How to power an appliance (laptop) in a car
#11
12-31-2014, 10:07 AM
Tigger,
Thank you so much for confirming. And thank you for those 2 Targus links. I'll read the description of those two later. But I just saw that the price of one of them is $6. Wow, 6 bucks for a universal (or at least a multi-plug) charger!
Thank you so much for confirming. And thank you for those 2 Targus links. I'll read the description of those two later. But I just saw that the price of one of them is $6. Wow, 6 bucks for a universal (or at least a multi-plug) charger!
Last edited by DaHonDa; 12-31-2014 at 10:21 AM.
#12
12-31-2014, 10:10 AM
The Targus Charger (your 2nd link) you linked to is 750W, according to a reviewer.
My laptop's "power-brick" makes no mention of wattage. What's the significance of wattage? Is there no mention of wattage on my power-brick because wattage is not a factor with AC-to-DC power bricks? What am I not understanding, or what do I not know?
My laptop's "power-brick" makes no mention of wattage. What's the significance of wattage? Is there no mention of wattage on my power-brick because wattage is not a factor with AC-to-DC power bricks? What am I not understanding, or what do I not know?
Last edited by DaHonDa; 12-31-2014 at 10:16 AM.
#13
12-31-2014, 03:05 PM
Someone on another forum said that even a DC adapter could kill the car's battery pretty quickly, if the car is off. And I plan to use a DC adapter when the car is off.
Here's what he said:
I'd love to have your thoughts, folks.
Here's what he said:
Most people have a standard Starter Lights Ignition (SLI) battery in their car, which is *not* designed for substantial, sustained electrical draws. A laptop definitely counts as a major draw, it's not like a cell phone charger that has a teeny weeny draw. Not sure how long it would take to kill a SLI battery "unrecoverably dead", gone forever, but it's not much. I wouldn't even run a laptop for 20 minutes, you're probably doing damage to the SLI battery. 5 minutes I might not worry about. SLIs are designed to be depleted at most 10% before being recharged. They provide a massive amount of power, to start the engine, for a very short period of time.
I bought the deep cycle battery to overcome this problem, as they are designed to be 50% depleted, and may survive further depletions without too much damage. However, there's a further problem: car alternators generally don't have the charging profile that some of these deep cycle batteries want. I never got the performance out of that Odyssey battery I was expecting. I probably prematurely killed it. I think their advertizement is a bit slimy, in hindsight, as it's pitched as a straight replacement for a regular car battery. But it doesn't *charge* like a regular car battery, and expecting someone to always use an external charger to get the right charging profile, is an unrealistic bait-and-switch IMO. I haven't researched up alternative deep cycles, if any of them have charging profiles more compatible with a standard automotive alternator, as my needs have changed in recent years.
As for replacing the alternator, with one that has the right charging profile for an Odyssey or other AGM battery, I did research that up. There are no cheap solutions in the automotive space, and I didn't find any with a lot of field deployment and customer testimonials. The idea of the alternator generating the right charging profile, is better known in the marine space where people more commonly use deep cycle batteries. You can probably buy something off-the-shelf for a boat that works.
I bought the deep cycle battery to overcome this problem, as they are designed to be 50% depleted, and may survive further depletions without too much damage. However, there's a further problem: car alternators generally don't have the charging profile that some of these deep cycle batteries want. I never got the performance out of that Odyssey battery I was expecting. I probably prematurely killed it. I think their advertizement is a bit slimy, in hindsight, as it's pitched as a straight replacement for a regular car battery. But it doesn't *charge* like a regular car battery, and expecting someone to always use an external charger to get the right charging profile, is an unrealistic bait-and-switch IMO. I haven't researched up alternative deep cycles, if any of them have charging profiles more compatible with a standard automotive alternator, as my needs have changed in recent years.
As for replacing the alternator, with one that has the right charging profile for an Odyssey or other AGM battery, I did research that up. There are no cheap solutions in the automotive space, and I didn't find any with a lot of field deployment and customer testimonials. The idea of the alternator generating the right charging profile, is better known in the marine space where people more commonly use deep cycle batteries. You can probably buy something off-the-shelf for a boat that works.
#14
12-31-2014, 09:52 PM
Well, I can run my stereo for several hours on my battery. I have two amps, one is a 600 watt sub amp and one is a 200x2 amp for the speakers.
You tell me which draws more power.
20 minutes and it's doing damage? A standard battery has a 65 minute reserve at 25 amperes. By his calculations, a laptop would have to pull 75 amperes. (a household circuit is 15 - 20 amps. A 20amp circuit at 120v can handle 2400 watts. A computer runs about 300 watts.
Here is a calculation I found based on using an inverter. Since you wouldn't be using that, the time would be longer.
For an inverter that could handle it however, revised values:
120V x 1.4A = 168W
84W/12V = 14A (DC)
14A X .1 (inverter consumption, estimated) = 1.4A
total DC load = 15.4A
1000AH/40 (max recommended discharge for lead acid = 40%) = 400AH
400AH/15.4A = 25 hours
You could discharge it further, but if you're planning on doing this frequently, it will adversely affect your battery's longevity.
Car battery powering a laptop?? | Overclockers Forums
No matter what you do, you want a good battery and don't draw it down to far. Start the engine and run it for a while - 7 miles or 20 min will recharge a battery. A deep cycle is a good idea if you plan on doing this often.
I am not an electronics expert so your mileage may vary.
You tell me which draws more power.
20 minutes and it's doing damage? A standard battery has a 65 minute reserve at 25 amperes. By his calculations, a laptop would have to pull 75 amperes. (a household circuit is 15 - 20 amps. A 20amp circuit at 120v can handle 2400 watts. A computer runs about 300 watts.
Here is a calculation I found based on using an inverter. Since you wouldn't be using that, the time would be longer.
For an inverter that could handle it however, revised values:
120V x 1.4A = 168W
84W/12V = 14A (DC)
14A X .1 (inverter consumption, estimated) = 1.4A
total DC load = 15.4A
1000AH/40 (max recommended discharge for lead acid = 40%) = 400AH
400AH/15.4A = 25 hours
You could discharge it further, but if you're planning on doing this frequently, it will adversely affect your battery's longevity.
Car battery powering a laptop?? | Overclockers Forums
No matter what you do, you want a good battery and don't draw it down to far. Start the engine and run it for a while - 7 miles or 20 min will recharge a battery. A deep cycle is a good idea if you plan on doing this often.
I am not an electronics expert so your mileage may vary.
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