Overlanding battery

bibanul

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Yeah, that’s a pretty different application than it’s intended for. Not saying you couldn’t make it work, but just not as straightforward.

If I were you, I would start by completely removing the Aux battery, and in its place, hook up DCC50S “ALT+“ going towards the PCR relay (and ultimately the alternator if/when the PCR relay allows it).

Hook up DCC50S “OUT+“ to both the LiFePo battery and “N1,” to supply the vehicle electronics. You would still need to connect the “IGN” signal wire to Fuse 50 (or equivalent, like just jumping it to the “ALT+“ might work since that’s coming from the alternator anyway).

The only remaining question would be the PCR /Aux battery check when starting up. I don’t know if the voltage is read on the “N1” side or the ”PCR” side as they are normally one and the same with no DC-DC in between (read the @Jebiruph ESS guides for more info). If it’s the former, then you should be good to go. If it’s the latter, then unplugging the PCR “C2” connection should do it, which permanently engages the relay.

YMMV and do all this at your own risk, I take no responsibility if anything goes wrong, big or small. But do let us know how it goes!
Sounds good thanks for the heads up. I had same setup in mind, however the DCC50S will isolate access to PCR > N3 hence the startup check might not happen if on the PCR side even with the C2 pulled just because DCC50 might not have a closed circuit to AUX unless it's charging. The chain will be as follows: N3 > DCC50 > PCR > N1+AUX Batt.

If the startup check happens on the N1 side then this becomes less of an issue (most likely since IBS is on negative terminal, probably for that reason :D).

Still, the main question remains that while ALT is running the PCR normally closed passed ALT current to N1 hence powering the electronics besides charging AUX. Injecting the DCC50 will make that "trickle charge" that 30 sec N1 is on battery then switches to BATT+ALT as DCC50 charges, then DCC50 reads batt fully charged and disconnects and the cycle starts over. Weird stuff.

Maybe I will just leave the AGM in AUX and put a solar MPPT only on top of the Main batt and call it a day :). TBH, I'm annoyed that on ACC with engine off both batteries are drained, yes technically until main drops to 12.7v then apparently PCR opens (on ACC still) to protect the main and allow AUX to continue to power ACC. Which makes sense for startup check when ECU decides if AUX is too discharged to be reconnected to Main or keep PCR open until engine cranks up then reconnect to charge both batteries.





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remlemasi

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Sounds good thanks for the heads up. I had same setup in mind, however the DCC50S will isolate access to PCR > N3 hence the startup check might not happen if on the PCR side even with the C2 pulled just because DCC50 might not have a closed circuit to AUX unless it's charging. The chain will be as follows: N3 > DCC50 > PCR > N1+AUX Batt.

If the startup check happens on the N1 side then this becomes less of an issue (most likely since IBS is on negative terminal, probably for that reason :D).

Still, the main question remains that while ALT is running the PCR normally closed passed ALT current to N1 hence powering the electronics besides charging AUX. Injecting the DCC50 will make that "trickle charge" that 30 sec N1 is on battery then switches to BATT+ALT as DCC50 charges, then DCC50 reads batt fully charged and disconnects and the cycle starts over. Weird stuff.

Maybe I will just leave the AGM in AUX and put a solar MPPT only on top of the Main batt and call it a day :). TBH, I'm annoyed that on ACC with engine off both batteries are drained, yes technically until main drops to 12.7v then apparently PCR opens (on ACC still) to protect the main and allow AUX to continue to power ACC. Which makes sense for startup check when ECU decides if AUX is too discharged to be reconnected to Main or keep PCR open until engine cranks up then reconnect to charge both batteries.
You have the DCC50S in between N3 and PCR.

I’m suggesting putting the DCC50S in between the PCR and N1+LiFePo.

DCC50S “ALT+“ goes to PCR, DCC50S “OUT+” goes to the N1+LiFePo.

AB3A8A14-3414-4573-A069-1051D7D4ED03.png


Won’t the way I suggested solve most of the issues you bring up?
 

bibanul

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You have the DCC50S in between N3 and PCR.

I’m suggesting putting the DCC50S in between the PCR and N1+LiFePo.

DCC50S “ALT+“ goes to PCR, DCC50S “OUT+” goes to the N1+LiFePo.

