Second battery

[Paul Scott Lurker Find all posts View Profile Close Paul Scott]

Hi all
I am currently running a 110ah agm under bonnet with standard wet cell as starting battery
I use an idc25 to charge second battery as well as solar
I have seen a video where you can have two agm’s under bonnet with both being charged via alternator until power is disconnected and starter battery is then disconnected
does anyone know if there is a way of achieving this incorporating solar so I can then double my amp hour for of camping
thanks

[sparksy Senior Member Find all posts View Profile Close sparksy]

If you can fit the 2 agms under bonnet ( noting AGM's dont like heat) just connect them in parallel using the same dcdc. In my 120 I have 2 x 80Ahr agms where left rear seat was connected in parallel charged of a 20A dcdc which is also connected to a 250W panel on roof rack. those 2 batteries are for my second fridge. Under bonnet I have a 100AHr deep cycle charge connected by a Redarc SBI relay, that is for main fridge in back and caravan anderson is also connected to it.

[Paul Scott Lurker Find all posts View Profile Close Paul Scott]

Sounds good but the starter battery is charged via alternator which I need to take into consideration

[sparksy Senior Member Find all posts View Profile Close sparksy]

When towing I am powering a 3 way fridge via anderson, a 60L ARB fridge in rear, a 35L waeco set as a freezer. All this is powered by the batteries charged by the standard alternator. the alternator charges the 100 AHr century deep cycle via a redarc relay, that deep cycle powers the Van fridge and the DCDC in van run directly off the anderson ( fridge draws 15A and DCDC tops up the vans 120Ahr AGM ) as well as the ARB fridge
Then connected to the deep cycle is a supply to a 20A DCDC which charges 2x 80AHr AGMs in parallel fitted in second seat row that power the Waeco fridges. DCDC also has a 250w solar panel on roofrack but that only comes into play when car stopped. The factory alternator is more than capable of running all of my gear and works well. I did try a alternator booster diode for a while but it didnt make the system work any better so removed it. The DCDC in van is a Thunder 20A unit. The DCDC for fridge batteries is a Jaycar unit and the redarc relay is just the standard SBI 12v 100A. All very simple and all wiring is 25mm2 flex. dont scrimp on wiring size.