Sanyo Eneloop batteries - charging and analyzing questions

[Handruin]

I just recently purchased some new Eneloop XX AA 2500 mAh batteries to replace and add on to some of my aging AA Eneloops 2000 mAh. Since I have many more batteries now, I decided to also get another charger. I purchased the Powerex MH-C9000 charger figuring it would give me another charger to charge more cells in parallel plus this one also does analysis on the cells to help me match them in groups of four and to test the older cells that I have laying around. I have a few questions to see what feedback some of you might be able to provide.

First, is 1000 mAh charging rate reasonable for the 2500 mAh Eneloops? What about the 2000 mAh cells?

When I perform the analysis of the cells I set the charge rate to 1000 mAh and the discharge to 500 mAh. Should I be testing with different rates for this exercise? The test supposedly waits 2 hours in-between each charge and discharge cycle to allow the cells to cool down.

On the new Eneloop 2500 mAh cells I'm seeing the analyzed rate around 2330 mAh (give or take a few mAh). All the cells I've been able to test so far are pretty much in this range. Sanyo claims minimum 2400 mAh and maximum 2500 mAh. Are the values I'm seeing reasonable or expected? The documentation does say +/-5% of the rated capacity which means these numbers fit if I go with the minimum capacity of 2400 mAh. That puts me in -3% capacity...but if I use the 2500 mAh capacity it's about -6.8% of capacity. I analyzed the new cells right out of the package. They haven't been used or charged prior to the test.

 

[LunarMist]

I just recently purchased some new Eneloop XX AA 2500 mAh batteries to replace and add on to some of my aging AA Eneloops 2000 mAh. Since I have many more batteries now, I decided to also get another charger. I purchased the Powerex MH-C9000 charger figuring it would give me another charger to charge more cells in parallel plus this one also does analysis on the cells to help me match them in groups of four and to test the older cells that I have laying around. I have a few questions to see what feedback some of you might be able to provide.

First, is 1000 mAh charging rate reasonable for the 2500 mAh Eneloops? What about the 2000 mAh cells?

When I perform the analysis of the cells I set the charge rate to 1000 mAh and the discharge to 500 mAh. Should I be testing with different rates for this exercise? The test supposedly waits 2 hours in-between each charge and discharge cycle to allow the cells to cool down.

On the new Eneloop 2500 mAh cells I'm seeing the analyzed rate around 2330 mAh (give or take a few mAh). All the cells I've been able to test so far are pretty much in this range. Sanyo claims minimum 2400 mAh and maximum 2500 mAh. Are the values I'm seeing reasonable or expected? The documentation does say +/-5% of the rated capacity which means these numbers fit if I go with the minimum capacity of 2400 mAh. That puts me in -3% capacity...but if I use the 2500 mAh capacity it's about -6.8% of capacity. I analyzed the new cells right out of the package. They haven't been used or charged prior to the test.

Those charge/discharge rates are reasonable. However, if the batteries will be charged in a warm environment you may want to use a small fan.
The capacities will vary bit and the charger is probably not calibrated to a NIST traceable standard. IOW, just use them and don't get too crazy.

 

[jtr1962]

I tend to charge my 2000 mAh Eneloops at 600 or 700 mA. This is gentler on the cells than the default 1000 mA. I also have some Duracell ion-core cells (the made in Japan ones are most likely rebranded Eneloop XXs). I usually use 1000 mA for these, although lower currents work fine. The MH-C9000 terminates using either negative delta V or voltage (1.47V). Eneloops typically are a few hundreths of a volt higher than most other NiMH, so they usually end up terminating by voltage. This means I don't need to worry about setting the charge current high enough so the charger gets a reliable -dV signal. Note that once the fast charging terminates, the cell gets a topping charge of 100 mA for the next 2 hours. That's why the voltage on cells which are "DONE" will continue to rise.

As far as capacity, there's only one reliable, consistent way to determine true capacity-use the break-in function. Yes, it typically takes 39 hours, but it uses the standard IEC algorithm to determine cell capacity. In truth, the MH-C9000 does things slightly differently than the IEC algorithm (it uses pulsed charge/discharge) but the capacity calculation is reasonably close. I'll guess that you might see an extra 100 to 150 mAh using the break-in cycle. Refresh/analyze typically gives lower values because you really can't top off a cell completely in less than about 16 hours.

