Dual batteries, DC to DC chargers, isolators, AGM... HELP!

[unsavory]

Apologies for the long post, but I've been super impressed with the technical knowledge I've seen in on this forum and am hoping someone might be able to help.

I own a 2019 Jeep Wrangler, and have installed a Genesis dual battery system into it for running various accessories. The system is basically two 12v Odyssey dual purpose AGM batteries, with a smart isolator between them, that will automatically disconnect the accessory battery from the starting battery when a certain voltage is reached to avoid draining the starter battery, and then reconnect them when the vehicle is running for charging.

The problem I am having, is that I am not able to get these Odyssey batteries to charge properly in the Jeep Wrangler, because it has a very funky "smart charging system", that varies the charging voltage as you are driving to "save gas mileage". The voltage will fluctuate between 12.7v and 14.7v depending on the battery voltage and accelerator pedal.

Apparently Odyssey batteries only like to be charged at 14.7 volts for bulk charging, and 13.7 for float charging to top them off.

So now I'm looking into DC to DC chargers in order to get my charging voltages up to the correct level. Has anyone had any luck installing a DC to DC charger along side an already existing dual battery system that has a smart isolator built into it?

All of the DC to DC chargers seem to want the starter battery separated from the accessory battery, as they already have an isolator built in.

The other option I am exploring, is just disabling the smart charging in the Jeep by disconnecting the Intelligent Battery Sensor. But this causes the alternator to put out a constant 14.5v, and I'm worried this will actually OVERCHARGE my batteries... but I'm not sure?

Any other creative ideas I can try?

[NRALIFR]

The PCM modules available from US Alternators in Landyacht318’s link look really interesting. Unfortunately, it doesn’t look like they have one for any Jeep products. That’s too bad, because that would be the best way to address this problem IMO.

I can certainly understand your desire to replace the OEM battery setup with something more robust and reliable. To be honest, the OEM system sounds like a trouble prone POS. You would think a vehicle that comes with AGM batteries would have a charging system capable of charging them properly. But then, I also think that if Genesis is going to market a replacement battery system for the Jeep, it should work with the Jeep charging system.

Good luck, and please let us know what you do and how it works out.

:):)

[unsavory]

NRALIFR wrote:
You can probably disable the Genesis solenoid by simply unplugging the connector on the Cole Hersee charge controller. The solenoid will never energize and connect the two batteries that way. If you ever need to combine the two batteries because the starting battery is run down, just plug the charge controller back in, and use the start boost button.

The DC-DC charger input power wire (from the starting battery) does need to be on its own ignition activated solenoid though, so it will switch off when the engine isn’t running. I’d put a fuse in the ignition activated wire close to the solenoid in an in-line fuse holder, and use that to disable the DC-DC charger in the event you need to combine the batteries.

:):)

I'm starting to think this might be the best solution to my problem, if I want to do it right.

Thanks to everyone who contributed in this thread! I have learned a lot of very valuable information here.

[landyacht318]

Looks like some companies are addressing the weird fuel saving voltage regulation with aftermarket products for some brands of vehicle:

http://www.usalternators.com/pcm-module/

[LittleBill]

time2roll wrote:

unsavory wrote:

NRALIFR wrote:
I think (hope) LittleBill meant “Put the output of the DC-DC charger on the main lugs of the secondary battery”

Now I'm even more confused. How can I charge the secondary battery if the input and output are the same? 😃

The DC-DC charger will have power input connection and power output connection.
Connect the input to the start battery. Connect the output to the accessory battery.
Remove the other charge control relay.

yea don't do this, this will kill the start battery if you run down the secondary, not to mention the constant drain from the charger running all the time

[NRALIFR]

You can probably disable the Genesis solenoid by simply unplugging the connector on the Cole Hersee charge controller. The solenoid will never energize and connect the two batteries that way. If you ever need to combine the two batteries because the starting battery is run down, just plug the charge controller back in, and use the start boost button.

The DC-DC charger input power wire (from the starting battery) does need to be on its own ignition activated solenoid though, so it will switch off when the engine isn’t running. I’d put a fuse in the ignition activated wire close to the solenoid in an in-line fuse holder, and use that to disable the DC-DC charger in the event you need to combine the batteries.

