Minimum voltage to crank LC?

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JS114

JS114

10 Year
Joined
Dec 1, 2011
Threads
20
Messages
92
Location
Atlanta, GA
Does anyone know or have a rough estimate of the minimum battery voltage required to turn over the LC, reliably?

I ask because I'm installing a remote starter, Viper 5704. One of the specific reasons I went with this model is the Smart Start feature. It will start the truck automatically if the voltage drops to a certain point. Clutch when in the wilderness running a fridge, fan, lights, stereo, whatever... (pretty nice for tailgating at football games too). It's set at 10.5v from the manufacturer, but can be adjusted in 0.5v increments.
 
I have not done any tests on the 100 but on the 80 I vaguely recall that come about 11V or so I was not too confident about it cranking so well.
My general impression is that 10.5 is rather low for a lead acid, I'd guess fully discharged. Without going back to my notes, were I to do this, I'd probably start at least at 11.5V and see what happens.
It's easy to test in principle, leave the lights on, get the battery to 10.5 and try, but not a great thing for a starting lead acid battery of course. Then again if you are concerned about it getting that low, you should get a dual purpose (starting and deep cycle) battery instead in any case, I would think.
 
e9999 said:
It's easy to test in principle, leave the lights on, get the battery to 10.5 and try, but not a great thing for a starting lead acid battery of course.
Click to expand...

Well, for the past hour and a half I've been doing just that. Blower on high, high beams on, DVD playing...just hit 10.50v and it cranked right up. Will go to 10.4 and call it test complete.

If anyone's interested:
9:30 pm 12.31v
9:43 12.0v
10:20 11.5v
10:31 11.28v
10:40 11.03v
10:50 10.50v
 
I would bet the LC can start using some pretty low voltage. I have essentially killed my battery and she cranked up with a few slow turns. I would bet the LC could crank off 9.6V. Just be careful if you do have a auto start that you don't go on vacation and the truck runs for 5 hours in the airport parking lot. I'll be the first to say it's a great idea, however I would not want my truck to turn on automatically on the streets of Atlanta. AAA is cheap to get a jump, alerting homeless people and thugs that my truck is running with nobody in it would be bad.
 
You have to activate the feature with the remote when you want to use it and it only stays active for a preset time (I'll be setting mine to 12 hours) and runs for a preset time (10 minutes). My primary interest in that particular feature is camping and tailgating where I want the stereo on, lights on, a fridge, etc and don't want to have to worry about killing the battery.

That said, I've always had remote start in my vehicles and have yet to lose one on the mean streets of Atlanta.
 
JS114 said:
You have to activate the feature with the remote when you want to use it and it only stays active for a preset time (I'll be setting mine to 12 hours) and runs for a preset time (10 minutes). My primary interest in that particular feature is camping and tailgating where I want the stereo on, lights on, a fridge, etc and don't want to have to worry about killing the battery.

That said, I've always had remote start in my vehicles and have yet to lose one on the mean streets of Atlanta.
Click to expand...

That is a good idea like I was saying. I guess I spoke to soon, not knowing about the system. I thought the truck would start with or without you wanting it to, I figured after an extended stay, at the airport or open parking garage the truck would start an stay running until the voltage went back up for another few days. That's always something I worry about at camp, 550W of light can kill a Diehard Platinum quite quickly.
 
Keep in mind that the starter contacts are a weak point on the LC. The lower the cranking voltage the higher the cranking amps and the more likely it is that the starter contacts will get very hot. Good to keep that in mind, and maybe set the threshold a little higher than the lowest possible cranking voltage.
 
Good advice. Considering what I run overnight, I think I'm going to go with 11.2 volts as my threshold and a 10 hr activation time. We always start the truck first thing when we wake up anyway. The system is in and works great, but I need a DEI Bitwriter to adjust these particular settings. Incidentally, the night I posted my test I lost track of time and it dropped to 8.7v. I turned off the blower, radio, and headlights and turned the key. It cranked twice slowly. Then number on the multimeter slowly rose. At 9.8v I tried again and it started up. This was a brand new DieHard Gold AGM battery.
 
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