Renogy DC-DC charger, where to connect mains charger?

[Slunkie]

Evening all,

Hoping for a bit of help from the electrical gurus please.

I haven't been using my van so much recently and with the light fading up in Scotland, my solar panel doesn't seem to be keeping things topped up. I clearly need to get it on trickle charge but not sure where to connect it to top up both the starter and leisure batteries. I have a renogy DC-DC, wired like this.


I've tried connecting my CTEK mxs 5.0 to the starter battery and leaving it but even after 24hrs it doesn't seem to be getting any meaningful charge to the leisure battery. I don't find the renogy home app remotely intuitive so not sure what's going on (screenshots taken whilst charger is connected to the starter battery).





Any pointers on what's going on and where I should connect the CTEK charger to sort both batteries?

As a side note, additional to the renogy home app being quite unintuitive, the shunt always used to report the leisure battery as 50% charge except now when it says 0%, so I'm not even sure it's working/connected correctly...

Cheers

 

[Salty Spuds]

I’m willing to stand corrected, but I don’t think you can charge both batteries with one mains charger with that setup. I would connect the charger to the leisure battery and then fit something like an AMT 12 to trickle the starter battery from the now fully charged leisure battery.

 

[Sim60]

You don't show how your shunt is connected .It could be mis-wired.
I would say that the DC -DC thinks the leisure battery is fully charged.

Simon

 

[Slunkie]

I’m willing to stand corrected, but I don’t think you can charge both batteries with one mains charger with that setup. I would connect the charger to the leisure battery and then fit something like an AMT 12 to trickle the starter battery from the now fully charged leisure battery.

Ahh that's interesting. The DC-DC charger does obviously charge the leisure battery from the (smart) alternator when conditions suit (once the starter battery is fully charged, according to the manual), so I'd guessed a mains charger connected to the starter battery would also eventually trigger that function.

There's a connection on the DC-DC charger for ignition signal which is necessary when a smart alternator is installed, perhaps that could be hijacked somehow trigger the leisure charge function?

I'll look into the AMT 12.

Cheers

 

[JumpShip]

The mxs5 doesn't have a lithium charging option , just a lead acid or AGM .

 

[Dellmassive]

Drop some pics

I think you are bypassing the shunt.

Any chargers need to have the NEG connected to the van chassis, and not direct across the battery.

The top pics show your start battery at 14.9v


.

 

[doncarlyon]

Trickle charge the starter battery and then when you drive anywhere, the DC charger will sort the leisure battery. Unless you only drive 5mins down the road ofcourse.

 

[Slunkie]

You don't show how your shunt is connected .It could be mis-wired.
I would say that the DC -DC thinks the leisure battery is fully charged.

Simon

Ok I'll check the wiring of the shunt today, presume it was done as per the manual but perhaps something is amiss.

Interesting you say you think the DC-DC thinks the leisure battery is fully charged. It's showing as 14.4V (DC-DC) and 14.3V (shunt) which seems good. If that's the case I don't understand why stuff powered by the leisure battery is cutting out after a short while like there is insufficient charge, and the DC-DC charger is slow flashing red (over discharge warning) and shunt is giving the low soc warning.

Everything was working just fine until I stopped using the van so much and the days started getting shorter.

 

[Slunkie]

Drop some pics

I think you are bypassing the shunt.

Any chargers need to have the NEG connected to the van chassis, and not direct across the battery.

The top pics show your start battery at 14.9v


.

Yeah it occurred to me that one of the accessories might have its own earth which would then create a bypass around the shunt to earth. Thanks for this, I'll disconnect the busbar connection to earth and check if it's still got continuity to earth with a multimeter.

 

[Slunkie]

The mxs5 doesn't have a lithium charging option , just a lead acid or AGM .

Good point, I hadn't noticed. Time for an upgrade maybe.

 

[rippelep]

I have a similar wiring as you, also a complete renogy setup, but without a shunt, monitoring with a renogy one M1 or app. As my T6 has a smart alternator, I also wired the ignition on wire from the bcm to the dcdc.


So then the second batterie is only loaded via main battery from the alternator if this signal is active, means if the car is running and producing higher voltage. So in case loading the main battery directly the aux. batteries will not be loaded due to the missing signal.
But in my constellation it works the other way round if I remember right. If I load my aux. batteries with a ctek loader (ctek one ?? which is litium enabled) and if these are full, then the main battery is also loaded via dcdc (same as if fully loaded by solar panels) But not 100% shure, I will check that

 

[Sim60]

Good point, I hadn't noticed. Time for an upgrade maybe.

mxs5 doesn't need a lithium profile if it's connected to the starter battery.
The dc-dc convertor is handling the lithium profile for the leisure battery. - assuming your leisure battery is Lithium - I don't think you say anywhere.

Simon

 

[prog99]

Slightly different answer.
What size is your panel? I'm north of Inverness and a 150w panel keeps everything topped up over the winter.