AB3A8A14-3414-4573-A069-1051D7D4ED03.png


Won’t the way I suggested solve most of the issues you bring up?
Yup, I can do that too. I still fear on engine start if check for AUX happens and with C2 pulled, the electric circuit won't close because DCC50 will be isolating the AUX part from the PCR since it's not actively charging it and engine is off.
 

remlemasi

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Yup, I can do that too. I still fear on engine start if check for AUX happens and with C2 pulled, the electric circuit won't close because DCC50 will be isolating the AUX part from the PCR since it's not actively charging it and engine is off.
From Jebiruph's thread on Cold Starts:

Sometime between the pressing of the Start switch and the starter cranking, The PCM briefly activates the PCR, separating the batteries. Both the Keyless Ignition Node and Radio-Freq Hub modules are then powered only from the Aux battery. If the Aux battery cannot provide enough power for the modules, the status of the start switch is lost and the starting process terminates.

starting relays 4.PNG

This also explains why it will start with just the Aux battery, but not just the Main battery. With just the Aux battery connected, the status of the Start Switch is maintained while the PCR separates the batteries, and the starting process continues when the PCR reconnects the batteries. With just the Main battery connected, the starting process terminates as soon as the PCR separates the batteries and the KIN and RFH modules lose power.
Based on this, it's my understanding that the Aux battery "check" is really just the KIN / RFH maintaining power when the PCR is blipped. It's not "measured" per se. Not at N1, not at PCR. It's just making sure the KIN / RFH still have power, which, when the PCR is blipped, comes exclusively from the Aux battery.

The LiFePo battery will be connected directly to N1 and thus provides power to KIN / RFH, assuming the LiFePo battery isn't dead, and cranking is allowed to proceed.

If the LiFePo battery IS dead, then jumping N1 to N2 should solve it and provide power from the starter battery to N1 / KIN / RFH so cranking can start. However, I would NOT leave N1 and N2 permanently jumped as it would cause the starter AGM battery and the LiFePo aux battery to cycle charge back and forth...

With this deeper understanding now, I think that pulling C2 on the PCR will NOT do anything as the DCC50S does NOT complete a circuit between "ALT+" and" OUT+". There's a whole bunch of electronics and DC-DC conversion going on between those two lugs. The only way to start if the LiFePo aux battery is dead is to jump N1 and N2 temporarily.
 

bibanul

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From Jebiruph's thread on Cold Starts:



Based on this, it's my understanding that the Aux battery "check" is really just the KIN / RFH maintaining power when the PCR is blipped. It's not "measured" per se. Not at N1, not at PCR. It's just making sure the KIN / RFH still have power, which, when the PCR is blipped, comes exclusively from the Aux battery.

The LiFePo battery will be connected directly to N1 and thus provides power to KIN / RFH, assuming the LiFePo battery isn't dead, and cranking is allowed to proceed.

If the LiFePo battery IS dead, then jumping N1 to N2 should solve it and provide power from the starter battery to N1 / KIN / RFH so cranking can start. However, I would NOT leave N1 and N2 permanently jumped as it would cause the starter AGM battery and the LiFePo aux battery to cycle charge back and forth...

With this deeper understanding now, I think that pulling C2 on the PCR will NOT do anything as the DCC50S does NOT complete a circuit between "ALT+" and" OUT+". There's a whole bunch of electronics and DC-DC conversion going on between those two lugs. The only way to start if the LiFePo aux battery is dead is to jump N1 and N2 temporarily.
Thanks for the detailed answer, I learned a lot. One more thing bothers me. the AUX is wired to N1 and the PCR connects the alternator to N1+AUX as well. Moreso at rest, both batteries are connected via PCR/N3. I have to run the DCC50S after the PCR to the battery BUT when the engine is on, the ALT amperage is passed to the N1 ONLY if the LiFePo4 needs to be charging AND limited to 50A, otherwise DCC50S isolates the ALT path hence while the engine is running, the N1 receives AUX battery current only until AUX drops enough to tell DCC50S to start charging again, then once charged the cycle repeats.

Another complication is the max current expected on N1 with all electronics and AC on while ALT is supposed to send 200Amps there and in fact sees only 30 or 40 as the LiFePo4 can put out.

All in all, huge headache, might just get a beefier AGM AUX, relocate under passenger seat or trunk and just let alternator do its thing and use the LiFePo4 as standalone house batt to power whatever I run in the trunk. Or better DEL AUX, wire up N1+N2 and done deal. Pitty, i wanted to run the Alpine while at the beach :(...

Any other thoughts on this setup?

Thanks a lot!
 

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