Consumer Li-Ion "cradle" charger roundup...

[leukos]

If you want to charge cells one at a time, batteryspace has a few such as this one with CC/CV for $10: http://www.batteryspace.com/smartcharger15afor37vli-ionpolymerrechargeablebatterypack--celisted.aspx

 

[KiwiMark]

The Million Dollar Question:

Anyone tested one of the cheap popular hobby chargers to ensure that they are terminating correctly?

My Turnigy Accucel 6 & Accucel 8 both seem to terminate correctly. After the CC stage they use CV until the amperage drops below 1/10 of the starting amount, so if you charge a 32600 at 2A then once the charging current drops below 0.2A the charger will completely stop the charge process and indicate that charging is complete with no trickle charge happening.

 

[mdocod]

Hello LEDadd1ct,

I didn't even know about the shekor until a couple days ago when someone here in a thread pointed it out. The graph they have posted on the sales page for this charger on e-lectronics looks very good and if it's true, then this would probably be the holy grail of cheap chargers we have been looking for.

Hopefully I'll have an opportunity to test one sometime.

------------------

Hello leukos,

The charger you have linked to, says right in the product specifications PDF that the output is a clamped standby of 4.20V+/-1%, it also specifically mentions that the light "turns green" when current drops to 150mA but does not say anything about termination.

On the product sales page, it says that it holds CV until current drops to 0, then terminates, well, holding a CV on a cell will always result in some current to hold the cell at that voltage, in other words, it won't ever terminate.

At least they are honest 🙂

-------------------

KiwiMark,

That's excellent to hear. Thank You!

Eric

 

[hazna]

I notice you don't like the nano-charger. I have been using them to charge smaller cells such as 10180. My experience with them is they drop in charge current as the battery fills. Light turns green before 4.20V (~4.15V), but continues to charge at a low rate ~20-30mA. When it reaches 4.19-4.20V, there is continual trickle charge of ~3mA. ~3mA seems like its such a low trickle charge, will it actually be bad for the cell (if you take it off within a few hours)?

Please I'm using a cheap DMM, so my measurements might not be 100% accurate.

 

[mdocod]

Hello hazna!

The behavior you have just described is identical to the behavior I have just tested in the YOHO-122, and both Cytac chargers. The measurements you have just taken show that the charger never terminates and will feed whatever current is required to try to hold a cell at 4.20V. I seem to recall on the nano that I was testing, that the clamp voltage was much higher than 4.20V though.

On my YOHO-122, the current flowing into an 18500 to hold 4.20V was just 2.5mA give or take.

This doesn't seem like a big deal, but the effects of this type of charger on an older more worn out cell, especially if the user allows the cell to stay on the charger for long periods of time, could be very dangerous.

The 3mA rate required to hold it at 4.20V now, will some day be 10mA, after that, eventually maybe 20mA. As the cell ages, the current required to hold a charge voltage on it will increase.

Any form of trickle charging on a li-ion cell is considered bad.

If a user comes along and always makes sure to manually remove a cell shortly after the light "turns green" or "goes solid" or whatever on one of these chargers, then the poor design of the charger will have been offset by user intervention. If you can trust yourself to do this, then that is fine, but would you give this to a family member?

Eric

 

[DHart]

Everything involves pluses and minuses, and compromises between opposing factors.

So true about just about everything in life, isn't it! There's something that must be given up for everything you gain.

If a user comes along and always makes sure to manually remove a cell shortly after the light "turns green" or "goes solid" or whatever on one of these chargers, then the poor design of the charger will have been offset by user intervention. If you can trust yourself to do this, then that is fine, but would you give this to a family member? Eric

Eric... sage consideration... li-ions and flashlights are a wonderful godsend for the highly conscientious light nut (they're all I use, generally speaking), but not likely a good recommendation for anyone who isn't really conscientious about such things.

 

[mdocod]

3 more chargers added to the list of reviews.

 

[Superorb]

This is an awesome thread, keep up the great work!

I've got a DX SKU.6105 and noticed that the voltage keeps climbing after the light turns green. Is there a way to measure charge current with my DMM? I've been pulling them from the charger once it turns green.

 

[mdocod]

Hello Superorb,

Great question!

Yes, there is a way to measure the trickle rate.

