Member Since: 08 Sep 2020
Location: Buckley, North Wales
Posts: 1150
Power drain issue part 182639
Hi all
So I’ve been trying to figure out why I keep coming to low voltage every day for about a year
This time I undone my split charge setup by disconnecting the positive terminal from the main battery
But the split charge box still is lit up after the car is turned off and the positive terminal is disconnected
And my main battery is reading 12.8v when disconnected from the split charge box
Is this normal?
Do people usually leave the split charge set up or do people disconnect it unless it’s needed?
It appears the drain is happening on shut down I can see the bolts going down for a minute or so. Which is what lead me to check the S.C
I’m wondering have I disconnected it properly or should I also disconnect the negative also?
Should the SC box stay active when disconnected?
I have earthed the SC box to the chassis rather than the battery negative
In fact I’ve attached an image of my setup for someone to check if it’s ok please and thanks
I have my winch earthed to the chassis instead of the negative - as instructed on here. Nora ire if that makes a difference.
Disco 3 SE Manual 2005 V6 2.7
Buckley, North Wales
7th Dec 2022 1:21 pm
Coo
Member Since: 01 Jun 2015
Location: Fife, Scotland
Posts: 284
To rule out a dodgy relay on the split charge, isolate that by removing the fuse for it from main battery.
7th Dec 2022 1:39 pm
Flatlander
Member Since: 20 Jul 2015
Location: Here
Posts: 575
To confirm and isolate any battery drain, you need to be measuring current, not volts. Maximum allowable current draw with a 'sleeping' vehicle is 50mA, although anything over 40mA should be investigated.
12.8VDC indicates a healthy battery that is fully charged. Have you connected the split charge relay the correct way round? I can't see which type it is but you need to get the in & out terminals the correct way round as the switching voltage is sensed from the 'in' terminal - i.e. the one that should be connected to the starter battery.
7th Dec 2022 1:50 pm
cmb2020
Member Since: 08 Sep 2020
Location: Buckley, North Wales
Posts: 1150
Thanks all
Here’s this mornings results:
Yesterday 3.30pm - 12.75v
Today 9.30am - 12.35v
So that’s 0.4v lost over 18 hours
Usually 11.6v within 30 minutes of shutting down
So looks like the split charge wiring. I’ll reconnect it today and see how it goes with the new earth.
Is it normal to have 12.35 next day or should it be staying at 12.6 lowest?
May be because I did drain it a bit reconnecting briefly and then charging for 1 minute running so didn’t get a good full charge back.
…..
Replying to your posts:
Yes I’m certain it’s the correct way round I triple checked
I redone the split charge earth terminal and tested ground point 100% is earthed properly
I can not for the life of me figure out how to do the parasitic drain mate - as the alarm goes off when it’s shut down and asleep and I try to test. I’ve been looking for how to do this. Do I have to stay in the car for 30 minutes while it’s deadlocked? And find an internal cab battery source? Any vids or links please?
I’m certain this has been the drain. Or at least one of the drains.
Thanks againDisco 3 SE Manual 2005 V6 2.7
Buckley, North Wales
8th Dec 2022 11:04 am
Flatlander
Member Since: 20 Jul 2015
Location: Here
Posts: 575
Basic parasitic drain test method:-
You'll need an inline ammeter - not clamp as they drift over time except the really expensive ones, the leads will need crocodile clips.
Remove the battery box cover, open the bonnet then push the latches closed, close all the doors and lock the car.
Leave 30 mins to fully 'go to sleep'
With the leads in the correct terminals of your ammeter, clip the +ve to the battery +ve terminal, clip the -ve lead to the palm of the lead that goes to the BJB from the battery terminal.
Remove the bolt that holds the BJB supply lead to the battery terminal and place some insulating material between them, observe the ammeter display, it should be reading 0.05A (50mA) or less, some peaks will be seen, particularly if the air suspension self levels, but in the main, you should see an average of 30-40mA. Monitor over as long as you can, ideally use a meter that has a peak hold facility.
If the drain is below 50mA, this is within design specification (just!) if over, then you have an issue. At this stage, don't go pulling fuses and relays out, that'll just muddy the waters but you can disconnect the split charge relay as that won't 'wake up' any vehicle systems.
0.4VDC drop overnight especially at this time of year is of no concern at this stage - unless you have it in a garage that has a relatively stable temperature.
ETA - they key point to remember is that you have to connect the ammeter in circuit before opening the circuit, which then means the circuit is uninterrupted and the current will flow only through the ammeter.
