Running two Batteries off the stock Alternator.

[Tritanium]

I have a 150 watt laptop that I'm trying to have hooked up to my Camaro. I would like to be able to power it while the car is off and I am fairly certain I will need a second battery for that. I plan to buy a deep cycle battery, and have it charge while I'm driving(I will be on many long rides.) However I'm worried about the stock alternator handling that. Is this something that is doable or should I look for some other way of charging the second battery.

[CamAnon]

How long do you expect to be able to run with the car off?

Can you get a lower-watt adapter for the laptop? Some have "travel" adapters.

Can you get just a charger for laptop batteries? Why do all this work to the car, when you could just run the laptop off a handful of spare laptop batteries.

Have you optimized the laptop's runtime? SSD drive? BIOS and power settings?

[Hetfield03]

Power inverter is what us truckers use.

[Gee]

I think you're asking for an answer to your question, instead of asking for a solution to your problem.

What is your main goal?

Why do you need this laptop to run while the car is off?

For how long?

What have you tried so far?

This solution you're looking for is way more expensive than buying 3 or 4 laptop batteries, a laptop battery charger and a car power invertor.

[CamaroCracka]

Running two batteries correctly requires some additional wiring so when one battery dies, it does not kill the other battery. It's essentially some relays that disconnect the connection when it's under a certain volt level. I don't think it would kill your alternator, but your alternator may not be able to keep up. There are also additional considerations with these cars since the alternator output is controlled by the ECU. I am not familiar with how that might affect the charging system.

Rather than use two batteries, you should probably just go to the largest battery you can fit. I forget who makes them, but there was a battery that allowed you to turn an extra cell on and off. It let racers have a 14v battery while racing and also gave a little extra juice to start if you drained your battery too far. That might be something you want to look into as well.

[MLL67RSSS]

Wow what a can of worms to open. The Camaro is a bit removed from the days of a simple alternator dumping current to a battery. By monitoring a current sensor attached to the battery output and the BCM to see what mode the car is operating in, the PCM/ECU then decides one of six different charging methods and pulse-width-modulates the charging current going to the battery for that charging method. Not sure about adding another battery into this system and what it would do to it.

[Red2014SS]

It would be a whole lot simpler to just buy a couple of extra batteries for the laptop.

[two_wheel_mayhem]

You can run both batteries in a parallel hookup fashion, and they will both just drain equally but will last longer.

Or you can go to the car stereo shop and buy a battery isolator. That allows you to drain one battery while the car isn't running and saves the primary battery for starting the car when you want to drive again.

Either method used, the alternator charges both batteries when the car is running.

[ToddB]

Just get a second battery and wire it in parallel to the other battery and you will be fine. I have 3 battery in my car for my stereo system with a high output alternator. The stock alternator should be fine for your use. Way to much confusion in this thread.


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[two_wheel_mayhem]

Most guys only do this when they have large stereo amps on board.

I'm skeptical that any laptop consumes 150watts though. That may be the rating on the transformer but laptops operate on DC voltage, and low voltage at that.

[KaBoom1701]

Originally Posted by Comrando

He has to use it when he is parked in the motel lot to access the free wi-fi.

[maddoggyusa]

Originally Posted by two_wheel_mayhem

You can run both batteries in a parallel hookup fashion, and they will both just drain equally but will last longer.

Or you can go to the car stereo shop and buy a battery isolator. That allows you to drain one battery while the car isn't running and saves the primary battery for starting the car when you want to drive again.

Either method used, the alternator charges both batteries when the car is running.

Ding Ding Ding... this is the correct answer.

But you don't want deep cycle batteries. Deep cycle is really more for seasonal vehicles because the battery can be dead and recharge without much harm. I'd recommend red top optima batteries.

you could also just get one of those lithium ion battery starters... keep it in the car if needed. They are pretty sweet and can power your laptop directly.

http://www.amazon.com/Antigravity-Ba.../dp/B00FDYYK4A

[Tritanium]

Wow there are a lot more post on this thread then I expected so thanks for all the help everyone. Im going to try to answer some of the response get more help figuring this out.

The laptop is a high end laptop and it actually will use over a 100w most of the time but it maxes out at 150w. Not to many laptops have accessible batteries these days, and this one definitely does not so I can't just get more batteries. Also it can only run full power when plugged in. I have found a DC/DC Converter to get the power from the battery to the 19v the laptop requires so thats all figured out.

I want a deep cycle battery because it will be getting run down and charge backed up almost daily. But i don't really want to run it in parallel because I don't want the starter battery to get drained to low.

I am a residential electrician and went to school for it so I have a decent amount of knowledge about all of normal battery stuff. Its really the alternator Im not sure about. I don't know if as others have said the alternator is computer controlled or if it can handle charging a battery as often as I would like it to.

I figure I will run the laptop for 4 hours or so a day at around 8 Amps so that would be 32Ah off the battery almost every day. Now obviously I probably won't actually be using it in the car this much but I want to figure out for the worst case scenario.

[two_wheel_mayhem]

I don't think you need a full size battery for your secondary. Look into some car audio products. There's all kinds of batteries out there these days.

If one of those motorcycle size secondary batteries will run a 600 watt amp for 4 hours it would surely run your laptop.

An no your alternator won't care, the only time the car's charging is gonna spaz out is if the primary battery has low voltage.