another battery ??

hi guys,allright,what i want to know is this,,is it possible to run a third battery (which will live in the camper) and charge it off the existing dual battery set up.........i have installed a projecta dual battery system and have a battery in the back of the ute which has all been working fine but now i need a third battery so can i just connect the third battery via a anderson plug straight to the second battery and charge it that way when i'm driving,,the battery in the back is a 150 amp hour agm & the one i want to put in camper will be 100-120 amp hour,this is the dual controler unit
Projecta
will this work or are there any better ideas out there.

any help would be great

cheers

craig

I dont know for sure but I would think it would recharge fine. At most it may take a bit longer for all your batteries to fully charge as opposed to now.

You could add a redarc if you wanted the third battery to charge after the second battery reached full charge. Or you could just add a battery as you described.

One thing to remember is that a battery will only pull the current it requires to charge. So in effect two batteries in parallel could draw different amperages when charging.

thanks for the response mate

bump.............

Hmmmm......I've given this some thought and I'm not really closer to an answer, you have the 2 options that you said, I can see drawbacks with each.

1. Single controller, 2 rear batteries in parallel, if one is flat, and the other is charged up when the 2 are connected together you could get a fairly large current run between the batteries for a short time while they equalise with each other.

2. Cascading battery controllers, this could work, but I'm not real sure about it, when the alternator voltage reaches 13.8v or thereabouts it turns on and sends power to the 2nd battery, now if this voltage stays up for long enough it could cause the 2nd controller to also kick in which would defeat the point of the 2nd controller.

I think just go with them in parallel, it appears to be what most do in this situation, just keep in mind you probably should use similar batteries for the 2nd and 3rd battery, ie. don't mix one AGM with a wet cell.

thanks shonky,i'll use the same brand and type of battery as in the tray of the ute.the battery in the ute being a 150 amp hour agm is going to be running the fridge and i feel will be the one that will require more charging than the one in the camper which will only be used for the water pump and lights and i was going to get a 100 or 120 amp hour agm battery for this job,can anyone see any problems with that????

cheers

craig

shonky,this large current draw you talk of,, could putting a 50 amp cicuit breaker at each end help with that if not what are they there for?????

Check the redarc link out page 5.

http://www.redarc.com.au/pdfs/20081112 NEW SBI inc. Redarc auto-electrical catalogue.pdf

Cheers
STC

A circuit breaker acts like a fuse. It will trip if the current passing through it exceeds the rating (or a short).

It would not limit the current draw at all.

As Shonky said with batteries in parallel they will equalize when connected. So if you drain the fridge battery down and the trailer battery is near full the fridge battery will suck a large amount of charge leaving you with 2 half full batteries untill they recharge.

Cant see too much of a problem as long as you don't connect the trailer battery until you will be running the engine for a while.

No problem in doing what you are suggesting. I run a cranking battery isolated from 2x105AH all rounder aux batteries in a compartment in my storage unit in the tub and a 120AH AGM in my campertrailer. The campertrailer is coupled to the vehicle vide an Anderson plug which is wired directly to the cranking battery. No worries about this drawing down my cranking battery because as soon as I pull up I unplug. Simple eh?

would recomend putting a GU ZD30 alternator, as is has an extra 50 amp charge, put a isolator on the starting battery and have the other 2 charge together. That way if lights and water pump not used on trailer, the fridge has 2 batteries to run on over night, and or same as above but have a manual switch between the trailer and 2nd battery and get voltmeters for all of them.