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Partial vs full recharge of devices from a bank

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Partial vs full recharge of devices from a bank

Old 12-18-20, 12:21 AM
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gauvins
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Partial vs full recharge of devices from a bank

I came across an entry somewhere, essentially stating that lithium batteries charge faster between 0%-50%, than above. (see representative entry). And somewhere else that you should not discharge batteries below 50% (which I think is wrong and refers to lead acid batteries, but what do I know... Well, I actually know that lead acid batteries are sold as starting vs deep discharge batteries, and that starting batteries will not withstand more that a couple of deep cycles, whereas deep discharge batteries can go through hundreds of them. I am under the impression that Li-ion are impervious to deep discharge).

In my case, I travel with a large battery bank ( 95Wh), a couple of headlamps (2.5Wh), an activity watch (1Wh), 2 smartphones (including one backup, 13Wh and 11Wh) and a Kindle (6Wh). And on occasion with a tablet and Bluetooth keyboard (if I travel with a laptop, it is because I have regular access to the grid and therefore do not care about this). My objective is to maximize efficiency (i.e. how many usable hours I can get from my devices on a single battery bank charge).

(1) Faster doesn't necessarily mean more efficient, especially if you recharge from a smart charger. If it is more efficient, then partial recharges would be preferable. Otherwise, it might be counterproductive (and annoying). Someone can educate me?

(2) I know that my bank will stop charging if a device draws a very small amount of energy, to avoid unnecessary drain. Still, I'd probably want to avoid leaving devices connected to the bank all night while I am sleeping. Since my devices can operate for several days on a full charge, it is entirely possible to "try" to partially recharge when the device is at, say 25%, up to, say 75% (difficult to be precise without a meter, which I will not carry). I guess that I am back to the first question. But stated differently, what might be the maximum difference in efficiency if recharging is "optimized" (e.g. fully optimized, based on meter readings, vs fully recharging devices, will increase effective usage by X%). What improvement can be expected with an eyeballed strategy that would use the device's meter (all devices except headlamps display somewhat accurate information. The headlamps give a very rough feedback). The answer could be something like "as long as you avoid recharging the last 10%, you'll be close to the best that can be done, and increase efficiency by something like 25%".

To restate a bit differently, what difference would that make if I do not fully recharge my devices.

Thanks
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Old 12-18-20, 12:51 AM
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Lithium batteries have much longer life if you charge them before the cliff where the voltage really starts to drop. I'm sure they charge faster if discharged too much, but that's not really that important in my estimation
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Old 12-18-20, 03:00 AM
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Fast charging is usually done roughly between 15% and 85% state of charge. One has to discern between phone batteries and typical cylindrical cells: the former is usually a lithium-polymer battery (with a polymer electrolyte, also used in many bike lights with internal cells, or as battery for fancy toys like model airplanes and the like), which behaves a bit different than a lithium ion round cell (with a liquid electrolyte).

If you want to maximize your battery life, as a general rule of thumb:
- do not discharge below 15% and do not charge above 90%.
- You can recharge any Lithium battery at any time, it then counts only as "partial charge/recharge cycle" in terms of numbers of cycles before the battery dies.
- Avoid drawing high currents (above 1C, which means power draw which would empty a full cell within 1 hour) at charging states below 40%
- Do not charge a battery at (cell) temperatures below 5-10C celsius
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Old 12-18-20, 06:24 AM
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Higher charging rates always mean you're losing more heat to resistive losses in cables and connectors (P=I^2*R), even with everything else being equal. Short thick cables will help, though it's difficult to tell if thats significant.
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Old 12-18-20, 07:18 AM
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I am no expert, but everything I have read in the above posts concurs with what I have read elsewhere.

I can add that my summer bike tour in 2019, five weeks where I tried to be self sufficient on power from a dynohub, that my phone burned through the battery very fast when the battery was cold. But warm battery had much longer life. This was so significant, that I warmed up my phone inside my sleeping bag in the morning before I used it to obtain a weather forecast. In this case using my phone in morning temperatures in the 40s (F) (or 5-10 degrees (C)) had a very noticeable impact on battery life if I did not warm it up first.

On my Android devices I am using an app called AccuBattery, it can provide good information on rates of discharge, etc. I have it configured to give me an audible warning when my battery reaches 80 percent charge when charging. And I learned that I want to have that audible warning shut off during sleeping hours.

A Li Ion battery can be physically damaged if power is drawn too low. I have had some camera batteries that started to bulge from internal pressures. And some batteries have an internal circuitry to prevent them from being charged if they are discharged to too low a voltage. For that reason, I try to avoid running my Li Ion batteries all the way down and when they do go way down, I try to recharge them as soon as practical (days instead of weeks, etc.).

