Auxiliary Battery - Interior Lights and Cigarette Lighter - Help Needed (1 Viewer)

[nineosixdave]

Since purchasing my 2003 LX 470 last January, I have been researching how to get full time power to my dome lights and power outlets. I have installed a second (auxiliary) battery and a National Luna dual battery system.

There are a couple of threads already written on how easy it is to put all the accessories on full-power for a pre-2003 vehicle. It simply requires a jumper in one of the fuse boxes from the main battery. However, the fuse system was changed on the 2003 models and the fine writeup on the pre-2003 models basically says, "It's a pain in the ass to do this to post 2002 models due to the location of electrical panel.

I spent a lot of time tracking down the wiring system and agree, too get to the panel to jump all the accessories at once is both a pain in the ass to get to and most likely to cause other electrical issues once all the cabling disconnections are made and then reconnected.

So... After literally months of thinking about this, it came to me. Why don't I just jump the individual systems I want on full auxiliary power such as my interior lights and power outlets? I can add a fused positive jumper blade into the OEM fuse box on the "device" side to have power on all the time.

However, if I jump power from the auxiliary battery, the ground will still come from the main battery. Will this cause a problem?

All my other connections to the auxiliary battery are both powered and grounded directly to the auxiliary battery. Need advice on if I can power from Auxiliary and Ground from the frame ( Main Battery.)

Appreciate your help.

 

[Sean9421]

If I'm following what you want to do, maybe you're over thinking this. Why not use a switch like this and split the main power and ground cables to each battery? The only problem would be you would have to manually turn the dial under the hood (if that's where you mount it)

 

[e9999]

I don't know what this "full power" issue is TBH but NMT. Sounds odd, though.
Later on when you mentioned " the ground will come from the main battery", that sounds also odd. Are you thinking that you will use the positive terminal from the second battery and the ground from the main one? Cuz that won't work unless the grounds are connected together.

 

[nineosixdave]

To be more clear.

I have a two battery National Luna system. The idea is to run the refrigerator and other camping items off the second battery ( using both the negative and positive terminals direct but fused ) and when necessary, in an emergency provide power to the OEM electrical system.

What drives me nuts about the OEM system is I need the key ON to power the cigarette lighter power adapters with USB connections. In the LX400 there are 4 of these. Additionally, if I could, I would power all the systems that turn ON with the key in AUX mode with the second battery and run them "HOT."

It would be nice to turn the radio on or off at any time without needing the key. And because you would do this with the second battery, you would not be in fear of draining the main OEM starting battery.

I thought removing the fuse from the fuse box for the power adapter (Fuse 67?) and then tapping into the "device" side of that fuse terminal with a HOT from the second battery would accomplish an always ON power adapter. However, it occurred to me that all I was doing is adding a positive line to the power adapters when in reality, the negative was coming from the OEM battery through the frame ground.

I know the AUX battery runs a ground to the main battery. Just not sure how this works through the National Luna system.

There has got to be an easy solution to this problem. I am not the first guy in 17 years to want to run the AUX system through the second battery.

 

[e9999]

It's easy to find out if/when your second battery's ground is connected to the first one's by checking with an ohmmeter between the 2 grounds and you can do that with and without the key on and/or Luna system switching. If the grounds connection is interrupted during some of those combinations then of course it won't work and you need to make that happen again or have some ground connection directly from the second battery to the devices you want to use.

 

[nineosixdave]

It's easy to find out if/when your second battery's ground is connected to the first one's by checking with an ohmmeter between the 2 grounds and you can do that with and without the key on and/or Luna system switching. If the grounds connection is interrupted during some of those combinations then of course it won't work and you need to make that happen again or have some ground connection directly from the second battery to the devices you want to use.

This was helpful. Hadn't thought about the ground test. It worked. Both the OEM and Auxiliary batteries are grounded in parallel to the frame through the OEM connection.

 

[nineosixdave]

Figured it out. I am able to to make the power outlet and cigarette lighter outlets full-time ON by running a hot line from the Auxiliary Battery to the DEVICE side of the OEM fuse block. And what is interesting is that three of the four outlets are connected to the cigarette lighter fuse and only one to the outlet power. The outlet next to the ashtray, the outlet in the center console and the outlet in the back of the truck are all part of the cigarette lighter fuse. Only the outlet on the dash next to the passenger is on the power outlet fuse - as far as I can tell. I'll post pictures after all the wiring is complete.