Ctek250se Solar Input Charging Both Batteries Via Victron Mppt

[col661]

Here's a question. I have a CTEK250SE installed and also use a Victron 75/15 MPPT controller with a 160w solar panel. During the current travel restrictions, I see my starter battery dropping sometimes down to 11.5v so leave it running for 15mins to get it back up into 12v territory every 3-4 weeks.

The Victron MPPT 75/15 has 2 outputs, one to load and one to the battery which is set up correctly for me and I see that working fine through the app.

The CTEK250SE has a solar input which is currently unused because I use the Victron but I know the CTEK will trickle charge the starter battery once the leisure battery is in float. So, can I take the battery feed from my Victron and wire that to the solar input of the CTEK? That way, the load still goes to the 12v distribution while the sun shines and power is needed but the battery feed goes to the CTEK and charges both batteries?

I don't see any technical reason why this wouldn't work as the CTEK just see's a 12v current coming in from the Victron and treats it like a solar input?

Has anyone tried this and or offer any advise?

Thanks

 

[Phil_G]

I dont know specifically about the Ctek but normally a solar input wouldnt even trigger on 12v, its expecting a minimum panel voltage of 18v upwards.
I'd make up a simple copy of the Victron (?) top-up charger described here a few threads back, basically its just a lead connecting both positives (start & leisure) with a schottky diode and a low-value (half ohm?) resistor in series. If you have a fag socket on each battery its really easy to do, the dash socket is normally on the starter and the rear accessory socket is normally off the LB. Two plugs, a bit of wire, a diode & a resistor. Fused plugs both ends of course!

 

[Ads_Essex]

I think Phil means this:

...
Votronic 2A 12V DC to DC battery to battery trickle charger / standby charger | eBay

If you crack open the case you will find one diode and one resistor.........that's it!!!!

You can make the same for £2

It's just a diode to stop verse current flow and a current limiting resistor, ..... when the aux voltage is higher than starter current will start to bleed over upto the max rate of the limiting resistor and will rise the starter battery voltage up to the same as the aux feed minus the 0.6v drop across the diode. So it's kinda working like an unregulated low mA trickle charger.

These are certainly not chargers in the modern sense ..... but can work in some circumstances..,

 

[Lowlec]

The easiest way to do this,and it works.....
Connect The battery positive out of the Victron MPPT to the starter battery input of the Ctek unit,what this does is to charge the starter battery up to float level,(user defined)when this threshold is met and within the detection voltage of Ctek parameters,the Ctek will kick in to charge the leisure battery as the engine detection mechanism assumes the engine is running with the increased voltage,you will have tweak the charge levels in the Victron app to trigger the Ctek!

 

[Dellmassive]

The easiest way to do this,and it works.....
Connect The battery positive out of the Victron MPPT to the starter battery input of the Ctek unit,what this does is to charge the starter battery up to float level,(user defined)when this threshold is met and within the detection voltage of Ctek parameters,the Ctek will kick in to charge the leisure battery as the engine detection mechanism assumes the engine is running with the increased voltage,you will have tweak the charge levels in the Victron app to trigger the Ctek!

could i ask you for a bit more info pls:?

so what happens at night when the Victron MPPT will draw power from the leisure battery and output-it via the LOAD-output terminals, which is connected to the starter battery. (assuming the leisure battery is higher voltage)

isnt this cyclic charging and just connecting the two batteries together via the 15A/25A victron load output fuse? (or are you saying the Victron has an internal diode that blocks reverse current flow from the LOAD terminals back to the leisure battery?) - or would it be that at night both batteries would be drawn down to the same level, minus the victron losses~?

what happens when the engine is running and the starter battery starts back feeding @ 15v via the victron load terminals.



im just trying to get what you have done straight in my head =]

 

[Lowlec]

could i ask you for a bit more info pls:?

so what happens at night when the Victron MPPT will draw power from the leisure battery and output-it via the LOAD-output terminals, which is connected to the starter battery. (assuming the leisure battery is higher voltage)

isnt this cyclic charging and just connecting the two batteries together via the 15A/25A victron load output fuse? (or are you saying the Victron has an internal diode that blocks reverse current flow from the LOAD terminals back to the leisure battery?) - or would it be that at night both batteries would be drawn down to the same level, minus the victron losses~?

what happens when the engine is running and the starter battery starts back feeding @ 15v via the victron load terminals.



im just trying to get what you have done straight in my head =]

1....not using the load output of Victron MPPT.
2....Victron MPPT is not connected to leisure battery,(the battery positive of the MPPT,is taken off the leisure battery terminal and swapped over to the starter battery terminal or at the Ctek..A-terminal)....as Along as you’ve got a large enough solar panel,the leisure battery will be charged thru the Ctek unit only!

on my van if I tweak my float voltage of my Orion smart dc/dc charger lower than the Victron MPPT float voltage the Orion engages and starts the adaptive 3 stage charge cycle to leisure battery when the MPPT is connected to the starter battery and generating power!.if I get time tomorrow I will do a few pics or a video of the set up in action working

 

[col661]

I asked CTEK regarding this. Here is their answer.

The MPPT from Victron should not be connected to the solar panel input of D250SE, it will only create one extra conversion step and you would loose ~10% of the power in that.

