remote start problem w/ backup battery

Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=106685
Printed Date: April 23, 2024 at 8:49 PM

Topic: remote start problem w/ backup battery

Posted By: 33up
Subject: remote start problem w/ backup battery
Date Posted: August 10, 2008 at 10:58 AM

Hello all,
I've recently added a DEI 520T backup battery to my Viper 5900. The remote start feature of my alarm worked flawlessly until I added the backup battery. With the backup battery, the car remote starts without any problems on some occasions, but sometimes it will not start (the engine will start to crank, but never turn over and start). The backup battery is wired correctly in that it does what it should when main battery is disconnected.
Any ideas on whats causing this or how to get around it?
Thanks.

Replies:

Posted By: johnmax
Date Posted: August 11, 2008 at 1:08 PM

WHat did you tie the gray power output wire of the battery to? Hopefully to only the red on the main harness, NOT the heavy red wires for the remote start relay pack.

Also the blue trigger wire for the battery is it on its own trigger input? if not did you diode isolate it from other sensor inputs if you shared a trigger input wire?

Posted By: 33up
Date Posted: August 11, 2008 at 7:07 PM

The gray +12v output of the backup battery is tied to the brain power supply only, not to the remote start relay pack. The backup battery trigger shares the same input as the hood pin switch. I did not see the reason to diode isolate the two. Do you think that it may interfere with remote starting somehow?

Thanks.

Posted By: johnmax
Date Posted: August 12, 2008 at 8:49 AM

Yes definitely. Diode isolate them. There can be a ground feedback out of the battery's trigger wire causing a hood shunt thus no start.

Posted By: 33up
Date Posted: August 12, 2008 at 10:02 AM

You're right! I've temporarily disconnected the BUB's blue trigger wire and the car now starts everytime. I then reconnected it and it was back to sometimes starting and sometimes not.
How would I go about diode isolating these two? I know how diodes work as I've diode isolated my door triggers, I just don't see how to prevent the "ground feedback" as you've called it by diode isolating.
Thanks!

Posted By: johnmax
Date Posted: August 12, 2008 at 5:22 PM

take the hood input on the alarm by itself and connect 2 diodes to it. The non band side ends of the diodes go to the hood pin input on the alarm. Then the 2 ends of the diodes are left (band sides). Connect the blue from the battery backup to one of them, and the other gets your hood pin switch.

Posted By: 13 volts
Date Posted: August 12, 2008 at 8:15 PM

By the way, using the backup battery system from DEI can drain a car battery over a FEW days. Talk to a tech at DEI about that nice feature.

Posted By: 33up
Date Posted: August 12, 2008 at 9:11 PM

How will the diode stop the alarm negative input wire from receiving the negative "ground feedback" if I connect BUB side diode as you say (cathode towards the BUB's negative trigger and anode towards the alarm's negative trigger input)? That is what has me stumped...
Thanks.

Posted By: 33up
Date Posted: August 12, 2008 at 9:15 PM

13 volts wrote:

By the way, using the backup battery system from DEI can drain a car battery over a FEW days. Talk to a tech at DEI about that nice feature.

I had the car sitting unused with the alarm armed for over a month once, and the car's battery was fine when I went to start and drive it.

Posted By: johnmax
Date Posted: August 13, 2008 at 6:02 PM

33up]H wrote:

w will the diode stop the alarm negative input wire from receiving the negative "ground feedback" if I connect BUB side diode as you say (cathode towards the BUB's negative trigger and anode towards the alarm's negative trigger input)? That is what has me stumped...
Thanks.

Just put the diode inline with the band side of each facing each sensor, and connect the other ends together and to the trigger in on the alarm. The diodes will block the ground from seeping out of the BUB and shunting the hood input. Thats how diodes work.

Posted By: johnmax
Date Posted: August 13, 2008 at 6:04 PM

13 volts wrote:

By the way, using the backup battery system from DEI can drain a car battery over a FEW days. Talk to a tech at DEI about that nice feature.

Maybe you can enlighten us on this? I've been putting in their batteries for way too many years- probably have done a few hundred- and havent seen this problem. Including in all my cars which do sit from time to time with no problems.