A small number of stores in USA accept for no charge Li Ion batteries for recycling that you want to dispose of. I do not have any such list, but I have used Home Depot a few times to drop them off.
https://www.homedepot.com/c/ab/how-t...-of-batteries/

Agree with previous poster that good cables are important. On my 2019 bike tour, for the first few weeks I was using a bad cable to charge my powerbank from my Sinewave Revolution (a USB charger powered by a dynohub) and that cost me a lot of power. Switched to a better cable and had much more luck after that.

I do not think I answered any of your questions, but maybe answered a few that were not asked.

I store my batteries between uses in the fridge. That includes Li Ion, NiMH and disposable batteries.
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Old 12-18-20, 08:24 AM
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Originally Posted by znomit View Post
Higher charging rates always mean you're losing more heat to resistive losses in cables and connectors (P=I^2*R), even with everything else being equal.
just to be sure that I understand when you say "charging rate": you mean the voltage applied to the device, right? My bank is Anker powercore. I doubt I can trick it into applying a lower voltage. Would you have an idea? (I realize that most people care about charging time, so I assume that the charger tests acceptance and will push as hard as it can.)

Originally Posted by znomit View Post
Short thick cables will help, though it's difficult to tell if thats significant.
Good point. Any brand comes to mind?
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Old 12-18-20, 08:35 AM
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Originally Posted by Tourist in MSN View Post

On my Android devices I am using an app called AccuBattery, it can provide good information on rates of discharge, etc. I have it configured to give me an audible warning when my battery reaches 80 percent charge when charging.
Thanks for the tip. Much better than looking at the number of bars every 15 minutes.

I think I'll run a "quick" experiment with my backup phone. The idea would be to count the number of full cycles, and the autonomy of the phone (hrs: mins) of runtime, vs half cycles, that I can get from one fully charged bank.

Does your app keep a log of runtime? (I.e. how long does the phone stayed on, on a charge)
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Old 12-18-20, 08:45 AM
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Li-ion batteries charge most optimally between about 62F-72F, don’t charge your batteries in really hot or cold conditions. Heat is the enemy of Li-ions, if you have a case take the device out of the case so the battery can be at the optimal temperature. Don’t leave the devices in a place that can get hot, like a car in summer this will reduce battery efficiency a lot.
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Old 12-18-20, 12:47 PM
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Originally Posted by gauvins View Post
Thanks for the tip. Much better than looking at the number of bars every 15 minutes.

I think I'll run a "quick" experiment with my backup phone. The idea would be to count the number of full cycles, and the autonomy of the phone (hrs: mins) of runtime, vs half cycles, that I can get from one fully charged bank.

Does your app keep a log of runtime? (I.e. how long does the phone stayed on, on a charge)
It can provide a lot of info and graphs, data that I never looked at, so you might want to research that yourself.
https://play.google.com/store/apps/d...es.accubattery

I assume that the app is available in Canada, but I could be wrong. Before my bike tour in Canada, I was loading stuff into the phone for the trip and learned that I could not load a Canadian weather app unless I was in Canada. Then once I arrived in Canada, could not load it because my phone was mostly used in USA. Some of this stuff gets a bit weird.
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Old 12-18-20, 12:54 PM
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Originally Posted by gauvins View Post
just to be sure that I understand when you say "charging rate": you mean the voltage applied to the device, right? ...
...
I am not the person that you directed this question to, but I think the answer you are looking at is measured in milliamps.

USB should always be near 5 volts but if your device is capable of drawing power faster than the charger can deliver it, the voltage can drop some.
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Old 12-18-20, 05:56 PM
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Originally Posted by Tourist in MSN View Post
I am not the person that you directed this question to, but I think the answer you are looking at is measured in milliamps.

USB should always be near 5 volts but if your device is capable of drawing power faster than the charger can deliver it, the voltage can drop some.
The newer devices using USB-C power delivery can charge at 20V, which is how they can charge things to 50% in 30 minutes, (a charge rate of 1C, C being the capacity of the battery), and can deliver up to 100W.

OP, you can get usb power meters which might give you a better idea what your specific battery/cable/device is doing. I found most of my cheap hardware store USB chargers aren't delivering their rated currents.

https://www.banggood.com/RIDEN-UM24-...e=CN&ID=511646
https://www.ebay.com/itm/173721508478

For home use I use a Belkin charger that has a fast USB-C port and a USB-A port. C is for my tablet and A is for my phone because the slower charge rate should help with battery longevity (unless I'm in a hurry).
https://www.belkin.com/us/p/P-F7U097/
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