Trickle charge'n

[Professor_Chaos]

So my jeep has had to sit for a week and its looking like atleast another week or two before I can drive it long enough for a good charge.

Have an adjustable trickle charger but this is my first dual battery so before I just hook it up thought it would be worth asking if that changes anything.

Any specific considerations? The batteries are of the same chemistry I assume right?

So, just roll like normal? Thanks.

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[Radio Guy]

I leave some of my vehicles parked for weeks at a time and have used a 60 watt solar panel and MPPT charge controller to keep the battery topped off. But my new Mojave has a dual battery setup and I assume a battery isolator, which means you cant charge both batteries by connecting to just one. Does anyone have an electrical diagram of a dual battery Gladiator? I suspect connecting a charger of any type would be best done at the large cable connected to the alternator. Problem is I don't know if any voltage regulator circuitry within the alternator will try and fight the outboard battery charger.

 

[Hootbro]

Stole the pic from the JL folks but it is the same on the JT 3.6. The main and aux battery are basically on a parallel circuit to each other.

Trickle charging to the the main battery hookup will eventually charge both batteries. Most trickle charges will charge to and maintain a 13.6V DC surface charge and will be to both batteries as they are in parallel to each other VIA the high current fuse block.

That being said, I use a Schumacher 800ma trickle charger/maintainer on my JT hooked to the main battery terminals when it sits for two weeks ever other two week and have had no issue.

Unless you got a really old or cheap Harbor Freight special trickle charger/maintainer, most of the newer ones are rated for multiple chemistry type batteries.

 

[Radio Guy]

I'm surprised there is no battery isolator as paralleling two batteries accomplishes almost nothing except for adding a little to the amp hour capacity. The reason you would ever install a second battery is to run accessory equipment which might drain the auxiliary battery and you want to keep the starter battery isolated, always charged and available.

In the diagrams posted here if the aux battery is powering electronic stuff and you leave it on overnight or longer it will kill the starter battery along with the aux battery, so what would be the point of a second battery? Another problem is when starting the vehicle a huge amount of current will be shared by both batteries and the aux battery in my opinion is not up to that task. I believe the diagrams posted here are not complete and there is a battery isolator somewhere in the circuit, or at least I hope there is.

I can't get to my truck until next week and then I'll run some tests like pulling current from the aux battery and see if the starter battery gets pulled down with it.

@Professor_Chaos

Yes, a battery tender /maintainer attached to the pos and neg terminal of the Main battery will charge/maintain both the Main and ESS battery at the same time

Just use a tender/maintainer though and not a full blown battery charger connected this way.

The ESS/Aux battery is a 200CCA 12Ah AGM battery and will not handle high amperage well, where the larger Main, AGM battery will.

So with that said, you are better off using a battery/maintainer that has a max output of no more then 5 amp. Many JL owner's use just a little 1.25 amp battery maintainer/charger.

With a low amp maintainer/charger it will take a few hours before you see the maintainer/charger signal you the charging process has completed.

 

[jebiruph]

I'm surprised there is no battery isolator as paralleling two batteries accomplishes almost nothing except for adding a little to the amp hour capacity. The reason you would ever install a second battery is to run accessory equipment which might drain the auxiliary battery and you want to keep the starter battery isolated, always charged and available.

In the diagrams posted here if the aux battery is powering electronic stuff and you leave it on overnight or longer it will kill the starter battery along with the aux battery, so what would be the point of a second battery? Another problem is when starting the vehicle a huge amount of current will be shared by both batteries and the aux battery in my opinion is not up to that task. I believe the diagrams posted here are not complete and there is a battery isolator somewhere in the circuit, or at least I hope there is.

I can't get to my truck until next week and then I'll run some tests like pulling current from the aux battery and see if the starter battery gets pulled down with it.

I can certainly relate to your surprise, I didn't believe they would implement a dual battery system without an isolator either, but they did. Here's my newest diagram for anyone interested.

 

[Radio Guy]

If my testing shows pulling the aux battery down also pulls the starter battery down then I will consider installing a battery isolator and rewiring a few things.

I can certainly relate to your surprise, I didn't believe they would implement a dual battery system without an isolator either, but they did. Here's my newest diagram for anyone interested.

 

[Radio Guy]

Looking over both diagrams posted I would say (to myself) its incorrect so as not to offend anyone. The little I know is there is a programmable relay to supply some aux power all the time or only when the ignition is on, that could be the PCR shown in the diagram here. If PCR is the programmable relay it sould be between a battery and the switched aux power. The diagram for the aux battery and PCR doesn't make any sense. The PCR relay instead is shown connecting or disconnecting the aux battery from the main battery and not really controlling any electronics down stream.

 

[eaglerugby04]

Mine sat for about 3 weeks total when I first injured my knee. Auto stop start didn't engage for a while after the first time I drove it, other than that though everything started up just fine. The JTs are pretty solid. My Sienna on the otherhand will die if it sits for like a week

 

[jebiruph]

Looking over both diagrams posted I would say (to myself) its incorrect so as not to offend anyone. The little I know is there is a programmable relay to supply some aux power all the time or only when the ignition is on, that could be the PCR shown in the diagram here. If PCR is the programmable relay it sould be between a battery and the switched aux power. The diagram for the aux battery and PCR doesn't make any sense. The PCR relay instead is shown connecting or disconnecting the aux battery from the main battery and not really controlling any electronics down stream.

Don't worry about offending me, if I'm wrong about anything feel free to point it out, but know that I've been looking at this for 3 years and an fairly confident I know how it works.

