IPVMU Certified | 07/11/14 07:29pm
Battery packs can be sized that give days of recording, but they'll take up space. If covertness is key, you're not going to get much recording time.
You mention portability, but how much space do you have? How is light inside the freezer?
I also assume the batteries will need to be located in the freezer too - or can you run a cable from an outside power source to an inside camera/P12 imager box.
Options like Veracity's PointSource are out there, but they may not be a good fit without some other details.
I need between 8-16 hours of continuous recording. Covertness is critical in this scenario. We like the P12's because I can remote my recording box along with whatever battery source I can come up with.
Here is a pic of the back-side of the shelving system we would be installing the covert camera. I would like to fabricate a box that we can stick on with magnets. Installation has to be very quick and discrete. Lighting is "meh."
Running the cable outside of the fridge is not an option.
Here is a pic of the front of the rack. We are going to use the peg-holes for the sensor.
This is the sub-zero area. Same concept.
IPVMU Certified | 07/11/14 10:05pm
Yikes. This is tough. One question:
Would it be possible to place the camera/power sources in an empty food box or storage container?
Not only do we have an issue with capacity, we have a problem with the cold.
The customer would prefer not to have it stored in a box.
That Veracity PointSource looks rad. I think that might address my modular power needs. Looks like it is rated for -4F which might not be quite what we need for the sub-zero area. He doesn't have as much shrinkage in the freezer as he does in the fridge.
I like the portable PoE option vs. the aux 12V. Makes the deployment plug and play.
You have a power and heating requirement. I tried the following Examples with 10hr and 20hr. If using lead acid batteries the enclosure size for 10hr will be 1 cu.ft. for 20hr will be 2 cu.ft. Used insulation factor of R=1 and R=2. Assumed the 20degF freezer, tried target heating to 32deg and 50deg.
With 20hr requirement, won't be too portable. But gives some idea of the challenges. Don't let the batteries discharge and freeze, will crack and you will have to start over. Li-Ion will likely improve portability but more costly. If you had two boxes and were substituting, you will need a heavy duty charger to have time to recharge before the other box was drained and frozen. Didn't try the -12F, but I would look at how to get a power chord to it first.
The box needs to be big enough for the battery and have room for the insulation??
The R value past 1 gives diminishing returns, the volume for insulation will require a bigger box, hence greater surface area for heat loss. Assume 1 cuft, ambient is 20deg F, enclosure target is 32degF.
R0:37W heating, R0.5:25W, R1: 20W, R2:16W, R3:14W, R4:12W, R6:11W, R10:10W.
Depending on the insulation material chosen will have different R value for unit thickness. R10 will be 10 times the thickness of R1.
Here's something that just might work, the oft-maligned Everfocus Sidekick
Even tho I mocked its thrown together construction, in this case it comes in handy since you can detach the main unit from the router and bag. Its way smaller than the pointsource and its lithium, with over 10000 mah capacity. Its POE will run the camera and you can even use the wifi for live viewing. I have one and will try putting one in an otterbox with insulation and seeing how cold it gets, tho i'm out of liquid nitrogen so I can only go down so low...
"Cold temperature increases the internal resistance and diminishes the capacity. Batteries that would provide 100 percent capacity at 27°C (80°F) will typically deliver only 50 percent at –18°C (0°F). The capacity decrease is linear with temperature. The capacity decrease is momentary and the level of decline depends on the battery chemistry."
"The performance of all battery chemistries drops drastically at low temperatures. At –20°C (–4°F) most nickel-, lead- and lithium-based batteries stop functioning. Although NiCd can go down to –40°C (-40°F), the permissible discharge is only 0.2C (5-hour rate). Specially built Li- ion brings the operating temperature down to –40°C, but only on discharge and at a reduced discharge."
Battery University - Discharging at High and Low Temperatures
Rukmini thanks for doing this, I like real testing validating theories. I am finding it difficult to follow with the pictures. Could you show a diagram of what is in the fridge and the interconnections.. I didnt see the battery, can I assume you are powering it remotely from a chord to a powersupply outside thw freezer? What are the inside dimensions of the insulated bag and, thickness of insulation of the bag? What is the power being fed into the devices in the bag? You seem to be inferring that you cant measure accurately the temp inside freezer, but relying on the manual? Rob
I am trying to do the same thing with the same camera, although it will not be in a freezer. Does any one have any suggestions for a small battery to power the camera for 48 hours?
Chesapeake & Midlantic | 07/14/14 04:52pm
I wonder if this thing could be hacked to work. It's small and powerful- 61,000 mAh.