Technical Batteries

[hymerlou]

We have a 1993 Hymer on the 2.5 Ducato base. It has been stood 3 years and the leisure battery was completely shot so was replaced with new 110 amp.Our first weekend away went very well until we got home when the engine battery was completely flat the next day only showing 2 volts.Before we went away i checked the alternator was charging ok it showed a constant 13.5 volts at all RPM.
First problem is battery is taking ages to recover IS it shot?
second problem is getting engine running again to check alternator working ok if faulty how easy are thet to replace?
Third problem is what drained the engine battery so quickly ( no warning light on etc)
Any help much appreciated

 

[ken page]

hi i would presume that the battery is shot the alt should show 14.4 volts tested at the battery when the engine is running as the battery is not recovering it looks terminal its worth taking the battery to have it tested though be lucky ps had the same thing on my autotrail

 

[mikey72]

Only time my van did that the spilt charger relay for the fridge stuck in, and the fridge flattened the van battery overnight.

 

[hymerlou]

Charged the battery up then the starter motor stuck so had to let it roll slightly in gear to free it then it started first go.
showed 14.5 volts when ticking over then dropped to 13 when all lights heater fan switched on then back up to 14.5 on a fast idle.
So i think alternator ok
battery suspect unless it holds the charge
starter motor suspect any way of checking?
Then theres the split relay as the fridge was on 12v for the drive home and left on for next 2 days so if this relay was faulty it could have drained the battery(the fridge has been playing up previously not working at home on hook up then working fine when on site all weekend thats why i switched it to 12v for the journey home)

Thanks to all for your help

 

[mikey72]

Charged the battery up then the starter motor stuck so had to let it roll slightly in gear to free it then it started first go.
showed 14.5 volts when ticking over then dropped to 13 when all lights heater fan switched on then back up to 14.5 on a fast idle.
So i think alternator ok
battery suspect unless it holds the charge
starter motor suspect any way of checking?
Then theres the split relay as the fridge was on 12v for the drive home and left on for next 2 days so if this relay was faulty it could have drained the battery(the fridge has been playing up previously not working at home on hook up then working fine when on site all weekend thats why i switched it to 12v for the journey home)

Thanks to all for your help

I replaced the relays in my charger and it fixed the problem. Make sure you turn the fridge off 12v when you get home as well.

 

[PeterM]

Make sure you turn the fridge off 12v when you get home as well.

Better still, buy a FridgeSwitch: http://www.rvelectronics.com.au/page.asp?parentid=3&parent2id=14. It turns off the power to the fridge when the van stops.

 

[mikey72]

Better still, buy a FridgeSwitch: http://www.rvelectronics.com.au/page.asp?parentid=3&parent2id=14. It turns off the power to the fridge when the van stops.

That would turn off every time my kids moved when we're parked up on site.

 

[PeterM]

That would turn off every time my kids moved when we're parked up on site.

No. When you are on site the fridge is set to run on gas if its a 3 way! Or on 230 V if its a 2-way!

 

[mikey72]

No. When you are on site the fridge is set to run on gas if its a 3 way! Or on 230 V if its a 2-way!

So that totally negates the device anyway, if you actually have to switch the 12v off on site, at least my split charger takes care of that for me as well.

That would turn off every time my kids moved when we're parked up on site.

Meant to say turn on there.

 

[FreeSpirit]

Hi
I think a few things need clarifing as to whether you have a compressor fridge or a 3 way gas/12v/240 fridge. From what mikey72 has said it seems he has a 12v/240volt (or whatever volt fridge) which has a relay built in to the charger ??? which connects the house & chassis batteries together when the engine is running & disconnects automatically when engine is off which of course also still applies to vehicles fitted with 3 way fridges with chassis & house battery/ies installed.
I think 12v/240v compressor fridges use between 3-5 amps max which is not an excessive amount.
What peter is talking about is the 3 way fridges in which the 12 volt side of a gas/12v/240v fridge consumes between 15 & 20 amps & is only used when travelling & the alternator is charging the battery to cover the large current draw. Also when running on 12v with these 3 way fridges the thermostat is inoperatable as well, at least on Dometic 3 way fridges it isn't.
If the 3 way fridge was left on 12v without the alternator running I doubt the battery/ies would last much over an hour. Hence the reason for the "fridge switch" which disconnects the 12v automatically when the vehicle stops & saving of you having to turn off the 12v side when stopped (in case you forget) for short periods & with no engine running. It has been said it is OK for 10-20 minute stops but this is still a great current draw on the battery & will probably shorten the life of the battery & I wouldn't recommend it. When camped it would either be run on gas or mains power if it is available.
This is also the reason that 3 way fridges cannot (I shouldn't say can't) be run off solar panels as the current draw is too great & the number of panels required makes it impractical. From my experience with both types I would not have a 12v/240v compressor fridge unless I have enough P.V. panels installed to run it & other normal 12 volt loads etc away from mains power.
Cheers

