Need some charging advice (Eneloop and Duracell 2650).

[Bobo The Bear]

Long time lurker, first time poster. I've been looking for some type of "charging FAQ" but did not see one.

I'm just getting into the rechargeable battery scene after seeing my 4 year old burn through alkalines with all his toys.

I have a La Crosse BC-900 which I'm pretty happy with. I'll probably get a Maha C9000 someday, but not anytime soon. I use Duracell 2650 mah non-LSD rechargeables and Eneloop 2000 mah LSDs, depending on the application (nothing fancy, toys, remotes, etc.).

My question is pretty simple, what's the correct charging (and discharging) rate for these?

Everything I've read prior to discovering these forums is that lower is better. Heat is bad. So I've been charging everything at 200 ma (and discharging at 100 ma). Printed on the sides of my Duracell 2650s it even says "Standard charge 270mA for 16h". It takes forever but I'm in no rush.

After spending a couple days doing searches on "Eneloop" I'm reading different now. I see people recommending charging at 0.5C to 1.0C which if I understand correctly means 1000 to 2000 mah for the Eneloops and 1325 to 2650 mah for my Duracells. Is this correct?

While I'd love for this to be true (I could recharge more batteries in less time) it kinda goes against everything I've heard up to now.

Thanks for any insight.

 

[Mr Happy]

What you have read about charging at 0.5C to 1.0C is correct, but with provisos.

The "standard charge" is 0.1C for 16 hours, and this is used to measure the standard capacity of the cell, and when coupled with a slow discharge can be sometimes be used to recover older cells that are no longer performing well. This charge is always safe, and only requires a timer to decide when to stop charging.

The normal rate for everyday charging is a fast charge up to 1.0C, but this requires an accurate means of charge termination so the batteries do not get overcharged. If the charge is not stopped at the right time with such a high rate, then the batteries will overheat quickly and can be damaged.

Chargers like the BC-900 have a good system for stopping the charge at the right time, so it is quite safe to use higher charging rates with that charger. You may want to watch the progress and feel the temperature of the batteries the first time just to satisfy yourself that everything is working OK. It is normal for batteries to get warm to the touch at the end of the charge, even slightly hot, but no more (say about 100 F).

[Edit: I should mention that there is not really a good middle ground. Either a slow charge of 0.1C, or a fast charge of 0.5C or greater should be used. The danger with a charge rate somewhere in the middle is that sometimes the end of charge signal produced by the batteries may be too weak for the charger to detect it, but the charging current is still high enough to overheat the batteries and damage them if the end of charge signal should be missed.]

 

[Bobo The Bear]

Thank you very much for the post. This is good news for me. I can start charging both my Eneloops and Duracells at 1000 mah now. Would this be a big problem for my 2650 Duracells? It's either 1000 or 1500.

[Edit: I should mention that there is not really a good middle ground. Either a slow charge of 0.1C, or a fast charge of 0.5C or greater should be used. The danger with a charge rate somewhere in the middle is that sometimes the end of charge signal produced by the batteries may be too weak for the charger to detect it, but the charging current is still high enough to overheat the batteries and damage them if the end of charge signal should be missed.]

How real of a problem is this? Sometimes I like to charge a set before I go to bed or before I go to work. I'd prefer not to have to watch these charge.

 

[Mr Happy]

How real of a problem is this? Sometimes I like to charge a set before I go to bed or before I go to work. I'd prefer not to have to watch these charge.

I'm not sure I can say for sure. I don't own a BC-900 myself. I believe there have been some reports of the very early models having overheating problems, but the later ones seem to be fine.

Missed charge termination is something that tends to be more likely with older cells that are in poor condition, and when using lower charging currents. As long as you use the 1000 mA or 1500 mA charge you should be good. In any case, it would always be advisable to put the charger in a location that won't be damaged by heat if something did go wrong.

(Just FYI, Sanyo makes a charger specially for Eneloops that uses a 2000 mA charging rate.)

