Trinket Draw Questions...

[nuclearmonkey]

So I'm finally getting around to being responsible, and not just assuming that a group 31 is going to handle all of my charging requirements indefinitely while at camp. Started taking down numbers on amp draw for different items, and approximate length of time they will be used. All was going well until I hit the iDevices... :snorkel:

I'm running a slew of Blue Sea dual USB chargers that provide up to 2.1 amps per slot. Things plugged in to the Blue Sea's are iPhones (x2), an iPad Air, Delorme inReach. I'm having quite the difficult time finding info on how much the iPad will draw overnight while charging. Considering it still draws down the battery percentage when the screen is on (and charging), we always arrived at camp with the iPad at about 20-30%. For the life of me tho, I can't find total amps required to charge the iPad completely, and what a reasonable expectation would be for having it plugged in throughout the evening and night (screen off at this point). I did find somewhere a test that someone posted that said roughly 4.5 amps. However, assuming a charge of 2.1 amps per hour, I know for a fact that we're not hitting 100% charge in 2 hrs, so either I'm lost somewhere, or I'm lost somewhere... :elkgrin:

I haven't started on the iPhones yet, but I'm assuming I'm going to be in the same boat...

Other items I've been adding up (just as a 'hey - I've been doing my homework'):
Fridge
LED lighting for setting up camp
LED map lighting for cooking, etc
Water pump
Coolant pump (keep water hot when truck isn't running for shower)
Battery charger for AA's & AAA's...

Thanks in advance!!

 

[4x4junkie]

2.1 amps at 5V (what USB uses) is 10.5 watts... At 12V, 10.5W would theoretically be 0.875 amps, though there is a slight bit of energy lost in the DC-DC conversion from 12V to 5V. Figure worst case it draws about an amp off your truck battery for whatever the charge duration is if your device is making full use of that 2.1 amps. (use 12W × [charge time in hours] if you need it in watt-hours).

What I would do is simply measure the current draw going into the USB charger while you have a device plugged in and charging (get some alligator clip leads and just hook everything up to your battery or main power lead with an ammeter inline).

 

[Hopeless Diamond]

Keep in mid, the Dual USB chargers have a parasitic draw of 15ma, so if you're trying to calculate overall usage and run capacity, add those in too

 

[nuclearmonkey]

I knew I was missing something! 2.1 @ 5v makes much, much more sense. With respect to the parasitic draw, is that per dual, or each port? Also, is that only when something is charging on say port 1, there is an extra draw on port 2, or is it more like - each blue sea dual usb charger has a parasitic draw of 15ma no matter what, all the time?... If it's the later... sheesh... (I have 4 in the truck)

 

[Hopeless Diamond]

I believe its per dual port. Yes, all the time

 

[Hilldweller]

...
Btw,
Off topic, but why are all these newfangled electro-doohickies (phones, tablets, et.al)referred to as "devices" ?
Flys against long standing engineering terminology where devices are objects what control or convey electrical energy.
Appliances are assemblages what consume electrical enegy...

I suspect its driven by PR & marketing.
Cant allow folks to equate their Superphone of the month being on par with a toaster...

Technical term is doo-hickey or farkle.

 

[snowblind]

Btw,
Off topic, but why are all these newfangled electro-doohickies (phones, tablets, et.al)referred to as "devices" ?
Flys against long standing engineering terminology where devices are objects what control or convey electrical energy.
Appliances are assemblages what consume electrical enegy...

I suspect its driven by PR & marketing.
Cant allow folks to equate their Superphone of the month being on par with a toaster...

Not marketing at all. If it was it would be an idevice or something similar.

I always thought "device" came from the airlines calling them "electronic devices" in the pre-flight talk. They were always worried about the "electronic emissions" of computers, laptops, walkmans, etc.


Matt

 

[snowblind]

SNIP
(use 12W × [charge time in hours] if you need it in watt-hours).

What I would do is simply measure the current draw going into the USB charger while you have a device plugged in and charging (get some alligator clip leads and just hook everything up to your battery or main power lead with an ammeter inline).

7-11 Watts is the draw I see when charging an ipad3 via a GoalZero Yeti 400 USB port. These ports are rated as "5V, up to 2.1A (10.5W max), regulated"

10Watts is the spec for ipad 1/2 wall charger. 12Watts is the spec for the Ipad3 wall charger.

I also found this @ http://www.macworld.com/article/1150356/ipadcharging.html:
third-generation iPad has considerably more battery capacity than the first two iPads—42.5 watt-hours, compared to 25 watt-hours
third-generation iPad takes noticeably longer to fully charge.
third-generation iPad because the new iPad’s electronics—its screen, processor, and the like—require more overall power than the previous models’ components
when connected to a lower-power USB port, the iPad will charge—very slowly—only when asleep; when in use, a third-generation iPad will likely use more power than it gets, resulting in a gradual decline of battery level


Matt

 

[nuclearmonkey]

Thanks for the follow up! It seems that using 4.5 to 5 amps for the charge seems pretty close. Can you double check that link?... It's giving me an invalid message.

I can attest that running the iPad, while plugged into the Blue Sea (2.1 amp) USB outlet, does drain the battery if the screen is on. Slowly maybe, but on the way from NC to UT, it was a bit annoying.

 

[Bbasso]

Or maybe you can do as I did...
I added a small round rocker switch (next to) to shut the power off to the Bluesea USB outlet.
As I'm nearing completion of my solar setup I don't want to have ANY drain unless it's actually being used because I'm staying with a smallish battery for a while to see how it meets my needs, then grow... maybe.