Last edited by Flatlander on 8th Dec 2022 1:03 pm. Edited 1 time in total
8th Dec 2022 12:59 pm
gstuart
Member Since: 21 Oct 2016
Location: kent
Posts: 14004
Hiya
Also been through this with regards to a parasitic drain, plus as a reference if I don’t use my disco , my battery will last roughly 3 1/2 x weeks @12.7 Vdc before I have to reconnect CTEK battery charger
Last edited by gstuart on 8th Dec 2022 1:16 pm. Edited 1 time in total
8th Dec 2022 1:00 pm
gstuart
Member Since: 21 Oct 2016
Location: kent
Posts: 14004
Flatlander wrote:
Basic parasitic drain test method:-
You'll need an inline ammeter - not clamp as they drift over time except the really expensive ones, the leads will need crocodile clips.
Remove the battery box cover, open the bonnet then push the latches closed, close all the doors and lock the car.
Leave 30 mins to fully 'go to sleep'
With the leads in the correct terminals of your ammeter, clip the +ve to the battery +ve terminal, clip the -ve lead to the palm of the lead that goes to the BJB from the battery terminal.
Remove the bolt that holds the BJB supply lead to the battery terminal and place some insulating material between them, observe the ammeter display, it should be reading 0.05A (50mA) or less, some peaks will be seen, particularly if the air suspension self levels, but in the main, you should see an average of 30-40mA. Monitor over as long as you can, ideally use a meter that has a peak hold facility.
If the drain is below 50mA, this is within design specification (just!) if over, then you have an issue. At this stage, don't go pulling fuses and relays out, that'll just muddy the waters but you can disconnect the split charge relay as that won't 'wake up' any vehicle systems.
0.4VDC drop overnight especially at this time of year is of no concern at this stage - unless you have it in a garage that has a relatively stable temperature.
ETA - they key point to remember is that you have to connect the ammeter in circuit before opening the circuit, which then means the circuit is uninterrupted and the current will flow only through the ammeter.
Hi
Apologises as posted the same time as ur good self
8th Dec 2022 1:07 pm
cmb2020
Member Since: 08 Sep 2020
Location: Buckley, North Wales
Posts: 1150
Thanks all and I’ll do this test if I get any more issues
I’m told winter time parked outside 12.4v is normal in cold
Didn’t realised cars could be so sensitive to weather and power consumption
So is it normal to supplement charge with a mains power this time of year once a week?!
Also do people leave the split charge connected constantly? Or do we need to only switch it on when the aux battery as and when it needs charging please?
As I’ll get a switch on it if it needs turning off when not in use
Thanks as always!Disco 3 SE Manual 2005 V6 2.7
Buckley, North Wales
8th Dec 2022 2:28 pm
gstuart
Member Since: 21 Oct 2016
Location: kent
Posts: 14004
Hi
Regarding a VSR/ relay split charge system here’s a link for u , they also sell the proper kits as it needs to be wired up correctly with a suitable relay/ VSR , most importantly fused and suitably sized
Personally I fitted one from tmax, but if u look at that link there are VSR etc
Ur battery should last at least 3 x weeks if not being used and at a minimum of 12.6Vdc , then when mine drops to around 12.4Vdc I plug my Ctek in , indeed they are very sensitive with low voltages and need a good quality battery
There’s also apps u can get with a Bluetooth BM2 module , that allows u to see via ur iPhone / iPad what ur battery voltages are , have to fit a BM2 module on each battery
Hope that also helps
8th Dec 2022 2:58 pm
gstuart
Member Since: 21 Oct 2016
Location: kent
Posts: 14004
Hers that battery monitor , need one for each battery , Bluetooth range isn’t brilliant, around 15-20 feet , but very handy as u can also do a crank test etc
Member Since: 20 Jul 2015
Location: Here
Posts: 575
cmb2020 wrote:
Thanks all and I’ll do this test if I get any more issues
I’m told winter time parked outside 12.4v is normal in cold
Didn’t realised cars could be so sensitive to weather and power consumption
So is it normal to supplement charge with a mains power this time of year once a week?!
Also do people leave the split charge connected constantly? Or do we need to only switch it on when the aux battery as and when it needs charging please?
As I’ll get a switch on it if it needs turning off when not in use
Thanks as always!
Firstly, a split charge controller should disconnect the aux. battery & associated circuits once the system voltage falls below a pre-set level, this varies dependent upon the system and it's intended application but is generally in the range of 12.7 - 13.5VDC
If yours isn't disconnecting the vehicle and aux. systems, then you have a problem.