 

[mubs]

In general, charge at 33% or 35% nominal (not minimum) capacity, and discharge at 25%. This slow charging puts in more of a charge and keeps the batteries cooler. But: older / infrequently used cells need a higher charge to break up crystallization which won't get broken up with a lower charge rate.

I spent way too much time on this topic a few months back. I can provide you some info I;ve gathered in the form of Word docs. Do PMs allow attachments?

 

[Handruin]

Thanks everyone for the feedback on this. I've done the base analysis using the 1000mAh/500mAh for charge/discharge on all the new cells and they all seem to be within <0.1% difference from each other for capacity. Even if the absolute value I'm seeing isn't consistent with what is advertised I can at least see the cells are all consistent and seemingly healthy.

mubs, I had read similar info that I should be charging at 33% of nominal capacity but I couldn't tell if this was recommended universally. Since these batteries discharge so slow, I don't see any issue using that guidance and it fits inline with the charging rates jtr suggested. I didn't know that Eneloops had crystallization. I thought NiCd had that issue? I'd be interested in the info you have. I don't think the PMs allow word attachments. Do you use or have a google docs account? Maybe put it there and send me a shared link? If that doesn't work I can figure out another way.

I'll probably base my charging rates like these. I rounded my numbers a bit but it fits close to 33%.

Charge:
AA 2500 mAh @ 800 mAh
AA 2000 mAh @ 600 mAh
AAA 800 mAh @ 300 mAh

 

[Stereodude]

I've already heard that you want to charge good NiMH batteries at 1C because at lower charge rates the deltaV detection may not work correctly.

 

[Handruin]

I've already heard that you want to charge good NiMH batteries at 1C because at lower charge rates the deltaV detection may not work correctly.

I also thought I read that newer version of the MH-C9000 fixed that issue with poor deltaV detection?

 

[Tannin]

A very interesting thread, gentlemen. I've had an MH-C9000 for quite a while - 5 or 6 years maybe? - and I've nearly always just used the default charge values. The only batteries I've run the refresh/discharge cycles on is the motely collection of ancient high-self-discharge (I forget what you call them, not the new LSD ones anyway) Evereadys, all mismatched and with different specs. (My newer batteries - all LSD types of numerous different brands, I just charge in the ordinary way at the default settings.) The crappy old Evereadys, which seemed to be not worth keeping, spruced themselves up a bit after a couple of good cycles, and - more importantly - I was able to sort them into sets of roughly equal charge capacity (ignoring their printed nominal capacities). Those sorted sets have done good duty in various low-priority applications: torches, radios, GPS, a few other things - and are still useful now that no set has a single bad battery to drag all the others down. Yep, new ones would be better, but these are good enough and I hate to throw out stuff that still works. I reserve the newer LSD cells for the important stuff, mainly camera flashguns.

As for battery brands, I've not observed a great deal of difference in the newer ones, and (don't laugh!) I mostly buy not by brand but by colour - I try to avoid getting any two sets of four the same brand and colour, 'coz otherwise it's too hard to remember which goes with which! I once saw a packet of 20 Eneloops - by chance, just about the only brand I don't have - in five different rainbow colours on special at some brilliant price, but by the time I got there they had sold out and only had plain-coloured ones, and I don't want five sets all the same colour.

Ahh ... the trivial things that cause the wallet to come out of or stay in the pocket! It's just as well we have Mubs and JTR here to lift the technical content of the thread up to something reasonable.

I daresay Tea will be along shortly to inform me that a single cell - an AA for example - is not a "battery" and I should say "cell" for one and use "battery" only for two or more. (To which I will say "So sue me.")

 

[mubs]

I didn't know that Eneloops had crystallization. I thought NiCd had that issue? I'd be interested in the info you have. I don't think the PMs allow word attachments. Do you use or have a google docs account? Maybe put it there and send me a shared link? If that doesn't work I can figure out another way.

I've read that if a cell is just sitting around for months/years, it will eventually develop crystallization. I have some Eneloops that have sat around; I tend to recharge and reuse the same two or three sets.

Oddly, I found that I had 8 brand new AA and AAA Eneloops purchased more than 6 years ago, left untouched. After multiple Break-in & Refresh & Analyze cycles, the AAAs are at nominal capacity, the AAs are at minimal capacity. Go figure.

