Electrical Another dual battery question

[navmatt]

Hi all, after a bit of advice on this. Not sure which way to go.

So the new BT50 is on order delivery late jan or early feb, it is coming with the factory dual battery set up. The housing it comes with will only fit a 100amp/hr battery, feed via an isolator. Not sure if it is fed from the starter battery or alternator. My current setup in the nav I run a ctek dc-dc charger in the tray feeding the 125amp/hr battery which runs my 80l waeco. The fridge in the van is run off the starter battery whilst underway and I dont have a "hotwire" running direct to the battery. My solar on the van keeps it topped up and this system has been working fine even while free camping. Though we haven't come across any rainy/cloudy days to limit the charge of the solar to the van battery. I was going to get around to run power to the battery but time passed and now the tuff old reliable nav is heading out the gate.

Ok so how do I set up the BT, well I was thinking about utilising my Ctek in the tray to give it the best available charge. Then run my fridge from a outlet there, now should I run the van fridge from this battery as well as the hotwire to charge the battery in the van?? Or run the usual way of from the starter battery to the van fridge (with relay)and a hotwire from the dual to the vans batt? I'm not sure if this will be too much for the dual battery or not having everything running from there. The cetek is a 20amp charge, all up the amps wanted would be over this if they are all asking for full power ie first up in the morning when getting under way. Maybe I shouldnt worry about charging the van battery at all as it hasnt needed it before and I carry a generator in case the cloudy days take hold and runs it down to much.....

Thoughts?

 

[ROnEM]

@navmatt,

You will probably find that your new BT50 will have a "smart" alternator, thereby only designed to provide enough charge to the starter and 2nd on board battery.

As I have done with the Cruiser, put the CTEK D250S DC-DC in the van - as close to the battery/ies as possible. and run a 6mm or bigger (6B&S - 13mm2) from it to an anderson plug on the BT-50 through to the 2nd battery via a low-voltage isolator with 30amp fuse.
This will allow the CTEK to step-up what voltage it can get form the BT-50's 2nd battery. You can also add the solar panels to the CTEK (if their VOC is lower than 22v) and have it use the MPPT feature to maximise the voltage from your solar panels and car (when attached).

You can have your fridge attached to the van's battery and use wither an isolation switch or motion activated fridge switch to keep the fridge running. As there is a high probability that you will not get 12v to the fridge from the vehicle due to the "smart" alternator and voltage drop due to cable distance, you are better off drawing power from the van's batteries as they are closer to the fridge.

Hope this makes sense.



Cheers,

Rohan.

 

[rjstokes]

Hi guys,

Just wanting to confirm Rohan, that the Isolator may not be needed in your case as the CTEK in the Van will isolate the batteries once your 2nd car battery runs down to 12.7V? If not, I might need an isolator!

Also, if anyone's in the know - my setup is as follows :

I have a dual cab, caravan and 2 x 250 Dual units. 1 250 is connected to the trailer plug as a source then to the caravan battery. The other is used to charge an auxillary battery in the tub of the ute. 6 B&S cable connected the car battery, though a fuse to the CTEK AND to the trailer plug.

I am concerned about the situation when the caravan is connected. In that case the dual in the ute is connected to the car battery and the dual in the caravan is also connected to the car battery, through the trailer plug and same cable. In effect the input to both CTEKs is the same battery through the same cable. Presumably this is OK and once the car is running and the voltage increases, both CTEKS will charge their respective battery's. If the car is off, the voltage drops, both are isolated and the CTEKS isolate their respective battery's.

Otherwise, think I might just use the cable from the car battery to the CTEK in the tub to charge the aux battery, and connect the trailer plug to the aux battery via an anderson plug. Then the van CTEK will be powered from the aux battery in the ute.

Thoughts?

Cheers, Ryan.