# Can someone help me figure out how long this battery will last? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [October 2, 2023, 5:05pm UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016 "2023-10-02T17:05:02Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![filmore](https://avatars.discourse-cdn.com/v4/letter/f/7993a0/32.png) [@filmore](https://boards.straightdope.com/u/filmore)\ **Post date:** [October 2, 2023, 8:12pm UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/21 "2023-10-02T20:12:42Z")
Some libraries and electric companies have a ‘Kill-a-Watt’ device that you can check out. It’s a device which is like a power strip that can tell you how much power is being used. It will tell you how much is being used at any moment, as well as how much you used over time. If you can get one, you can plug in all your stuff to see how much power it’s using and get an idea of how long it would last with that power station. ---
**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\ **Post date:** [October 2, 2023, 8:21pm UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/22 "2023-10-02T20:21:14Z")
> [@Dorjan](#): > > … Deep cycle batteries on a 12V circuit like you would find on a boat or car. Most car batteries are designed for starting and not deep cycling. Of course, ‘car battery’ can mean a lot of different things. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [October 3, 2023, 9:01am UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/23 "2023-10-03T09:01:17Z")
> [@filmore](#): > > Some libraries and electric companies have a ‘Kill-a-Watt’ device that you can check out. It’s a device which is like a power strip that can tell you how much power is being used. It will tell you how much is being used at any moment, as well as how much you used over time. If you can get one, you can plug in all your stuff to see how much power it’s using and get an idea of how long it would last with that power station. **[The real Kill-a-Watt sells for $35, and there are competing products available for as little as $14](https://www.amazon.com/s?k=kill+a+watt&crid=261H13BOAMPF3&sprefix=kill+a+watt%2Caps%2C90&ref=nb_sb_noss_1)**. I bought a Kill-A-Watt many years ago, and it’s been handy for understanding power consumption of household appliances - especially those that run intermittently, like a refrigerator. It tells you not just instantaneous power consumption, but also total energy usage over a given time period. Quite handy. ---
**Author:** ![FloatyGimpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/floatygimpy/32/7750_2.png) [@FloatyGimpy](https://boards.straightdope.com/u/FloatyGimpy)\ **Post date:** [October 3, 2023, 2:57pm UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/24 "2023-10-03T14:57:39Z")
> [@Machine\_Elf](#): > > Battery University suggests that you get better longevity if you run a battery between 85% and 25% than you do running it between 100% and 50%. Should it be fully recharged after use or just up to 85%? ---
**Author:** ![filmore](https://avatars.discourse-cdn.com/v4/letter/f/7993a0/32.png) [@filmore](https://boards.straightdope.com/u/filmore)\ **Post date:** [October 3, 2023, 3:06pm UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/25 "2023-10-03T15:06:39Z")
For a backup device like this that’s only used rarely, it’s probably best to have it plugged in 100% of the time. You’ll want it at max capacity for the rare times that you need it. Even if a different charging strategy would extend its life, it would likely end up being too much of a hassle for the benefit. It would be easy to forget to plug it in, and then months later it’s dead when you need it. If you don’t want to have it charging 100% of the time, one strategy would be to plug it into a plug timer that’s only on for an hour or so per day. ---
**Author:** ![Shalmanese](https://avatars.discourse-cdn.com/v4/letter/s/45deac/32.png) [@Shalmanese](https://boards.straightdope.com/u/Shalmanese)\ **Post date:** [October 3, 2023, 3:06pm UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/26 "2023-10-03T15:06:41Z")
> [@FloatyGimpy](#): > > Should it be fully recharged after use or just up to 85%? You’re more likely to throw the thing away before you deplete the cycles. The difference between optimal battery management and standard management might be the difference between 2000 cycles and 5000 cycles. But 2000 cycles is a power outage a week for 40 years. ---
**Author:** ![FloatyGimpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/floatygimpy/32/7750_2.png) [@FloatyGimpy](https://boards.straightdope.com/u/FloatyGimpy)\ **Post date:** [October 3, 2023, 3:09pm UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/27 "2023-10-03T15:09:34Z")
Ah ok, good to know! ---
**Author:** ![Pork\_Rind](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pork_rind/32/111_2.png) [@Pork\_Rind](https://boards.straightdope.com/u/Pork_Rind)\ **Post date:** [October 3, 2023, 3:12pm UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/28 "2023-10-03T15:12:24Z")
Yeah. Given the hundred bucks this unit cost, I’d say use it in the way that’s most conveninent for you. Which means keep it stored at 100% and run it down as far as needed during the power outage. All this messing around with 85% to 25% just means it might not be ready when you need it. Run this thing to death and plan on getting another in 5-10 years. And I’d bet this thing will run your aquarium for a good 24 hours or possibly much more since we know your heater runs only intermittently. I propose you test this out by deliberately running the aquarium on it for at least a few hours to monitor the trend. ---
**Author:** ![FloatyGimpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/floatygimpy/32/7750_2.png) [@FloatyGimpy](https://boards.straightdope.com/u/FloatyGimpy)\ **Post date:** [October 3, 2023, 3:14pm UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/29 "2023-10-03T15:14:21Z")
> [@Pork\_Rind](#): > > Given the hundred bucks this unit cost, It’s not quite that cheap! It’s around $650 on amazon but on sale for $550. ---
