OT: Powerbank & air travel question

[The Natural Philosopher]

Oh dear. It tells you what the voltage is dear. and that coupled with knowing what the Ah is, gives you the stored energy.

[Dave W]

12,000 mAH probably means that the battery can give no more than 12A for 1 hour. The 5V output will come from only one cell and won't be able to supply more current than the full stack. So 12A x 12V x 1H = 144WH, less than the 150WH allowed, so why worry?

[Dave W]

I disagree. 12AH has to apply to the whole battery, otherwise it's a lie. However it could mean that the battery can only give a maximum 1A for 12 hours.

[Peter Parry]

given it's uncertain best Chinese quality the end of the saga might be the following.

"Batteries and cells must be of a type which meets the requirements of each test in the UN Manual of Tests and Criteria, Part III, subsection 38.3. It may be necessary to contact the manufacturer to confirm that they have complied with this."

[Tim+]

Well my wife has pointed out that we're flying with KLM, not BA. Their rules seem a little less restrictive.

Tim

[Peter Parry]

The rules on dangerous air cargo are made by IATA and the CAA, not the airlines. Whether being relaxed about the rules is good or bad depends -

[Theo]

I've run the numbers for a few of these (in fact, the car start packs discussed recently) - they are indeed described based on a single cell voltage of 3.7v, irrespective of how the cells are wired internally.

It is possible that some of them have a single cell or bank of parallel cells, and the 12v is generated by a DC/DC converter. But that can't apply for the car start packs, which can supply hundreds of amps from a powerbank-sized unit - those must be series wired.

It's easy to tell by a simple sanity check. Look at the size/weight of a drill or laptop battery - eg 4Ah @ 18V = 72Wh. How does the powerbank compare? It's not going to be radically different in density. If it was

144Wh then it would weigh a few kilos.

(This doesn't work the other way round - some 'high capacity' batteries are padded out with cement to make them feel heavier)

Theo

[Dave Plowman (News)]

mA.hr is just fine when the voltage is quoted too. It's fairly obvious if it can do lower voltages than the base voltage of the cells, the mA.hr figure will be higher - assuming an efficient voltage convertor.

[Dave Plowman (News)]

Yes. The Lidl one I have which works out at approx 24 Wh weighs 0.4 kilo.

[newshound]

But there are two voltages.

[newshound]

Agreed. But at least the upper bound one is apparently below the limit.

An interesting thought, would it be safer to have these in the cabin or the hold?

[newshound]

That KLM advice seemed pretty sensible though.

[Graham.]

No, there is only one voltage that matters, the voltage across the battery of cells. The voltage derived from the various buck and boost converters in the unit is irrelevant.

Good luck to the OP in getting this "car starter" on the plane by the way, I'm just glad I'm not flying with it in the hold.

[newshound]

Brain fade, you are right it is probably three cells.

[Tim+]

Cabin! How do you put out a hold fire? Much easier to deal with any problem in the cabin.

Tim

[Tim+]

It won't be in the hold though. It looks like it's covered by "power bank" rules for transport.

Tim

[dennis]

I thought explosives were banned and it would make a bomb if you just shorted it with the battery clips. I won't post which pins to solder blob onto.

[dennis]

Do they have buckets of carbon granules in the cabin then?

[Dave Plowman (News)]

If the amp.hr is quoted at that.

Except that if you only quote the amp.hr at that lower voltage it will be a higher figure and look good on paper.

[newshound]

NO, because you don't know which voltage the amps are being taken from in the quoted Ah. You will (should) get more Ah from the lower voltage.