Topic
Does it save power to charge phone to just 80%?
Forum Posting
A Membership is required to post in the forums. Login or become a member to post in the member forums!
Home › Forums › Gear Forums › Gear (General) › Does it save power to charge phone to just 80%?
- This topic has 7 replies, 7 voices, and was last updated 1 year, 10 months ago by Rex Sanders.
-
AuthorPosts
-
Apr 28, 2022 at 9:28 am #3747847
I got one of Rex’s USB meters that measure mWh when charging phone from USB power supply
I have a Galaxy S9 phone and an Anker 20,000 mAh USB power supply
Rex said that a phone’s lithium battery will have a longer lifetime if you never charge it above 80% or let it go below 30%. I wonder if that would also save USB power supply life when charging the phone?
I use about 50% of my phone battery per day. I could charge it back up to 100% at the end of the day and let it run down to 50% the next day, or I could do 80% and 30%. Would that save significant energy from the USB power supply?
I charged phone to 100%. Ran Gaia with the display on so maybe the load was constant. It took:
65.8 min to go from 100% to 80%
126.8 min to go from 80% to 50%
73.1 min to go from 50% to 30%
Then I charged it back up and recorded mWh:
2156 mWh to go from 30% to 50%
3305 mWh to go from 50% to 80%
2235 mWh to go from 80% to 100%
% is not linear with actual power consumed. 100% to 80% took 65.8 min. 50% to 30% took 73.1 min. Charging form 30% to 50% resulted in more minutes of run time than 80% to 100%. So I corrected for that – 2156 mWh * 65.8 / 73.1 = 1941 mWh to get the same amount of run time.
Using that correction, it took 5540 mWh to charge from 50% to 100%. 5246 mWh to go from corrected 30% to 80%. 5246 / 5540 = 0.95 – it saves 5% of power if you charge from 30% to 80% each day, vs charging from 50% to 100%.
So, bottom line, it doesn’t really make enough difference to worry about. But, it saves a little. When I’m charging phone, if I notice it’s above 80% I’ll turn it off, but don’t worry much. When it get’s to 100%, it will continue to trickle even though it’s not adding to the phone charge so turn it off then.
Aside – if you could possibly be in a survival situation, you should charge to 100%. Obviously.
May 4, 2022 at 3:25 pm #3748363Interesting. Since listening to the podcasts on batteries I am not leaving any device plugged in overnight/while I sleep. I have already noticed a difference. Not sure if the NB1000 was more susceptible to this plugged in overnight drain but I have changed my habits.
May 5, 2022 at 1:44 am #3748402Most smartphones slowly ramp up and ramp down recharging power in order to extend battery lifespan, at the expense of total recharge time.
As Jerry measured, that barely affects the energy consumed. Thanks!
Based on my not-yet-published measurements of battery packs other than the Nitecore NB1000, the overnight energy waste is an iPhone problem (at least), not a battery pack problem.
Best advice is what Brad is following: unplug when full, usually a couple hours or less. Don’t let devices stay plugged into portable battery chargers overnight.
— Rex
“A watt-hour here, a watt-hour there, and pretty soon you’re talking real energy.”
May 5, 2022 at 8:47 am #3748415Never thought of the power savings, but I always charged to 80% for the health of my battery.
I have an original iPhone SE (2016) and it still has 90% battery capacity, so I think it works quite well. :)
May 5, 2022 at 11:04 pm #3748568My phone occasionally burns a lot of power either because it’s getting wet and turning the screen on constantly, or an app is kinda crashing/stuck in a loop and working hard. So on trips where power is precious I like to charge lower – only about 50% – to avoid having all my “eggs in one basket”.
May 5, 2022 at 11:58 pm #3748569I bought* the largest lithium battery for 2000 miles around (until you get to Moss Landing in California). 46.5 MW and 93 MWh (or, if you prefer it in Anker units, 93,000,000,000 mWh). Enough energy to recharge my iPhone 12 fully, twice a day, for 12,300 years. Alas, it’s not very portable.
If you cycle it fully (charge it from the grid and discharge it to the grid), it is 85% round-trip efficient – 15% of the energy goes away in charging and discharging. If OTOH, when cycled between 70 and 85%, it is 93% efficient, roundtrip.
I’m more interested in its losses if used at 20 MW versus at 46 MW, but I haven’t gleaned that information yet.
* I was the deciding vote among 9 directors. It wasn’t my $40M.
May 6, 2022 at 8:08 pm #3748628You won’t regret it.
Neither will they.Cheers
May 6, 2022 at 9:42 pm #3748635The Moss Landing giant pile-o-batteries keeps popping up in the local news due to fires or overheating. Hope your local fire department is well-equipped and well-trained on dealing with these problems.
And with extremely rare exceptions, you don’t need to worry about a mainstream smartphone battery or battery pack catching fire or exploding. Unless you drop it into the campfire :-)
— Rex
-
AuthorPosts
- You must be logged in to reply to this topic.
Forum Posting
A Membership is required to post in the forums. Login or become a member to post in the member forums!
Our Community Posts are Moderated
Backpacking Light community posts are moderated and here to foster helpful and positive discussions about lightweight backpacking. Please be mindful of our values and boundaries and review our Community Guidelines prior to posting.
Get the Newsletter
Gear Research & Discovery Tools
- Browse our curated Gear Shop
- See the latest Gear Deals and Sales
- Our Recommendations
- Search for Gear on Sale with the Gear Finder
- Used Gear Swap
- Member Gear Reviews and BPL Gear Review Articles
- Browse by Gear Type or Brand.