Hobby Charger VS Cheap Chinese Charger [ charger behavior ] some thoughts

Batteries and Chargers Rechargeable Batteries
4

very good post old.

i think some people think the higher the charge rate the better, yes it will be faster but all in all the battery will sag and it will hold less mAh in the end, not to mention it will raise the internal resistance of the battery and shorten its life.

the issue i think is not the hobby charger holding the charge rate longer or stressing out the battery, its people over charging the batteries take an 18650 since the charger will cut out at 4.2v or what you have set it to if you push to much current into the batteries they will rise in voltage hit the 4.2v cut off early and cut off they will not have time to absorb all the mAh and then once the cell is rested and the voltage is check it will be lower then 4.2volt and the battery will not give its full run time once used cause it didn't get to take its full mAh and its full voltage and I'm hopping we all understand the more mAh the longer the torch will run before needing a recharge, this also works for all rechargeable batteries.

there is other factors in this the charge mode used on the charger for example a fast charge will only charge to 80 to 90% the batteries will also make a difference the cheaper the battery will impact discharge and charge rates, a cheap hobby charger will also make a difference and because hobby charger,s let us humans do the thinking and we are an impatient breed we tent to over charge then ask why the rested voltage is different

I'm into remote control (RC) as a hobby have been for 20 years or so i have always had hobby chargers over the years and i run a middle of the road hobby chargers for my RC and my 18650,s i find it is more precise then the cheaper stuff but there need,s to be some understanding and knowledge, i could not go back to plug and play chargers as i would need so many.

while I'm new to 18650 batteries I'm not new to li-xx batteries i use slow charge,s and i always balance charge my 18650,s its slower, the charge rate ramps down giving the batteries time to normalize and this is where they will take a bulk of the mAh back.

i charge my 18650,s at a max charge rate of 0.5 amps (500 mAh) and i only use cheap batteries the trustfire flames, this is about the Maxim i believe these batteries can be pushed over a slow balance charge to take the Maxim mAH , this works out at around 0.4C for the charge rate, i believe 0.2C is better but then i pick the higher charge rate (C) to save time.

with my hobby li-po batteries there normally is a 1C charge rate so 1 x capacity of the battery divided by 1000, so if you have a 2200 mAh battery its 2.2 amps most li-po,s can be charged at 2C + so 2 x capacity, i mention this so people might understand the above when i say 0.4 and 0.2C.

over the years Ive found most cheaper chargers will do the job and some do it well, i would not recommend people who are not into RC to spend big $$$ on chargers and power supply,s as there is no need a couple of cheaper chargers like the WF-139 or the WF-188 would be fine if they don't over charge if they under charge no problem but most batteries are protected.

but also over the years i have noticed a lot of the cheaper chargers not to be 100% accurate or calibrated to there full potential and have noticed differences of .01 to 0.4 volt + some under charge some over charge and there is a difference between each charger i guess this comes down to quality control and some times you get what you pay for but we all want to save money.

i cant say a WF-139 is better then a $200 hobby charger that's full programmable, with calibration features that's accurate with in 10 mv (0.01v) or as accurate as your fluke DMM,s as i personally don't think it is, but like i said i cant recommend torch addicts to spend that money on what i call a half decent charger and power supply set up just for torch batteries, i also cant recommend the cheap imax b6 balance chargers due to there inaccuracy and there poor performance with accuracy and nimh charging.

like you say knowledge is the king, there needs to be some understanding and often to save time charging will shorten the life of your batteries and they will have slower resting voltage, its a give and take to me, the user needs to find the middle ground between Maxim mAh good rested voltage and charge time, one thing i will say that's good about the hobby chargers is understanding as you see whats going on and after a while to will make sense to most people.

with hobby chargers on the display screen you can actually see what your charging and discharging habits are doing to your batteries, you will see voltage sag with high discharge rates and you will see the voltage rise with high charge rates but once the battery has normalized or rested it will show other wise so then you know your over charging.

