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iPad charging

I know the iPad will often not charge when connected to just a USB source (i.e. not plugged into an electrical socket), but it will say "Not Charging". I am experimenting at home to see if this will sustain the charge the battery already has, i.e. stop it from going down, but I don't know if the USB power output from a PC is higher than say a cigarette lighter in a small plane and whether the results will be the same.

Has anyone any experiences they can share with me?

The USB spec allows a device to draw up to 500mA at 5V (= 2.5W). An iPad 4 has a 43Wh battery capacity (11560mAh at 3.7V).

If the iPad 4 was able to keep its battery level with a standard USB, it means that its current mode of operation would allow it to run on battery for 43/2.5 = 17.2h which is unrealistic.

In a more realistic scenario, the iPad lasts 4-5h which means 8.6 watts. An extended spec (well, Apple proprietary) provides up to 10W of USB charging, the newest Apple incarnation up to 12W.

So the answer is: no, it will not be able to keep its battery level on a standard USB charger.

Thanks. So far, with SkyDemon running in simulation mode for 20 mins, attached to USB 2.0 on my home PC, it hasn't dipped below the 95% it started at and says "Not Charging", but I guess the output from the aircraft will be less.

This looks quite useful :-)

This thread might be relevant.

I think my Ipad2 just about keeps itself "level" when connected to a full-spec (500mA) USB port, though it will depend on the screen brightness.

Many laptop ports are only 100mA...

One hassle with all this is that a "2A" Apple USB charger is not the same as a "2A" non-Apple USB charger. The former has a resistor of a specific value across the two data pins; the latter has a short across the two data pins.

I am about to knock up a USB output cable for a multi-output power unit I built for the plane years ago (19V 4A, 10V 1A, 5V 2A) and I won't be able to have a single USB cable which can charge at up to 2A either an Ipad or a non-Apple device like the Lenovo Tablet 2.

Obviously this is an issue with car cigar lighter USB adaptors too.

Administrator
Shoreham EGKA, United Kingdom

I too have been considering this issue.

I've fully charged my iPad 3 and left it in the window and it runs with EasyVFR for about 7 hours. It's on auto brightness, but in the window in daylight, so presumably pretty near full brightness.

Inflight usage seems to be closer to 5 or 5.5 hours. I'm not sure why the difference but if could be:

a) the screen being in bright sunlight so the screen is brighter b) EasyVFR has some power saving functions built in for low demand situations (eg left in my living room window, and not moving and me not playing around with it vs moving and doing a lot with it inflight) c) presumably the iPad itself has some power saving features for low demand situations.

The issue start to arise on long trips when I could easily be flying for 5 or more hours. Throw in some ground time for briefing etc, and a way of charging starts to look like a good idea.

I got a 2A car charger from ebay (cost very little, maybe €2 from memory). It works great if used with the Apple power cable. However this is too short for me, as the power socket in the aircraft is on the far right of the panel.

I got some longer leads from ebay but the iPad would not charge using any of the longer leads, even from the Apple charger plugged into a domestic power socket.

I got a '12,000mah' batter from eBay and tried using that with the short cable. It only added about 8% to the iPad power level before it was flat :( 12000mah....yea right!

In fairness to the ebay suppliers, all refunded the charges when I pointed out that they didn't work.

I'm not sure what the answer is to this one, but would appreciate anyone else's experience!

By the way someone earlier mentioned charging from their pc. Most PC's seem capable of charging an iPad but not by default. There is a small app that you can install on your PC, and then it seems perfectly capable of charging the iPad. I've no idea what it does, but it works!

I can dig it out if anyone is interested, but it's not a lot of use for charging inflight!

Colm

EIWT Weston, Ireland

I got a '12,000mah' batter from eBay and tried using that with the short cable. It only added about 8% to the iPad power level before it was flat :( 12000mah....yea right!

They don't tell you the voltage. 12 000mAh at 0.1V is just 1.2Wh whereas 12 000mAh at 5V (the USB voltage) would be 60Wh. I have one of those 12 000mAh batteries as well and judging from its size and weight, it's no more than a tiny fraction of the integrated iPad battery.

I got some longer leads from ebay but the iPad would not charge using any of the longer leads, even from the Apple charger plugged into a domestic power socket.

That is weird... faulty cables?

I have seen a faulty USB cable, so they do exist. That cable cost me some wasted hours, because I was trying to download a data log from the EHSI with it, and was getting weird problems.

A lot of stuff on Ebay is junk, fake, etc. Amazon is normally better.

OTOH, 2A is a lot of current and I can imagine say a 5m USB cable dropping too much voltage, and the Ipad then refusing to continue.

Interestingly the charger which came with my Lenovo tablet 2 is 5.3V, not 5.0V.

I did a quick google on Ipad charging and it is a nightmare. For example this site suggests that it isn't just a simple resistor but actually you need to set up specific voltages on the two data pins, to get the Ipad to draw the full 2A.

Administrator
Shoreham EGKA, United Kingdom

I too have seen even only 2 metre cables on Amazon that say for the iPad it will only do a data sync, and not charge. Does seem to be a common theme.

@Dublinpilot - I too saw reference to a PC app you can install that will allow you to charge an iPad over USB but it was on a forum, and they said it had a success rate of 7/10 so it wasnt entirely ideal. And as you say, no use in a plane. I've ordered the charger in my link above. In flight, I think I would just under 5 hours on the iPad 2, but maybe it drains quicker in the air, rather than motionless at home because of the additional computations needed a) when the location co-ordinates are changing constantly b) notifications about airspace and other warning. Just my guess...

I can't see how a Windows app can alter the current a PC USB port can deliver - unless the PC is specially designed to support that.

A full spec PC port can deliver 500mA. The current limit (if there is one) is not configurable. Maybe some recent motherboards have this as an enhancement?

Administrator
Shoreham EGKA, United Kingdom

I have recently run ForeFlight on my iPad 2 with a BedElf GPS on some long(ish) x-country flights in the US. While I never ran out of juice, it would appear that the iPad in this configuration (i.e. where the BadEld also draws current from the iPad battery) would last about 3.5 to 4 hours. There is, however, one great thing about the BadElf, i.e it has a through-charging port that accepts a mini-USB plug. All you therefore need is a car charger for the iPad with a mini-USB on the other end (my iPad car charger has the Apple connector). This time can, of course, be greatly extended if you just shut it off for phases of flight where you don't need it.

One thing to watch out for in real life is the overheat shut-off. On one of the flights I left the iPad in the sun on the dashboard for perhaps 15 minutes and it shut off. Came back to life after cooling down or a little while in the back, but something to be aware of. No big deal in my situation as I had ForeFlight running on the iPhone also and, of course, had the panel-mounted 430 (plus VOR), but could be disconcerting if it happened at an awkward moment.

All the above said, the combo iPad / iPhone / ForeFlight is absolutely fabulous - a real pity there are no European Jepp charts available for it. I also think there probably won't be, as Jepp are in the process of creating their own product.

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