ESS Dual Battery Management

Jebiruph

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I've always thought it would be good to be able to isolate the aux battery and keep it as a reserve battery, especially when overlanding. Here's what I've come up with to implement that, and for managing the batteries in general. It uses a battery switch connected to the aux battery ground cable, a bypass jumper and a voltage gauge for each battery.

It's still somewhat of a prototype, I still have to figure out some way to mount the volt gauges.
bmp prototype.jpg


To hook it up, you remove the aux battery ground cable from the main battery ground terminal and connect it to the battery switch stud and connect the battery switch cable back to the main battery ground terminal.
The red cables connect to N1 and the main battery positive terminal. You should remove the fuse when connecting the red cables to avoid accidentally shorting them out. Here's a diagram.
ess bmp simple 3b.PNG


Here's running with the batteries separated, the volt meters show the main battery charging and the aux battery not.
bmp running seperate.jpg

Battery charger charging just the main battery.
bmp charging main.jpg

Battery charging just the aux battery. EDIT- You should be able to leave the positive cable on the main battery and just move the negative cable to the aux battery.
bmp charging aux.jpg

Here's with the main battery disconnected after a successful test of starting with just the aux battery. EDIT- It's not necessary to unplug the battery sensor.
bmp starting aux.jpg
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WranglerMan

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Very cool....I took the cheaters way, it does not isolate like yours but I guess I could unplug the smart isolator to do it if I chose to but the thing is the way the JL is wired from my understanding is the fuse box comes off the main crank battery regardless so if your running the radio, lights etc...or have your auxiliary items like winch connected to the main it’s pulling off power so I wanted to do a few things by going the genesis route.

1. get rid of the tiny ESS battery
2. Always have a battery to crank off of to keep me from being stranded.
3. Give me the option to give myself a boost just incase the main somehow gets sucked down.
4. Be able to run aux accessories and still have 12.7 volts to crank with.

I have heard to many stories about that ESS battery leaving guys stranded, I know there is a patch for the 2018’s to not do this as when it sees the voltage is down the patch still allows you to crank up but gives you a error message but if that ESS battery is bad it will pull off the main crank battery to equalize and if it’s shorted I figure it will suck the main down and I have just hated that ESS battery since day one.

I can honestly say my JL has never ever left me stranded but I did have to have the main battery replaced after 7 months of ownership so like Sept of 2018 and up until I had the genesis system put it it’s never ever gave me trouble but I figured I was on borrowed time with my ESS battery and I’m out of warranty and the whole idea of pulling a fender flare or going thru the top to get to the battery is BS ........ I know some will argue it’s a 15-30 min job and you can break a few fender clips going from the bottom or if you go thru the top you could possibly damage one of the fuse box connectors and that would be a huge headache so for me it was worth the expense to have to full size batteries and a built in jumper and when it comes time to replace batteries I can do it all up top and don’t have to remove much.

Will what I have be 100% perfect .......it’s doubtful as with any electronics bad things happen so we will just have to see how it plays out, but kudos to you brother for coming up with ways to work with a factory setup, you have been great on the whole battery design and operation since day one and the jumper you sent me I still have and have tested it but never used it for emergency so not sure what I will do with it now since going the route I chose.

276FC49A-C953-4514-95C3-105D00876402.jpeg
 
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Jebiruph

Jebiruph

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1. get rid of the tiny ESS battery
2. Always have a battery to crank off of to keep me from being stranded.
3. Give me the option to give myself a boost just incase the main somehow gets sucked down.
4. Be able to run aux accessories and still have 12.7 volts to crank with.
Well, it's not quite the deal the Genesis system is, but it's little bit lower cost to implement.

1. It gets rid of the tiny ESS battery's negative impact on the system by isolating it (if you choose).
2. As long as it's isolated and monitored (by occasionally checking the meter), the aux can do this.
3. I wouldn't recommend this, save the aux for an emergency starting battery.
4. See 3.
 

