Secondary battery questions : JL/JT

[Johnny O]

Hoping some folks on here are familiar with the JL/JT dual battery system.

I am confused.

Basically, JLs and JTs have a second, smaller battery installed under the main stock AGM. Online documentation is a mess.

Best I can tell is that this secondary battery exists to supply power to the secondary systems (infotainment, outlets, and 120V inverter) when the main system is off due to Auto Start/Stop system.

As is the norm Wrangler forums are a mess of idiocy and ignorance.

Am hoping folks here can answer my question: Does the secondary battery power these systems when the Rubicon is in ACC mode, or only when AS/S is active?

I ask as am about to install additional 12v, USB, USB-C, and a another 120V remote outlet. I am considering an upgrade to the stock Rubicon inverter from 3amp to 10amp...plus integrating my solar system and second AGM from Bert.

 

[CheddarGau]

So the aux battery essentially powers all your computers etc, especially in start stop mode. So the system is really a mess. If that battery is dead or low, you will not be able to start your vehicle even if your main battery is good. That particular battery constantly drains, and for whatever reason will be below 70% state of charge (will not run the start stop function below 70%). Making use of the AUX switches to add more accessories shouldn't effect the aux battery, it should all run off the main battery. That said the aux battery will ready up some of the modules in the Jeep.

Word of advice, I would get a NOCO charger that has the AGM charging function. Charge the system every so often to maintain a good state of charge. You will also need to charge the battery before the IBS, so the vehicle knows its being charged. A proper charge is done by isolating both batteries. Disconnect main battery first, followed by AUX battery. To do this remove main battery negative, then you have have a 2nd smaller (still big) cable on the one you took off, and remove that one. Both batteries are now isolated (you can remove the main battery positive if you want). . The fuse box right beside the battery has i think 5 or 6 postive terminals. The one closest to the firewall is the is the aux positive cable. Connect your charger to that one, and the smaller of the 2 isolated negative cables.

 

[CheddarGau]

My opinion is that you should look into getting a full size battery on the same circuit as the aux battery. The main issue after that is if the IBS or PCM will charge it. It would essentially delay the discharge of that system. Thats the main issue with the AUX battery in the first place. Chrysler doesn't publish what the charge strategy is, or how to force charge it while driving.

We had a customer tell us about a place that is doing larger battery retrofits for the AUX/start stop battery. He mentioned they need to upload a tune, which likely takes into account the new larger battery.

 

[CheddarGau]

Hoping some folks on here are familiar with the JL/JT dual battery system.

I am confused.

Basically, JLs and JTs have a second, smaller battery installed under the main stock AGM. Online documentation is a mess.

Best I can tell is that this secondary battery exists to supply power to the secondary systems (infotainment, outlets, and 120V inverter) when the main system is off due to Auto Start/Stop system.

As is the norm Wrangler forums are a mess of idiocy and ignorance.

Am hoping folks here can answer my question: Does the secondary battery power these systems when the Rubicon is in ACC mode, or only when AS/S is active?

I ask as am about to install additional 12v, USB, USB-C, and a another 120V remote outlet. I am considering an upgrade to the stock Rubicon inverter from 3amp to 10amp...plus integrating my solar system and second AGM from Bert.

I didn't see the part about the inverter. You may want to run a separate aftermarket inverter and bypass the whole factory system altogether. We do a lot of these on F150's and Transits and they seem pretty reliable. You can tuck them anywhere there is a spot. The 600 watt ones are good and small ish, the 2000 watt ones are really nice but big. May have trouble tucking that under the seat. Very primitive(reliable) and you won't have the chrysler system getting angry at it all the time. Power, ground and body ground. Some come with a remote switch, but it's not necessary. Xantrax is the brand.

 

[Johnny O]

So the aux battery essentially powers all your computers etc, especially in start stop mode. So the system is really a mess. If that battery is dead or low, you will not be able to start your vehicle even if your main battery is good. That particular battery constantly drains, and for whatever reason will be below 70% state of charge (will not run the start stop function below 70%). Making use of the AUX switches to add more accessories shouldn't effect the aux battery, it should all run off the main battery. That said the aux battery will ready up some of the modules in the Jeep.

Word of advice, I would get a NOCO charger that has the AGM charging function. Charge the system every so often to maintain a good state of charge. You will also need to charge the battery before the IBS, so the vehicle knows its being charged. A proper charge is done by isolating both batteries. Disconnect main battery first, followed by AUX battery. To do this remove main battery negative, then you have have a 2nd smaller (still big) cable on the one you took off, and remove that one. Both batteries are now isolated (you can remove the main battery positive if you want). . The fuse box right beside the battery has i think 5 or 6 postive terminals. The one closest to the firewall is the is the aux positive cable. Connect your charger to that one, and the smaller of the 2 isolated negative cables.

Thanks for the clarification! The extra outlets are all easy enough, but had read quite a few horror stories about the secondary... most of which were written by folks that don't know electricity.

 

[Johnny O]

My opinion is that you should look into getting a full size battery on the same circuit as the aux battery. The main issue after that is if the IBS or PCM will charge it. It would essentially delay the discharge of that system. Thats the main issue with the AUX battery in the first place. Chrysler doesn't publish what the charge strategy is, or how to force charge it while driving.

