Using Aux battery setup for useful purposes

[Zandcwhite]

The biggest problem with the aux battery and keeping it tied to the charging system/using it in any way is its size. Too small to be meaningful and charging 2 different batteries of different sizes and different states of charge is hard on the whole system. It's the reason why both batteries usually die around the same time. If you want a dual battery set up, spend the $ for a proper one with 2 same size batteries. Or you could just not bring tvs, coffee makers, blenders, and scene lighting and actually camp?

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[GATORB8]

Which battery chemistry and manufacturer do you use? I've had bad luck with small forgettably named "lithium" packs.

For jump packs, I recently changed to NOCO after being impressed by their charging products on my boat. I have a GBX55 in my 2500. That said, I have a "Gooloo" from Amazon that's been working for the boat (that we tend to kill repeatedly at the sandbar) for 5 years and probably 20+ uses.

I built a big 300 AH Lifepo4 setup for the off road camper so I don't carry a PPS, that's a combo of Litime batteries and Renogy hardware. I've been impressed with the Renogy stuff for both value and quality and wouldn't shy away from their PPS. Otherwise I'd probably look at the bigger names that go on sale often. I was considering EcoFlow and Jackery on prime day.

 

[hamiamham69]

I guess this is an over-simplification but Every boat I have owned as well as my 1997 LR Defender 90 had a dual battery setup and a $50 manual dual battery selector switch. Typical one battery was the “starter” battery and the other a deep cycle “house” battery at least for the boats. Using this system I never had any issues. No issues starting, no issues running house loads, no one battery pulling a vampire on the other one. It’s manual but not allows you to draw from battery 1, battery 2, or both batteries. Similarly it also lets you choose which battery - or both - to be charging.

 

[GATORB8]

I guess this is an over-simplification but Every boat I have owned as well as my 1997 LR Defender 90 had a dual battery setup and a $50 manual dual battery selector switch. Typical one battery was the “starter” battery and the other a deep cycle “house” battery at least for the boats. Using this system I never had any issues. No issues starting, no issues running house loads, no one battery pulling a vampire on the other one. It’s manual but not allows you to draw from battery 1, battery 2, or both batteries. Similarly it also lets you choose which battery - or both - to be charging.

Not an oversimplification, and very similar to what the Genesis dual battery setup accomplishes with an automated relay system.

However, the Aux battery is too small to be a useful house battery and by the time you spend the money to get a suitable house battery and make an automated system like the Genesis you'd likely be better served and have more power utilizing a PPS.

 

[flick2614]

In theory, your proposal could work. But keep in mind the AUX (ESS) battery might have to power post ignition-off Jeep electronics processes (e g. evap system) without the help of the CR[an]K (aka main) battery. That probably wouldn't leave much power for you (if there's even enough power for those processes).

In general, the AUX (ESS) battery capacity is too small to be of much value as an external accessory power supply.

I figured an upgrade to the aux battery would be necessary to really be of any use. Line of thinking is even with an upgrade to both batteries I would still be way behind on cost of a dual system.

The biggest problem with the aux battery and keeping it tied to the charging system/using it in any way is its size. Too small to be meaningful and charging 2 different batteries of different sizes and different states of charge is hard on the whole system. It's the reason why both batteries usually die around the same time. If you want a dual battery set up, spend the $ for a proper one with 2 same size batteries. Or you could just not bring tvs, coffee makers, blenders, and scene lighting and actually camp?

I'm pretty minimalistic at camp hence why I said a full on dual battery system was not a necessity. Just scene lights occasionally and a speaker is all the power I need. Makes sense that the system struggles to equalize two different sized batteries so an external charger like solar may be the answer along with sizing up the aux battery itself.

 

[Zandcwhite]

I figured an upgrade to the aux battery would be necessary to really be of any use. Line of thinking is even with an upgrade to both batteries I would still be way behind on cost of a dual system.

I'm pretty minimalistic at camp hence why I said a full on dual battery system was not a necessity. Just scene lights occasionally and a speaker is all the power I need. Makes sense that the system struggles to equalize two different sized batteries so an external charger like solar may be the answer along with sizing up the aux battery itself.

