Jumperless Aux Battery Bypass

[THAW]

PCR = Power Control Relay? If so, what's its functioning?

Looks like you already found your answer, but....

Yes. The PCR opens to break the connection between the batteries during ESS events.

More specifically, it breaks the connection between N3 and the AUX (ESS) battery. leaving the AUX (ESS) battery to power N1 -> PDC (fuse box) -> system electronics, and leaving exclusively the CR[an]K (main) battery attached to the starter and N2 -> N4 through N8 (radiator fan, power steering, alternator).

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[Jammer]

But isn't the purpose of the auxiliary battery also to help charge the other battery and if you disconnect it there's nothing to keep charging it something like that I was told. I remember one time my chief would not cut off I could not turn the motor off disconnected the big battery and it kept running and they said because my little battery was bad that's why it wouldn't cut off so I should have pulled the fuse eventually cut off but it was weird because even with the big battery cables disconnected the motor kept running

 

[ScotM]

Found it, thanks.

Yes, the PCR is on the firewall behind the AUX (ESS) battery box.

[borrowed image]

one more quest.ion. Once the N1, N3, PCR relay, aux positive and negative cable, along with the aux negative off the main are pulled out per your picture, is any jumper required, or is it just take all that out and good to go with fuse 42 removed? Very much appreciate your expertise here!

 

[THAW]

one more quest.ion. Once the N1, N3, PCR relay, aux positive and negative cable, along with the aux negative off the main are pulled out per your picture, is any jumper required, or is it just take all that out and good to go with fuse 42 removed? Very much appreciate your expertise here!

N1 needs power, so a properly-rated connector (cable or shunt) between N1 and the remaining battery positive or N1 and one of the other High Current Fuse posts (e.g. N2) is required.

 

[T-Rob]

But isn't the purpose of the auxiliary battery also to help charge the other battery and if you disconnect it there's nothing to keep charging it something like that I was told. I remember one time my chief would not cut off I could not turn the motor off disconnected the big battery and it kept running and they said because my little battery was bad that's why it wouldn't cut off so I should have pulled the fuse eventually cut off but it was weird because even with the big battery cables disconnected the motor kept running

Your alternator is what charges your battery. Trust me when I tell you that you don’t need the aux battery. I’ve been running without my auxiliary battery for almost 4 years now. My Jeep runs perfect!

 

[jludave]

But isn't the purpose of the auxiliary battery also to help charge the other battery and if you disconnect it there's nothing to keep charging it something like that I was told.

Whomever told you that has no idea how a vehicle’s charging system works, nor how a dual battery setup in a vehicle works.

 

[ScotM]

Anyone have any idea why [Banned Site] Jeep is telling folks not to delete the aux battery? He states that Jeep engineers told him that in the long run the aux battery protects the jeeps computer from surges during start up, and over time a missing aux will damage the computer. I’ve joined his forum to get more details, but am awaiting approval.

 

[ScotM]

N1 needs power, so a properly-rated connector (cable or shunt) between N1 and the remaining battery positive or N1 and one of the other High Current Fuse posts (e.g. N2) is required.

Did you fuse it? I was thinking battery cable or 14 AWG with a 30 amp fuse between n1 and n2

 

[jludave]

Anyone have any idea why [Banned Site] Jeep is telling folks not to delete the aux battery? He states that Jeep engineers told him that in the long run the aux battery protects the jeeps computer from surges during start up, and over time a missing aux will damage the computer. I’ve joined his forum to get more details, but am awaiting approval.

Because he’s full of crap.

Look at how many people on here that have bypassed the aux battery without issue. That should tell you all you need to know.

 

[ScotM]

N1 needs power, so a properly-rated connector (cable or shunt) between N1 and the remaining battery positive or N1 and one of the other High Current Fuse posts (e.g. N2) is required.

Currently, with my aux ground isolated off the main battery, I'm a bit confused as to how N1 is getting any power now? Can anyone explain that to me ? At least based on the diagram. It would seem that the N1 in stock configuration is getting power constantly by virtue of it all be connected to the main battery, and N3 gets power only when being energized by the PCM when the start stop is activated.

