# external recharge batteries for phone -- how many charges? **URL:** \ **Category:** Factual Questions\ **Created:** [December 13, 2017, 3:52am UTC](https://boards.straightdope.com/t/external-recharge-batteries-for-phone-how-many-charges/804362 "2017-12-13T03:52:51Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [December 13, 2017, 3:52am UTC](https://boards.straightdope.com/t/external-recharge-batteries-for-phone-how-many-charges/804362/1 "2017-12-13T03:52:51Z")
There may be too many variables for this to be answered properly, but… I’ve got a fairly boring Motorola Android phone…and recently got an external battery, which can re-charge the phone when the phone’s battery runs low. I know it can charge the phone up from no-charge at all to a full charge. (Nice.) How many times? How many full phone charges do I get from the external battery, before _it_ needs to be recharged? (Also…how long does the charge last in an external battery of this sort, before it needs recharging?) Naturally, the durn thing didn’t have any documentation. I had to figure out how to use it all on my own (okay, not too hard, given the way the plugs and sockets go.) ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [December 13, 2017, 4:04am UTC](https://boards.straightdope.com/t/external-recharge-batteries-for-phone-how-many-charges/804362/2 "2017-12-13T04:04:16Z")
I just looked at my Anker, the model, capacity and all that is printed on one end slightly-lighter black on black. A strong magnifying glass and light will be needed if yours is similar. You need the phone battery and the external battery ratings in mAH. Usually, those will only give 2/3 of stated capacity. Divide external battery by phone battery. In my case 10,000 x .67= 6700/1500=4.46 charges. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [December 13, 2017, 1:45pm UTC](https://boards.straightdope.com/t/external-recharge-batteries-for-phone-how-many-charges/804362/3 "2017-12-13T13:45:23Z")
I have a 10,000mAh Anker battery pack too. It has four lights on the front showing the remaining capacity, which roughly represent one charge of my phone (iPhone 6) for each light. As for how long it lasts when fully charged, I’ve left it for a few weeks before now and it still seemed to be charged up after that. ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [December 13, 2017, 2:38pm UTC](https://boards.straightdope.com/t/external-recharge-batteries-for-phone-how-many-charges/804362/4 "2017-12-13T14:38:51Z")
> [@Trinopus](#): > > How many times? How many full phone charges do I get from the external battery, before _it_ needs to be recharged? It depends on the capacity of the power pack and the capacity of your phone’s battery. The smallest power packs usually will charge the average phone once. Bigger power packs that still fit in your pocket will charge most phones up to 4 times. While not completely linear, the size/weight of a power pack is typically proportional to its capacity. ---
**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\ **Post date:** [December 13, 2017, 2:54pm UTC](https://boards.straightdope.com/t/external-recharge-batteries-for-phone-how-many-charges/804362/5 "2017-12-13T14:54:44Z")
It depends on the capacity of the external battery, the capacity of the phone battery, and the efficiencies of moving energy from one to the other. In practice, this will have to be determines empirically since rated battery capacities are, at best, speculative. ---
**Author:** ![JHBoom](https://avatars.discourse-cdn.com/v4/letter/j/13edae/32.png) [@JHBoom](https://boards.straightdope.com/u/JHBoom)\ **Post date:** [December 15, 2017, 7:18pm UTC](https://boards.straightdope.com/t/external-recharge-batteries-for-phone-how-many-charges/804362/6 "2017-12-15T19:18:53Z")
nm… ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [December 15, 2017, 9:43pm UTC](https://boards.straightdope.com/t/external-recharge-batteries-for-phone-how-many-charges/804362/7 "2017-12-15T21:43:43Z")
How many mah is your phone battery and how many mah is the external charger? How big is the charger? Lipstick sized ones are about 3000mah. Candy bar ones are about 5000. Ones shaped like a thick phone are about 10,000. Your phone battery is probably 1500-2000mah. Divide the numbers together to get a rough idea of how many charges you’ll get. Word to the wise, avoid knockoff external chargers. In my experience they only carry half the advertised charge. Only buy anker or another good brand.