Disco 3 (LR3) Split charge

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gstuart

gstuart

D3 Grandad
Full Member
Posts
29,881
Location
Kent
Hi

so after an issue with my t max split charge system I’ve been monitoring the Vdc daily

abit of history

with the engine running or charging via the CTEK the aux battery wouldn’t charge and the main battery was being drained

so found that the fuse by the aux battery had blown, was because I installed a too low amp fuse, upgraded it from 40 to 80 amps

Used a clamp meter to see what the residual Vdc was when the disco was alarmed and into sleep stat

noticed today the Vdc is now higher than the main battery

here are some readings

with engine running

96B2B8CA-B8FF-4015-BBA7-B995E24C032E.png
2216954A-DBF9-4B03-A071-0A2D23421125.png



On charge


2BAE7443-D010-481C-A3DD-F5D53963A32C.png



Vehicle locked and alarmed
54221B4D-A3BD-435C-9D70-9B2F88FC2648.jpeg





After 30 x mins , sleep state

5987734C-0D12-4AA6-AEC7-A71153A3A51B.jpeg



After I had replaced the aux battery blown fuse

A152A07A-680D-437C-BF89-EC389D5AC943.jpeg
 
This is what the residual readings should be and indeed mine is under 22

0CBEACAF-1F1C-47DB-9138-6789B9B658D3.jpeg
 
Last edited:
These are my daily readings, with the vehicle locked and alarmed

would u consider this to be a normal drain please

also the clamp meter readings I don’t mind admitting I always get confused , the last one does that mean 0.15 Vdc

apologises for the daft questions and many thks as always as this has been a bit of a nightmare with battery draining and been trying to work out according to the daily VDC of how long the battery should in theory last

is there a formula plse that I can use to work this out

thks again and am always so grateful



plus new battery bought , yuasa YBX019 , capacity 900CCa 100 A/h

C1AC9BAD-4368-4A4C-B650-DEA3D2C44B1F.png
FE6B1080-9B9A-46E0-94D9-F347113A12A9.jpeg
826A47F3-CCC9-4B2F-904E-726706323B35.png
3C99C380-26F5-46F1-B205-229E5AED8545.png
 
Last edited:
So think it’s easier if I list the daily readings here instead of posting pics , will update each day so can get a record all in one place

Vdc

8/1 Main 13.04 Aux 12.50
9/1 Main 13.03 Aux 12.99
10/1 Main 12.88 Aux 12.90
11/1 Main 12.76 Aux 12.87
 
gstuart said:
also the clamp meter readings I don’t mind admitting I always get confused , the last one does that mean 0.15 Vdc

apologises for the daft questions and many thks as always as this has been a bit of a nightmare with battery draining and been trying to work out according to the daily VDC of how long the battery should in theory last
Click to expand...
Hi, the last pic with the clamp meter as it's set is 0.15A (150mA) which is high in sleep mode. I didnt try it myself as i was not pleased with the description of thr T-max "split charge" system cos as it's described it's most of a "split - discharge" than charge system, too rudimentary setup IMO and the gist of it is this:
"The T-Max dual battery system automatically links two batteries for charging, but isolates them when discharging."
which means that two different batteries are linked in parallel to the alternator which is not the best at all, such system would be efficient only with two 100% identical batteries which are installed both from new.

So as long as t-max it doesnt have some sort of isolation solenoid to bypass it with ignition off that high quiescent draw can be caused by the system too... to rule out the vehicle's equipment you should measure the drain with the t-max and secondary battery isloalted as the vehicle to be hooked only to the main battery as it left the factory... these cheap(ish) VSR based "split charge" systems are not compatible with ''smart" alternators link3d to the ECU like the D3 has, ... you need a "battery to battery" charger for this one... see this https://www.12voltplanet.co.uk/battery-to-battery-chargers.html but i'm a bit out of date with this so you can make some more resarch yourself maybe there is some better technology but what i'm certain is that the VSR based t-max is not something to fit on vehicle with smart charging system
 
sierrafery said:
Hi, the last pic with the clamp meter as it's set is 0.15A (150mA) which is high in sleep mode. I didnt try it myself as i was not pleased with the description of thr T-max "split charge" system cos as it's described it's most of a "split - discharge" than charge system, too rudimentary setup IMO and the gist of it is this:
"The T-Max dual battery system automatically links two batteries for charging, but isolates them when discharging."
which means that two different batteries are linked in parallel to the alternator which is not the best at all, such system would be efficient only with two 100% identical batteries which are installed both from new.

