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Auxilliary battery for auto engine compartment

Auxilliary battery for auto engine compartment

Auxilliary battery for auto engine compartment

We manufacture a device for chasing pack rats out of auto engines, it is normally powered by by the 12V battery in the car. In some cars the battery is located in the trunk, back seat or other not easily accessible place.
So, here is the problem, alkaline batteries are only rated to 140 deg F, and engine compartments exceed that especially in the desert southwest. If our device is powered by an alkaline battery pack in this type of heat, it has a tendency for the batteries to corrode and shortens their life,not to mention the liability involved in the leakage problem of battery chemicals leaking on engine and body components.
A lithium Thionyl Chloride battery is rated up to 180 deg F, and yes, I know that even in a relatively cool day the temperature exceeds that especially in heavy traffic. The major drawback to this battery is that it is not easily available in hardware stores,and the cost is rather high. This is quite an inconvenience for our customers.
Now for the specs on the unit. It operates from 6 to 16 Vdc and draws approximately 400 micro amps average current with a pulse peak of 140mA. The capacity of a AA lithium battery is about 2400mAH giving a life approaching 1 year.
Now for the question, What sort of power source can I use to power my device? It must last 6 months minimum, be able to withstand engine heat, and must be easily replaceable by the consumer.

RE: Auxilliary battery for auto engine compartment

The 6 month spec might be overkill.
Thanks to burglar alarms and other 'off' loads, a modern car's battery will discharge completely in 4 months or less.

I suppose you could separate the battery pack from the device by a short cord. Since the battery pack is not huge, you could specify mounting it forward of the radiator and condenser, or in the wheelwell, or in the windshield plenum. ... or taped to the larger refrigerant line.

Mike Halloran
Pembroke Pines, FL, USA

RE: Auxilliary battery for auto engine compartment

Why not draw your power from the alternator lug?

RE: Auxilliary battery for auto engine compartment

Or underhood fuse box

RE: Auxilliary battery for auto engine compartment

Or the remote jump lug.

RE: Auxilliary battery for auto engine compartment

Or put another regular car battery in parallel with the exiting??/ What is a pack rat - like a real rat?? How does your device work??

RE: Auxilliary battery for auto engine compartment

Hey, thanks, some great ideas, hadn't thought of the alternator terminal!
In response to some of your questions, a packrat is similar to a city rat or mouse and makes nests in car engines and then proceeds to chew on the car wires causing many thousands of dollars of damage. Using a strobe light scares them away and prevents such damage. This is not meant to be an ad but check it out at rid-a-rat.com. Note that this packrat problem is more prevalent in the desert southwest area, but does exist from Mexico on up into Canada.


RE: Auxilliary battery for auto engine compartment

I would think it would be tough to fit them under the hood. lol

RE: Auxilliary battery for auto engine compartment

Black snakes work well.


The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Auxilliary battery for auto engine compartment

Squirrels did a pretty good job on my neighbors pickup..... COULDN"T beleive it!!

RE: Auxilliary battery for auto engine compartment


Looks like you've seen first hand the type of damage critters can do to automobile engine wiring. If you'd like to see some really severe cases, look at mrpackrat.net in Tucson. This is the type of damage that we face and are trying to control in this desert area. Our rid-a-rat has done a very good job so far. The problem is that this is a consumer installed device and a 12v source is not always so easily identified, especially in many luxury cars. (Rolls Royce, Mercedes, are only a couple I have encountered) That is why I decided to use a separate battery pack for those type of vehicles. So, the real problem arises when an overheated battery pack decides to leak its guts onto the inside of some guys prized Rolls Royce. A sealed battery compartment would be one answer to the liability issue but I don't see where such a device is commercially available.
Cats, dogs, snakes and other predators of packrats may seem to be an answer, but out here in the wilds of the Sonoran desert the coyotes are a bit further up the food chain and like to dine on delicacies such as family pets.
Thanks for your inputs, it has given me some new directions.

RE: Auxilliary battery for auto engine compartment

Bonus points for incorporating the device into some "anti-flat spot" tire ramps.

I'll let you know where to send my check bigsmile

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