We had a customer tell us about a place that is doing larger battery retrofits for the AUX/start stop battery. He mentioned they need to upload a tune, which likely takes into account the new larger battery.

Good to know! I loathe the thought of letting someone mess with the software, but in my case may be a necessity. Then again if it ain't broke I generally don't fix it.

With this information I may just go with an external power pack for the solar system. I only have two pieces of equipment that need 120v beyond a laptop for the DNA sequencer, and both are low voltage wall-wart powered.

My only real concern is it takes 2 to 4 hours to do a sequencing run which will be harsh on a vehucle battery charge.

 

[CheddarGau]

Good to know! I loathe the thought of letting someone mess with the software, but in my case may be a necessity. Then again if it ain't broke I generally don't fix it.

With this information I may just go with an external power pack for the solar system. I only have two pieces of equipment that need 120v beyond a laptop for the DNA sequencer, and both are low voltage wall-wart powered.

My only real concern is it takes 2 to 4 hours to do a sequencing run which will be harsh on a vehucle battery charge.

I would look up any dual battery set ups on a grand cherokee, pacifica and wrangler/gladiator for a dual battery set up (dual main battery). They all use the same engine and will have similar computer set up/charging. The main difference will be the execution of the power. People that are into van life(live in their vans) will likely have good resources for adding a dual battery. If it works in a pacifica, it will work in a wrangler. Same with gladiator people. We have a couple overland rigs that come in here for service. I haven't looked to see if they are running 2 batteries though.

 

[CheddarGau]

Good to know! I loathe the thought of letting someone mess with the software, but in my case may be a necessity. Then again if it ain't broke I generally don't fix it.

With this information I may just go with an external power pack for the solar system. I only have two pieces of equipment that need 120v beyond a laptop for the DNA sequencer, and both are low voltage wall-wart powered.

My only real concern is it takes 2 to 4 hours to do a sequencing run which will be harsh on a vehucle battery charge.

Oh and if you ever need to jump start the vehicle and you can't get it going, you need to jump the aux battery. Usually jumping the main battery will do the trick though.

 

[klc]

Good to know! I loathe the thought of letting someone mess with the software, but in my case may be a necessity. Then again if it ain't broke I generally don't fix it.

With this information I may just go with an external power pack for the solar system. I only have two pieces of equipment that need 120v beyond a laptop for the DNA sequencer, and both are low voltage wall-wart powered.

My only real concern is it takes 2 to 4 hours to do a sequencing run which will be harsh on a vehucle battery charge.

Do you know your power requirements for a sequencing run? That will help determine what kind of power bank you need.

 

[turblediesel]

Do you know your power requirements for a sequencing run? That will help determine what kind of power bank you need.

A "Kill-a-watt" meter can provide that info. Mine got a little hot and melty when connected to a heater so don't do that.

Old school dual battery systems used a battery isolator gadget that charged the secondary battery but kept it isolated from most of the vehicle electronics which were a lot simpler. Pretty easy to wire in a circuit with a Ford starter solenoid to self jumpstart with a switch on the dash.

 

[Johnny O]

Do you know your power requirements for a sequencing run? That will help determine what kind of power bank you need.

Runs on an Asus Laptop...so 2.5-5amp draw off the power cord transformer. Gets about an hour of runtime off the battery. depending on the run its up to four hours total time between the actual sequencing and the processing power required to translate the output for bioinformatics software. When I have a 4g or better available I just dump straight to the cloud and they can process at the labs, but often I'm lucky if I have one bar of cellular data. Other limiting factor is storage. One run pretty much fills the SSDs and data transfer is slow over USB so makes for even longer times if I have to dump to an external drive.

 

[CheddarGau]

Runs on an Asus Laptop...so 2.5-5amp draw off the power cord transformer. Gets about an hour of runtime off the battery. depending on the run its up to four hours total time between the actual sequencing and the processing power required to translate the output for bioinformatics software. When I have a 4g or better available I just dump straight to the cloud and they can process at the labs, but often I'm lucky if I have one bar of cellular data. Other limiting factor is storage. One run pretty much fills the SSDs and data transfer is slow over USB so makes for even longer times if I have to dump to an external drive.

Jeep Dual Battery Kits | Genesis Offroad

I did a little reading on that and it seems people are happy with it in the JL community.

 

[Drag Line]

Be aware that the Genesis dual battery system will not let you use the under hood snorkel routing system(s) according to the FAQs on the Genesis website. You will have to use one that routes along the side of the hood and then cut into it. So if aesthetics are not a concern, not a problem.

 

[Johnny O]

Be aware that the Genesis dual battery system will not let you use the under hood snorkel routing system(s) according to the FAQs on the Genesis website. You will have to use one that routes along the side of the hood and then cut into it. So if aesthetics are not a concern, not a problem.

yep! got a Mopar external snorkel sittin’ here waiting for installation. Not impressed with the under hood snorkels after more research . ultimately skipped the Genesis system though for the solar system from Cascadia as described elsewhere.