2nd Battery Setup - Toyota Nation Forum : Toyota Car and Truck Forums

Anshu · 08-23-2006, 02:52 PM

Hi, Im planning on installing a 2nd battery in my car to power my carpc. I have a quick question, im planning on going with a relay system fused mabye circuit broken somehow. The question Is my alternator fuse is at 100a, leading me to believe that I had a 100a alternator. Does all that juice go to both batteries? I was wondering I could get a 80a relay, Ive heard that power is split or something. I was hoping to get the far cheaper 80 as opposed to the 200 as I cant find a middle ground
Cheers
Anshu

Anshu · 08-23-2006, 02:53 PM

This is my proposed diagram. The only major difference that I can see with popular ones is that there is no direct route from the alternator to the relay, instead it goes from the main battery to the relay to the aux battery.
I would mabye design a delay circuit on the the relay to allow the car to turn on totally with the main battery before chargig the aux one.

Curry · 08-23-2006, 03:39 PM

What would be the purpose exactly of the second battery? To use the PC while the car is off?

Anshu · 08-23-2006, 03:58 PM

sort of, to prevent drain on the main battery so theres no problem with cranking every. There is some draw on the battery at night, so I dont want to screw it over.

Curry · 08-23-2006, 05:16 PM

Don't forget, when your car is running, its going to have 2 batteries to charge... not just one. Also keep in mind, isloaters can be very inefficient and waste power.

I'd go for an Alt upgrade, upgrade your stock batt (if possible), then the second batt.

EDIT:

I doubt you'll have any drain to make you car not start, Which power supply are you running? If you are still worried about drain just get an optima yellow top and replace your stock battery.

If you still want that second battery, upgrade the alt, get that battery and wire them with just a fuse between them.

Anshu · 08-23-2006, 05:35 PM

I know itll have the two batteries to charge, but It wont be too much more, because the hood battery will be used only for starting and the stock electronics(not much), all the ICE will be on the 2nd Battery.

Diode Isolaters are inefficent with a power drop of .4-.6votls, im planning on running a relay style one. http://www.oznium.com/relay80

My power supply is a carnextix cp160 IIRC. The extigy runs the entire night, and I want to have the option of fans on every now and then etc etc. I already own a 2nd battery which i want to use for this application.
Im also worried that being in College, Ill leave the carpc on for a few days and forget to turn it off, which will kill the battery. This makes me have piece of mind. Upgrading the alt wont help me much right now, its not so much power im worried about its drain.
Im just wondering If i can get away with an 80 amp relay, or do i need to shell out the extra cash for the 200

silverxls · 08-24-2006, 11:19 PM

your plan looks pretty good...i'm not an engineer so i have no idea what it may cost for your setup...but as an RVer i have dealt with the battery isolators in them. a good rv store may have some...or go to campingworld.com and check them out. they do just what you want to do. isolate the aux battery to prevent drain from hood one, and charge both from the alternator...you can even get a solenoid put in, to jump both batteries together, to use the aux to crank the engine should the hood battery fail. and in RV's, i've always seen an 80 amp breaker no matter what the alternator size, 95 or 120 or whatever.
ps, i hope you are planning on using a deep cycle battery for the aux. if you forsee running it dead on occasion, you'll get many times more life from a deep cycle battery than a regular car battery. car batteries aren't designed to be run to total discharge, and each time they are will shorten the life significantly.

Anshu · 08-24-2006, 11:26 PM

Well i decided to go with the 200, just incase I ever step up to the highlander alt or something more(hehe). I didnt want to go with a diode style isolater because of the voltage drop, the system does that on its own(:-P) My only question is here to tap for the relay to kick on, I was thinking just from the alternator wire(by the time its providing power, the car should be running) and then wiring a bypass switch from the battery so it can kick on and self jump!