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Hey guys, wanted to introduce myself and give you guys a quick run down of my recent purchase and what my plans are. Thanks in advance for any help with questions I have right now and I’m sure there will be many more.

2018 extended 350
Dual battery with 250amp alt
Full window XLT Rv upfitter van

This van was ordered by a company that must have went out, picked it up with 62 miles on it ready to build.

I guess my first question, I’m having trouble finding out about is the battery setup. When searching the web most dual battery info is in regards to adding battery not OEM. Just wanted to pick someone’s brain that has this setup in regards to limitations and maybe adding a 3rd deep cell. Doubt I’m going solar so I want to run off batteries 50% of the time and shore power/generator the rest.
Building double duty rig for racing motorcycles as well as traveling to hike/MTB/Beach. Not looking to power the world but would like my vent fan/leds and shower pump to be available when not plugged into shore power.
Thanks again
 

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The dual batteries are tied together, so if you use them heavy it is possible they won't start the van later. Lighter use here and there should be okay.
The folks relying on battery power much when in remote areas usually use separate house batteries and various charging/isolating solutions.
 

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2016, MR, 130"
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In my mind if you go camping in the bookies, having the dual batteries is great but makes no difference in wanting a house battery. Just no fun to be in the middle of nowhere. I am a super low budget, KISS van owner and I added a house battery almost right away. We did do three trips with using the starter batteries for lights and radio but would start and run for a while periodically to make sure we didn't screw ourselves.
 
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We have the factory dual battery and hi-output alternator, and it is sufficient for our setup.
No house battery, and we run a fridge, vent fan, and occasionally the stock sync3 w/ an aftermarket sub all off of the dual batteries.

We're mostly MTB riding and camping, and usually drive the van daily on our trips, so we don't tend to drain them very far.
I've only run the batteries down once, and that was leaving the fridge on and not driving the van for a week in 90 degree temps.
 

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I've only run the batteries down once, and that was leaving the fridge on and not driving the van for a week in 90 degree temps.
When you ran down your batteries, were they actually dead or did the battery guard shut down the system to save starting power?
 

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When you ran down your batteries, were they actually dead or did the battery guard shut down the system to save starting power?
I believe they just died. The van would not start, and I needed a jump to get it going.
 

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2020 T350 EB SRW AWD HR EL
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Is that directed my way...? am I doing harm I don't know about?
For a lead-acid battery, one should not run below 80% of its rated capacity or less than 10.5 volts. If you did, your battery will not last much longer. Just be mindful. :)
 

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A regular SLI battery, such as a car battery, creates electricity in shorter bursts. These bursts of electricity are then used to “crank” start a motor, for example, a car engine. Regular car batteries produce a shorter burst of electricity.

Deep cycle batteries produce ongoing, lower yet consistent, levels of power.

Deep cycle batteries have thicker metallic elements. Thicker metal plates allow the battery to release electricity more consistently. Regular car batteries have thinner plates. These have a larger surface area. This helps them to create a larger, electrical charge in a shorter time.

A deep cycle battery may produce only one half of the Cold Cranking Amps that a car battery will. Whereas it will have 2-3 times the Reserve Capacity.

A deep cycle battery should run until all the electricity is completely discharged.

A regular car battery only discharges the battery by about 1-3% each time. The vehicle’s alternator then recharges the battery. In fact, it may never lose more than 20% of its charge during its lifespan.
The design of the regular car battery is more suited to shorter use. its metal platings are not designed for ongoing use. In fact, they can warp after a short time at such high power.
 

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Is that directed my way...? am I doing harm I don't know about?
I'm not battery expert, but the limited use you describe of your dual AGMs sounds okay except the leaving the fridge running for a week, lol
It's the draining way down and recharging regularly that is not the best practice.
Your routine sounds more like draining part way and topping them back off which should not be such a problem.
 

