Bei meinem etwas älteren Fahrzeug hängt nur eine 15A Siliziumdiode zwischen dem Lastausgang des 70/15 und der Starterbatterie.
Hello everyone,
perhaps you can explain this — I’m close to despair…
I parked our motorhome (Citroën Jumper base, 2023 model) on 2 June 2026 and started it again for the first time on 2 October 2026. Four months standing idle — an absolute first in our 20-year motorhome history…
What can I tell you? The vehicle started less than two seconds after I turned the key!?!
But since, according to this thread, that simply can’t happen, I’m now trying to find the fault — but where do I start? Could it be that only my starter battery is in good condition, or that the vehicle electrics are working properly, or perhaps both???
I’m sure you know more about this than I do. Thanks for your help…
A few details are still missing. Solar panels installed? Which controller? StandbyCharger installed? How much current does the marten deterrent draw?
My motorhome starts up any time too. But I know why.
@Hannus
I think you joined in a bit late here…
Maybe I should have made the sarcastic part clearer, though. 
Hi. I approached it in a different way. I have two solar arrays, one of which charges my chassis battery so that I can always start my RV motor and do not need to worry if it is parked up for prolonged periods. My Orion XS then charges my house battery from the chassis battery, with engine shutdown parameters set such that the Orion stops when the chassis battery is resting. This also means that when my motor is running, once the chassis battery is full any excess power goes to my house battery.
The system works perfectly.
There are of course other chargers for the house battery, the second solar array, ip22 & multiplus, but in terms of what I think your trying to achieve my solution works and is fully programmable
I’m really pleased that the topic of trickle-charging a starter battery, along with my little build guide (< €10), has attracted so many interested readers and continues to generate lively discussion to this day.
The build guide is at the beginning of the article, with the electronic components a few posts further down.
8th place in the German-speaking section 
I never would have expected that
What does it achieve 
Maybe a few comments on that. The PTC in standby chargers isn’t a fuse that switches on and off; it’s just a current limiter.
Your simple solution is also active while driving. With newer vehicles in particular, which have a low battery voltage, some of the booster current always flows back to the starter battery (circulating current). Switching it off via D+ might not be a bad idea.
To support the starter battery in winter too—which is certainly feasible with today’s battery sizes—I would lower the switch-on threshold to 13.3 V. Solar power isn’t always enough in winter to get above 13.8 V.
Hi @Hannus,
Thanks for your comments. The solution doesn’t claim to be perfect, but it solves the problem for me.
I use an ESKA FRG300 PTC fuse; my aim was to limit the charging current.
In the event of a fault or short circuit, hopefully the SmartSolar’s 20 A fuse will blow.
Since I have a conventional alternator with a 14.4 V output, there is no circulating current of the kind you described, because after the two diodes there’s only 13.2 V, compared with 14.2 V at the service battery. The 13.2 V also won’t activate the charge booster’s automatic engine detection. The diodes also block reverse current to the SmartSolar. It takes a bit of trial and testing to find the right combination of diodes.
But the issue with smart alternators is a good point for anyone else building this, since their batteries only get partially charged and are never fully charged (I’m a long-suffering customer of a well-known car manufacturer whose vehicles have this type of alternator).
Winter poses a completely different challenge. Below 5 degrees, I switch off charging to the lithium batteries, which means the circuit is deactivated. But there’s also a changeover switch to connect the SmartSolar directly to the starter battery.
I monitor the vehicle with a Globallink…
But I can’t fit any more blue boxes in the vehicle…
It looks like maintenance charging for the starter battery with the Orion XS is on its way.
This has already been discussed at length in all the other threads about bidirectional charging with the XS.
The current “15-minute emergency landing” is only the first step.
I must have missed that… I thought until now they were all just “wishes and rumours”. It was the first time I heard it officially in the video…