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Battery/ECM wiring questions

hokie_yj

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I've got a couple questions I'm looking for some input/ideas on.

Question #1
On my new buggy I'm using dual Odyssey 925 batteries and a Blue Sea 4 position battery switch (batt. 1, batt. 2, 1+2, and off). I plan to normally run it selected to just one battery alternatiing which battery I use, and if needed use both batteries if I'm doing a lot of winching. My question is how/where should I run my charge wire? If I run it to the battery side of the switch I can only hook it to batt. 1 or batt. 2, not both, because then the switch is pointless because the batteries will be in parallel all the time, right? I know I can use an isolator and that will allow both batteries to be charged without connecting them, but I'd really rather keep the wiring as simple as possible.

I know I can hook the charge wire to the output side of the switch and it will only charge whichever battery I'm selected to, but if it's hooked to the output side turning the switch to off won't kill the engine because the alternator will still be powering everything. My switch panel has a main ignition switch though that will supply 12V+ switched to the ECM harness. Flipping that switch off will de-energize relays that pass power to the ignition and fuel pump. In my mind that's sufficient for a kill switch. The pic below shows the switch panel and the battery switch just for reference. What do you think? How would you wire it?



Question #2
This is somewhat related to the first question. The engine is a LQ9 from an '03 Silverado SS. I had a custom harness built by Pacific Fabrication. Along with the 12V+ switched wire the harness also has a wire with a fusible link labeled 12V+ battery that's laid out to hook to the stud on the alternator. I'm assuming this supplies power to the harness that the relays mentioned above pass to the ignition, fuel pump, fans, etc. I'm assuming this wire also be supplying a constant 12V+ to the ECM for memory? I'm going to call Pacific Fab. in a couple hours when they open and confirm this. If that's the case and I run the charge wire to the output of the battery switch like I mentioned above turning off that switch will kill the memory to the ECM. How important is the ECM memory? Without it it will have to re-learn every time the engine is started? I guess I could pull that wire back out of the harness and re-route it straight to one of the batteries if necessecary. I just don't want to do that If i don't have to.

Hopefully you can make sense of this post. I think I've overthought this so much that I've completely confused myself. :dunno:
 
Run your alternator output to the B+ starter post. It will charge whatever battery you select to start/run on.
 
That would be the same as putting it on the output side of the switch, which is most likely what I will do. That still allows the alternator to power the buggy with the battery switch off. My question is whether or not the ignition switch on the panel is sufficient for a kill switch. I think it is, but I'd like to hear some other opinions.
 

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