But if you're going to an independent charging system and a new battery, why not just go jackery or other battery power source that can be moved not only around camp but from vehicle to vehicle?

 

[flick2614]

But if you're going to an independent charging system and a new battery, why not just go jackery or other battery power source that can be moved not only around camp but from vehicle to vehicle?

Yeah fair enough for camp items. Hard to plug in scene lights mounted on the Jeep or jump a battery from a jackery. The ultimate solution though is a larger main that can handle what is mounted on the Jeep and a power station for stuff around camp.

 

[AndySpill]

In theory, your proposal could work. But keep in mind the AUX (ESS) battery might have to power post ignition-off Jeep electronics processes (e g. evap system) without the help of the CR[an]K (aka main) battery. That probably wouldn't leave much power for you (if there's even enough power for those processes).

In general, the AUX (ESS) battery capacity is too small to be of much value as an external accessory power supply.

I don't understand this post and could use clarification.

To the extent that I do understand what the OP proposed, when "stationary," which to my mind means parked with the engine off, is sort of recreating the functionality of the Power Control Relay (PCR) during ESS events during such parked situations: the PCR being a normally closed relay that is energized during such ESS events to separate the two batteries, so that the OP can break the connection between the two batteries, so as to not tax the cranking battery while running accessories at, say, a parked camping site.

The small size of the Aux battery limiting this functionality notwithstanding, but in no way detracting from his good concept: one that a bigger Aux battery might address--I am confused as to what appliance draw occurs while parked, that normally occurs exclusively against the Aux battery, as it is my understand that with the PCR deenergized while parked, the batteries are normally connected for either/both to run the small appliance draw during these times.

I've heard of Jerry @Jebiruph describe appliance draw, even during ESS events that does happen against the main battery--I think power steering being one (and likely why ESS events won't engage if the steering wheel is turned too much) but I haven't head of--if I understand you correctly--appliance draw while parked that is the exclusive realm of the Aux battery to provide electrical current for.

 

[GATORB8]

I don't understand this post and could use clarification.

To the extent that I do understand what the OP proposed, when "stationary," which to my mind means parked with the engine off, is sort of recreating the functionality of the Power Control Relay (PCR) during ESS events during such parked situations: the PCR being a normally closed relay that is energized during such ESS events to separate the two batteries, so that the OP can break the connection between the two batteries, so as to not tax the cranking battery while running accessories at, say, a parked camping site.

The small size of the Aux battery limiting this functionality notwithstanding, but in no way detracting from his good concept: one that a bigger Aux battery might address--I am confused as to what appliance draw occurs while parked, that normally occurs exclusively against the Aux battery, as it is my understand that with the PCR deenergized while parked, the batteries are normally connected for either/both to run the small appliance draw during these times.

I've heard of Jerry @Jebiruph describe appliance draw, even during ESS events that does happen against the main battery--I think power steering being one (and likely why ESS events won't engage if the steering wheel is turned too much) but I haven't head of--if I understand you correctly--appliance draw while parked that is the exclusive realm of the Aux battery to provide electrical current for.

It's difficult to find an OEM diagram with all of the direct main battery (post N2) connections, this is the closest and looks to have the majority:

Here's a non-OEM diagram that appears to show them all:

And the J continuation from that diagram:

 

[AndySpill]

It's difficult to find an OEM diagram with all of the direct main battery (post N2) connections, this is the closest and looks to have the majority:

Here's a non-OEM diagram that appears to show them all:

And the J continuation from that diagram:

Thanks Matt.

What I can't help but take away from this is that worse case scenario, a fused jumper between N1 and N2: (Jerry's @Jebiruph original method for rerouting calls for power exclusively from the Aux battery before his F42 fuse discovery, like for an instant pre-crank,) with an on-off switch on that fused jumper, might allow the OP to temporarily break the connection between the main and Aux battery (albeit practically speaking a larger Aux battery) to have it run accessories, while the fused and switched jumper, set to the on position while camping, would allow calls for power to exclusively the Aux battery by vehicle appliances not involved in the OP's camping experience, to get rerouted to the main battery.

