in car charging for a 12v battery pack?
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=117358
Printed Date: May 15, 2025 at 8:35 AM
Topic: in car charging for a 12v battery pack?
Posted By: machine154
Subject: in car charging for a 12v battery pack?
Date Posted: October 30, 2009 at 10:21 AM
I am putting in surveillance video in my Tundra. The power outlets turn off after 2 hours and I am thinking that I could put a 12V battery pack in my console to run the DVR. It would need to charge when my truck is on and provide power when the truck is off and the 2 hours have passed. Should I connect the battery pack straight up to 12v (13.5V charging) or do I need a more sophisticated means to charge the battery pack. I haven't chosen the battery pack yet, but suppose it is a bundle of AA rechargeables.
Replies:
Posted By: paidnfull
Date Posted: October 30, 2009 at 10:54 AM
You might take a look at these for an extra battery. They are lead acid 12v batteries. Just a stepped down version of a car battery. Mostly used in home surveilance stuff, cameras, lights etc. I'm guessing you would want to put some sort of isolator so it would be separated from the rest of the car unless the car is running. Kinda the same thing you would do if you were adding a second battery for an audio system, if it were a different type from the battery under the hood. https://www.frys.com/search?search_type=regular&sqxts=1&query_string=12volt+lead+acid&cat=
Posted By: machine154
Date Posted: October 30, 2009 at 12:50 PM
Would you have any problem putting a lead-acid battery in the interior of your car? Is it safe?
Posted By: oldspark
Date Posted: October 30, 2009 at 3:29 PM
That Fry NP7-12 is probably the Yuasa NP7-12 (ie 12V &AH).
Calling it a "Sealed Lead Acid Battery" is ambiguous.
The Yuasa NP7-12 is a Recombination aka AGM (Absorbant Glass Mat) battery.
Hence no free acid etc and legal for boot mounting etc here n AussieTralia (flooded/wet cell batteries are not unless in a sealed enclosure & vented to outside).
FYI:
- they have normal 6.3mm (0.25") spade terminals as well as the smaller spade (~4mm?) variants - get the right one.
- they also have deep cycle variants; I think NP is NOT deep cycle.
- 12V-7AH is a VERY common battery, hence one of the best "bang for buck" sizes. (EG - being the same price, I got a 7AH to replace a 4AH. Though the NP4-12 has lasted 23 years in an alarm backup application so I wasn't complaining!).... and ....
- oddly enough, those Yuasa AGMs are CHEAPER than flooded & gel cell equivalents here downunder (ie, $35 vs $50).
As to charging and connecting....
No, I've rambled enough for now.
Posted By: Mike M2
Date Posted: November 01, 2009 at 8:53 AM
I don't really know squat about this, but shouldn't the 2 hours be plenty of charge time? It seems to me you might want the camera to activate only when your alarm is triggered(afterall, nothing to see until then) and that wouldn't use much power. Or are you looking to see outside the truck too?
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Mike M2
Tech Manager
CS Dealer Services
Posted By: oldspark
Date Posted: November 01, 2009 at 3:54 PM
I interpret it as charging whilst the vehicle is running, then running off the new battery for 2 hours (before something shuts the DVD down).
(FYI - a typical system would be a relay that connects the 2nd battery to the main battery or alternator when the vehicle is charging. The relay solenoid could simply be connected between chassis and the charge light circuit (from the alternator/regulator) or from a high-voltage sensor (eg - above 13.5V). A low voltage cutout could be used between the 2nd battery and the load/DVD for protection.)
A consideration is that during charging, AGM batteries like the Yuasa NP need to be current limited and not exceed 14.5V. Excluding safety concerns (thermal runaway), at the price it may just be worth trying....
Posted By: machine154
Date Posted: November 02, 2009 at 8:39 AM
Thank you for the replies. My goal is to monitor the outside of my truck (parking lot). The truck can sit for 72 hours regularly and often longer, so I need to account for that. I measured the amp draw on the system and it comes in right at 0.25 Amps. To meet only 72 hours, I would need 18 AH of capacity. Ideally I would want to go longer. The truck, when driven, is probably 2 hours per day. I have a full size battery, but no convenient place in the engine bay. It looks like I would need low voltage protection also if I try to run it continuously with anything less than a full size car battery. I am starting to question whether I am going to follow through with my plan, since there seem to be so many obstacles. I still haven't figured out how I am going to inconspicuously mount the board camera and hide the wires. I probably need to find a new micro connector for the board camera so that I can put longer leads that don't have jacks with 10" of the camera.
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