 

[45/70]

I charge my AA's at 1000mA most of the time with the BC-900. In the summer when it's really hot, I use 700mA. Just a personal preference. 1500/1800 seems to get the cells hotter than I care for and, of course, there's the inconvenience of only being able to charge two cells at a time.

Dave

 

[Bobo The Bear]

Great stuff guys, thanks. At the 1000 mah charge rate I'll just stop doing overnight charges.

In any case, it would always be advisable to put the charger in a location that won't be damaged by heat if something did go wrong.

Hmm, I better move my charger away from my wife's Faberge egg collection...

 

[coppertrail]

I charge my cells between .5 and .6 C. If I'm in a hurry I might bump it up to 1C, but this is a rarity. I discharge at .2C when putting them through a discharge cycle.

 

[jpmacg]

Is it acceptable to charge eneloops at 0.1 C or is it actually better for the cells to charge them at 0.5 to 1C? I would like to charge at 0.1 c as that is the charger I have on hand. I don't mind charging for 14 hours or so.

 

[SilverFox]

Hello Jpmacq,

Welcome to CPF.

No problem at all. The standard charge is 0.1C for 16 hours. With Eneloop cells that amounts to charging at 200 mA.

Tom

 

[abhi555]

Hello Jpmacq,

Welcome to CPF.

No problem at all. The standard charge is 0.1C for 16 hours. With Eneloop cells that amounts to charging at 200 mA.

Tom

hi Tom,

Is there any harm charging NiMH below 0.1C (in smart charger)?
What are the condition when sensors gets strong delta v, tempt signals?
I will also like to know your openion about
1. cutoff when there is certain voltage is achieved and hold by battery for certain time ("hot" in the charger)
2. necessity of trickle charge for LSDs/regular NiMH.

Thanks,
Abhi

 

[SilverFox]

Hello Abhi,

Welcome to CPF.

There is no problem charging at below 0.1C as long as you terminate the charge on time. You can do harm if the cell is left to charge at 0.1C for an extended period of time. GP states that their cells can handle a continuous 0.1C charge for a year, but after that the cells should be replaced.

Under normal conditions, there is no damage done during a 16 hour charge at 0.1C. If you charge at less than that you would have to adjust the time accordingly.

The battery manufacturers have stated that in order to get a reliable and strong -dV charge termination signal you should charge in the 0.5 - 1.0C range.

Normal charge termination using peak voltage doesn't hold the cell at the peak voltage, but once the peak voltage is reached, the charge is terminated. Hooking the cell up to a power supply and holding a maximum voltage can cause some damage to the cell depending on what voltage you choose to hold at.

Trickle charging is another way to cook your cells. A short term trickle charge is OK, but leaving cells on the charger in an effort to make sure they are always ready to go will result in redyced cycle life from your cells.

With that said, there are some chargers that are designed for the LSD cells and they have very low trickle charge rates. LSD cells can be damaged from normal trickle charge rates, and these very low trickle charge rate chargers are very kind to these cells.

These chargers include the Maha 8XX series and the Maha C9000.

Tom

 

[krayzeemofo]

Hi, I've been reading through the forums for a while now and just now decided to register. I was going to make a separate thread but this topic matches what I was after .

Since recommended charging rates are 0.1C or 0.5C-1.0C, does that mean that I should not use Sanyo's own MQN06 charger as it charges at 300mA for AA (0.15C)?

Thanks in advance

 

[Bones]

...

Since recommended charging rates are 0.1C or 0.5C-1.0C, does that mean that I should not use Sanyo's own MQN06 charger as it charges at 300mA for AA (0.15C)?

...

There are better choices than the MQN06 krayzeemofo. Not because of its charge rate, however, but because it's a two-channel, four-place charger. This means that it requires two cells to complete one of its charging circuits. In turn, this causes it to overcharge the first cell to reach a fully charged state in order to finish charging the second. Fortunately, its charge rate is low enough that the overcharge shouldn't harm the first cell during the time it takes to finish charging the second.

There are currently two four-place chargers bundled with the Eneloop that are also equipped with four independent charging channels. The MQN05 and the MQH03. I consider both to be first-rate choices to charge your Eneloops, with the advantage going to the MQH03 for the reasons set out in the linked post.

