Li-ion Batteries - Care Of

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lazybloke

Considering a new username
Location
Leafy Surrey
Leaving li-ions in a flat condition is supposed to cause permanent damage, hence there is a protection circuit that retains some residual charge as a safety margin. Bike lights stored in a cupboard over a summer are a scenario where the batts could be damaged (when the residual charge leaks away).

Storing li-ions fully charged is also supposed to be 'less than ideal'. The general advice seems to be to charge to about 2/3s capacity before storage, and maybe periodically top-up.
 

sight-pin

Veteran
[QUOTE 5031729, member: 9609"]s it OK just to pop them on the charger and bring them back up to full charge after just a short use ?[/QUOTE]

I have Li-ion in the drill i bought in 2007, I've charged them from when they have run out of juice and after short use loads of times....still going strong.
 

lazybloke

Considering a new username
Location
Leafy Surrey
I have Li-ion in the drill i bought in 2007, I've charged them from when they have run out of juice and after short use loads of times....still going strong.
Yet the capacity of laptop batteries degrades noticeably after 2-3 years of regular use, and eventually hold no charge at all. A different pattern of usage.
one of my work laptop batteries (8 years old) just died and wouldn't hold any charge. I swapped it with one from stores which is older but still works, but the laptop only lasts about 40 mins rather than the expected 3 hrs.
 

Bazzer

Setting the controls for the heart of the sun.
I understand that if the battery does not have protection circuit, which prevents the charge going too low, if you flatten these batteries, then your only hope of recovery is equipment which can trickle charge (very low voltage) the battery back to its minimum charge point. Otherwise you are stuffed.
IIRC a "flat" Li-ion battery with a protection circuit isn't actually dead, as you might discover if you start to abuse it.
I thought recharging a Li-ion battery to its full capacity was not recommended, although most domestic equipment means either a full charge, or a guess at the charged state.
I also understood a chemical reaction took place as part of the charging process. Given that batteries, even Li-ion ones decline in capacity over time, which is presumably linked to the charging and discharging process, I would have thought less frequent charging was preferable.
 
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gbb

Legendary Member
Location
Peterborough
Yet the capacity of laptop batteries degrades noticeably after 2-3 years of regular use, and eventually hold no charge at all. A different pattern of usage.
one of my work laptop batteries (8 years old) just died and wouldn't hold any charge. I swapped it with one from stores which is older but still works, but the laptop only lasts about 40 mins rather than the expected 3 hrs.
I wonder if the drain has an effect on that. At the end of the day, the drain on a Li-on battery is very low from cycle lights (in most cases) and very high (probably) from laptops. Laptops may be far more sensitive to the loss of one cell in a pack than cycle lights. Ive stripped supposedly dead laptop batteries to only find one or two of the many cells are actually dead, the rest are fine.

On another note, my homebrew 4x18650 Panasonic battery pack i made from a 'dead' laptop battery is still going strong after at least 7 years (although it hasnt had much useage over the last 3 years) and the last time i got it out after nearly a whole year of inactivity, it still ran my 2 x 1Watt light for several hours. It wasnt charged prior to being put away either.
 

mjr

Comfy armchair to one person & a plank to the next
Storing li-ions fully charged is also supposed to be 'less than ideal'. The general advice seems to be to charge to about 2/3s capacity before storage, and maybe periodically top-up.
You can't easily measure the current charge state or the current maximum, can you? So how do you follow that general advice? Do I just put it on the mAh-counting charger until it's had 2/3s of theoretical?
 

Bazzer

Setting the controls for the heart of the sun.
You can't easily measure the current charge state or the current maximum, can you? So how do you follow that general advice? Do I just put it on the mAh-counting charger until it's had 2/3s of theoretical?

I know there are USB devices you can buy from eBay* which show the current draw. I would guess, although some research would be advisable, or perhaps one of the electricians on here could advise, that the current draw would decline as full capacity was approaching.

* Edit For example https://m.ebay.co.uk/itm/USB-Charge...d=271523165409&_trksid=p2349624.c100408.m2460
 
Last edited:
Location
Spain
I know there are USB devices you can buy from eBay* which show the current draw. I would guess, although some research would be advisable, or perhaps one of the electricians on here could advise, that the current draw would decline as full capacity was approaching.

* Edit For example https://m.ebay.co.uk/itm/USB-Charger-Doctor-Capacity-time-Current-Voltage-Detector-Meter-Battery-Tester-U/222046795095?var=520907514099&_trkparms=aid=222007&algo=SIM.MBE&ao=2&asc=20150519202351&meid=ff747e0edaf64bf4a9b137bea11c5f72&pid=100408&rk=8&rkt=25&sd=271523165409&_trksid=p2349624.c100408.m2460
Battery charge should have no effect on the demand for current until certain protection devices kick in.
 

