Bcm sensor bypass

meirikm · July 3, 2021

Hey all, has anyone bypassed the bcm sensor to achieve steady alternator current? I’ve done the big three and have a yellow top optima as of yet.

CamGTP · July 3, 2021

It's not just the BCM that controls it. The PCM also has a very large say in what the charging systems does.

I personally don't know of a way that you can just make it charge at 13.5-14 volts all the time.

MikeBMW · July 3, 2021

8 hours ago, CamGTP said:

It's not just the BCM that controls it. The PCM also has a very large say in what the charging systems does.

I personally don't know of a way that you can just make it charge at 13.5-14 volts all the time.

Neither do I, Cam, and I wonder why one would find this necessary.
The charging system seems to work as designed to preserve battery life?

meirikm · July 4, 2021

It’s more about fuel efficiency. My amplifiers run better when above 14V. It’s designed to drop down to about 12V when the battery is sufficiently charged. My amps draw a lot of power quickly. I need it constantly charging.

meirikm · July 4, 2021

It’s more about fuel efficiency. My amplifiers run better when above 14V. It’s designed to drop down to about 12V when the battery is sufficiently charged. My amps draw a lot of power quickly. I need it constantly charging.

meirikm · July 4, 2021

I saw a pcm module in another forum that’s supposed to help a lot

MikeBMW · July 4, 2021

34 minutes ago, meirikm said:

It’s more about fuel efficiency. My amplifiers run better when above 14V. It’s designed to drop down to about 12V when the battery is sufficiently charged. My amps draw a lot of power quickly. I need it constantly charging.

You're going to have to install an auxiliary battery.
There are posts in this forum regarding this via using the space where an extra one would be without the diesels.
@tenscourtsseems to be well versed in a successful install.

Edited July 4, 2021 by MikeBMW

kickass audio · July 4, 2021

One of my friends Steve Meade has it working as a bypass. You will just need to jumper the OEM 2 pin connector at the alternator and get an external regulator for the alternator. You can adjust the voltage manually with the external regulator to your liking.

Since you are in Canada i'm not sure if there are any alternator guys up there but Mechman alternators is where I bought my last 3 alternators from and they sell an external regulator: https://www.mechman.com/accessories/voltage-control-modules/adjustable-external-regulator-w-2-pin-alt-harness/ that you can hook up and use to fine tune your voltage to stay stable.

My voltage was climbing up really high at first start and anything above 15v would make the HVAC shut down and come back on several times until after about a solid minute of running from startup it would drop the voltage down to 14.7 and keep the HVAC running fine. Prior to today I did have my OEM battery as well as an aftermarket battery under the hood and I only ran one of the 1/0 gauge ground cables to the OEM battery from the alternator and had it go through the hall effect sensor. I had the other 1/0 gauge ground cable go from the alternator to the second battery under the hood and since the factory hall effect sensor is so small I couldn't jam that through the sensor if I tried. I only took my truck out for a test ride today and my voltage didn't seem that high to shut off the HVAC so time will tell. If it keeps that crap up I am definitely getting an external regulator and jumping the OEM 2 pin connector out to remove the check battery light on the dash.

edit: my voltage was perfectly fine with 2 batteries until I swapped out the alternator from the stock alt to a 370A alternator. once I did that then my voltage climbed a ton and would fluctuate even with no music on and no change in load other than having the truck just sit at idle. If I rev up the engine the fluctuating voltage would be fine.

here is the link on the forum from what I mentioned to just short the alternator connector: https://www.stevemeadedesigns.com/board/topic/210401-2015-cadillac-escalade-sound-system-install-the-box-is-started-6-12-subs-clear-acrylic-on-the-menu-update-page-10/?do=findComment&comment=3250545

Edited July 4, 2021 by kickass audio