I have a Gmail account, but don't use it and don't have a Google docs account. Maybe I'll open one now. I'll get back to you.

I'll probably base my charging rates like these. I rounded my numbers a bit but it fits close to 33%.

Charge:
AA 2500 mAh @ 800 mAh
AA 2000 mAh @ 600 mAh
AAA 800 mAh @ 300 mAh

They are a little low for my comfort. I suggest that for the AA, you round up instead of down. 900 and 700 respectively. Your AAA value is 37.5%, so that is fine.

I've already heard that you want to charge good NiMH batteries at 1C because at lower charge rates the deltaV detection may not work correctly.

SD, the cells can handle this (as per spec), but they will get hot. And it is the heat that kills. Remember that the outside temp you feel on touching them is much lower than the temps inside. I would not recommend a charge rate greater than 0.5C. If for whatever reason you do want to charge at 1C, please make sure you have a fan pointing at the cells. IMHO you will reduce the cell life, but sometimes you do want charged cells in a hurry and don't mind a shorter life.

All good chargers do correctly determine deltaV if the charge rate is at least 0.3C. The C9000 is among the best chargers out there, if not the best.

 

[mubs]

I uploaded the dcos to Google Docs. How do I share it with you, Handy?

 

[LunarMist]

I've read that if a cell is just sitting around for months/years, it will eventually develop crystallization. I have some Eneloops that have sat around; I tend to recharge and reuse the same two or three sets.

Oddly, I found that I had 8 brand new AA and AAA Eneloops purchased more than 6 years ago, left untouched. After multiple Break-in & Refresh & Analyze cycles, the AAAs are at nominal capacity, the AAs are at minimal capacity. Go figure.

I have a Gmail account, but don't use it and don't have a Google docs account. Maybe I'll open one now. I'll get back to you.



They are a little low for my comfort. I suggest that for the AA, you round up instead of down. 900 and 700 respectively. Your AAA value is 37.5%, so that is fine.



SD, the cells can handle this (as per spec), but they will get hot. And it is the heat that kills. Remember that the outside temp you feel on touching them is much lower than the temps inside. I would not recommend a charge rate greater than 0.5C. If for whatever reason you do want to charge at 1C, please make sure you have a fan pointing at the cells. IMHO you will reduce the cell life, but sometimes you do want charged cells in a hurry and don't mind a shorter life.

All good chargers do correctly determine deltaV if the charge rate is at least 0.3C. The C9000 is among the best chargers out there, if not the best.

Normally I charge the 2000mAh Eneloop AA cells at 700mA. I maintain a nearly constant 22°C temperature year around, so there is no issue with heat.
I don't think you should rely on old batteries, especially if they have not been charged for 6 years. However, Eneloops last longer than most. I have some from 8 years ago that have not been charged since 2011. I may just see if they are in good shape.

 

[LunarMist]

Normally I charge the 2000mAh Eneloop AA cells at 700mA. I maintain a nearly constant 22°C temperature year around, so there is no issue with heat.
I don't think you should rely on old batteries, especially if they have not been charged for 6 years. However, Eneloops last longer than most. I have some from 8 years ago that have not been charged since 2011. I may just see if they are in good shape.

The capacities were in the 2.04 to 2.10 range after two cycles.

 

[mubs]

The capacities were in the 2.04 to 2.10 range after two cycles.

I guess those #s are Ampere-Hours? So these were Eneloop XX cells?

 

[LunarMist]

I guess those #s are Ampere-Hours? So these were Eneloop XX cells?

Not made in 2006.

 

[sechs]

I never found that doing analysis of apparently fine cells did anything for me. If you buy good quality batteries, you should get 90% of the stated capacity without issue.

 

[LunarMist]

I never found that doing analysis of apparently fine cells did anything for me. If you buy good quality batteries, you should get 90% of the stated capacity without issue.

My point is that the battery longevity is quite good. Normally I only run a test on new cells.
I remember when rechargeable AA cells had a capacity of 450mAh and could barely hold a fresh charge after four years of age.

 

[mubs]

Bought a dozen Eneloop XX AA batteries from a local source. 2nd gen - HR-3UWXB. Has a sticker on the back of each package that says "Imported and Marketed by Panasonic", and maximum price listed at $15 (current exchange rate). That's a tad lower than Amazon's price, and it seems everywhere else only the first gen is available. That god of Eneloops, Thomas Distributing, does not say which gen they sell, other than "latest generation".