When I test these chargers, I purposely use 18500 size cells instead of 18650s because it makes it much easier to complete the circuit with a DMM for testing current. With an 18650, it can be harder, often requiring an external fixture to get the circuit setup through the DMM.

The way this is done, is to move the test lead to the "10A" or "20A" plug on the DMM, then set the DMM to the corresponding setting.

In order to measure current, you have to have the DMM in SERIES with the circuit. Putting it in parallel is a good way to short things out and cause damage to cells, DMMs, and chargers, so be very careful and think through how you are going to do this to get a series connection.

The way I do it with the 18500 size cells, is to just put the 18500 size cell in the slot, and then push/hold one test lead against the back of the cell, such that the front of the cell is held against the positive contact in the charger, and then take the other test lead and hold it to the negative spring good and tight, this creates a series circuit where the charger is charging the cell "through" the DMM as part of the electrical path. This way I can see the current flowing. (the 50mm length cell does not "reach" the spring, so the only place for electricity to flow when I do this is through the DMM).

The 6105 that I tested will trickle cells to ~4.24-4.26V and hold them there if left unattended.


Eric

 

[Superorb]

Hello Superorb,

Great question!

Yes, there is a way to measure the trickle rate.

When I test these chargers, I purposely use 18500 size cells instead of 18650s because it makes it much easier to complete the circuit with a DMM for testing current. With an 18650, it can be harder, often requiring an external fixture to get the circuit setup through the DMM.

The way this is done, is to move the test lead to the "10A" or "20A" plug on the DMM, then set the DMM to the corresponding setting.

In order to measure current, you have to have the DMM in SERIES with the circuit. Putting it in parallel is a good way to short things out and cause damage to cells, DMMs, and chargers, so be very careful and think through how you are going to do this to get a series connection.

The way I do it with the 18500 size cells, is to just put the 18500 size cell in the slot, and then push/hold one test lead against the back of the cell, such that the front of the cell is held against the positive contact in the charger, and then take the other test lead and hold it to the negative spring good and tight, this creates a series circuit where the charger is charging the cell "through" the DMM as part of the electrical path. This way I can see the current flowing. (the 50mm length cell does not "reach" the spring, so the only place for electricity to flow when I do this is through the DMM).

The 6105 that I tested will trickle cells to ~4.24-4.26V and hold them there if left unattended.


Eric

Thanks. 4.25v was as high as I let mine get before pulling. I'm trying to think of an easier way to monitor voltage of the charging cells without cramming the probes between charger contacts and the cell.

 

[recDNA]

Thanks. 4.25v was as high as I let mine get before pulling. I'm trying to think of an easier way to monitor voltage of the charging cells without cramming the probes between charger contacts and the cell.

Would copper tape or aluminum foil wrapped around the probes and inserted between the charger leads and battery work? I don't want to blow up my battery trying to be super safe!

 

[Bullzeyebill]

Scroll through this DMM instruction thread and you will find out how to monitor your charging. http://www.candlepowerforums.com/vb/showthread.php?t=236906

Bill

 

[Superorb]

Scroll through this DMM instruction thread and you will find out how to monitor your charging. http://www.candlepowerforums.com/vb/showthread.php?t=236906

Bill

Awesome, thanks!

 

[recDNA]

Scroll through this DMM instruction thread and you will find out how to monitor your charging. http://www.candlepowerforums.com/vb/showthread.php?t=236906

Bill

Hey - I guessed RIGHT! LOL That's a first.

 

[mdocod]

Good idea 🙂

 

[sandysim]

Hi all

I bought a Cytac CY015 from 47s and can confirm that even after the green light comes on, i measured a steady current of about 13mAs flowing thru the 16340. For info, with no batteries in the bay, the voltage across the terminals is 4.23V. I did feel it charges my 18650s rather slowly though.

Sandy

 

[pae77]

I received one of the Trustfire 001's from DX last week, so it is likely a recent version. I used it to charge 2 new (never before charged by me) AW unprotected 10440's, one in each of the chargers two slots. It took about an hour for the LED's on the two slots to go from red (charging) to green (trickle, I assume). I pulled the cells from the charger as soon as the LED's turned green.

Since I don't presently own a DMM, I measured the voltage of each cell in my LF2XT, which has a function for that. Since the light has to be on to engage the voltage measurement function, the cells were under a slight load (on low) while the voltage was being measured. The results were that the battery in Slot 1 measured 4.12 volts and the one in Slot 2 measured 4.16 volts. Both cells stayed nice and cool throughout the entire charging process.