 

[mikey72]

The normal type of fridge in a motorhome is the absorption fridge, as opposed to the compressor type fridge. (mines the absorption type)
As said, they use a lot of current, and flatten the battery very quickly.
The most basic type of spilt charger runs off the alternator warning light, when the light goes out, the relay pulls in, and connects the fridge and camping battery to the main battery.
Stopping the engine causes the relay to drop out, switching the fridge off, and isolating the camping battery, the fridge, and the van battery from each other.
I have a slightly more intelligent charger, which also plugs into the mains, and runs the fridge on 240v as well, but the principle is the same, and has the same basic relays in it.
These are usually what burn, and stick either open or shut, shut in my case so it left the van battery connected to the fridge, and ran it flat.
It did disconnect the camper battery, so that actually still had a full charge.
Even the old vw camper had a split charge relay, so the switching unit above isn't really needed in most motorhomes, the control is already built in from the factory.
If it works properly (which it usually does) the fridge can’t be switched on 12v without the engine running, and the alternator charging. The unit above sounds like it would switch the fridge onto 12v whenever my little hoard of elephants charge around.

 

[FreeSpirit]

Hi
Thanks mikey72 for that clarification on your system, in OZ the standard seems to be on most motorhomes etc, is the isolating relay which simply just disconnects the chassis battery from the house battery/ies when the ignition is turned off. Which is why Peter mentioned the fridge switch, as it saves having to remember to turn the fridge off 12v when stopped either for a short period - lunch etc or when camped which it then would be turned manually to gas or mains power if mains is available.
Maybe some of the more expensive models might have a system fitted similar to yours but I have yet to come across any.
Most manufacturers are now fitting the AES (Automatic Energy Selection) fridges to most models but not to the cheaper models. Most of the rental MotorHome companies only use the compressor type fridges for reasons of safety so the renters don't manage to blow themselves & the vehicle up somehow. Maybe as you said the kids jumping around would turn it on, but if camped it would have been set to either gas or mains manually anyway so this wouldn't happen.
Cheers

 

[mikey72]

Hi
Thanks mikey72 for that clarification on your system, in OZ the standard seems to be on most motorhomes etc, is the isolating relay which simply just disconnects the chassis battery from the house battery/ies when the ignition is turned off. Which is why Peter mentioned the fridge switch, as it saves having to remember to turn the fridge off 12v when stopped either for a short period - lunch etc or when camped which it then would be turned manually to gas or mains power if mains is available.
Maybe some of the more expensive models might have a system fitted similar to yours but I have yet to come across any.
Most manufacturers are now fitting the AES (Automatic Energy Selection) fridges to most models but not to the cheaper models. Most of the rental MotorHome companies only use the compressor type fridges for reasons of safety so the renters don't manage to blow themselves & the vehicle up somehow. Maybe as you said the kids jumping around would turn it on, but if camped it would have been set to either gas or mains manually anyway so this wouldn't happen.
Cheers

Yes, all the uk split chargers have two terminals, one terminal goes to the leisure battery, one goes to the fridge, the other side of both go to the van battery, and they only pull in when charging.
My fridge is quite old now, but it has seperate switches for 12v, 240v, and gas. I know I can have gas and electricity on at the same time, but I can't say if the 240 and 12 v work together, as I always stop and get out to connect the hook up, so the 12v is off, and I always disconnect the 240v before starting and driving off.
I'll have to try next time I'm out.

 

[DENNIS SPAIN]

Only just found this item when browsing today. I have a Dometic (RM7851L) 3 way fridge fitted to my motorhome. After using the 12 volt operation I have to turn the selector switch to the off position, otherwise power continues to be supplied from the house battery for the interior light and the electronics. Should the fridge door be left slightly open for ventilation between uses, the house battery will have a constant drain on it.