Hello all,

I am just starting out with this project. I have attached the data sheet for the camera I am planning on using. I am going to need to power the camera, and an air card from a battery pack. The camera runs at 5vdc 1.2 amp, and the air card will run on on 5vdc at 6 amps (currently usb). My question is, how many and what size batteries do I need. I would like the unit to run for a minimum of 30 days. I have looked around on the internet to come up with a calculation for this, and don't have any confidence in my results. This forum has really helped me out in the past, so I thought I would throw this to the experts on here.

Eventually I would like to power this unit using a solar panel. Once again, the question would be what size?

Thanks,

 

The current you've mentioned seems very high. For the camera at least, I think you've misread the specs, though the data sheet certainly isn't clear. It says:

+ Input: 100-249 V AC, 50/60Hz
+ Output: 5 V DC, 1.2A
+ External AC-to-DC switching power adapter
+ 2W Max Power Consumption

I think the power adapter is capable of providing 5V/1.2A, which would be 6W, but the camera actually draws just 2W max, or .4A. It still seems like a lot for a small device, but that's what they say. The aircard I don't know about, but you'd never get 6A from USB, so I wonder what the numbers really are there.

This is seeming like a very large amount of power to get from a battery, if you want a month's operation. Could the unit be powered intermittently, and switch itself on at intervals to make a transmission? That might make it possible.

 

I read on Wikipedia that a USB port is basically 5vdv at a max of 6 amps depending on the device. I have not purchased the card yet, so I don't know the exact draw of the card. I was figuring worst case.

Turning it on intermittently to send a transmission is not a bad idea, but I am just below the novice level when it comes to this stuff and I wouldn't know where to begin on that one

 

Well then, I suggest that when you look for aircards, you check for power consumption, as it's an important issue if you need battery operation. You might go into this with the knowledge of how much energy you can possibly have if your battery is very large. So say you'd be willing to use a deep-cycle lead-acid battery, the kind that might power a small outboard motor. Allowing for some self-discharge, how much power could that supply on a continuous basis over a month? That's your power budget for the camera and aircard. If it turns out that you have power to spare, then you can consider a smaller battery. If even the largest battery won't do the job, you'll have to think about ways to reduce power consumption, like not operating continuously.

 

Wow! I was hoping like AA or C. Not deep cycle. This is probably a dumb question, but how do you quantify battery life?

 

Sorry to be so pessimistic, but you can't talk about multiple amps with a small battery. The capacity rating is in amp-hours, or milliamp-hours for a small battery. An alkaline AA cell has about 2 amp-hrs capacity. That would be 2 amps for an hour, or 1 amp for 2 hours, except that in fact the ratings are based on a particular discharge rate, which will be set so as to make the battery last for a while; draw a very large current and you'd find the capacity would be a lot less.

But all is not lost. Figure out what the real current draw is likely to be for your camera and airport card, and it'll be more clear what kind of battery can do the job.

 

Will do. Thanks for the help John.

 

As I read that spec sheet I don't see where there is an opportunity to power the camera from DC. It sure looks like an AC Input ONLY. BTW - what exactly is an "aircard"?