The only purpose for the aux battery is to power the interior electronics during an auto stop event, conserving the main battery power for the restart. The PCR separates the batteries during an auto stop. Otherwise, except for a quick aux battery test during a cold start, the batteries are always connected in parallel. Always means running and not running.

 

[Radio Guy]

When you say "The only purpose for the aux battery is to power the interior electronics during an auto stop event, conserving the main battery power for the restart", that is more in line with what the posted diagram shows, meaning the aux battery is not a typical 2nd battery to power electronics in order to save the starter battery.

In that case the aux battery would provide continuous power for "something" when the engine is temporarily off during an auto stop and without the typical dip down to 11 volts or lower when the starter is engaged after an auto stop. In most of my vehicles full of 2-way radio equipment, most of the radios will power cycle if turned on when the vehicle is not running and you then hit the starter, so Jeep has gone to some extreme lengths to avoid that.

So if all of the above is true the PCR relay is not the programmable relay for aux power switches giving you continuous power or power only when the ignition key is on. Its only for the auto stop thing which I don't plan on using. This has been very interesting, thank you. I think.

Don't worry about offending me, if I'm wrong about anything feel free to point it out, but know that I've been looking at this for 3 years and an fairly confident I know how it works.

The only purpose for the aux battery is to power the interior electronics during an auto stop event, conserving the main battery power for the restart. The PCR separates the batteries during an auto stop. Otherwise, except for a quick aux battery test during a cold start, the batteries are always connected in parallel. Always means running and not running.

 

[Professor_Chaos]

If my testing shows pulling the aux battery down also pulls the starter battery down then I will consider installing a battery isolator and rewiring a few things.

Let us know

 

[jebiruph]

When you say "The only purpose for the aux battery is to power the interior electronics during an auto stop event, conserving the main battery power for the restart", that is more in line with what the posted diagram shows, meaning the aux battery is not a typical 2nd battery to power electronics in order to save the starter battery.

In that case the aux battery would provide continuous power for "something" when the engine is temporarily off during an auto stop and without the typical dip down to 11 volts or lower when the starter is engaged after an auto stop. In most of my vehicles full of 2-way radio equipment, most of the radios will power cycle if turned on when the vehicle is not running and you then hit the starter, so Jeep has gone to some extreme lengths to avoid that.

So if all of the above is true the PCR relay is not the programmable relay for aux power switches giving you continuous power or power only when the ignition key is on. Its only for the auto stop thing which I don't plan on using. This has been very interesting, thank you. I think.

It's as simple as this. The original auto stop systems used a single battery and if you think about it, the odds were very good that the battery would fail trying to restart in the middle of traffic. The aux battery was added to supply power to the electronics during an auto stop to avoid draining the main battery and reduce the likelihood of the main battery failing during an in traffic restart.

I think that part works as designed, but a dual battery system using dissimilar batteries and no battery isolator has introduced a lot of other issues.

 

[Radio Guy]

I for sure and I suspect many others assumed the aux battery was just another aux battery, but apparently not. I agree on the dual battery, no isolator setup is not going to live a long life, one or both batteries will fail prematurely.

If anyone has worked in the marine electronics industry or anywhere that lots of big batteries are directly connected in parallel, you know that equal length cable paths to each battery is very important, even if the interconnect cables are the diameter of a baseball bat. Not doing this will take a normal 5-7 year battery life down to 2 years or maybe less.

I think retrofitting a Gladiator with a battery isolator will accomplish the original goal of the aux battery for auto stop and protect them, giving a longer service life.

It's as simple as this. The original auto stop systems used a single battery and if you think about it, the odds were very good that the battery would fail trying to restart in the middle of traffic. The aux battery was added to supply power to the electronics during an auto stop to avoid draining the main battery and reduce the likelihood of the main battery failing during an in traffic restart.

I think that part works as designed, but a dual battery system using dissimilar batteries and no battery isolator has introduced a lot of other issues.

 

[jebiruph]

I for sure and I suspect many others assumed the aux battery was just another aux battery, but apparently not. I agree on the dual battery, no isolator setup is not going to live a long life, one or both batteries will fail prematurely.

If anyone has worked in the marine electronics industry or anywhere that lots of big batteries are directly connected in parallel, you know that equal length cable paths to each battery is very important, even if the interconnect cables are the diameter of a baseball bat. Not doing this will take a normal 5-7 year battery life down to 2 years or maybe less.

I think retrofitting a Gladiator with a battery isolator will accomplish the original goal of the aux battery for auto stop and protect them, giving a longer service life.

Feel free to join the discussion. https://www.jlwranglerforums.com/forum/threads/ess-dual-battery-management.60034/

 

[Radio Guy]

Thanks for the link, I'll check it out. In the mean time I would like to find out exactly what the aux battery powers. It probably only powers a few things critical during auto stop mode and not all the accy items we may usually run from a typical aux battery.

If that's the case then running your radio too long or having lights on too long with the engine off will still potentially kill the main battery used for starting so its almost a moot point to diode isolate the two batteries. If that is done and you don't use the auto stop mode like I will you will just have an aux battery that is charged separately but otherwise shares some of the load and is mismatched in size and charge components which will contribute to poor battery life.

I read where the JT battery tray will accept a larger battery and when it comes time for a new main battery I will be sticking in the highest capacity thing that will fit. Another test I think is needed is to disconnect the aux battery from N1 to see what's affected and to also measure how much current might be drawn from the aux battery. That might pave the way to just run one larger capacity battery for those not wanting auto stop and simplify the electrical system. I suspect it will also give longer main battery life.

Feel free to join the discussion. https://www.jlwranglerforums.com/forum/threads/ess-dual-battery-management.60034/

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