I would conenct it to the starter battery if the problem you describe is due to other loads than the D250SE. WHen the Starter battery is being charged by the victron so will the service battery be by the D250SE, which believes it is an alternator that is up and running.

So, on that basis I think I'm going to connect the 'Battery' output of the Victron Solar MPPT to the 'Alternator in' on the CTEK so that it charges the starter battery first via solar and once above the kick over voltage of 11.8v will charge the leisure battery also. Although, I am wondering that the ignition might have to be on as teh leisure battery is an AGM battery with a voltage sensing circuit to the fuse box? I've asked CTEK the question and here is their reply.

Nope, as soon as the voltage output from the Victron is above 13.1V the D250 will kick in.

Do not be surprised ( or worried ) if the D250 will turn on and off since it will must likely press the input voltage below 12,8V where it turns off and then the voltage will rise above 13.1V and... At the end of the day the Victron will have charged both batteries.

I'll have a try with this at the weekend and see what the output is.

 

[Lowlec]

The ignition pilot wire for the Ctek doesn’t need to be on for the above to function!.
i experimented with this set up over the Christmas holidays when my van was parked up for 2 weeks,so I know it works!....but I’ve ripped out the Ctek now,not compatable with my Victron setup. @Dellmassive

#you could install a 20A DC changeover switch.......
1 side...charge leisure battery only
the other side...charge both batteries(above method)

 

[Ads_Essex]

..So, on that basis I think I'm going to connect the 'Battery' output of the Victron Solar MPPT to the 'Alternator in' on the CTEK so that it charges the starter battery first via solar and once above the kick over voltage of 11.8v will charge the leisure battery also.

Doesn’t the CTEK engineer mean you should connect your solar output to your starter battery - and not to your CTEK - so the solar tops up the starter battery, which in turn tops up the leisure battery via the CTEK?
That’s how their reply reads to me.

 

[Lowlec]

Connecting it to the A terminal on the input of the ctek unit, is the same as connecting it to the starter battery!.....the mppt & ctek are usually within close proximity to each other near the leisure battery!...

 

[col661]

Doesn’t the CTEK engineer mean you should connect your solar output to your starter battery - and not to your CTEK - so the solar tops up the starter battery, which in turn tops up the leisure battery via the CTEK?
That’s how their reply reads to me.

Yep, there is a fused 30A cable from starter battery to CTEK. Connecting solar to the CTEK input will be exactly the same.

 

[Dellmassive]

works!....but I’ve ripped out the Ctek now,not compatable with my Victron setup.

What ctek wasnt compatible?

 

[Lowlec]

What ctek wasnt compatible?

Not the way I’ve set my system up!....
remember we talked about it in a previous post.

 

[Dellmassive]

Not the way I’ve set my system up!....
remember we talked about it in a previous post.

i cant find a link to the previous post . . . . . . can you? (wasnt it ctek to orion victron? swap)


so just to clear things up . . .

**********************************************************************************************************

we are talking about..

using the fitted solar panels to charge up the starter battery via the Victron MPPT solar controller 24/7. . . . . which will keep the starter topped up in sunny conditions . . .

Then using a DC-DC charger to charge the leisure battery, which would normally be done when driving, but in this instance with the engine and ignition OFF as well as ON. (24/7 scenario)

This was first via his CTEK D250 DC-DC but has now been swapped out to a Victron Orion 12/12/30(?) DC-DC charger . . . .

The original issue may have been that the DC-DC charger would NOT kick in with the ignition switch OFF, but in this case the setup allows the DC-DC to start charging automatically (kinda VSR style) with the ability to tweek the charge profiles of the Victron MPPT and Victron DC-DC.

**********************************************************************************************************


so @Lowlec

can you tell us your Victron MPPT & DC-DC thresholds/settings on your setup pls? (preferably some screen shots of Victron connect APP also?)

and confirm is this is a temporary setup while the van is off the road? or if its a permanent solution?




......


This could be a good solution for some people,

I agree that there will be come efficiency losses going from Solar>MPPT>Starter>DC-DC>Leisure Battery, instead of Solar>MPPT>Leisure (but these would be negated during summer with better weather)

This work around will aslo be specific to equipment, as some DC-DC WILL start AUTO CHARGING with a high enough starter battery voltage . . . . BUT . . . . some DC-DC units WILL-NOT Auto charge when set to stop/start mode and using the BCM run/ignition feed.

One option to get around the above ignition feed maybe to set the DC-DC to standard EU5 mode and let it auto stop start during summer/sunny times but switch it back to Eu6 mode during winter months?

 

[Dellmassive]

if I get time tomorrow I will do a few pics or a video of the set up in action working

come on then . . . . . =]

Lets see it . . .

 

[Lowlec]

come on then . . . . . =]

Lets see it . . .

What firmware are you running in your Victron MPPT?

 

[Dellmassive]

Looks like I've missed an update on the V5.2 app version....

Just updated now....

..

 

[Dellmassive]

V1.46 & V2.23

(I'll need to update the other kit shortly)

 

[Lowlec]

V1.46 & V2.23

(I'll need to update the other kit shortly)

View attachment 66491

 

[Lowlec]

Just installed and configured my Victron gsm,so now have full control of the MPPT,BMV,eberspacher heater,and geofencing on the van from anywhere in the world!