Incidentally, there is nothing inherently wrong with charging at less than .5C. The only real deterrent is that at lower charge rates, the detection of a fully charged state becomes more problematic. As long as your charger can reliably detect when to terminate its charge, the lower rates are perfectly acceptable, and may even be desirable. Lower rates tend to create less heat while imparting a more complete charge.

As well, Sanyo recommends against charging the Eneloop at rates above .5C in item 12 of its Eneloop Q & A:

Can I use a "Quick Charger" to charge an eneloop battery?

Though it is possible to charge an eneloop battery in a "Quick Charger", it is not recommended. We recommend charging eneloop batteries in a NiMh charger that is 2 hours or more. Charging eneloop batteries in a "Quick Charger" can reduce the overall life of the battery.

Anyway, I wouldn't hesitate to use the MQN06, but would also look for a replacement with fully independent channels should time and circumstances permit.

 

[Mr Happy]

As well, Sanyo recommends against charging the Eneloop at rates above .5C in item 12 of its Eneloop Q & A

Oddly, this is somewhat at variance with the existence of Sanyo's own 1-hour charger bundled with Eneloops: http://www.costco.ca/Browse/Product.aspx?Prodid=10317279

Maybe it's a case of one hand not quite knowing what the other hand is doing? :thinking:

I think on balance though, there is no problem charging Eneloops at a 1-hour rate if the charger is well designed. Even the Eneloop AA data sheet gives 2000 mA as a recommended charge rate.

It's a real pity that Costco bundle is not more widely available outside Canada.

 

[krayzeemofo]

Thanks for the reply Bones .

There are better choices than the MQN06 krayzeemofo. Not because of its charge rate, however, but because it's a two-channel, four-place charger. This means that it requires two cells to complete one of its charging circuits. In turn, this causes it to overcharge the first cell to reach a fully charged state in order to finish charging the second. Fortunately, its charge rate is low enough that the overcharge shouldn't harm the first cell during the time it takes to finish charging the second.

There are currently two four-place chargers bundled with the Eneloop that are also equipped with four independent charging channels. The MQN05 and the MQH03. I consider both to be first-rate choices to charge your Eneloops, with the advantage going to the MQH03 for the reasons set out in the linked post.

So...is it not possible to charge 1 cell at a time?

It was actually after I read the thread you linked to that made me wonder about the MQN06; actually it was that original thread (about the MQH03) which made me want to get the family pack in the first place .

Incidentally, there is nothing inherently wrong with charging at less than .5C. The only real deterrent is that at lower charge rates, the detection of a fully charged state becomes more problematic. As long as your charger can reliably detect when to terminate its charge, the lower rates are perfectly acceptable, and may even be desirable. Lower rates tend to create less heat while imparting a more complete charge.

As well, Sanyo recommends against charging the Eneloop at rates above .5C in item 12 of its Eneloop Q & A:

Hm, perhaps I have missed something; doesn't the MQH03 charge in 1 hour, thus at 2A? If so, then doesn't that mean that Sanyo's own charger doesn't meet, or rather exceeds, the recommended charge rate?

Anyway, I wouldn't hesitate to use the MQN06, but would also look for a replacement with fully independent channels should time and circumstances permit.

Ya, I have been looking around a bit and it seems that I will go with either the Maha C9000 (~$77 CAD), La Crosse BC900 (~$60 CAD), or the Eneloop Power Pack in the MQH03 thread (currently ~$65 CAD) - all prices are after shipping.

Any suggestions?

Thanks again

 

[Bones]

...

So...is it not possible to charge 1 cell at a time?

...

Not to my knowledge with the MQN06, but it won't hurt anything to try. Be sure to let us know if it works though. It's not impossible that Sanyo has issued an upgraded version.

...

Hm, perhaps I have missed something; doesn't the MQH03 charge in 1 hour, thus at 2A? If so, then doesn't that mean that Sanyo's own charger doesn't meet, or rather exceeds, the recommended charge rate?

...

