Your battery voltage - truck off and at rest

[ShadowsPapa]

That makes sense for where to connect the negative side of the charger, but where are you putting the positive side of the charger to charge the Aux battery by itself?

If you use the positive side of the main battery, you will charge the Aux battery with the PCR in the circuit. If you put the positive of the charger on the N1 terminal, it will charge the Aux battery directly. Do we know which is preferred?

Frankly, IMO, it should make no difference. It's like a common neutral for two circuits in a way.
We have multiple things all "grounded" through the chassis ground without issue.
You are charging both through the common negative and common positive when the vehicle is all together and driven. The factory charges both batteries in parallel.
The PCR is basically a NC relay that opens when ESS has shut the engine down and is closed during driving or when the vehicle is off, connecting the positive of the batteries together. It must be a hefty relay as charging current goes through it all the time you are driving or any time you charge the batteries in parallel (without disconnecting anything).
If you break only one of the connections, in this case, the negative, they are no longer in parallel.
(Consider a transformer with a center tap...............)

To answer your question - I put the positive of both chargers on the positive connection to the main battery.
I put the negative of the 1.5 amp charger on the main battery, I put the negative of the 800mA charger on the negative cables removed from the IBS.
The chargers acted exactly like they would with any other charging scenario. They acted independently. No reason they would not.

Image below -
my 1.5 amp smart battery tender negative was connected to A and positive to C,
my smaller 800mA charger/maintainer was connected negative to B and positive to C
~I did use a block of wood to hold the negative cable higher, more securely away from the main battery negative post.~
I posted the voltages after charging in a post above.

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[ShadowsPapa]

We took the truck to an event last evening, about an hour after I had charged the batteries using two chargers, independently.
I noticed very different behavior - all the way down (about 45 minute drive) the voltage on the cluster read a very solid, steady 14.6 volts. It never wavered.
We were there for about an hour so the truck sat an hour.
Then most of the way back it read a solid, steady 14.5 volts - when the headlights came on it mostly read 14.5 but flipped back and forth to 14.4 once in a while, going back to 14.5.
Normally it starts at one reading and changes over time. This time it did not and stayed at the same reading for the whole trip - save for an occasional flip down to 14.4 then back to 14.5 when the headlights came on.
I'm used to seeing the voltage vary a lot more. Will be interesting to see how things progress now.

 

[jac04]

Good info. Keep us posted.

 

[jebiruph]

We took the truck to an event last evening, about an hour after I had charged the batteries using two chargers, independently.
I noticed very different behavior - all the way down (about 45 minute drive) the voltage on the cluster read a very solid, steady 14.6 volts. It never wavered.
We were there for about an hour so the truck sat an hour.
Then most of the way back it read a solid, steady 14.5 volts - when the headlights came on it mostly read 14.5 but flipped back and forth to 14.4 once in a while, going back to 14.5.
Normally it starts at one reading and changes over time. This time it did not and stayed at the same reading for the whole trip - save for an occasional flip down to 14.4 then back to 14.5 when the headlights came on.
I'm used to seeing the voltage vary a lot more. Will be interesting to see how things progress now.

If you charged the batteries with the IBS removed, the reinstalled IBS has to relearn the main battery and you'll probably get max voltage output until that process is complete.

 

[chorky]

What about using the genesis dual battery tray but instead of using it as a dual battery system using the second battery as the factory Aux.

it weirds me out they use two different battery sizes considering everyone knows thats never a good idea.

 

[ShadowsPapa]

If you charged the batteries with the IBS removed, the reinstalled IBS has to relearn the main battery and you'll probably get max voltage output until that process is complete.

Yes, and that was one thought I had on the trip down - it's going to need to work off a default until it has learned again. I've seen as high as 14.7 and 14.8 on this truck so I was sort of surprised it didn't settle there, but different ABS battery makers seem to have a range of what it takes to charge each of their batteries so perhaps that middle 14s area is the default.
Time will tell. Seeing it solid on a voltage without fluctuation did make sense.

it weirds me out they use two different battery sizes considering everyone knows thats never a good idea.

I also wondered - why two different size/capacity batteries when most vendors say "don't do that".

 

[Maximus Gladius]

What about using the genesis dual battery tray but instead of using it as a dual battery system using the second battery as the factory Aux.

it weirds me out they use two different battery sizes considering everyone knows thats never a good idea.

Love that idea.

 

[ShadowsPapa]

Love that idea.

Assuming you could buy the tray only and not all of the other stuff............. 600 bucks is crazy high to change how the batteries sit just to get two same-size batteries in place.

Anyway, back on the voltage checks - 12.37 mid-morning today, after sitting about 14 hours. Lower than I expected for having them fully charged at roughly 4pm last night, driving it 45 minutes home and then sitting only 14 hours. I was hoping for at least 12.5 or so.

 

[jebiruph]

Assuming you could buy the tray only and not all of the other stuff............. 600 bucks is crazy high to change how the batteries sit just to get two same-size batteries in place.

Anyway, back on the voltage checks - 12.37 mid-morning today, after sitting about 14 hours. Lower than I expected for having them fully charged at roughly 4pm last night, driving it 45 minutes home and then sitting only 14 hours. I was hoping for at least 12.5 or so.

You might get a couple tenths of voltage back if you disconnect the battery. The voltage goes down a little when it's under load. I've never had a vehicle that sparked as much as the JL/JT when the battery gets connected.

Have you considered what impact adding proximity door handles added to your key off battery drain?

 

[ShadowsPapa]

You might get a couple tenths of voltage back if you disconnect the battery. The voltage goes down a little when it's under load. I've never had a vehicle that sparked as much as the JL/JT when the battery gets connected.

Have you considered what impact adding proximity door handles added to your key off battery drain?

I added the passive entry so long ago - and things were working quite well for months after that, so this has pretty much started well after that time, months after.

I find it amazing how FAR the voltage drops on these batteries with that slight load. I can load a standard battery with a much larger drain and not drop the voltage that much. These just can't handle much draw at all.

 

[jebiruph]

I added the passive entry so long ago - and things were working quite well for months after that, so this has pretty much started well after that time, months after.

I find it amazing how FAR the voltage drops on these batteries with that slight load. I can load a standard battery with a much larger drain and not drop the voltage that much. These just can't handle much draw at all.

From your experience, who makes the best batteries?

 

[chorky]

Assuming you could buy the tray only and not all of the other stuff............. 600 bucks is crazy high to change how the batteries sit just to get two same-size batteries in place.

Anyway, back on the voltage checks - 12.37 mid-morning today, after sitting about 14 hours. Lower than I expected for having them fully charged at roughly 4pm last night, driving it 45 minutes home and then sitting only 14 hours. I was hoping for at least 12.5 or so.

They do sell the tray by itself I believe. just looked couple days ago I think it was less than half the price.

 

[ShadowsPapa]

They do sell the tray by itself I believe. just looked couple days ago I think it was less than half the price.

Still not cheap but if I still have this truck when the warranty is up, it's at least a thought.

For now I'm looking for excuses to drive this silly truck so I can cycle things a few more times for the IBS to learn.

 

[Rusty PW]

They do sell the tray by itself I believe. just looked couple days ago I think it was less than half the price.

The brackets are $249.00.

 

[ShadowsPapa]

From your experience, who makes the best batteries?

I can't speak to the AGM types, but I'd had excellent luck with NAPA's best batteries in the past. The one in my 73 has been abused for about 7 years and is still good, I have a NAPA battery in my Eagle as well. They seem to handle non-use pretty well. But those are the more conventional batteries.

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