Leisure Battery help please

Fishinbrine

Member
VCDS User
VIP Member
T6 Pro
Good evening all, we are currently away and after a 4 hour drive yesterday I was amazed that the leisure battery status on our Sargent panel shows it as flat with the 1 single red LED. Anyway,day I thought will leave the solar to do it's thing, and after returning from a day out panel showed all the nice green LED'S like a nicely charged leisure battery. Victron solar app showed 12.88v
Worth pointing out only consumer we have had during this time has been the fridge turned down to 1.
Right, back to the story, night has approached, so put the interior lights on from the panel, and got a single red LED on the Leisure Battery, checked the solar app and battery down to 10.2v
Have I done something here? Do I or should I do something to enable the charging from the vehicle when driving? Is there anything I can check? Although I don't have a multimeter with me I'm very competent with the use of but I honestly have no real idea how the system is meant to work.
I assumed, van running, a fancy version of a split charge relay will charge the leisure battery - in my case a Sterling Power box. During sunny days,the solar will do it's own thing through the Victron unit.
Is there anything I should do with anything here? The Sargent fuse box, has a big switch for charger that again I thought was just for electric hook up - which we don't have on this trip.
Any advice gratefully received, currently sat with very limited lighting after I convinced the Mrs that we be fine without electric....
Van is a T6.1, solar on roof, single leisure battery under a cupboard, all 4 years old.

Screenshot_2025-04-18-19-30-58-93_30b6efbd53acd6f273baafa7ca03da38.jpg

Screenshot_2025-04-18-19-31-09-78_30b6efbd53acd6f273baafa7ca03da38.jpg
 
Looks like you have a dead leisure battery.
The smart solar is showing min battery voltage of 9.74V. This looks to me like it needs replacing .

Simon
Thanks Simon, I will get it on a refresh cycle when I get home and see how it performs, but other than that, there's nothing else that could be causing this? Nothing silly that could need doing with any of the panels/controllers? I honestly need to get a better understanding of how the system actually functions, I haven't bothered with it at all until now as it's been ok, yet the Mrs loaded the van alone as I was working and now I have this issue,call me sceptical of you want but I'm sure we have all been here before!
 
Despite the solar charger going through, bulk, absorption and float cycles, your battery is now flat, so either it’s not holding charge or there is big drain on the battery.
 
Sounds like a dead battery. As for the Sterling Power box? a picture showing the unit and the connections might help determine if it also charges from the alt but going from your OP (4 hour drive, battery dead) it doesn't sound like it does but a picture would help confirm.
 
Not sure if there is potential that your sterling unit might have been knocked when SWMBO was packing. I wouldn't know where to begin trying to tell you what charge profile you need on the sterling charger, nor would I have the first clue how to change it. I'm guessing the solar charges your battery through an MPPT so this is likely ruling out the chances of it being the sterling?
 
Thanks all, this morning the solar controller shows the voltage climbing to 14v then suddenly drip to 10v and after a few seconds it climbs again. Is that normal??

Screenshot_2025-04-19-08-14-14-94_30b6efbd53acd6f273baafa7ca03da38.jpg

Screenshot_2025-04-19-08-14-30-22_30b6efbd53acd6f273baafa7ca03da38.jpg

Screenshot_2025-04-19-08-14-34-24_30b6efbd53acd6f273baafa7ca03da38.jpg
 
No, that’s not normal almost certainly a knackered battery, especially given its age and having gone totally flat. Or possibly a loose connection somewhere.
 
Ok thanks again will get it sorted when I get back. Since looking at this though I have seen many posts about these sterling units going faulty. Are these purely responsible for battery to battery charging? What charges the leisure battery when on hook-up? Is that the Sargent unit's job?
 
The all in one units don't really have a "charger" they have a constant 13.8v supply that runs your 12v leisure electrics and will slow charge a standard flooded battery.

It was a very cheap simple robust system for leisure electrics when the only load was lighting, it's not ideal for modern systems with an electric fridge, though if you are just hopping from EHU to EHU it's fine.

It's not that they are faulty, just they are increasingly not a good match for vehicles with smart alternators and heavy electrical loads like compressor fridges.

Lead Acid batteries must never be regularly drained below 50% (12v) otherwise they are damaged very quickly. I agree with others your battery is now expired with those voltages - chargers offering "reconditioning" don't really work if the battery has been damaged.
 