I suppose from Sanyo's point of view, if a customer insists on charging the Eneloop at rates greater than .5C, it's preferable that it be done with their charger. They, rather than a competitor, may as well get the profit from the sale if a customer is going to be purchasing one anyway.

However, I also like to think that because they know the characteristics of the Eneloop under charge far better than anyone else, they were able to design the MQH03 to minimize the damage at rates above .5C, and prefer that it be used for this reason as well.

It should also be noted that the MQH03 can still charge any combination of cells at its lower charge rate. As long as at least one cell is inserted in an inner bay, all bays will default to a .5C rate of charge for the Eneloop.

...

Ya, I have been looking around a bit and it seems that I will go with either the Maha C9000 (~$77 CAD), La Crosse BC900 (~$60 CAD), or the Eneloop Power Pack in the MQH03 thread (currently ~$65 CAD) - all prices are after shipping.

...

In an ideal world, I would go with an MQH03 and an MH-C9000. I honestly don't believe there is a better charger for the Eneloop than the MQH03, but the forming and analytical functions of the MH-C9000 are also necessary to maximize the performance and longevity or your cells. Besides, when you consider that a break-in (or forming) charge necessarily takes upwards of three days on the MH-C9000, you're going to want an alternate charger anyway.

As noted in my post on the MQH03, it's currently selling in a bundle at Costco stores for 39.49 CAD, but depending on where you are, you can also get delivery included with a much larger bundle online for 64.99 by Costo.ca.

 

[Power User]

Can I charge Eneloop AAA battery (800mAh) using 45mA charging rate?
I only have this old charger on hand.
I intend to charge only fully discharged battery and prepare to manually stop the charger when the charging completes.
What is the appropriate charging time?
Will there be damage to the battery for frequent prolonged charging (without overcharge)?

 

[mfm]

Incidentally, there is nothing inherently wrong with charging at less than .5C.

As you can learn on Battery University, 1C[FONT=Verdana, Arial, Helvetica, sans-serif] charging is preferred because of reduced crystalline formation (memory). [/FONT]http://www.batteryuniversity.com/partone-11.htm

As well, Sanyo recommends against charging the Eneloop at rates above .5C in item 12 of its Eneloop Q & A

That is an old FAQ entry written by someone in the marketing department (probably outside Japan). It is also someone else than the engineers that decided that they should make slow chargers.

The engineering department already wrote "Datasheet for Sanyo Twicell Type HR-3UTG" that states that 1C is the recommended charge rate.

With the new NC-TGR01 Eneloop charger released at the same time as the 1500 cycle eneloops (HR-3UTGA) it is possible to charge one AA Eneloop in 75 minutes and one AAA Eneloop in 65 minutes. If it wasn't a matter of cost, all Eneloop chargers would charge all cells that fast.

 

[Mr Happy]

As you can learn on Battery University, 1C[FONT=Verdana, Arial, Helvetica, sans-serif] charging is preferred because of reduced crystalline formation (memory). [/FONT]http://www.batteryuniversity.com/partone-11.htm

Against this is the fact (verified several times in my experience) that a forming charge (0.1C x 16 h) is the only thing to remove high internal resistance in an Eneloop and restore the cell to full performance in cases where any number of refresh cycles at higher charge rates has failed to do so.

There may certainly be a difference here between NiCd and NiMH chemistry, and between traditional and low self-discharge NiMH chemistry. Battery University does not speak to low self-discharge cells, being written before they were introduced.

 

[mfm]

Against this is the fact (verified several times in my experience) that a forming charge (0.1C x 16 h) is the only thing to remove high internal resistance in an Eneloop and restore the cell to full performance in cases where any number of refresh cycles at higher charge rates has failed to do so.

That is a special case, battery university talks about charging in general.

The misconception about "gentle charging" is surely not from peoples personal experience with Eneloops that have developed a high internal resistance but rather an old urban myth. I also haven't read anyone here saying that fast charging is good for normal NiMH but not LSD.

And even if we assume that everything on battery university is wrong, both my and your testing have concluded that 1C charging is better than slow charging.

I'm sure a timed forming charge can be useful maintenance, but thats not what people use anyway.