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nitroben2 t1_jdw1jjj wrote

Reply to comment by Friendly-Rock3226 in Which MagSafe power bank brand are you choosing for your iPhone 14? by AptCovering

According to my quick web search the TSA asks for spare batteries to be carry on (not checked bag) and under 100 watt hours (exceptions on request for 101-160Wh).

The largest MagSafe battery bank I’ve seen so far is 10,000mAh which at the typical 5V only comes to 50Wh so it should be a non-issue so long as you keep it in your carry on.

TSA website link: https://www.tsa.gov/travel/security-screening/whatcanibring/items/lithium-batteries-more-100-watt-hours
Let me know if I misunderstood what that’s saying

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jway5929 t1_jdwsqmn wrote

Just an FYI, the nominal voltage of most battery banks is 3.7v. The circuitry bumps it up to 5v (or higher) to charge the phone. However the 3.7v should be used when calculating the overall capacity. So 37wh for a 10ah (10,000mah). So a 3.7v nominal battery pack with a mah rating under 27,000 can be taken on aircraft. Which make sense why manufacturers top out near that rating.

One exception is the apple MagSafe battery pack. That uses a 7.4v nominal voltage. This is why despite the lower mah rating it still has similar overall capacity to the Anker options.

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nitroben2 t1_jdwusen wrote

That is good to know! It can be hard to find the official Voltage on electronics batteries.

That the Apple pack uses double the voltage explains why its performance Is so close to the 5,000mAh options from others even though it’s posted capacity is under 2,000mAh.

I wish all battery products would use Watt-Hours for capacity measurements instead of Amp-Hours with varying degrees of obfuscation on the voltage.

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jway5929 t1_jdx84sx wrote

I could not agree more! Many times the only way to know is to take it apart and look at the marking on the battery cells. However you also need to look at the wiring of the battery cells. For example that apple battery pack actually uses 3.7v battery cells, but has two is series for the total 7.4v. Other brands, like Anker use one larger cell or several 3.7 cells in parallel. Knowing the number of cells, their configuration and their individual rating is all needed to truly understand the battery bank’s raw capacity.

However, raw capacity doesn’t mean much. It’s the net capacity the battery bank can output. Some brands use more efficient circuity than others. Therefore it is entirely possible a lower [raw] rated battery bank can outperform one with more raw battery capacity.

Thank goodness for YouTube channels that take everything apart and do rigorous testing.

Wish manufacturers listed raw wh rating and charging efficiency, but we are stuck with less meaningful, but bigger, more impressive sounding numbers.

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