E.g when charging a 18650 at 1 amp say is you start the charge at 3.2 volt you will see the battery voltage climb up as soon and the charger kicks in but if you stop the charger you will see the battery voltage fall back to where you started, the same goes for discharging your 18650,s (but back to front) if you discharge a 18650 at 2 amps with the batteries resting voltage of 4.18v and you set the charger to shut down when the discharge hits 3v you will notice the charger will shut off when the battery hits 3v under load but once the load is taken off the battery will climb back up the battery has not had the time to take in or out its mAh.

this is why slower charge and discharge rates are better as the batteries will be closer to true rested voltage and mAh or normalized like you say, now like we said knowledge is power, but with the WF-139 you can not see this happening in front of your eye,s on the screen and a lot of people most likely will not research this and if they don't have a back ground in electric,s or RC so they might be surprised if they get one it will genrate questions.

also some hobby chargers are good for knowing how much mAh is going into the battery so you know truly how the battery performs plus features like data logging internal resistance testing comes in handy and can help you pick and chose what batteries to use say for direct drive torch,s and watching a good hobby charger in action will help people understand voltage drop and sag and voltage rise when charging over time.

Ive read on here in the past and even today plus of other forums in the past of these cheap chargers not shutting off and over charging and so on, but in other peoples eye,s they are the bee,s knee,s, i believe my $200 hobby charger and power supply is better then a WF-139 or an imax b6 not because it cost more and makes me better then every one else, its better cause its programmable it has more features i can charge multiple li-po,s at 10 amps for my remote control cars i can charge my xbox 360 controller batteries my camera batteries my torch batteries my radio batteries my 9v nimh,s its more accurate and it will work in the car on 12volt and it works at home i even take it on holidays to charge camera batteries it is used attest every couple of days and has payed for its self already.

i can easily see people with out a RC or electrical knowledge not understanding loaded and unloaded voltage and not understanding rested cell voltage and they would be seeing data they are not used to yet, if any one with a hobby charger is questioning the rested voltage of there batteries then they are over charging the batteries most likely.

instead of charging one battery at 1 amp with a hobby charger your much better off charging 2 to 6 or more at 0.5 amp the batteries will charge better hold more mAh giving them more run time and longer shelf life and because you are charging multiple batteries it works out much quicker then trying to force feed one and there will be less or no rested voltage difference because its being charged at a lower charge rate but your still saving time as your charging mutable batteries.

i like you believe knowledge is power but i don't believe its the hobby chargers fault i believe its user error mostly wrong charging modes cheap batteries and over charging a good hobby charger used correctly with a half decent battery will not stress out a battery or let the battery sag to 4.15v after its rested

5

My hobbychargers (Graupner, Robbe) decrease the current when hitting the 4,2V mark and push the last 5% of energy very slow with still decreasing current into the battery. I get them with perfekt 4,20V from the charger and they hold this voltage. Checking about a week later it is of course a bit lower at about 4,17V or so, nothing to worry about.

The charging method is called CC-CV, constant current-constant voltage.

6

I agree , chargers are tools and as such need to be used correctly ..

Unfortunately - while many express the virtue of hobby chargers , they seem to ignore the pitfalls , and give bad advise on there use .

I honestly dont understand how people can knock the 18650 chargers [ Trustfire TR-001 etc ] since the majority do a great job .

But then there are some seriously good hobby chargers out there if you want to pay the price ...

7

That is the methode the LiIon cell manufacturers recommend.

A typical charge specification has a maximum voltage (4.2 volt) and maximum charge current (Like 0.5C) and a minimum charge / cutoff current (like 80 mA). The hobby charger follows this, except the cutoff current is usual defined as charge current/10. I.e. when charging with 1 A, the cutoff current will be 0.1 A.

This charge methode will not force a high voltage on an old cell (This is damaging to the cell), but will stop charging when the cell cannot accept more current (Defined with the cutoff current).

8

And many dedicated 18650 chargers do exactly the same thing ... [ Sensitive to the internal resistance of batteries - therefore terminating early ]

And yes there are some chargers that force batteries to a higher voltage state , but depending on the school of thought ?

There are those who believe in conditioning batteries , even Li-ion ..

And some Li-ion get better after some use ? If you cant condition Li-ion, this should not happen .

Can you bring back degraded cells ?

One of these days , Im going to look into it , probably when school finishes , I will run some experiments , to see , condition new cells , or recondition old cells in any shape or form

9

Imho chinese cheap chargers are great if you use protected litio battery, because the only cons is that them usually over-volt or can broke keep charging and making burn/explode the battery(very remote case).

