liIon Battery charge time, and advice

[fredted40x]

Hi,

Have just recieved my first liIon battery today, i have got the aw 18650 2200mAh li-ion battery with the ultrafire wf-139 (450mA), i know these are dangerous batteries if they are not cared for,

could anyone tell me how long this charger will take from when my olight m20 starts flashing because of low battery?

also is the best time to charge the battery when my flashlight says the battery is low?

Is there anything else really important i need to know?

thanks in advance


edit, sorry have just thought of another question,
do these batteries come charged?

 

[mdocod]

Hi,

Have just recieved my first liIon battery today, i have got the aw 18650 2200mAh li-ion battery with the ultrafire wf-139 (450mA), i know these are dangerous batteries if they are not cared for,

could anyone tell me how long this charger will take from when my olight m20 starts flashing because of low battery?

2200mAH/450mA= ~5 hours theoretical, most of the WF-139's I am aware of fall a little short of 450mA charging rate. I would expect more like 6 hours.

also is the best time to charge the battery when my flashlight says the battery is low?

With the WF-139, I would suggest charging when the cell drops below ~3.9V (50% capacity give or take) if you get the chance, this charger can do weird things if a near-full cell is installed on it so best to drain down the cell a bit before charging again.

You can charge a li-ion cell at pretty much any time with a good charger and it will be fine.

It is considered better for cell health to cycle in the top 80% of available capacity, or, when the cell is down to ~3.7-3.8V is a good time to charge.

Li-Ion does not develop any sort of memory effect or anything like that. (actually no consumer cells in consumer devices do, but that's a different story all-together),

Is there anything else really important i need to know?

A multi-meter is the easiest and fastest way to check state-of-charge on Li-Ion cells and is just plain handy to have around for all sorts of things. Get one.

thanks in advance


edit, sorry have just thought of another question,
do these batteries come charged?

they usually come partially charged. Li-Ion has the best shelf life when stored somewhere around 3.9V, so most batteries ship in the 3.8-4.0V range.

I just bought a nuclear reactor and was thinking about setting it up out back this afternoon. Is there anything I need to know to prevent myself from growing extra limbs?

Just kidding.....

 

[SilverFox]

Hello Eric,

With the Li-Ion charging algorithm you can't do a direct division of charge rate into cell capacity.

If you charge at 0.5C, it usually takes about 3 hours to obtain a full charge. If this also holds true for charging at less than 0.5C, then a 2200 mAh cell charged at 450 mA would take a little over 7 hours to charge from empty.

Tom

 

[mdocod]

Hello Eric,

With the Li-Ion charging algorithm you can't do a direct division of charge rate into cell capacity.

If you charge at 0.5C, it usually takes about 3 hours to obtain a full charge. If this also holds true for charging at less than 0.5C, then a 2200 mAh cell charged at 450 mA would take a little over 7 hours to charge from empty.

Tom

Howdy Tom

It's a WF-139, it doesn't have a CV stage.




[edit in]
I was reading around somewhere else earlier, and the charge rate for that charger may be lower than I thought, one report said something like 300mA IIRC, so in that case, it would probably be closer to 8 hours...

 

[fredted40x]

thanks, alot of info there,

when you say 7-8 hours is that when it reaches 3.9v?

I dont suppose you know what voltage the olight m20 starts saying the battery is low do you, if not dont worry i will test when i get it?

thanks again

 

[mdocod]

The WF-139 will charge with a continuous ~300-400mA charge rate (depending on luck of the draw it seems) until the cell voltage reaches ~4.25-4.30V while charging. The charger will then terminate, and the cell will settle to somewhere around 4.20V.

I have no idea when the lower battery warning kicks in... and am frankly a little confused as to how a flashlight could have a useful low battery warning system that is designed to be compatible with anything from an 18650 to 2xRCR123.... I'm guessing that the system would only work on the 18650, as it is the lowest voltage source possible... Even with that in mind, designing a low-battery warning system can still be difficult because there are a wide variety of 18650s available on the market, and different cells are going to have a different behavior under the load of the M20. With that in mind, a set voltage point where it starts indicating low battery could be hard to implement. The voltage at which the flashlight starts to indicate "low-battery" would have to be different for each mode, as the cell would "sag" to different voltage levels in each mode. On a low mode, the cell would operate above ~3.6V pretty much all the way till near the end, where it would very suddenly die, under the load of high, the battery would be steadily dragged down to around 3.2V (estimated) under a load moments before being totally depleted. If you remove the load by turning off the flashlight, the battery voltage will then rebound to a resting state, at which point, in theory, a low mode could be activated and the low-battery warning would go away (in theory) for awhile...

If you get the chance to take some voltage readings of the resting cell when the light gives you the low-battery warning, I'd be very interested in hearing the results.

Eric

 

[fredted40x]

hi, so the charger will automatically turn off then, so i dont need to time it and worry that i havnt fully charge it

and yeh sure when i recieve my light(hopefully tomorrow or tuesday) i will let you know the voltages when the light is on high and then i will try it when its on med, i will let someone else try it on low:tinfoil:.

keep an eye on this post

 

[mdocod]

The older WF-139 chargers would continue to charge the cell after the light went "green" at a slower pace, which would eventually over-charge the cells and could be dangerous. The more recent WF-139 chargers do not seem to have this problem. I still wouldn't recommend leaving cells on it indefinitely as I just wouldn't trust the charger 100%.

To see which version you have, check the open circuit voltage of the charger, if it's ~5V, then you have one of the newer ones, the older ones would measure ~11V.

Eric

 

[fredted40x]

i dont have either lol, trust me to be different

model: wf-139
input1:100-240v~50-60Hz
input2:12V-...400mA
output:4.2V-...450mA

any ideas?
just answered my own question
is the charger supposed to flash green every couple of seconds when its charging and the red lights are on. yes

 

[mdocod]

you have to MEASURE the output voltage, every WF-139 has that printed on it.

and yes, most of them blink green every couple seconds while charging. From what I can tell, this is when the charger checks the open circuit voltage of the cell during charging.

 

[fredted40x]

o yeh, it measure 4.9V, i have just charged my new batteries until the charger went green and they are now at 4.10V.

thanks for your help and i will post the low battery voltage asap