised?
> ...


It still surprises me how much the fridge takes out of the LB charging; on ours it typically reduces it by about 0.5v and 5A so the only way to get a good charge into the batteries when touring (eg between aires) is to turn the fridge off or to gas when driving.


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## Eisbaer (May 1, 2005)

Again thanks to everyone for the input. My fridge is the standard three-way jobbie i.e. gas, 12v and mains. Of course I understand that it can and should only run on 12v if the engine is running. I don't want to run it on 12v while stationary for obvious reasons. My only issue is that the alternator does not charge the leisure batteries while driving!


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## rayc (Jun 3, 2008)

Eisbaer said:


> Again thanks to everyone for the input. My fridge is the standard three-way jobbie i.e. gas, 12v and mains. Of course I understand that it can and should only run on 12v if the engine is running. I don't want to run it on 12v while stationary for obvious reasons. My only issue is that the alternator does not charge the leisure batteries while driving!


Then a simple dual split charger is what you want. The fridge will be powered and the leisure battery charging whilst the engine is running.


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## 1302 (Apr 4, 2006)

The vehicle alternator is more than powerful enough to power both the fridge and leisure battery when engine running - your fridge running off your leisure battery would last a very short time 

I assume you have checked your leisure batteries condition - I recently changed ours as it was lasting just a hour or so (with telly on) regardless of its original state of charge ...


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## Penquin (Oct 15, 2007)

Thanks for the clarification, I think most of us have been working under a misapprehension after your initial post included the phrase;



Eisbeer said:


> For example, the fridge will only run on 12v and unless we turn it off


at that point it was not clear that your fridge would do anything else since the alternative seemed to be to just turn it off......

From what you have described the charging of the leisure batteries seems to be at fault - that needs checking, it could be due to a faulty relay (the circuit for the fridge is separate from the circuit for the battery - there are effectively two relays built in I believe). It may well be that one of the two is not closing properly - on ours there are two fuses one for each relay circuit, but they are nowhere near the other fuses but are mounted near the air filter (for some unknown reason - but they are by the double relay which is there).

So check the relay is closing when the engine is running and check the fuse for that relay.

If it is not that then there could be a break in the wire to connect to the leisure battery = or even at the terminal - check for tightness there too.

Charge the leisure battery separately and see how long it lasts with the fridge on gas while stationary - as it should usually be unless you are on EHU.

If the battery will not hold a reasonable charge that may be where the fault lies since, if one cell goes down, the whole battery is effectively useless and will not hold much charge......

Hopefully by checking through with a multimeter you can trace the fault.

Dave


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## rayc (Jun 3, 2008)

I may be a bit slow but does the OP have leisure battery charging from the alternator which has gone faulty or does he have no split charging system installed?


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## clive1821 (Mar 27, 2010)

rayc said:


> I may be a bit slow but does the OP have leisure battery charging from the alternator which has gone faulty or does he have no split charging system installed?


Yes ray i read it the same no split charge and your post is corect... :wink:


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## Eisbaer (May 1, 2005)

OK - it's becoming clearer. From the feedback I see the issue like this:

1. While driving there is no charge going to the leisure batteries 
2. It could be that there is a split-charge relay but it's not working
3. It could be that there is no split-charge relay/wiring 
4. If 3 above is correct then the 3-way fridge is functioning as it should except that it is (wrongly wired) running from the leisure batteries
5. If 3 & 4 above are correct, then I need to fit a voltage sensing split-charge relay so that, while driving, the leisure batteries will charge and the fridge will run off 12v. Stationary/not driving = no charging and fridge running on gas or mains.

Thanks for your input and advice! I'll get me a relay and sort this out for once and for all before we hit the road again...


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## Penquin (Oct 15, 2007)

I think we are on the same wavelength, have you got the facility to check whether you have such a relay already installed but not functioning?

As I said the relay on ours is nowhere where I would have expected, so if someone has a similar vehicle they may be able to give specific advice about where to look - such guidance could save a vast amount of time 

BUT I do not know the details of your vehicle so I cannot give you any help there - good luck.....

do let us know how you get on - this is a mystery that we will all be glad to hear the outcome of! :lol: 

Dave


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## Eisbaer (May 1, 2005)

Thanks for your input Dave. Upon more reflection, I think there must be some form of relay installed since the fridge does run on 12v while driving - but (as it should be) not when stationary. Something must be switching the 12v supply to the fridge on/off, ah? Perhaps, as you suggest, because of a blown fuse or other wiring problem, the other circuit to the leisure batteries from the relay/alternator is not connecting, ergo no charging. I'll track down this relay and check it out. I take your point that the relay could be located anywhere.....

My motorhome is an Italian built Due Erre and the handbook I got with it is very poor, and also written in Italian. As in the past, I'll have to rely on my wits, the wisdom of others, and luck, in solving this one! I'll keep you posted.


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