WranglerMan

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Well, it's not quite the deal the Genesis system is, but it's little bit lower cost to implement.

1. It gets rid of the tiny ESS battery's negative impact on the system by isolating it (if you choose).
2. As long as it's isolated and monitored (by occasionally checking the meter), the aux can do this.
3. I wouldn't recommend this, save the aux for an emergency starting battery.
4. See 3.
Well the only part of the ESS I have left is the IBS ( if that’s part of it ) the ESS negative ( disconnected at both ends ) and there’s probably a relay in their somewhere but the ESS battery, main battery and factory tray are likely in recycle by now
 
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Jebiruph

Jebiruph

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Here's a schematic of how this is wired.
ess bmp simple 2b.PNG


Here's some pics showing more details of the latest version. I mounted the gauges in 1 1/4" PVC pipe endcaps and color coded the gauges and wires - blue= aux green = main.
bmp switch top.jpg

bmp switch bottom.jpg

bmp gauges top.jpg

bmp gauges bottom.jpg

bmp bypass jumper.jpg

bmp v2.jpg

bmp gauges lit.jpg
 

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Nice.

Do you get a warning on the dash that the ESS battery is 'disconnected'?

Could you post some pictures when you mount this in your vehicle?
What Amp isolator switch are you using? 100 Amp?

I was thinking I could do this with a bluetooth battery monitor on the auxiliary battery to monitor its SoC without having to open the hood. Murphys law is the auxiliary battery would have discharged at the same time my main battery fails!

My other thought was to use a 100 Amp relay and use the Aux switches to control it - but suspect if the main battery is dead then may not have enough power to close the relay!
 
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Jebiruph

Jebiruph

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Nice.

Do you get a warning on the dash that the ESS battery is 'disconnected'?

Could you post some pictures when you mount this in your vehicle?
What Amp isolator switch are you using? 100 Amp?

I was thinking I could do this with a bluetooth battery monitor on the auxiliary battery to monitor its SoC without having to open the hood. Murphys law is the auxiliary battery would have discharged at the same time my main battery fails!

My other thought was to use a 100 Amp relay and use the Aux switches to control it - but suspect if the main battery is dead then may not have enough power to close the relay!
The system doesn't know the ESS battery is disconnected, but when you run on a single battery it will limit ESS events to 6.

@Rhinebeck01 has been running with his ESS battery disconnected using a bypass jumper for a very long time. He's going to test this and I'm sure he'll post pictures. He also brought to my attention that there needs to be a way to prevent the meters from draining the batteries, so I'll being adding switches to the meters.

Here's the specs for the switch, it's just a generic Amazon battery switch.
bmp switch specs.jpg


Instead of a bluetooth device that will use power, I could see running the wires to install some meters in the cab.
 

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Those meters draw about 8mA. You can get a dual readout version that draws about 10mA.

A 650 CCA battery provides about 70AH at 20% discharge.

One way to look at this is that the meter will run for 7,000 thousand hours or about 9 months while retaining 80% capacity of a typical car battery that has been maintained in excellent conditions.

The parasitic draw on the JL series has been observed as approximating 10-20mA when the vehicle is "asleep". It could be a lot more depending on the type of upgrades you have attached.

Regarding the use of switches for disconnecting the meters, if one were to add switches for this purpose, there is a possibility of using one on-off-on switch and one meter. That's one less switch and one less meter.
 
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Jebiruph

Jebiruph

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Those meters draw about 8mA. You can get a dual readout version that draws about 10mA.

A 650 CCA battery provides about 70AH at 20% discharge.

One way to look at this is that the meter will run for 7,000 thousand hours or about 9 months while retaining 80% capacity of a typical car battery that has been maintained in excellent conditions.

The parasitic draw on the JL series has been observed as approximating 10-20mA when the vehicle is "asleep". It could be a lot more depending on the type of upgrades you have attached.

Regarding the use of switches for disconnecting the meters, if one were to use switches, there is a possibility of using one on-off-on switch and one meter. That's one less switch and one less meter.
A dual readout meter won't work because both readouts use the same ground. (Anybody want a good deal on a dual readout meter?) For this setup each meter's ground is to the battery it's monitoring.
 