:):)

[time2roll]

unsavory wrote:

NRALIFR wrote:
I think (hope) LittleBill meant “Put the output of the DC-DC charger on the main lugs of the secondary battery”

Now I'm even more confused. How can I charge the secondary battery if the input and output are the same? 😃

The DC-DC charger will have power input connection and power output connection.
Connect the input to the start battery. Connect the output to the accessory battery.
Remove the other charge control relay.

[LittleBill]

unsavory wrote:

LittleBill wrote:
already told you how to wire this, put the input of the dc-dc charger on the main lugs of the secondary battery option, this will charge the secondary battery correctly, but you will not be able to parallel them for additional capacity if this was your intention

It was partially my intention, yes. But also, it still doesn't address the need to properly charge the starting battery, since the OEM alternator will not do that properly for these types of batteries.

What is the purpose of connecting the DC to DC charger input to the Genesis output? Why wouldn't I just completely remove the Genesis isolator? Trying to learn here...

your not going to be able to do that, does this kit come WITH the battery's? its not worth the expense to try to change the start battery charging characteristics, personally i would change the battery to one that falls inline with the charging style of the jeep.

the reason to keep the isolater is simple, you run your accessory loads off the secondary battery, fridge lights radio's etc, and if you kill the battery, you will still be able to start the truck. thus the need.

you can take it a step further and add another solenoid to get your jump start feature back, but thats another topic.


and no the input of the dc-dc would come from the isolater terminals going to what was the second battery, the output of the dc-dc would connect to the 2nd battery.

[unsavory]

LittleBill wrote:
disconnect the second battery, connect the dc-dc charger to output of the second battery wiring from the genesis kit, and connect the output of the dc-dc to the second battery and that should be it.

So re-reading what he said, he is indeed talking about wiring the DC to DC input to the output of the Genesis dual battery wiring (these are the wires that would normally feed INTO the secondary battery). And then connect the output from the DC to DC charger to the secondary battery posts.

So my question still stands. Why not just get rid of the Genesis smart isolator in that case? What would I gain by leaving it in place?

[unsavory]

NRALIFR wrote:
I think (hope) LittleBill meant “Put the output of the DC-DC charger on the main lugs of the secondary battery”

:):)

Now I'm even more confused. How can I charge the secondary battery if the input and output are the same? 😃

[NRALIFR]

I think (hope) LittleBill meant “Put the output of the DC-DC charger on the main lugs of the secondary battery”

:):)

[unsavory]

LittleBill wrote:
already told you how to wire this, put the input of the dc-dc charger on the main lugs of the secondary battery option, this will charge the secondary battery correctly, but you will not be able to parallel them for additional capacity if this was your intention

It was partially my intention, yes. But also, it still doesn't address the need to properly charge the starting battery, since the OEM alternator will not do that properly for these types of batteries.

What is the purpose of connecting the DC to DC charger input to the Genesis output? Why wouldn't I just completely remove the Genesis isolator? Trying to learn here...

[LittleBill]

already told you how to wire this, put the input of the dc-dc charger on the main lugs of the secondary battery option, this will charge the secondary battery correctly, but you will not be able to parallel them for additional capacity if this was your intention

[unsavory]

theoldwizard1 wrote:

unsavory wrote:
Any idea what the potential repercussions might be? Everything seems to be working correctly with the battery sensor disconnected, other than the voltage just sits there at 14.7V instead of fluctuating with engine speed.

At a continuous 14.7V, you will kill your battery in MONTHS !

That's kind of what I was worried about. But doesn't this imply that I'm driving for hours at a time? If I'm only driving for an hour or two a day total, is this still a valid concern?

[unsavory]

NRALIFR wrote:

I think it would be better if the two Odyssey’s were separated all the time, except when you need them for emergency starting. That way, a DC-DC charger could be installed between them, and it would be simply another load on the starting battery and it’s charging system. But then you would need to make sure all of your “engine stopped” accessory loads are connected to the second battery. )

Yeah, that's not really a possibility without rewiring the entire Jeep, which is more than I want to try to take on.

I'm starting to think my best option is just to put it on the charger a couple times a week to keep the batteries topped off so they don't sulfate.

I might also look at installing a switch for the intelligent battery sensor, so I can enable and disable it manually. That way if I ever need to ensure my batteries get charged by the alternator, I just disable the intelligent battery sensor, which will trick it into doing 14.7 V until I enable it again.