Leisure battety not charging while driving

[Juzzy]

Hi,

We have a 1999 Elldis firestorm and are now having an issue with the leisure battery not charging whilst driving.
Charges on EHU
Battery status will show its in the green until I plug the car in and running, then the needle suddenly drops to red.
The fridge 12v light is on when car is running.
Have checked both 25amp fuses near the leisure battery and they are fine.
Whilst on our roadtrip the 7pin S plug on the caravan was acting up (seriously corroded) and you had to have it sitting just right for the 12v fridge light to be on. So I cut it off and fitted a new one following the wiring guide and also cheching the number/colour coding to the existing plug. Unfortunately I didn't think at the time to disconnect the leisure battery when cutting the old plug off. 5 days later with no EHU the leisure battery is flat. 1 night on hook up and its charged again.
Have I possibly fried the recharge box in the caravan?
Or is there another fuse in the caravan I am missing somewhere?
I double checked my wiring with the plug and everything seems to be in order.

We are currently still on the road so don't have access to a volt meter to check anything.
TIA

 

[borderbilly]

Dont think it charges when you are driving, only on EHU.

 

[Mr Plodd]

What are you towing it with? (Mke model and year)

 

[woodsieboy]

With a caravan of that year do you have a switch inside that needs to be set to car, it will probably be a rocker switch that toggles between car and mains hook up, probably naer to door and control panel

 

[Dustydog]

1. If the plug was corroded so will the socket. Spray it with electrical contact spray. Then check the outputs on the car with a multi meter, engine running.

2. Check the master fuse on the battery. Whilst hooked to the mains EHU, test the voltage across the battery. Should be 13.4 v or close
Let us know

 

[Sam Vimes]

I'm assuming that the battery charged correctly before you rewired the plug.

Wiring of caravans varies. If you have no physical switch to select between car or caravan for the 12v, then there maybe a habitation relay inside the caravan that will switch the leisure battery over to the car supply when the ignition is turned on. I think the supply from car to the relay comes from pin 6, so might be worth checking those pins.

 

[Juzzy]

What are you towing it with? (Mke model and year)

2009 Mercedes C class wagon

 

[Juzzy]

With a caravan of that year do you have a switch inside that needs to be set to car, it will probably be a rocker switch that toggles between car and mains hook up, probably naer to door and control panel

No, no switch on this one. Charged fine for the last 3k Miles we have done with it

 

[Juzzy]

1. If the plug was corroded so will the socket. Spray it with electrical contact spray. Then check the outputs on the car with a multi meter, engine running.

2. Check the master fuse on the battery. Whilst hooked to the mains EHU, test the voltage across the battery. Should be 13.4 v or close
Let us know

We only had the towbar fitted on the car a couple months ago so the plug on there is new. I did spray it with WD40 just to make sure but no change.

The two 25amp fuses are fine. Unfortunately don't have a volt meter but after the battery went flat, we got on a powered site for one night which recharged the battery.

 

[Dustydog]

We only had the towbar fitted on the car a couple months ago so the plug on there is new. I did spray it with WD40 just to make sure but no change.

The two 25amp fuses are fine. Unfortunately don't have a volt meter but after the battery went flat, we got on a powered site for one night which recharged the battery.

I suspect your charger has packed up l Not uncommon.
I replaced mine with one from these guys

Apuljack Electronics

default meta description (ContentText_DefaultMetaDescription)

www.apuljackelectronics.co.uk

 

[Tobes]

I suspect your charger has packed up l Not uncommon.
I replaced mine with one from these guys

Apuljack Electronics

default meta description (ContentText_DefaultMetaDescription)

www.apuljackelectronics.co.uk

Not sure that makes sense DD. As soon as the OP got on site, the battery was recharged. Thats not a charger issue, but is more likely a wiring issue for the caravan plug.

 

[Dustydog]

Not sure that makes sense DD. As soon as the OP got on site, the battery was recharged. Thats not a charger issue, but is more likely a wiring issue for the caravan plug.

What a donkey!