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Great thread! Subscribed!

Love this stuff.
 

Gee-pah

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Thanks for your research, work and publication of this Jerry, along with your initial N1 <-> N2 fused jumper hack from a while back that could allow, say, a 2018 3.6L JL[U] to crank even if its ESS/Aux battery failed to meet voltage thresholds for the vehicle to attempt the crank (which is otherwise energized by both batteries).

In your more recent diagram of this thread you defined three different states of operation based upon the a) presence/absence of the fused jumper between terminals N1 and N2 of the high current fuses in the Power Distribution Center (PDC) and the b) on or off state of the connect/disconnect switch that forms part of the hardware of this thread. You named these three states as 1) Normal Operation, 2) Separated Batteries and 3) Aux Bypassed, which I'll use below for clarity.

Three questions:

Q1) Is it correct to say that your "Separated Batteries" state is not one that model year 2018 3.6L JL[U]'s without the flash (discussed on prior threads on the forum) to allow them, like model year 2019 and beyond 3.6L JL[U]'s to cold crank off of both batteries, or just the main battery (if the ESS/Aux battery fails its pre cold-crank testing) can use? If no, why?

Q2) Is it correct to say that your "Aux Bypassed" state would never engage the ESS system, (independent of the state of the factory non-latching bypass switch of 3rd party gear to disable ESS) because the IBS would not detect a voltage from the ESS/Aux battery? If no, why?

Q3) As an offshoot of Q2) why would, in your "Separated Batteries" state the 3.6L JL[U]'s not know, as you've stated, that the ESS battery was disconnected? Perhaps to rephrase the question, isn't such knowledge of the state of the ESS battery derived from the IBS--to which the ESS/Aux battery would not be connected to in your "Separated Batteries" state?

Please appreciate that none of these questions are critiques--just me trying to understand.

Thanks.
 

WranglerMan

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I had Jerry’s hack with the jumper and tested it for several weeks but just have always hated that ESS battery since day one, even though the bypass jumper worked I just did not like the fact that FCA chose to bury that baby battery under the main crank battery so I opted for the Genesis system, yes it’s a pricy system and even a tad pricier for me as I had my favorite local shop do the install but it’s a great system that seems to be well designed and allows me to run all my aux equipment like winch, air compressor, second lights etc... from a dedicated aux battery and I still have a protected main crank battery and if I am stupid enough to leave my lights or radio on I can use the boost feature to get me going.

I have been running some tests on the Genesis system by doing voltage checks, running down the main and boosting from the second battery and it’s all been 100% solid and it just seems like a well made package.

I know some will argue that the baby battery is a breeze to get to but I just think a battery replacement should not be over complicated by having to pull a fender flare or pull the PDC to get to it, I know it does not happen often but it’s still going to happen at some point

Jerry has gone above and beyond on keeping us all educated on the JL battery system and even though i don’t have my original system left except for a few pieces like the IBS I will continue to read and enjoy his contributions on this subject

The one additional caveat I had going to the Genesis system was I had to ditch the lawn mower Deltran battery tender plus I was using on my original setup as the 1.25 amp tender just took days to go to float so stepped up my game a NOCO Genius 10 and it only takes a few hours to get me at 100% and by morning it’s in float and goes into maint mode.

The one additional thing I have also noted is on my original setup my EVIC displayed voltage was above 14 volts 99.99% of the time so either I had one or both original batteries going bad even though they passed a load test, never had any issues but very rarely saw below 14 volts on display but now with the new setup and the two full size Full River 750’s I see high 12’s to low 13’s after 30-40 mins of driving and both batteries even after sitting for a day or two still meter at 12.7+ but the 750’s are some beefy batteries but like any battery they will degrade and need replacing but it’s a pretty straight forward process to swap both out by taking about like (4) bolts and loosening (4) battery connectors
 
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