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Calling @OldMadBrit to the thread....
Responding :)
We are 19 months,19,000 miles and ~20 camping trips in on our build. We only use the dual AGM's that came with the van, along with its 250A alternator.

[NOTE the OEM dual AGMs are not like conventional SLI batteries. AGM's are closer to a deep cycle battery and used for Stop-Start and for contractors who need to charge hand tools, run laptops etc., while on site.]

We typically start our trips with at least a 4hr drive and move from location to location every other day. Our electrical loads are our roof fan, Webasto heater and interior lights and overnight charging of phones.

We have laptops, sound-bar, phone gear, flashlights and other stuff that we charge as we drive.

Zero problems so far and we have never seen less than 12.2V on the LED voltmeters. We carry 2 Li-ion emergency boost/starter batteries just in case. I think we have saved >>$3,000 and >>200lb in weight, going this route.
 

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4.5 years and ~33,000 mi. on the original dual AGMs doing much the same thing as OldMadBrit. About 80 W (true output in full sun) of solar on the roof keeps them topped off when parked for extended periods. The main load is a medium-size compressor fridge. Beyond that just some modest LED lights and a very efficient sound system, both of which are negligible compared with the fridge. I run a fan but only when the sun is shining. I kept track of consumption in the beginning with a data logger but no longer worry about it. It was rare to deplete the batteries more than 10%. So far so good. I just hope to get some warning when the batteries finally are ready to give up the ghost.

--Frank
 

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I am in search of the same answer, Can you add a third battery in parallel to the factory dual battery set-up to increase the capacity? I understand it will have to be an identical 72ah AGM as the dual stock battery , but are there any other limitations?
 

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I am in search of the same answer, Can you add a third battery in parallel to the factory dual battery set-up to increase the capacity? I understand it will have to be an identical 72ah AGM as the dual stock battery , but are there any other limitations?
I can't see any obvious reason why not, as long as the cable run isn't too long - you want each battery to see the same voltage.
 

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I have been contemplating using the OEM system rather than a separate house setup, in a weekender use scenario. I have the dual batteries and alternators, with upfitter switches and fuse panel. Seems a shame to not use that.

Sounds like that is possible - OldMadBrit does so but with few loads - primarily a roof fan.
Tonwagen does so with a fridge, but with solar to supplement.

The newer models have a standard battery guard that should alleviate worries about running them down (I think it cuts off at 80% SOC, so should not affect AGM life much - they are listed as deep cycle, though probably a hybrid). The BEMM shows how to wire in another battery if needed, with a cutoff relay to isolate and save the original system from drain.
The dual battery setup gives 70 Ah for each battery, so at 20% drain, that is about 14 Ah per battery max usage. 28 Ah stock, and 14 per each additional AGM added.

My only real concern is if I need to disable the battery guard timer (it will cutoff at 75 minutes), and if there may be warranty issues by doing so. There are 2 methods, a hardwired switch or a Forscan settings change.
I suppose I could hook the fridge up to the 3rd battery mentioned above that would be powered all the time, and would run down more than the stock batteries. I'm guessing that may cause charging issues with some batteries at different levels.
 

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Responding :)
We are 19 months,19,000 miles and ~20 camping trips in on our build. We only use the dual AGM's that came with the van, along with a 250A alternator.

[NOTE the OEM dual AGMs are not like conventional SLI batteries. AGM's are closer to a deep cycle battery and used for Stop-Start and for contractors who need to charge hand tools, run laptops etc., while on site.]

We typically start our trips with at least a 4hr drive and move from location to location every other day. Our electrical loads are our roof fan, Webasto heater and interior lights and overnight charging of phones.

We have laptops, sound-bar, phone gear, flashlights and other stuff that we charge as we drive.

Zero problems so far and we have never seen less than 12.2V on the LED volmeters. We carry 2 Li-ion emergency boost/starter batteries just in case. I think we have saved >>$3,000 and >>200lb in weight, going this route.
Thx for the reply!

We're at ~80k in 3.5years. All good so far...
 
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