Battery(ies) flatten after adding 12volt socket direct to leisure batt

[RichvanT6]

Hi,

I have a 2017 T6 with a factory fit leisure battery under the passenger seat and I recently wired up a combined USB, 12V socket and volt meter with a switch to the rear cabin area. I connected this directly to the leisure battery with an inline fuse (both positive and negative were direct to the the battery terminals). This all worked fine until the next day when I went to start the van and both batteries were flat so I had to use jump leads to get it running again. The switch on the additional circuit was off and nothing was plugged in so I don't understand why this drained the batteries. I have disconnected this and the van is all back to normal.

Can anyone tell me what is wrong and how to sort it out please?

 

[Loz]

Is there a switch to turn off the USB socket when not in use? These draw a small amount of power even if nothing is plugged in, as will the volt meter etc.

 

[RichvanT6]

Is there a switch to turn off the USB socket when not in use? These draw a small amount of power even if nothing is plugged in, as will the volt meter etc.

yes the switch is on the positive only. so positive goes batt - switch - 12v - USB - volt meter / negative goes direct from all bits excluding the switch back to batt

when the switch is off the volt meter and USB are not lit up / on

 

[Dellmassive]

Add a battery monitor to see what's going on.

Have you fully charged the battery to start off with?

Battery Monitoring -- How I Done It --

Battery Monitoring -- How I Done It -- Part #1 Battery monitoring is a very important part of your 12v system . . . . whether its just the vans starter battery or your leisure setup keeping an eye on the power in your battery bank will keep you from breaking down and make sure your weekends...

www.t6forum.com

.

 

[Skyliner33]

Is there a switch to turn off the USB socket when not in use? These draw a small amount of power even if nothing is plugged in, as will the volt meter etc.

Im sure an unused usb socket cant flatten 2 batteries overnight.

 

[RichvanT6]

Add a battery monitor to see what's going on.

Have you fully charged the battery to start off with?

Battery Monitoring -- How I Done It --

Battery Monitoring -- How I Done It -- Part #1 Battery monitoring is a very important part of your 12v system . . . . whether its just the vans starter battery or your leisure setup keeping an eye on the power in your battery bank will keep you from breaking down and make sure your weekends...

www.t6forum.com

.

as far as I was aware it was fully charged. I have had no problems before or after disconnecting the additional circuit - only had issues when it was connected. unless it was a complete flue of course?

 

[Dellmassive]

You can use a clamp meter to see where the current is flowing....

IE meter out what current is going out on the new circuit.

Clamp Meters

Any recommendations for clamp meters? They have been mentioned in a few threads but I can’t find suggested products. Suitable for small mA measurements with dc in the van and elsewhere and also if possible up to mains ac. I’m not sure how much I need to spend for a tolerably decent one with the...

www.t6forum.com

.

 

[Howzat]

There's no way that unit could flatten 2 batteries even with the switch on and the meter running so it has to be something else.
I have a meter and 12v socket wired to the leisure which are constantly on and running a small 12v fridge and the 80ah battery doesn't drop more than 10% overnight.

 

[RichvanT6]

Does it matter that I have connected the negative to the battery direct? should I be connecting this the body ground?

 

[Dellmassive]

@RichvanT6

Not for the LB....

Unless you have a shunt monitor connected to LB?.


.......

But that does apply to any starter battery connections


.....


Post some pics of the battery and connections.

Also any multimeter readings.

 

[Dellmassive]

Also how is the LB being charged?

 

[Loz]

Also how is the LB being charged?

That was going to be my next question

 

[RichvanT6]

@RichvanT6

Not for the LB....

Unless you have a shunt monitor connected to LB?.


.......

But that does apply to any starter battery connections


.....


Post some pics of the battery and connections.

Also any multimeter readings.

Hi @Dellmassive - thanks for the help

Additional pics below. The LB is charged from the factory fit setup - I don't know the details of how it is wired but is supposed to prevent the starter batt being allowed to discharge beyond a starting point so there is some sort of monitor somewhere. I have taken meter readings from both batts in the pics - unfortunately I don't have a clamp meter so cant give you an current readings. On the LB the Brown negative goes direct to the body work below the seat from where other grounds are being taken.











I don't know if it has a bearing but it does have start stop as well

 

[Ads_Essex]

The LB is charged from the factory fit setup

When you say you they were fully charged, do you mean that you’d driven long enough for them to have both charged to 100% via the OEM split-charger?

The Moll vehicle battery is likely not fairing well, particularly at 4 years old.

 

[Loz]

Check that the relay labelled 100 is clicking on and off when you start and stop the van. You can also remove this relay and see if the starter battery is failing on its own, as it's a Moll battery these are known to be duff.

 

[RichvanT6]

When you say you they were fully charged, do you mean that you’d driven long enough for them to have both charged to 100% via the OEM split-charger?

I had not been on a long drive so I cant say if they were fully charged - the new volt meter was reading 12.1V when I first used it before the van would not start so my guess is they should have been fairly well charged. I had only plugged in a couple of things to test the sockets for a min or 2 (and even started the van for a few mins) and then turned the switch off before leaving the van overnight. Was somewhat surprised it was flat in the morning.

 

[RichvanT6]

Check that the relay labelled 100 is clicking on and off when you start and stop the van. You can also remove this relay and see if the starter battery is failing on its own, as it's a Moll battery these are known to be duff.

Thanks will look into this - maybe it is just a fluke that the batt went dead at the same time unless there is any issue with connecting direct to the LB negative post?

 

[Deaky]

You didn’t have the radio on while you were working did ya?

 

[Howzat]

Your van only starts from the battery in the engine bay so were they really both flat or was that an assumption when it didn't start?
I'd follow the advice from Loz. Isolate both batteries by removing the relay. Reconnect the new USB/meter unit to the leisure. Test this setup for a few days. If the van doesn't start during this test then you can be sure the new unit you've wired to the leisure isn't responsible. Then you're looking at either the battery failing, parasitic draw, an alternator failing or some other starting fault that would require an OBD scanner to verify. Pretty easy to rule out the alternator by running the van and measuring the volts at the battery terms with your meter which should be around 14.5.