Litio are very solid but can be dangerous, on the other hand for nimh you need more care and a good smart charger to keep them healthy.

10

Can somebody also tell me how to recognize bad cells, by looking at there resting voltage?

I have some batteries, from a dead laptop....(not dead batterypack!) and would like to know if they are usable or not..
my TR001 only charged them up to 4.16-4.17V. (i dont know if my DMM is correct either)

If someone can give a link, then people dont have to explain it twice..

thanks

11

I noticed that my cheap charger charges at or outputs 600ma.

IF I get a charger that outputs 1 Amp- will this charge the batteries more quickly, and if so will it be 30 to 40% quicker?

Noticed an Ultrafire cheap dual charger that indicates 1 Amp.

12

High charger current will charge faster, but there are a couple of not as much faster as the current is higher.

With a CC/CV charger the charge phase is in two parts, first a CC (constant current), this part will be considerable faster. If you double the current, this phase will take less than half time.

The you have the CV (constant voltage), this is longer at higher charge current (because you reach the CV phase faster). How long it takes is also very much depend on the cutoff current, i.e. a charger that stops at 300mA will have a shorter CV phase, than one that stops at 100mA.

The above is only valid for chargers following a CC/CV charger curve, but very few chargers does that and on many cheap chargers you can not thrust the specified current either. You best bet is to find some reviews that uses comparable cells and see the actual charge time measured.

You could use the charger reviews on my website for that , the AW18650-22 cell I use has nearly the same capacity in all my measurements (albeit a low capacity).

13

Its very hard to determine that .. [ Cell condition ]

There are signs to watch for . but after charging and then discharging a bunch of 16340 ...

What to watch for =

Wont hold a charge , voltage drops faster than other batteries [ still not a sure sign ]

Sag after charging [ again not in any way 100% ]

To really sort out the crap from the crop so to speak , you need to discharge the cell , this is the only true way to tell ..

An example ..

I had a 16340 that charged to 4.2v and held it , voltage sagged very slowly over time [ as it should ]

There were no real warning signs that the cell had degraded , until discharged and the cell returned less than 200mAh capacity .

Originally it was maybe 530mAh , but after some 2 + years of light use , had degraded to under 200mAh

So if your hanging onto your batteries or trying to reclaim older batteries [ from laptops ] a hobby charger might be a invaluable tool to really know whats going on . [ running discharges ]

You dont need the most expensive , you just need one thats going to tell you what you need to know .

14

resting voltage will not always tell if you have a bad cell, discharging will, you can put them in a torch and gun them on high for a while then use a DMM but the best way would be to cycle them on a hobby charger, discharge and charge them a few times see how much mAh it give,s and takes and watch for voltage sag a bad cell will drop voltage quick once a load is put on it and maintained, the hobby charger will cutoff and stop if the cell,s voltage drops to low so there is no risk of over discharging.

the internal resistance of batteries play,s a big part in charging dishcarging and when people do current draw test on torches, imo cheap dedicated chargers would be affected by this more but thats mo.

ive tryed to bring back a couple of bad li-ion,s and li-po,s they dont realy come back i must admit i didnt spend much time on it but the mAh never improved and the the internal resistance only whent up and the li-po,s puffed, but ive been able to bring nimh back to life as my hobby charger has some good modes for that.

a good test to do is c rate,s over time say have 4 batteries with the same or close to internal resistance of each other and charge one at 0.2 amp one at 0.5amp one at 1 amp and the last one at 2 amp and then over time record the internal resistance and the amount of mAh they take.

ive noticed the battery charged at 0.2 amp will take more mAh and have a lower internal resistance then the one charged at 2 amp over time.

this is why parrallel charging in my mind is not the best as the cells spike quickly and dishcarge and charge each other at upto 2c + for li-ions even though its only for a short period i belive this will raise the internal resistance of the battery sorten its life and over time it will be able to give less current.

this is why i belive balance charging in series is better, but people want faster charge methods they want to charge one or two batteries at 1 + amps each unless they are top self batteries it will raise internal resistance of the batteries, i think your better off charging at lower charge rates like 0.5 amps yes it will take a little bit longer then charging at 1 amp but if you charge 6 at a time then its much quicker.

just my thoughts im half asleep

15

I would just like to confirm your results, I have noticed the same thing when testing batteries. I get them topped off completely with my TR-001 ~4.2v were my Accucell hobby charger leaves them a little off ~4.1v. I also get higher amperage readings from a battery that comes off the TR-001 compared to one that comes off the Accucell hobby charger. Thanks for confirming my suspicion.