**Author:** ![Pork\_Rind](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pork_rind/32/111_2.png) [@Pork\_Rind](https://boards.straightdope.com/u/Pork_Rind)\ **Post date:** [October 3, 2023, 3:18pm UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/30 "2023-10-03T15:18:48Z")
Oh! Somehow I thought I read $100 bucks. I bought a 400Wh unit for about $150 a while back for my CPAP. Sorry about that. My thinking still stands. Use this in the way that’s most efficient for you and understand that it’s product life will still be a decade or more. If it matters, I suspect a much cheaper unit will still cover you for 24+ hours if you figure that 50w heater is on a 10% duty cycle. ---
**Author:** ![FloatyGimpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/floatygimpy/32/7750_2.png) [@FloatyGimpy](https://boards.straightdope.com/u/FloatyGimpy)\ **Post date:** [October 3, 2023, 3:28pm UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/31 "2023-10-03T15:28:34Z")
At first I was going to buy the 240 but it did have some bad reviews so I decided I might as well just get the 500. Now I’m glad I did because, based on what people have said here, I can probably have the tank lights on as well. I’m going to test it out when it arrives. It’s supposed to be here sometime between Oct 6-12. ---
**Author:** ![Sam\_Stone](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Sam\_Stone](https://boards.straightdope.com/u/Sam_Stone)\ **Post date:** [October 3, 2023, 3:32pm UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/32 "2023-10-03T15:32:52Z")
Do you have LED tank lights? They consume a lot less power. Found a decent cite for the power needs of an aquarium: [Aquarium power consumption](https://www.algone.com/the-aquarium-and-energy-consumption) ---
**Author:** ![FloatyGimpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/floatygimpy/32/7750_2.png) [@FloatyGimpy](https://boards.straightdope.com/u/FloatyGimpy)\ **Post date:** [October 3, 2023, 3:40pm UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/33 "2023-10-03T15:40:46Z")
> [@Sam\_Stone](#): > > Do you have LED tank lights? Yes. The only problem with having the lights on during an outage is that I can’t cover it with a blanket. Or at least I assume I can’t because I don’t imagine it’s safe to put a blanket over lights. During a prolonged outage in winter the room temperature drops enough to be too much for the heater to keep the temperature up in the tank. So having the heater and sponge filter going and a blanket over top should be enough. ---
**Author:** ![FloatyGimpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/floatygimpy/32/7750_2.png) [@FloatyGimpy](https://boards.straightdope.com/u/FloatyGimpy)\ **Post date:** [October 4, 2023, 2:23pm UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/34 "2023-10-04T14:23:18Z")
I decided if I was going to go through all the trouble and expense of maintaining the tank during an outage, I should have a bit more life in there as half the time it looks empty so I got this guy yesterday. [![Imgur](https://live.staticflickr.com/65535/53233881506_63205dfec9_z.jpg "Peach") ](https://www.flickr.com/photos/56821557@N06/53233881506/in/dateposted-public/) ---
**Author:** ![FloatyGimpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/floatygimpy/32/7750_2.png) [@FloatyGimpy](https://boards.straightdope.com/u/FloatyGimpy)\ **Post date:** [October 24, 2023, 4:15pm UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/35 "2023-10-24T16:15:34Z")
Update. I finally got around to testing out the battery. I have both the heater and pump plugged in and it’s pulling 60 watts. I’m going to keep them plugged in for the day and see how long the power lasts. ---
**Author:** ![FloatyGimpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/floatygimpy/32/7750_2.png) [@FloatyGimpy](https://boards.straightdope.com/u/FloatyGimpy)\ **Post date:** [October 24, 2023, 5:17pm UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/36 "2023-10-24T17:17:38Z")
It went down 10% in an hour. ---
**Author:** ![DavidNRockies](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/davidnrockies/32/6279_2.png) [@DavidNRockies](https://boards.straightdope.com/u/DavidNRockies)\ **Post date:** [October 24, 2023, 5:32pm UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/37 "2023-10-24T17:32:42Z")
That tends to make priapism less likely. Ahem. Carry on. ---
**Author:** ![Al128](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/al128/32/16541_2.png) [@Al128](https://boards.straightdope.com/u/Al128)\ **Post date:** [October 25, 2023, 1:23am UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/38 "2023-10-25T01:23:19Z")
then your 518Wh battery is more likely a 100Wh battery … see how long until it stops … and send it back for a refund… ---
**Author:** ![FloatyGimpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/floatygimpy/32/7750_2.png) [@FloatyGimpy](https://boards.straightdope.com/u/FloatyGimpy)\ **Post date:** [October 25, 2023, 1:26am UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/39 "2023-10-25T01:26:17Z")
I think that’s right about what we thought it would be isn’t it? It would last about 10 hours? After 5 hours it was at 57% and I decided that was enough of a test and recharged it. ---
**Author:** ![Al128](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/al128/32/16541_2.png) [@Al128](https://boards.straightdope.com/u/Al128)\ **Post date:** [October 25, 2023, 1:38am UTC](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016/40 "2023-10-25T01:38:51Z")
ohhh … sorry, i MISREAD your post … I (erroneously) read it as “it went down **to** 10% in 1 hour” _facepalm_ 5 hours and about 50% charge - you are right on the money here … [Previous page](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016.md?page=1) [Next page](https://boards.straightdope.com/t/can-someone-help-me-figure-out-how-long-this-battery-will-last/991016.md?page=3)