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Aux Battery: real life functionality

4828 Views 48 Replies 8 Participants Last post by  zeph, 
zeph
So my ‘16 PV has the aux battery, and I’d like to figure out what I can realistically expect from it? Is it just there backing up the main battery just in case, or does it offer actual extra power for when the engine is off? Like can I run the interior lights and sound system for an x amount of time or what?
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P
To use it you can connect accessories to it. If it's stock you can get about 50ah from it when the van isn't running.
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focus805
zeph said:
So my ‘16 PV has the aux battery, and I’d like to figure out what I can realistically expect from it? Is it just there backing up the main battery just in case, or does it offer actual extra power for when the engine is off? Like can I run the interior lights and sound system for an x amount of time or what?
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There is no built in fuse box for it, but it does have an M6 stud on the positive terminal, and the ground point too. From there you would add fuses to what you want to power. Mine was 95ah, so you can safely use about 1/2 of whatever yours is rated. 50ah will run a refrigerator, some lights, with some fan use, for a day or so, in my experience. YMMV
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zeph
Thanks for your replies! I'm a little confused, the battery under the passenger seat is the main battery, not the aux, right?
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focus805
zeph said:
Thanks for your replies! I'm a little confused, the battery under the passenger seat is the main battery, not the aux, right?
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Right. If you have the factory auxiliary battery it's under the driver's seat.
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zeph
I'm still confused, so what does the battery under the hood do? I figured that was the main, and the one under the passenger seat the aux? Under the driver's seat is a cavity with a tool holder.
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G
zeph said:
I'm still confused, so what does the battery under the hood do? I figured that was the main, and the one under the passenger seat the aux? Under the driver's seat is a cavity with a tool holder.
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There is no battery under the hood. The box on the right side of the engine compartment contains fuses and relays. The big battery under the right front seat is the main, the little one behind it (if present) lets you put the gearbox in neutral if the big one dies, and the big battery under the left front seat is the optional auxiliary.
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zeph
Shoot, so I do not have the aux battery then. Guy told me it did, and I thought it was the one under the passenger seat.

Is it something that can be added?
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Davo
I added one, I removed the tool bag you mentioned from under the driver’s seat and installed a 50 AH lifepo4 lithium battery, I powered it with a Victron dc to dc charger to charge it when needed, around once a month for me. I normally run a auxiliary battery in my vans to power my laptop & printer to print invoices.
This setup works great for me, but when I found a 100 AH battery that fit under the seat I installed it and now only turn on the dc to dc charger around once every two months.

But before I started getting into and learning about lifepo4 batteries I had a AGM battery from Sam’s Club that I ran for a while in the area in back of the driver’s seat, it was pretty big and weighed around 42lbs, with around 50 AH, the 100 AH lithium is around 22lbs. There are many good write up’s on this forum of the different setup’s and batteries & dc to dc chargers that were used, I’ve learned a lot here.
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Davo
I do also run a couple of led lights in the cargo area with the auxiliary battery, and am planning to power two JL Audio amps with it in the near future, but the new head unit will be powered with the main starter battery, so I’m sure I’ll probably have to switch on the Victron more often? Time will tell.
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@zeph what do you want to power with an aux battery? What are your power requirements?

This will help us make some recommendations.
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Davo said:
probably have to switch on the Victron more often? Time will tell.
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Do you have an orion? Smart or the non smart?
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Davo
Victron Energy Orion-Tr Smart 12/12-Volt 18 amp 220-Watt DC-DC Charger, Isolated (Bluetooth)

I could have went with the 30 amp but figured an 18 amp would just take a little longer to charge and was in no hurry.
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Davo
Not to mention the 18 amps about $100 bucks Cheeper and thought it would easier on the charging system of the Metris? Now that I’m not positive on but thought it might be?
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@Davo the 30amp version works fine. I'm curious about your comment about turning it on. The smart version can sense when the van is running so you essentially leave it so it charges whenever the van is running. Do you have it connected in a way that you manually turn it on and off?
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Davo
Yep, In place of the jumper wire on the Victron, I ran two small wires from there to a spot in front that’s hooked to a small toggle switch, then when I’m ready to charge the battery “ every two months or so” I switch on the toggle switch and let the unit sense when the car is running till charged as high as I like, once charged, I turn the switch off till needed again.

Now when I was running the agm battery, I just kept the jumper on all the time to constantly keep the battery topped off like led acid batteries like. But now with the lithium battery I’ll bring it down to 20% or sometimes 10% then switch on again, I’m guessing it may be easier on the alternator? Better fuel economy? Maybe? It just seems like one of the advantages of a lifepo4 battery?

Plus this 100 ah lifepo4 battery has built in Bluetooth and by doing it this was its only had 2 complete cycles since the first of the year when it was installed.
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Davo
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Here’s the jumper wire which I’m sure you knew what I meant, and yea if I was to do it again I’d buy the 30 amp one too.
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P
Should not matter much to the battery if you topped it off each time you drove the van. If your battery app allows it you can back off the cell charge voltage so the bms cuts off the charge a bit earlier. That could mildly extend life. There is really no reason to try to deplete it before charging.
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Davo
Also by switching it on & off this way, I would make sure that if it was below freezing in my van, it wouldn’t try to charge the battery, because the 50 ah battery I was running had no low temp cutoff, but the 100 ah installed now does have a low temp cutoff. Even though it normally doesn’t get below freezing in my garage, once in a while it will, so I have the extra insurance of making sure the interior on the van’s temperature is above freezing before charging.
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Davo
pounce said:
Should not matter much to the battery if you topped it off each time you drove the van. If your battery app allows it you can back off the cell charge voltage so the bms cuts off the charge a bit earlier. That could mildly extend life. There is really no reason to try to deplete it before charging.
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I don’t think my battery app is that Sophisticated, but you’re probably right about letting it constantly be on, but this way I have options?
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