16

E1320 i would do a test use the same charge rate on the Accucell hobby charger as the TR-001 and see how that turns out as i asume your using a higher charge rate on your hobby charger then your TR-001

i would also test your Accucell hobby charger as i found them like the imax,s to be off .04 volt + or - per cell and the voltage on the main charge leads to be the same.

if your Accucell hobby charger is saying the battery is 4.2v and it stops charging but you check it with your dmm and its 4.1 there is a good chance its not charging them to full and your TR-001 could be charging them to full or slightly over charging them.

this could also be why people are questioning there rested voltage of the cells after comming of there cheap hobby charger over charging (using to high amps) or inaccuracy or both

17

Thanks for the info!

18

To test your hobby charger !

Verify battery voltage first , let it rest for a while [ like 24 hours ] , then verify with MM ..

Now place in Hobby charger , what ever function you chose , it should test battery state [ voltage ] first and give a read out , before continuing with the function .

If the read out = MM then its calibrated correctly , if not , say its a little out , then you should be able to adjust the calibration [ iMax B6 can be adjusted ]

Unfortunately one cant program the charge cycle behavior . [ B6 ]

19

hey old is the imax b6 still a one shot deal with calibration

20

If mem serves , its a one shot thing for balance charging , for voltage calibration , as many times as it takes ...

21

I haven't fully read the following posts, but I Disagree with the OP on several points

  1. How Resting Voltage works, vs the way a cell is treated
  2. The overall concept of why true (CC/CV) vs emulated CC/CV is better
Lets start with some battery stuff.

Termination voltage. All chargers should be trying to aim for 4.20V finish, without Ever exceeding this voltage (we all agree here). A true CC/CV charger will have voltage measurement systems in place to monitor this voltage, and will always stay below this. Consequently, achieving a cell resting voltage of 4.20V is very difficult when you cannot exceed this. This is because the cell has an internal resistance (which as the old points out, applies in both charging and discharging states).

Charging - CC/CV technique.
The CC part is where a cell can be charged at its recommended charging current, without exceeding the max charge current. In this part of the cycle, the voltage rises. Until which time it reaches 4.20V per cell, then the charger will reduce current to the cell to maintain 4.20V. This is all governed by the internal resistance of the battery.

SO, if we applied 1.0A charging current to a cell at 3.00V, its internal resistance of 500mOhms will result in the voltage of the cell to Rise under charging load. Based on Ohms Law, this setup will result in a 0.5V increase, and the cell voltage rises to (3.00 + 0.50 = 3.50V). Once we remove the charge current the voltage will drop back down.

Lets say this cell now reaches a resting voltage of 3.70V. The same 1.0A charging current, will give the same 0.50V increase, so the voltage of the cell under the charging current will now reach (3.70 + 0.50 = 4.20V)

Beyond this, the resting voltage of the cell will continue to increase past 3.70V, but the actual voltage at the cell due to the charging current will continue to rise past 4.20V. So we must now Reduce the current to maintain a maximum cell voltage of 4.20V. At this point, we say the charger transitions from the CC mode to the CV mode.

If the cell now has a resting voltage of 4.00V, there is a certain amount of current that we can apply that will not exceed the charging voltage of 4.20V. A charge current of 0.40A will cause a voltage increase of 0.20V, and so at this instant, we can only be applying 0.40A charge. Our charger is slowing down so as to not exceed 4.20V, but accordingly will be give the cell less and less energy.
The key to this is --> as the charging current drops, the difference between cell resting voltage and cell charging voltage will get closer and closer, but will take longer and longer because were giving the cell less charging power.

SO... To achieve a resting voltage of 4.20V, if we extrapolated the graphs, we will see that as voltage difference tends to 0, charging current also tends to 0. What does this mean? - to get a resting voltage of 4.20V, we need our charger to charge for an infinite amount of time.

