iPad Explodes - caution users

[Dafydd Llewellyn]

For voltage and current, think of it this way. The source supplies the voltage and the load draws the current. As long as the supply can supply as much current as the load needs, then everything is fine. You could have a supply that is capable of supplying 1000A and it would be quite safe to connect to your iPad, because it is the load (ie the iPad) that controls the amount of current drawn. On the other hand, if the supply can't supply enough current to keep the load happy, then the voltage will droop and all bets are off. So, if your genuine Apple wall charger that came with it is rated at 1A, then it means that the mini iPad must require less than that amount, and any cigarette lighter charger that can supply that much or more is fine (all other previously discussed issues being already accounted for, of course).

That's certainly the case where Ohm's law controls the charging current and there are no other constraints; this is usually the case with a lead-acid battery in a car. In that case, as you say, only the charger voltage matters - provided the charger voltage cannot exceed the fully-charged battery voltage, it can never supply more current that the back emf and the internal resistance of the battery allows. However, it is possible to damage a lead-acid battery that is close to fully discharged if the charger has more current capability than the battery can handle without physical damage - and Ni Cad aircraft batteries had to have the charge current regulated by the battery temperature. So it ain't necessarily that simple, I suspect.

 

What I do NOT know is (a) Whether there are constraints of that nature for the Ipad mini; (b) Whether there is protective charge control circuitry built into the Ipad to cover this - or whether it is controlled by limiting the output of the charger. An LT3083 can produce 3 amps. That's three times what the Apple-supplied wall charger can provide.

 

Further, I don't know whether the 1 amp Apple charger can keep up with the device if it's on full brightness continually, as it's likely to be in the aircraft. So it's not a given that 1 amp is sufficient. I suppose it's a case of suck it and see.

 

 

[frank marriott]

I (current) = E (voltage) divided by R (resistance i.e. Load)

 

Some opinions on a/hr ratings of batteries defies logic.

 

For small capacity batteries I agree with current limiting.

 

 

[rgmwa]

I've got nothing to contribute to this discussion, but just wanted to say that I'm impressed by the expertise that is available on this forum. I'm learning (I think).

 

rgmwa

 

 

[facthunter]

Electricity is smoke. After the smoke has come out there is No electricity. That's all you need to know. Nev

 

 

[sfGnome]

That's certainly the case where Ohm's law controls the charging current and there are no other constraints; this is usually the case with a lead-acid battery in a car. In that case, as you say, only the charger voltage matters - provided the charger voltage cannot exceed the fully-charged battery voltage, it can never supply more current that the back emf and the internal resistance of the battery allows. However, it is possible to damage a lead-acid battery that is close to fully discharged if the charger has more current capability than the battery can handle without physical damage - and Ni Cad aircraft batteries had to have the charge current regulated by the battery temperature. So it ain't necessarily that simple, I suspect.

Fair point. I will admit that I was thinking of equipment rather than batteries, but you're right. Batteries are the exact opposite of what I said. They have a very low internal impedance, and rely on the supply to limit the current.

 

What I do NOT know is (a) Whether there are constraints of that nature for the Ipad mini; (b) Whether there is protective charge control circuitry built into the Ipad to cover this - or whether it is controlled by limiting the output of the charger. An LT3083 can produce 3 amps. That's three times what the Apple-supplied wall charger can provide.Further, I don't know whether the 1 amp Apple charger can keep up with the device if it's on full brightness continually, as it's likely to be in the aircraft. So it's not a given that 1 amp is sufficient. I suppose it's a case of suck it and see.

Only guessing, but I'd be surprised if it drew more than the amp. However, even if it did draw more (say 1.5A to be excessive), then with the supply providing one amp, the internal batteries only have to supply the other half amp, and the iPad will still be running long after your bladder has exploded and you have to be on the ground anyway!

 

 

[Dafydd Llewellyn]

Fair point. I will admit that I was thinking of equipment rather than batteries, but you're right. Batteries are the exact opposite of what I said. They have a very low internal impedance, and rely on the supply to limit the current.

Only guessing, but I'd be surprised if it drew more than the amp. However, even if it did draw more (say 1.5A to be excessive), then with the supply providing one amp, the internal batteries only have to supply the other half amp, and the iPad will still be running long after your bladder has exploded and you have to be on the ground anyway!

Yes, that's about what I figured. I'll go look for a low-dropout 1 amp linear regulator.

 

 

[jetjr]

May not be useful but there is some smarts in the ipad regarding charging equipment.

 

Even a cheap cable and it wont charge, or maybe will begin then say not charging.

 

A std ipod charger is very slow to charge ipad compared with ipad unit.

 

Normal ipod style usb ciggy adapter, is 1 amp i think, ipad requires more, like double.

 

In flight with ipad running it does draw plenty, sure doesnt charge but just maintains bat level at best. I think this is with 1A unit.

 

I have a dual output USB cig adapter here and it is 3.1 A @ 5v, 12-24 v, recall its 1A on one output and 2A on the other, they are marked ipod/iphone and ipad/ipad 2. It does cause rf problems in flight as do three others ive tried.