All the cells are manufactured November 2013. Look to be genuine and not fake. Nominal mAh is 2550, minimum 2450 using the IEC61951-2(7.2.1) method.

I did a Refresh & Analyze in the Maha C-9000, and the results are disappointing. If I use the Break-in option on the C-9000 (which uses the IEC method) perhaps I will get a higher capacity. But not worth doing, at least right now, on new cells. The RA in the table below refers to Refresh & Analyze. Seven of these will go into my AA flashlights, and five are for the Nikon SB-900 Speedlight. My current white Eneloops will continue to service the point-and-shoot Canon camera. The weaker white cells will start seeing duty in remotes and alarm clocks.

Batt #	Test Date	RA-V	RA-mAH	%Min
X-007	2014-03-31	1.43	2,465	100.6%
X-006	2014-03-31	1.43	2,454	100.2%
X-002	2014-03-30	1.44	2,453	100.1%
X-001	2014-03-30	1.44	2,449	100.0%
X-003	2014-03-30	1.44	2,447	99.9%
X-004	2014-03-30	1.44	2,442	99.7%
X-008	2014-03-31	1.43	2,427	99.1%
X-011	2014-04-01	1.43	2,426	99.0%
X-005	2014-03-31	1.43	2,419	98.7%
X-012	2014-04-01	1.43	2,414	98.5%
X-009	2014-04-01	1.43	2,404	98.1%
X-010	2014-04-01	1.43	2,400	98.0%

Overall I think the white cells are better, but locally they are priced the same as the XX version!

 

[LunarMist]

I'm looking for a compact (one-piece) 100-240 VAC charger that will charge 4x AA cells independently, as I have some 1- and 3-cell devices. It seems that most of the fancy chargers (MAHA or Lacrosse, etc. ) are bulky and have an external power brick, which is not a good idea for the travel and tents. Thanks.

 

[time]

The Nitecore Intellicharger 4 has 4 separate channels and an integrated power supply.

 

[LunarMist]

The Nitecore Intellicharger 4 has 4 separate channels and an integrated power supply.

Yes it does. This charger is rather large, though not heavy. I am using a stub plug on it now.

 

[flexy]

Overall I think the white cells are better, but locally they are priced the same as the XX version!

About two or so years ago I spent some good money on the XXs for my camera.

I an extremely disappointed with those batteries.

They degraded VERY fast and also lost their charge (once charged and in the battery) very, very quickly. Basically after one week in the camera, unused they were dead. I though it's "LSD" batteries and was shocked really.
Now after two years, the batteries are basically dead. I charged them two weeks ago for my camera, put them in...two days later...dead.
TERRIBLE BATTERIES.

By the way I have normal white AAA Eneloops which are excellent and which I use for many years already. For my camera I now got the white AA Eneloops which seem to work great too. I recommend you do NOT get the "XX" since they're simply crap batteries, bluntly said.

I am using the Lacrosse charger for all my bats by the way.

 

[time]

The problem is most likely the camera, especially if it uses just 2 AA cells. Such cameras are unduly sensitive to battery voltage dips and will constantly moan that the batteries are flat.

If it's a 4-cell camera, the problem could be either your charger (no brand is perfect) or you may have fake cells.

 

[mubs]

If whites work fine in the same camera and XXs don't, your XXs are fake, no doubt about it. I don't know where you're located, but even Amazon has been known to ship fake Eneloops. In the US, the safest place to buy Eneloops, white or XXs, is Thomas Distributing.

I've bought from them multiple times before without a problem, but the last time I tried about a year ago, they cancelled my order since I was using a non-American credit card, citing possible fraud. The Target credit card breach had just happened. My order at FenixLights.com (if I remember the vendor name correctly) was canceled for the same reason. That's why I ended up buying the XXx locally. Fortunately, they are genuine and are serving really well in my flashlights.

 

[Handruin]

We have quite a lot of the XX Eneloops and have not experienced the issues you've described flexy. I've cycled all of them and marked down their capacity rating. I'll go through some and retest them to see if there has been any notable degradation. They're only used in Canon flashes so they get beat on quite a bit.