100 Series - Swapping Crank and Aux Battery Locations (1 Viewer)

[WTB]

Howdy! I’m planning on using my aux battery (group 35) as my crank battery and my crank battery (group 31) as my aux battery. This is done pretty easily in a 200 series as shown in the video below.



Unlike the 200 series, the 100 series has a fusible link, which makes things a bit more difficult.

Has anybody successfully swapped battery positions in a 100?

Any info or recommendations are greatly appreciated.

 

[LandLocked93]

Yes, I've heard of doing this. No I've not done it.
There's always a lack of reasoning for doing it, but it's doable.
And just to be clear, you aren't moving the batteries. You are actually wiring your starter (and presumably all harness power) across the engine bay to connect to your aux batt location, yes?
There was one very good reason for not doing this, but it escapes me atm. Maybe voltage drop? Don't recall exactly.

edit: (a day later) I recall the reason why doing this is unnecessary...and it is that if you have configured your dual-batt setup to bind the batts in the event of a drained crank batt, voila your aux batt is now the crank batt. And all harness power is coming off the aux batt...until you crank the truck and the alt begins charging the dead crank batt.
Not sure there would be a diff were you to use the crank batt location as the aux batt when employing a binding dual-batt setup.

 

[WTB]

Yes, I've heard of doing this. No I've not done it.
There's always a lack of reasoning for doing it, but it's doable.
And just to be clear, you aren't moving the batteries. You are actually wiring your starter (and presumably all harness power) across the engine bay to connect to your aux batt location, yes?
There was one very good reason for not doing this, but it escapes me atm. Maybe voltage drop? Don't recall exactly.

edit: (a day later) I recall the reason why doing this is unnecessary...and it is that if you have configured your dual-batt setup to bind the batts in the event of a drained crank batt, voila your aux batt is now the crank batt. And all harness power is coming off the aux batt...until you crank the truck and the alt begins charging the dead crank batt.
Not sure there would be a diff were you to use the crank batt location as the aux batt when employing a binding dual-batt setup.

Yes, the batteries will stay in their current positions but wiring will be rerouted so that the physically larger, higher capacity, battery located in the stock location will be the house battery and the smaller, lower capacity, battery located in the aux location will be the crank battery. With this configuration, I will be able to power accessories for longer without having to charge the house battery. The video of the 200 series explains it quite well.

The batteries will be isolated with my current Battery Doctor smart isolator. The smaller crank battery, which will only power the winch and harness power, can be jumped from the larger house battery if it dies.

Another benefit of swapping locations is that I could eventually fit a group 31 280Ah lithium house battery in the stock crank battery location, which would provide enough juice to run a Starlink.

 

[LandLocked93]

Are the battery locations not the same size on a 100? (as compared to an 80)
If not, then I guess you're committed lol.
Pics or it didn't happen!
Good luck!

 

[WTB]

Are the battery locations not the same size on a 100? (as compared to an 80)
If not, then I guess you're committed lol.
Pics or it didn't happen!
Good luck!

Nope! The aux battery location can only fit a group 35, which is significantly smaller than the group 31 that fits in the stock crank location.

I found the correct wiring diagram and have drawn up my own fusible link replacement, but I may just use the factory one. All other parts are on the shelf ready for install. I will definitely post pics.

 

[ntsqd]

I use a marine battery bank switch to designate which is the starting and which is the house battery, at least as far as the OEM loads go. My added house battery loads are direct wired to the added battery. Not in a 100 or a 200, but it seems to me that if the switch is placed correctly then no need to alter the OEM wiring, jut change what it's connected to.

 

[WTB]

I use a marine battery bank switch to designate which is the starting and which is the house battery, at least as far as the OEM loads go. My added house battery loads are direct wired to the added battery. Not in a 100 or a 200, but it seems to me that if the switch is placed correctly then no need to alter the OEM wiring, jut change what it's connected to.

How do you charge the house battery? Just select both batteries and let them charge off the alternator then switch to the desired battery later? I use a "smart" isolator / charger that would prevent me from using a switch.

But I had a similar though a couple days ago. Instead of building my own distribution panel to replace the fusible linkg, I could easily just mount the fusible link on a post near the factory location and run a cable from the new crank battery. It wouldn't look as clean, which would annoy me, but it would be cheap and effective.

 

[ntsqd]

I use a Blue Sea Systems Automatic Charge Relay wired across the marine switch terminals. Since it is dual sensing it doesn't matter which battery is the selected starting battery, they both charge. The switch also allows me to combine them for self jump-starting or winching. I've since moved the cable to the starter to the other side of the A/C tube, but this gives an idea:

Note that if your rig is equipped with an OEM so-called "Smart Alternator" that this will not work. For those just about the only option is a DC-DC converter.

 

[LandLocked93]

Note that if your rig is equipped with an OEM so-called "Smart Alternator" that this will not work. For those just about the only option is a DC-DC converter.

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