If I remove all the cabling ( Aux + & -, N1 & N3, PCM, the Aux Ground to Main and the aux battery, Both N1 and N3 will not have power. If I add a jumper off the main to N1, then the N1 will always be getting power, but that leaves N3 with no power during a start stop? If anyone can clarify this for me, that would be extremely helpful.

I do have the start stop disabled currently, but I'm just tring to better understand the electronics in play here. I have read this thread, but I'm still a bit confused on the above two points

 

[Terrymo]

Anyone have any idea why [Banned Site] Jeep is telling folks not to delete the aux battery? He states that Jeep engineers told him that in the long run the aux battery protects the jeeps computer from surges during start up, and over time a missing aux will damage the computer. I’ve joined his forum to get more details, but am awaiting approval.

He has some good knowledge and he’s also a good talker. You know that one friend you have that knows a lot of stuff but likes people to think he knows all the stuff, so he bluffs his way through some of the stuff. It seems like that sometimes. I like his videos except the unboxing at high volume segments.

 

[THAW]

Did you fuse it? I was thinking battery cable or 14 AWG with a 30 amp fuse between n1 and n2

14 AWG/30 Amp is far too small when the PCR and its wiring are removed. N1 powers the entire PDC (fuse box), so it should have a connection that can support at least a couple hundred Amps. [side bar: 14 AWG should probably be fused at 20A.]

The best option (if you can get one) is an N1 to N2 shunt from an eTorque/4xe.

Currently, with my aux ground isolated off the main battery, I'm a bit confused as to how N1 is getting any power now? Can anyone explain that to me ?

N1 is the direct connection to the PDC (fuse box). The other High Current Fuse posts (N2-N8) are all connected to each other.

With the Aux (ESS) battery ground cable disconnected, N1 (PDC/fuse box) is powered by the CR[an]K (main) battery through its positive cable to N2 to N3 to the AUX (ESS) battery positive cable (if the PCR opens, the connection is broken, thus the reason for removing the PCR fuse, F42).

Removing the PCR and AUX (ESS) battery cables breaks the connection between N1 (PDC/fuse box) and any power source.

 

[ScotM]

14 AWG/30 Amp is far too small when the PCR and its wiring are removed. N1 powers the entire PDC (fuse box), so it should have a connection that can support at least a couple hundred Amps. [side bar: 14 AWG should probably be fused at 20A.]

The best option (if you can get one) is an N1 to N2 shunt from an eTorque/4xe.



N1 is the direct connection to the PDC (fuse box). The other High Current Fuse posts (N2-N8) are all connected to each other.

With the Aux (ESS) battery ground cable disconnected, N1 (PDC/fuse box) is powered by the CR[an]K (main) battery through its positive cable to N2 to N3 to the AUX (ESS) battery positive cable (if the PCR opens, the connection is broken, thus the reason for removing the PCR fuse, F42).

Removing the PDC and AUX (ESS) battery cables breaks the connection between N1 (PCR/fuse box) and any power source.

super helpful.!!!

 

[Jebiruph]

Anyone have any idea why [Banned Site] Jeep is telling folks not to delete the aux battery? He states that Jeep engineers told him that in the long run the aux battery protects the jeeps computer from surges during start up, and over time a missing aux will damage the computer. I’ve joined his forum to get more details, but am awaiting approval.

An etorque engine always cold starts from a single 12V battery as designed by Jeep engineers, I wonder if that's damaging the computer. For etorque ESS restarts, the 12V battery doesn't crank the starter, so computer damaging 12V battery surges aren't an issue.

 

[Steve104]

An etorque engine always cold starts from a single 12V battery as designed by Jeep engineers, I wonder if that's damaging the computer. For etorque ESS restarts, the 12V battery doesn't crank the starter, so computer damaging 12V battery surges aren't an issue.

But wouldn't the voltage drop during cranking with both batteries in place be less than with just the one, assuming both are fully charged at 12.6 volts?

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