 

[ProfJohnL]

To me it sound more like a battery problem. If every thing works when the EHU is plugged in but as soon as the EHU is unplugged the 12V systems begin to fail, it suggests the battery has lost its capacity to accept and hold a charge.

If possible remove the battery and get it tested. Most car service centers or battery specialists should have battery testing equipment.

 

[Beardy]

To me it sound more like a battery problem. If every thing works when the EHU is plugged in but as soon as the EHU is unplugged the 12V systems begin to fail, it suggests the battery has lost its capacity to accept and hold a charge.

1 night on hook up and its charged again.

 

[Beardy]

I think that you're going to need a meter. Battery charges ok on EHU so caravan power supply and battery are good. You need to know whether 12v is coming from the car (could be a fuse / relay in the car). If you're getting 12v from the car then it's the caravan plug / wiring or a fuse somewhere.

 

[Woodentop]

A very common problem with 12N/12S wiring is pin trouble on the 12S.
The pins that matter are 3 which is earth (-ve) for the permanent live on pin 4, and 6 which is the 12V+ for the fridge and is only live when the engine is running.
The problem is that pin 3 cannot handle the -ve of all the current being drawn on pins 4 and 6 so you often end up with the -ve getting too hot.
Other readers will say I am wrong here but in earlier days pin 7 - which became the -ve for the fridge - was not used. The solution is to wire pins 3 and 7 together with decent sized cable - 4mm minimum - and to wire the cables to a piece of the substantial part car body. If twin cable is used for pin 4 and twin for pin 6 you can join the -ves at both ends, and since the twin cable will run all the way to the battery, the joined negatives can go direct to the battery -ve or the body earth nearby.
Been there, done that, etc etc.

 

[Juzzy]

Yes the previous 7s pin plug showed signs of overheating. Now with the new plug fitted this should not be a problem when first using it right? I think I need to get my hands on a volt meter!

 

[ProfJohnL]

Comment related to #14 by Beardy

The OP also stated that almost as soon as the EHU was disconnected the battery indicator turned red - implying a poor charge capacity in the battery.

I hope the OP will report back on their ultimate findings

 

[Beardy]

Comment related to #14 by Beardy

The OP also stated that almost as soon as the EHU was disconnected the battery indicator turned red - implying a poor charge capacity in the battery.

🤷‍♂️ I can't find that in this thread, maybe the OP edited their post.

 

[borderbilly]

🤷‍♂️ I can't find that in this thread, maybe the OP edited their post.

post 1, the original post.

 

[trevormonty]

The following should help isolate problem.

First thing you need to determine is if battery is OK.
Disconnect EHU after it has charged battery overnight and monitor battery voltage with some 12V lights turned on. Should drop from around 13.5 to around 12.5V. If it goes to 12V or lower you have a stuffed battery.

Assuming battery is Ok next connect car with ignition/ ACC turned off. Battery voltage shouldn't change, if fridge is switched to 12V as it shouldn't operate or draw from battery.
Now start car with fridge switched off ie 12v not selected. Battery voltage shouldn't drop, may go up if car is charging it.
Next switch fridge to 12V while car is running, if it drops as you stated I suspect van is wired incorrectly as battery should never supply fridge.

 

[Beardy]

post 1, the original post.

Nothing in the original post about the battery indicator turning red almost as soon as the EHU was disconnected.

The OP said.

Battery status will show its in the green until I plug the car in and running, then the needle suddenly drops to red.

I'm confused.

 

[ProfJohnL]

My apologies, my recollection of the OP's post was wrong. However its still worth getting the battery checked.

 

[Juzzy]

Thanks for all your replies... I got hold of a volt meter. Started at the plug while attached to the car with ignition on, and got 12.5-13.5v across all wired pins. Then checked the leisure battery with car off, read 12.5v
Then with car on and it read 13.5v. So the charging system would appear to be fine. Next is to get the battery tested.

 

[Buckman]

If the car has a Smart alternator, the feed will cut in and out depending on the load required. I think some type of relay needs to be fitted so that there is a constant 12v supply to the battery?