Who on this planet wired that Sterling up?
There's only supposed to be 1 wire in each terminal.
Left is supposed to be starter battery pos in, center is ground and right is out to leisure pos.
I'd imagine the red wire is going to your leisure battery but the blue wire is a mystery. Same for the other terminal. Black is maybe the feed in from the starter but again dunno what the brown wire is doing there?
Have a look at your starter battery to check if there is a black cable on the pos terminal running into the van to confirm the black wire on the Sterling is for that.
As for the blue and brown that looks like household wiring so you could do with finding out where they run to.
Can't get my head around your setup at all.
Having said all that it looks like you should have B2B capability if that black wire is running from the starter battery and the fact the liesure battery was dead after a 4 hour drive does suggest a dead battery unable to hold charge.
 
Blue and brown... I wonder if the other end of those two are connected to a plug that is next to the electric hook up sockets. AC to DC charging via a B2B Sterling?
 
More pictures and some wider ones for context would help folks see more and maybe advise better
 
Your smartsolar pictures show that every day it tries charging the battery - max value is 14.6V etc. but min voltage is 9.6V etc - so charge is not being held or you are discharging it every day. When you saw it solar charging and then drop to 10.17V, maybe the fridge kicked in - indicating it can't support the fridge load any more.
What might cause the sterling unit not to charge the leisure battery?
I don't know much about the Sterling unit - maybe it won't charge the leisure battery if the voltage is too low?
There should be a fuse fitted between the starter battery and the sterling unit - you could check that hasn't blown - and similarly between the sterling unit and the leisure battery.
What vehicle do you have? -is it T5, T6, T6.1? Does it have a smart alternator? If so, is there an ignition wire connected to the sterling unit? - There doesn't need to be, but it may help to narrow down the issue.
1745134885058.png
 
Who on this planet wired that Sterling up?
There's only supposed to be 1 wire in each terminal.
Left is supposed to be starter battery pos in, center is ground and right is out to leisure pos.
I'd imagine the red wire is going to your leisure battery but the blue wire is a mystery. Same for the other terminal. Black is maybe the feed in from the starter but again dunno what the brown wire is doing there?
Have a look at your starter battery to check if there is a black cable on the pos terminal running into the van to confirm the black wire on the Sterling is for that.
As for the blue and brown that looks like household wiring so you could do with finding out where they run to.
Can't get my head around your setup at all.
Having said all that it looks like you should have B2B capability if that black wire is running from the starter battery and the fact the liesure battery was dead after a 4 hour drive does suggest a dead battery unable to hold charge.
I will have a proper look when I'm back, I hate it when someone is alarmed by how it's connected, as I didn't do it, so you 'trust' it to be as it should. Looking at the van it looks like these extra wires come directly from the Sargent unit, but looking through the manual for the Sargent unit I cannot imagine/think why it should be? Unless this is how the Sargent is connected to the vehicles starter battery possibly?
I'm the kinda guy that will potentially take this all out when I get home and redo it correctly but also don't want to be doing something for the sake of it, if it's not right, it's wrong.
Thanks all for your advice so far.
 
Your smartsolar pictures show that every day it tries charging the battery - max value is 14.6V etc. but min voltage is 9.6V etc - so charge is not being held or you are discharging it every day. When you saw it solar charging and then drop to 10.17V, maybe the fridge kicked in - indicating it can't support the fridge load any more.
What might cause the sterling unit not to charge the leisure battery?
I don't know much about the Sterling unit - maybe it won't charge the leisure battery if the voltage is too low?
There should be a fuse fitted between the starter battery and the sterling unit - you could check that hasn't blown - and similarly between the sterling unit and the leisure battery.
What vehicle do you have? -is it T5, T6, T6.1? Does it have a smart alternator? If so, is there an ignition wire connected to the sterling unit? - There doesn't need to be, but it may help to narrow down the issue.
View attachment 283798
It's a 6.1 so yeah smart alternator.
I'm reading more and more bad stuff about these sterling b2b chargers so will likely replace with a Victron unit in the coming months.
Sterling units lights up when engines started, fuses all good, leisure battery scrap I would say.
Anyone have any decent AGM leisure battery recommendations or is Lithium the way to go? I know it's better technology, and it's not the costs or adaptions to my van I will need to be able to charge lithium, it's the worry of spontaneous combustion, rare I know, but still worries me a lot!
 
New leisure battery technology is lithium iron phosphate LiFePO4, not the lithium batteries in scooters that you see in the news catching fire and burning your home down. It’s much safer as long as it is fused properly and correct wire gauge used. You shouldn’t worry about changing over as it is much more efficient for camper vans.
 
Hi Fishinbrine

Sorry not much use!

No idea but watching as my setup confuses the hell out of me!

Put it on EHU and get alarms going off sometimes - but think the Sargent has been replaced by a different charger - leave it alone and solar runs everything fine for 3 days +

Have loads of boxes in the electric cupboard I just don’t understand - slowly getting my head around it - then my head explodes.

Maybe a T6 event to bring together people who know what they are doing with the rest of us who don’t ;)
 
Back
Top