 

 

[Chocolate]

I asked for a cig charger for ipad when at dick smith store and a young fella directed me to a dual Tom Tom charger. One side says 'fast charge' and I use it for ipad. Works a treat..it does fast charge.

 

Have to say I am not game to plug my ipad into my machine. I will stick to the aera with the ipad as the backup / planning tool.

 

 

[Old Koreelah]

Spoke today to Apple Support about how. "... permanent-magnet alternators regulate the charge by pulse width controllers which chop the alternator output into short pulses - but don't control the maximum voltage of the pulses."

 

Was advised that a cigarette lighter adaptor is ..."fine for occasional charging when necessary, (when charge is under 10%) but not recommended to be a daily practice."

 

Looks like I will only be plugging in iPad and iPhone when they get low.

 

 

[Dafydd Llewellyn]

Spoke today to Apple Support about how. "... permanent-magnet alternators regulate the charge by pulse width controllers which chop the alternator output into short pulses - but don't control the maximum voltage of the pulses."Was advised that a cigarette lighter adaptor is ..."fine for occasional charging when necessary, (when charge is under 10%) but not recommended to be a daily practice."

 

Looks like I will only be plugging in iPad and iPhone when they get low.

Yes - we're slowly getting the full picture. I wonder what the OzRunways people will think about this admission?

 

 

[dutchroll]

Be wary. Apple support representatives contradict themselves over the compatibility and usage of their own devices with monotonous regularity. This includes charging issues.

 

I don't really see a problem using a 12V cigarette lighter socket to charge an iPad in an aircraft at any time, provided the 5V adaptor (and the socket itself for that matter) you use is a quality one designed for the purpose and not cheap generic chinese junk. Anecdotally at least, the latter seems to be what causes fires and other malfunctions (and I've had one boasting of a total 3.1A capacity across 2 USB sockets which barely worked at all - that'll teach me for being a tightwad).

 

There's a lot of FUD out there about charging i-devices. The funniest I read was the guy who with absolute certainty decreed, resplendent with a completely misapplied Watts = Volts x Amps formula, that connecting a 10W Apple charger to an iPhone would ruin the battery through overcharging/excess current. Untrue. The device only takes what its internal charger (calling the Apple wall plug a "charger" is a bit of a misnomer - it's actually just a good quality 5V power supply) demands - up to 1A for an iPhone and up to a bit over 2A for an iPad. The same principle applies in your home. Your wall socket can pump out 10A but this doesn't mean plugging a 0.2 Watt nightlight into it will cause an explosion and fire. It demands what it demands, and barring an internal failure (again comes down to that quality thing), it'll be just fine.

 

All that being said, after hundreds of hours using the iPad & stock charger/adaptor plugged into the 110V cockpit power receptacle during my "day" job, I've not ever seen the max charging capability of the iPad3 manage to keep up with the demand of its retina display on full brightness while being used for cpu intensive apps, though the battery drain can be slowed to a very low rate.

 

 

[jetjr]

OzR recommend a battery power supply

 

How to tell whats a good and poor quality power supply, dont say price?

 

 

[dutchroll]

That's not always an easy question to answer. In this case brand can be a good indicator as the quality iPad accessory brands (Belkin, Griffin, etc) are in cahoots with Apple to have their stuff tested and certified, and they have a reputation to protect. Unfortunately though you are always going to pay a premium for this (e.g., Lone Star are the brand shown previously, and they do several TSO certified 5V adaptor products such as what I have in my plane, but they're expensive).

 

The big boys have been using and charging iPads in the cockpits of their Boeings and Airbuses for a while now (the only restriction is not having them plugged in for takeoff & landing, but you can plug them in on continuous charge in the cockpit for the rest of a 12 hour flight). Sure, these are certified power sockets using the Apple chargers (the quality thing again), but I think it's obvious that they don't consider having an iPad on long term charge connected to an aircraft power supply an inherently risky proposition.

 

 

[Dafydd Llewellyn]

That's not always an easy question to answer. In this case brand can be a good indicator as the quality iPad accessory brands (Belkin, Griffin, etc) are in cahoots with Apple to have their stuff tested and certified, and they have a reputation to protect. Unfortunately though you are always going to pay a premium for this (e.g., Lone Star are the brand shown previously, and they do several TSO certified 5V adaptor products such as what I have in my plane, but they're expensive).The big boys have been using and charging iPads in the cockpits of their Boeings and Airbuses for a while now (the only restriction is not having them plugged in for takeoff & landing, but you can plug them in on continuous charge in the cockpit for the rest of a 12 hour flight). Sure, these are certified power sockets using the Apple chargers (the quality thing again), but I think it's obvious that they don't consider having an iPad on long term charge connected to an aircraft power supply an inherently risky proposition.

Aye - but take a look at the power source they are using in those aircraft - it's probably from one phase of a 110V 400 Hz 3-phase source. As such, it will be a very high-quality power source indeed - at least as good as a domestic wall socket.

 

 

[dutchroll]

…..if you live where I live, a domestic wall socket is a horrendous quality power source. You'd almost be better off getting your power from a bicycle-driven generator.

 

Either way, I don't buy any excuses for having a poor quality power supply in your aircraft. It's not a risk worth taking, at any cost.