So as long as t-max it doesnt have some sort of isolation solenoid to bypass it with ignition off that high quiescent draw can be caused by the system too... to rule out the vehicle's equipment you should measure the drain with the t-max and secondary battery isloalted as the vehicle to be hooked only to the main battery as it left the factory... these cheap(ish) VSR based "split charge" systems are not compatible with ''smart" alternators link3d to the ECU like the D3 has, ... you need a "battery to battery" charger for this one... see this https://www.12voltplanet.co.uk/battery-to-battery-chargers.html but i'm a bit out of date with this so you can make some more resarch yourself maybe there is some better technology but what i'm certain is that the VSR based t-max is not something to fit on vehicle with smart charging system
Click to expand...

Thks a million as always and so grateful

so indeed that’s very high seeing it’s suppose to be below 22ma , think the first port of call will be to remove the 2 x BM2 battery monitors , is supposed to only use 1ma

will check it out and appreciate the link as it’s driving me nuts , longest the main battery has lasted is 3 x weeks

that’s another reason I’ll take some daily readings and write then down to see how much is drops , plus also thought the D3 will wake up to self level it’s self , wonder when that happens if the suspensions ecu is taking a lot of amps out the battery

hoping that I can finally resolve this as if I’m away , ie camping etc don’t want to worry that the battery will go flat , replaced all the interior bulbs with led ones

Also keep thinking if putting a solar panel on the roof would help

thks again
 
Just stated to read ref the DC to DC and see it prevents the batteries from taking Vdc from one another

according to my daily readings can see that’s happening because the aux is at a higher VDC than my main battery

think you’ve hit the nail on the head @sierrafery

will keep reading and see if it’s viable to fit solar as well, so that when I don’t use the disco for a month can have a system that can rip them up when i haven’t got access to a charger

thks again and feel this will be the way to go and finally sort this out
 
sierrafery said:
A solar pannel can't hurt just get one which already has the blocking diode fitted or if it hasnt dont connect it without one.
Click to expand...

many thks, will get a MPPT controller

I’m the mean time seeing it’s at 150ma got to get it below 22ma

wondering if the battery monitors are causing this drain , suppose to only use 1ma , will disconnect them and take another reading

maybe there using 1ma per hour ?? Which may go towards the explanation of why it’s at 150Ma

So if 0.15 is 150ma am I right then I need to see 00.22 or under to reach the 22Ma plse , or is it 00.02

many thks
 
sierrafery said:
You'll have to see 0.02 on the clamp meter, which means 20mA/h drain
Click to expand...

many thks and I think a plan of action will be to first disconnect the battery monitors then if there’s no change to then as u recommend remove the pos lead from the aux battery

plus at least now I know what readings I need to see on the meter , always got confused when trying to decipher readings

need to try and find something in the net

really am so grateful mate of the fantastic help ,Thk u and will update the thread, just need a sunny day , lol
 
Ref the solar am wondering if a 100 watt panel would be suffice

what do u think plse @sierrafery , hope u didn’t mind be bothering u again

BE427BF7-C392-4E58-9D6D-FA3ED6AB53F4.png
 
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Vdc

8/1 Main 13.04 Aux 12.50
9/1 Main 13.03 Aux 12.99
10/1 Main 12.88 Aux 12.90
11/1 Main 12.76 Aux 12.87
12/1 Main 12.69 Aux 12.86
13/1 Main 12.59 Aux 12.82
14/1 Main 12.53 Aux 12.82

well have had to order a new meter as my current meter won’t zero

pretty sure the split charge solenoid is stuck open allowing the aux battery to take power from the bigger Main battery , as after 7 x days the main battery is already down to 88%

will in the mean time disconnect the split charge system and plug the ctek back in so the new main battery doesn’t drop any lower

has driven me nuts and will definitely look into a solar panel later in the spring , might even do away with the aux battery and hook up the solar directly to the main battery
 
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So my new meter turned up this morning , just need a nice dry day and can then hunt for this battery drain

49473B1E-0D5B-459B-BCA6-639872858CCF.jpeg
 
Henry_b said:
Looks like an adventure with this System!

I need one on the P38, to run some accessories i have in mind,.

Watching!! ;) :)
Click to expand...

hi mate

indeed will update the thread , looks like next week as I want a dry day

will link out the bonnet switch , alarm the disco , then have to wait 30 x mins for the system to go into a sleep state

can then start testing one fuse at a time along with some loops which is another reason I got a clamp meter

I think it’s the split charge solonoid that’s stuck open and the aux battery is taking voltage out the Main battery but won’t know 100% until I test it

@Henry_b , have u been looking at multimeters then or wishing to get some aux fuse boxes plse
 
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