John the Monkey

Frivolous Cyclist
Location
Crewe
I've been told that running to empty every time is a bad idea- best to top the battery up from time to time, with some folk suggesting a monthly full discharge/recharge. In terms of storage, for Phone batteries, the advice I heard most recently is to store them for long periods without use at around 40% charge.
 

albion

Guru
Location
South Tyneside
Running towards empty - bad
Charging to full - bad
Charging fast - bad
Using in a hot or a very cold environment - bad.

I have also heard it said thst a device is only as good as its worst battery cell.
 

mjr

Comfy armchair to one person & a plank to the next
[QUOTE 5032909, member: 9609"]Can you not just measure the voltage ?
for example my camera battery (7.4v li-ion) varies from 7.27v when flat to 8.35v when full. It is now standing at 7.94v so is that not 62% ?[/QUOTE]
No, it's almost certainly not. There are three frustrations: flat is not 0% (the protection circuit kicks in and prevents it going completely flat), full is not 100% (maximum capacity reduces with each cycle), and the discharge curve is not a straight line (modern ones have a rapid voltage fall for the last few % - early cells were more linear over the whole range). I suspect blindly dumping 2Ah into a discharged-to-limit 3Ah cell would be a better estimate than a voltage measure but still incorrect.
 

Ajax Bay

Guru
Location
East Devon
Since 'Battery University' has not yet been linked to, on this thread, here's the link to the BU-409: Charging Lithium-ion lesson.
The bottom lines are:

Simple Guidelines for Charging Lithium-based Batteries
  • Turn off the device or disconnect the load on charge to allow the current to drop unhindered during saturation. A parasitic load confuses the charger.
  • Charge at a moderate temperature. Do not charge at freezing temperature.
  • Lithium-ion does not need to be fully charged; a partial charge is better.
  • Not all chargers apply a full topping charge and the battery may not be fully charged when the “ready” signal appears; a 100 percent charge on a fuel gauge may be a lie.
  • Discontinue using charger and/or battery if the battery gets excessively warm.
  • Apply some charge to an empty battery before storing (40–50 percent SoC is ideal). (See BU-702: How to Store Batteries.)
You can't easily measure the current charge state or the current maximum, can you? So how do you follow that general advice [to store at] 2/3s of theoretical?
Personally, I know how long my light will last on its battery pack, so I charge it up and then put the load (the light) on for 1/3 of the normal length I get with the headlight on my bike.
[QUOTE 5031729, member: 9609"] Q1: Do these batteries suffer from memory type issues or is it OK just to pop them on the charger and bring them back up to full charge after just a short use ?
Q2: When it says a battery is good for 300 recharges does that mean 300 recharges from being completely flat, and would that be equivalent to 600 charges from half flat ?[/QUOTE]
A1: "Li-ion is a low-maintenance battery, an advantage that most other chemistries cannot claim. The battery has no memory and does not need exercising (deliberate full discharge) to keep it in good shape. Self-discharge is less than half that of nickel-based systems" Source
non-A2: What is the (second word) "it" which says 'good for 300 recharges'? I think the best advice is to follow good charging procedures (in particular don't recharge with any load on the battery) - see my first link. These sort of claims on item description/specification material for general public purchase are very difficult to verify or contradict as there are so many variables. (Off topic) At least one (with the resources) could test the claimed 3000 lumens (Ha! Ha!) for a Chinese headlight and 100,000 hours life (light powered by 2 x CR2032 button batteries).
 

Ajax Bay

Guru
Location
East Devon
[QUOTE 5034125, member: 9609"]the question still remains, If they are quoting 50 cycles of fully charged to fully discharged Would you expect to get twice as many cycles if you were only discharging to 50%?[/QUOTE]
Sorry - don't know. But you may be able to answer your own question if you study the battery university lessons.
Do you keep a note of every time you recharge a battery and what state you thought it was in before starting the recharge? (Knowing your chain experiments I suspect you might ^_^.)
Isn't your derived/exam question whether or not you should discharge (either by deliberate load (eg indoors) or by riding a second night ride) the battery before recharging?
 

Ajax Bay

Guru
Location
East Devon
[QUOTE 5034120, member: 9609"]so may be measure voltage and cross ref with such a graph and you could get within ball park of 40 to 50%.
Mine was 4.2v after charging, and after tonights ride it was showing 3.78v, which would suggest about half discharged, (and consider they seem to die a death at about 90% discharge I'm probably a bit past half way.[/QUOTE]
I think the very slightly negative gradient of the graph means that method is subject to wide variation, for example what voltage did the 'charged' battery start at. You would have to 'get to know' your battery and maybe test it before first use after charging. Certainly sub-3.7v is a good indicator that it merits recharging immediately (or at least it would be imprudent to rely on the battery for much further power).
I think the best bet is to test your (fully charged) battery/light on full power and on half/one third power, and measure how long it lasts in each regime. Then you will be able to judge, after a night ride, how much charge (as a proportion of full capacity) it still has.
 
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