Secondly, car battery voltage with respect to ambient temperature is constrained by the laws of physics, it is also affected by the amount of charge, (and charge voltage) put back after every engine start. Generally speaking, it takes 20 minutes driving - not just running the engine, to put back the charge you take out of the starter battery just by starting the engine. This can be compounded by sitting in traffic, heated seats, screen, blower, lights on - which the alternator will generally cope with, but at idling speed, it leaves very little headroom for charge to be put back into the battery (there is an 'emergency charge' strategy in the ECM that will raise the idle speed to 1000rpm and the ATCM will switch off certain loads under very low voltage conditions). Now add an aux. battery into the list of current drains and you can see that, even with some reasonable runs, the starter battery charge level will start to suffer. In short, it does no harm to 'top up' the starter battery charge with the correct type of charger for your installed battery.
8th Dec 2022 3:15 pm
cmb2020
Member Since: 08 Sep 2020
Location: Buckley, North Wales
Posts: 1150
Yes, it'll be made from Chineseium but Schneider Electric are a brand with a reputation to keep up, they own/owned a big UK electrical wholesaler as well as making switchgear etc.
ETA - just seen the photo with a multimeter in ii, if that's yours and it has a DC mA scale, then you already have an inline ammeter (as opposed to a clamp ammeter).
11th Dec 2022 5:54 pm
cmb2020
Member Since: 08 Sep 2020
Location: Buckley, North Wales
Posts: 1150
Thank you and yes both my multimeters have the setting!
I’m just struggling to understand the sequence. If this is correct?:
.close latches and doors and lock car and wait 30 minutes
.put red multimeter wire on the negative battery terminal
.put the black wire on the negative battery terminal clamp
.turn multimeter on to specified settings with hold selected
.carefully remove negative cable off of negative battery terminal
.check reading, then leave for a hour, and check again
.if it’s over 40-50ma then try pulling fuses 1 by 1 and checking
Does that sound correct or am I misunderstanding?
Also, attached is image of the multimeter settings on 10a, is this the correct setting?
Disco 3 SE Manual 2005 V6 2.7
Buckley, North Wales
11th Dec 2022 8:54 pm
Flatlander
Member Since: 20 Jul 2015
Location: Here
Posts: 575
Firstly, it's much easier to use the +ve terminal, secondly, you have it in the (correct) mA terminal but you reference using the 10A scale. to do that, you'd need to have the lead in the 10A connector.
To reiterate how I'd do it (unfortunately I don't have a Disco3 to hand to do 'how to' pictures, but we're all adults here so hopefully a descriptive narrative will suffice....)
Open the bonnet, remove the battery cover, push the bonnet latches into the closed position, so the vehicle senses the bonnet is closed.
Turn on the ignition, turn off the ignition (to provoke a graceful shutdown), close all doors & windows, lock the vehicle. Leave well alone for 30 minutes or so.
During that time, get your multimeter/inline ammeter and put the leads in the receptacles for the correct range to be measured - i.e. DC milliamp range (mA). The positive terminal has three connections, one to the battery post, one to the starter motor via a 400A mega-fuse under the black plastic cover and one to the BJB, which is the flat 'palm' held on by an M8 bolt with a 10mm bolt head.
Connect the red lead to the battery terminal (not the flat 'palm' of the cable lug going to the BJB), easiest is the 13mm nut used to tighten the tapered connection to the battery post, connect the black lead to the flat 'palm' of the cable lug going to the BJB. turn on the multimeter to the correct measurement range, remove the bolt holding the flat 'palm' of the cable lug going to the BJB to the battery terminal, place some insulating material between the two, some cardboard will be fine.
Observe the meter reading, record the maximum current draw, if over 50mA then you have a problem, if under 50mA but greater than 40mA then you need to investigate why, if under 40mA then everything is normal.
Ideally you'd use a meter that can store min & max readings and has the ability to not switch off after <some_amount_of_time> and monitor for ~ 12 hours, the longer you can monitor for, the more accurate your test will be.
Pulling fuses can be counterproductive, if the fuse protects the supply to a control module it can interrupt the communication circuit and cause other modules to wake up and increase, not decrease the current draw. Much better to measure the mV draw across an installed fuse to determine which circuit is drawing current (yep, you read that right, measure voltage drop to determine current draw) and then investigate that circuit and it's consumers.
Last edited by Flatlander on 11th Dec 2022 9:38 pm. Edited 1 time in total
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