So again, lets put this down simply.
Because of the Internal Resistance of the battery, The ONLY way to achieve a resting voltage of 4.20V is to
a) While holding a charge voltage of 4.20V, apply a current that tends to 0mA, i.e. charge for an infinitely long time
b) Allow the charge voltage to go ABOVE 4.20V and terminate charge at a given current so that the cell resting voltage drops down to 4.20V

The number one rule of a True CC/CV charger is that it Never exceeds 4.20V, and because it usually terminates at a current above 0mA, (usually 1/10 charge rate), it CANNOT EVER give you a resting voltage of 4.20V.

So how does our budget a charger achieve a resting voltage of 4.20V??? Simple - It either charges for infinite amount of time, or it has allowed the cell voltage to exceed 4.20V
(remember, our cell protection circuits protect for over-voltage between 4.25 to 4.35V. It can stop huge over charging due to wrong chargers etc.. but it won't stop regular insidious overcharging with less accurately regulated chargers)

2) CC/CV charging profiles are the Ideal charging profile for lithium. Lithium cells that we commonly use, charge to a fully charged voltage of 4.20V. A cell at this voltage is safe, and this voltage Must not be exceeded at any time.

The CC part is where a cell can be charged at its recommended charging current, without exceeding the max charge current. In this part of the cycle, the voltage rises. Until which time it reaches 4.20V per cell, then the charger will reduce current to the cell to maintain 4.20V. This is all governed by the internal resistance of the battery.

*A budget charger doesn't have a true CC/CV profile, it only roughly emulates it, reducing current much earlier than necessary before the cell has even reached 4.20V. This is effectively means during the time in which a charger Can be very safely delivering charge power, the budget charger is already backing off. This period is also where charging time could be significantly reduced.
At the last part of charging, the CV phase, where the overcharging is done, the budget charger keeps going and as demonstrated above, Must be allowing a slight over-charge to achieve a 4.20V resting voltage.

So what does the budget charger give us? A Slower charge because its backing off too early, but an over-charged cell because its not truly regulating to a maximum 4.20V.

A resting voltage of 4.17 is therefor MUCH healthier than a resting voltage of 4.20V.

Lets have another example,
It is true that this voltage differential (and voltage settling) will occur with hobby chargers, simply because they usually terminate charge at 1/10 charge rate. A 0.5A charge will terminate at 50mA, and accordingly with a internal resistance of 500mOhms, this equates to a voltage increase of 0.02V.Therefore a charge that terminates at 4.20V, 0.05mA, will give a resting voltage of 4.18V.
If your budget charger that terminates at 50mA, gives a resting voltage of 4.20V, it must have terminated at 4.22V.
22

Ok the spaces have been lost in my post... (added spaces another way, formatting issue/quirk happened there due to a little glitch in the automatic spacing after playing around with dot points etc...)

Anyway, What I disagree with in particular are the arguments in the OP describing the "stressing" of a cell during charge, and "normalisation" of a cell.

Normalisation as I understand your description to mean, is describing how the resting voltage of the cell is able to stay at 4.20V following a charge. I.e. the difference between the charging voltage and the resting voltage is minimised. It was also mentioned that this will take an hour.

Your proof of "stressing" a cell argues that a cell that rests at 4.20V following a charge on the budget charger is proof that there is no voltage drop and therefore the lower charge current has been more gentle on the cell.

What the charger does to get the cell up into the 4.20V region does not influence the final resting voltage, simply because the hobby charger has a CV phase, which has the primary goal of allowing the cell to "normalise". Because of the high internal resistance of cells we normally use, even the hobby charger spends more than half its time in the CV phase, and it is during this time that current is reduced to the termination current. With a current that tends toward the same termination current, it will give no difference in settling time and the amount of settling off the charger. Cell health is a bigger determinant here, but thats another story.
So as demonstrated in my previous post, achieving a resting voltage of 4.20V is only possible if overcharged, or charged for an infinite about of time, and is additionally not relevant to the charging profile prior to the CV phase.
It was also mentioned was that a hobby charger charges too fast, 1A charging rate for a 16340 is too high for most cells, but at least with a hobby charger it can be set to any current, 100mA, 300mA, 500mA. 1A is not the only current that hobby chargers can charge at, it is up to the user to set the current.
23

Very informative and useful , okwchin . Thanks .