 

[zyt]

I have removed my aux battery and wonder if there would be any use for it at all. Can I fully charge it and use as a backup jumper in case there's a need?

 

[AndySpill]

I have removed my aux battery and wonder if there would be any use for it at all. Can I fully charge it and use as a backup jumper in case there's a need?

This video is queued at a point where the dual AGM JL is cranked exclusively from the Aux battery, let alone as a means to jumper the main.

Granted, this was an early model 2018, where cranking could not happen unless the Aux battery had ample current (Stellantis put out a TSB to remedy this functionality and incorporated it into all later model 2018 dual AGM battery JLs and those model years to follow such that a dead Aux battery would not strand you if your main battery had ample cranking power) but this example applies to all model years.

 

[Heimkehr]

I thought I could wire up a plug by the wheel well so I could help any motorcycle jump his bike. Thats all I got.

Honestly soon as the factory mini me battery starts to dump, it's gone, and a bigger main goes in.

More or less what I did: Out with the OEM H6 AGM and in with a new Interstate H7 AGM.
The OEM ESS battery was isolated in the usual manner (remove Fuse F42 and the related Negative cable.)
Done.

Which battery chemistry and manufacturer do you use? I've had bad luck with small forgettably named "lithium" packs.

I use and recommend Antigravity. It's a mainline brand with decent after-purchase support (as I've confirmed when I had questions about esoteric use cases.) Granted, Pay to Play, but quality usually is so.

NOCO is also on my radar, but it is mildly annoying that they use parochial connectors. The unversality of the EC5 plugs used by every other brand of lithium jump starters has allowed me to leverage my own jump pack for a variety of applications.

 

[AndySpill]

More or less what I did: Out with the OEM H6 AGM and in with a new Interstate H7 AGM.
The OEM ESS battery was isolated in the usual manner (remove F42 and the related Negative cable.)
Done.



I use and recommend Antigravity. It's a mainline brand with decent after-purchase support (as I've confirmed when I had questions about esoteric use cases.) Granted, Pay to Play, but quality usually is so.

NOCO is also on my radar, but it is mildly annoying that they use parochial connectors. The unversality of the EC5 plugs used by every other brand of lithium jump starters has allowed me to leverage my own jump pack for a variety of applications.

Hi James:

As I probably don't need to tell you, the LiFePO4 battery chemistry in Antigravity products (at least their batteries that is), has, as its
Achilles' heel IMHO the inability to charge at below freezing temperatures, without causing damage, unless that charge rate is significantly reduced below that which can safely occur at warmer temperatures.

I assume the battery has a BMS that prevents charging at such low temperatures, much that I'm confident that within a few minutes of vehicle operation the engine bay reaches temperatures, even in Minnesota winters, that allow for the alternator to charge up that battery, but I imagine that trickle charging, with the engine off, might need to involve battery warming blankets in some colder locales.

Thoughts?

 

[GATORB8]

Thanks Matt.

What I can't help but take away from this is that worse case scenario, a fused jumper between N1 and N2: (Jerry's @Jebiruph original method for rerouting calls for power exclusively from the Aux battery before his F42 fuse discovery, like for an instant pre-crank,) with an on-off switch on that fused jumper, might allow the OP to temporarily break the connection between the main and Aux battery (albeit practically speaking a larger Aux battery) to have it run accessories, while the fused and switched jumper, set to the on position while camping, would allow calls for power to exclusively the Aux battery by vehicle appliances not involved in the OP's camping experience, to get rerouted to the main battery.

If I'm reading you right, whether N1 and N2 are jumped or open, the NC PCR relay would have the two connected unless it was triggered.

My understanding is that the Aux battery is intended to work as a "buffer" to maintain sufficient voltage to vehicle modules during starting, kind of like the intent behind a capacitor in audio systems. Should the PCR relay be triggered and N1-N2 open, you would open yourself up to over discharging the Aux battery and could result in the Aux battery not providing sufficient voltage on startup (or discharging the main battery to a point it could prevent startup if it's reconnected and the batteries balance).

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