Dual Batteries Charging System

[jgpoirier]

I run a triple battery setup now, 1 main, 1st aux in engine bay, 2nd aux fitted in my canopy drawer system; all of which are Group 35 Yellow Tops. I have isolated the house battery from the auxiliary batteries with a RedArc SBI12 Smart Start Isolator. One question that I have come across is that everything I read determines that the best charging voltage for a deep cycle AGM battery is 14.8V. Of course the tacoma seems to have a peak of 13.8V. Now speaking of DC/DC chargers that some how bring the alternator charging output voltage to 14.8?? Is this really necessary? Will running a charging voltage of 13.8 vs 14.8 drastically reduce the life of my AGM's?

 

[john61ct]

Yes. Also take much longer to charge. Alt won't be getting them to full in less than an all-day drive anyway.

And they aren't really deep-cycling to start with.

What are your loads? Have you got solar? How often do you get to shore power overnight?

 

[jgpoirier]

I agree. Largest load is my fridge, the rest are all LED lights (awning, RTT, and Canopy), water pump (non-continuous load obviously), and an inverter (that is more of a parasitic loss than it's actually used). I have plans to go to solar next year most likely, and I never shore power.

 

[Ducky's Dad]

Depends on the battery. Optima has detailed charging specs on their website. Toys are notorious for low charging voltage off the alternator, but there are gizmos available from some of the Toy specialist shops that step up the voltage to be more suitable for AGMs. My 2008 Tundra has stock charging system and seems to have no trouble charging and maintaining a Northstar G31 AGM. My experience with Optimas in other vehicles (GM and Dodge) is that they are pretty tolerant of charging variations.