I realize that this is not a lot of data to go on and I understand that this charger is potentially dangerous and could also cause unnecessary wear/damage to cells left in the charger after the LED's turn green because of its failure to completely terminate when the LEDs go green, and that the charging algorithm is likely not ideal.

Nevertheless, am I correct in concluding that it appears that so long as I pull the cells within a few minutes or so of the LEDs turning green, that this charger appears to be safely charging my cells to a voltage that will likely promote long cell life, assuming the cells are not over discharged or otherwise abused?

 

[45/70]

Nevertheless, am I correct in concluding that it appears that so long as I pull the cells within a few minutes or so of the LEDs turning green, that this charger appears to be safely charging my cells to a voltage that will likely promote long cell life, assuming the cells are not over discharged or otherwise abused?

The biggest problem with using the TR-001 to charge a 10440, is that if it actually charges at 500mA as they say it does, you're dumping about 67% more current into that little 10440 (~300mAh cell, regardless of what it says on the side) than is recommended. Most likely it's not going to blow up or anything, but the cycle life of the cell will be shortened.

As for any of these chargers that don't use a proper algorithm, yes the best thing to do is pull the cells when charge termination is indicated. Personally, I wouldn't charge 10440's in the TR-001. If you want to go cheap for cells 600-700mAh or less in capacity, down to about 200mAh, go with one of these. They aren't perfect by any means, but they're built fairly well and the "trickle" charge is so small that it's not a major problem, however is still an undesirable aspect. Here's a post by wapkil describing how the charger works, from this thread.

Dave

 

[pae77]

I'm about to look at the links you posted, but I just wanted to say that my understanding is the TR001 doesn't really charge at the 500 mA rate indicated on the label. According to what I've read, lots of reviews mention that it is "slow" and at least one person who claims to have measured it said the charge rate adjusts depending on what type batteries are being charged. But I am going to get a DMM in the near future and attempt to check it for myself. At the moment, with my rather limited testing equipment (i.e., the LF2XT), all I can check is the voltage of 10440's after I pull them off the charger when the LED's have turned green. (I'll probably order a DMM from DX so it will take several weeks before I have one in my possession.)

Anyway, fweimbw, here's what one person who claims to have measured it had to say in a review at DX: http://www.dealextreme.com/details.dx/sku.12594

"I received it few weeks ago, and today (22.03.2009) I tested. It seems that has been fixed over-charging problem with the right slot. not necessary to add 2 x 4V3 zener diodes to limit charging over 4.2V! Now is working by default!
1st: 2 x 10440 Li-Ion accu partially charged (at 3.7 and 3.8V). I measured charging current and is 27-30mA on booth slots. When charging leds are RED. After 1.5H, booth leds become GREEN. I measured voltage and booth 10440! Now, have 4.2V! Super ok!
2nd: 2 x 14500 Li-Ion accu partially charged (at 3.7V booth). I measured charging current and is 65-68mA on booth slots. When charging leds are RED. After 3H, booth leds become GREEN. I measured again voltage and booth we have 4.2V! Super ok!
Cons: Not really a cons. I observed that metal spangles which holds battery are to flexible. In some circumstances may be ok, but in general, not! They should be a little sturdy/rigid! When you are inserting cells, spangles can be deformed!

Other Thoughts: They rated it at 500mA. It isn't. In my case is not a cons. I ordered for my 10440 unprotected cells. It should be charged at lower rates (less than 200mA), so 30mA is ideal. No matter that the charging time will be longer. This lower current is ideal!"

 

[mfm]

1st: 2 x 10440 Li-Ion accu partially charged (at 3.7 and 3.8V). I measured charging current and is 27-30mA on booth slots. When charging leds are RED. After 1.5H, booth leds become GREEN. I measured voltage and booth 10440! Now, have 4.2V! Super ok!
2nd: 2 x 14500 Li-Ion accu partially charged (at 3.7V booth). I measured charging current and is 65-68mA on booth slots. When charging leds are RED. After 3H, booth leds become GREEN. I measured again voltage and booth we have 4.2V! Super ok!

Do the math (charge current * time versus cell capacity) and you'll see that his measurements are quite off.