The elusive smart charger for Sanyo Eneloop AA/AAA batts

[Woodsroad]

Re: Questions about Eneloops and chargers for them

The Powerizer and Tenergy cells would not be low self discharge chemistry?

No, they are not. exactly how fast they self-discharge, I do not know. That would be a good thing to check on....I'll do it.
However, I have not had a problem rotating the 3 dozen AA's among several strobes and radios that get used on a semi-daily basis.
I might recharge batteries once a week, some batteries might sit in a case for weeks or even months before they are used. That's where the Eneloops go, where they are less likely to be used right away. Either way, I've never pulled out a dead box of batteries.

Good question, though, I'll keep tabs.

 

[tandem]

Re: Questions about Eneloops and chargers for them

Is a 2000mAh cell rated as 2000mAh per hour?

No, not quite. mAh stands for milli-Ampere hour, so you would never say 2000 mAh per hour but could say 2000 mA per hour. Clear?

If cells were able to deliver any current rate and deliver exactly their label capacity then a 2000 mAh (or 2 Amp hour) cell could deliver 2 amps for 1 hour, or as said above, half an amp for four hours.

As for load, it is what it is, and is determined by the device you are powering. If it is a flashlight, the load presented will vary if it has different output levels. There are different approaches to regulation - a constant current driver will maintain the same current draw from the cell(s) but voltage will change over the course of runtime.

Some cells deal with higher drain devices better than others. It turns out that rechargeable NiMH cells, especially the good ones like Eneloops, can pump out more current at a lower voltage drop than any off the shelf Alkaline cell can. Those who haven't experienced modern AA rechargeables might be surprised to learn that they are in virtually every dimension better than non-rechargeable primaries.

 

[SilverFox]

Re: Questions about Eneloops and chargers for them

Hello Woodsroad,

Welcome to CPR.

Yours is an excellent real world test. I love those.

It looks like your cells are holding up well and you should be able to get a couple of more years from your cells.

Now, all you have to do is train your daughter in how to care for her cells...

Tom

 

[SilverFox]

Re: Questions about Eneloops and chargers for them

Hello Al,

Tandem has covered your questions, but that doesn't stop me from also trying to add a little...

mA is current. mAh is capacity.

The load is what it is. You can find what it is by measuring it, or sometimes there are specifications that give you an idea. Another way to determine how much current is being used is to time how long it takes to empty your battery. If you know the capacity of the battery and the time they last, you can calculate the load.

I put numbers on my cells with a Sharpie and track them with a simple spreadsheet. When I get new cells I do a Break In on them and record the capacity. I follow that with a 1C charge and a 0.5C discharge and record that capacity. Beyond that I do special things for particular applications. I try to check my cells at least once a year to see how they are doing.

When my cells fall below 80% of their initial capacity when new, I recycle them and replace them.

Tom

 

[Woodsroad]

Re: Questions about Eneloops and chargers for them

Hello Woodsroad,

Welcome to CPR.

Thanks, Tom!

Yours is an excellent real world test. I love those. It looks like your cells are holding up well and you should be able to get a couple of more years from your cells.

That's the suspenseful part. Any minute now....they could DIE!

Now, all you have to do is train your daughter in how to care for her cells...

yeah, that's part of growing up. That's why my dad bought me my own tools when I was 8, so that I would ruin MY tools, not his! Then again, my dad and I built batteries, too...maybe I should do that with my daughter, too... of course, my dad is now 94. he grew up at a time when that's what boys did. They read science and mechanics magazines and built stuff.

Oh, and for folks looking for some good basic battery knowledge, look here: http://batteryuniversity.com/

 

[Al Thumbs]

Re: Questions about Eneloops and chargers for them

No, not quite. mAh stands for milli-Ampere hour, so you would never say 2000 mAh per hour but could say 2000 mA per hour. Clear?

If cells were able to deliver any current rate and deliver exactly their label capacity then a 2000 mAh (or 2 Amp hour) cell could deliver 2 amps for 1 hour, or as said above, half an amp for four hours.

As for load, it is what it is, and is determined by the device you are powering. If it is a flashlight, the load presented will vary if it has different output levels. There are different approaches to regulation - a constant current driver will maintain the same current draw from the cell(s) but voltage will change over the course of runtime.

Some cells deal with higher drain devices better than others. It turns out that rechargeable NiMH cells, especially the good ones like Eneloops, can pump out more current at a lower voltage drop than any off the shelf Alkaline cell can. Those who haven't experienced modern AA rechargeables might be surprised to learn that they are in virtually every dimension better than non-rechargeable primaries.

Clear, and thanks.

Al T.

 

[HighlanderNorth]

I'm going to say I agree with some of the chargers listed above, and also include the Nitecore I4 charger, which has 2 channels, and 4 bays, so you can charge 2 batteries at a time on 2 different channels if you want, and it charges Li Ion batteries if you decide to use them in the future too. It doesnt have folding prongs, because it doesnt have prongs to begin with, it has a removable cord that plugs into the back of it.

Its about $25.

 

[cdogg44]

Eneloop & Charger Advice

I'm getting into trail cameras and have ordered several eneloop AA's. I am looking for a charger to go with them. Obviously with the money I'm spending on batteries I want to use a good charger and prolong their life.

I've read a bunch here in the forums and like the C9000, but the capacity of only 4 batteries seems small. My cameras hold 12 AA's. How long does it take to charge 4 2000mah eneloops in a C9000?

Are there any other chargers I should be looking at? Specifically any that have a capacity of 8-12 AA? I really don't need anything too technical, just something that charges the batteries in a manner that prolongs their life.

Thank you

 

[Yamabushi]

Re: Eneloop & Charger Advice

Maha Powerex C800S, C801D and C808M each handle 8 batteries at a time.

EDIT: The C9000 terminates conservatively, stepping down at the end to a topoff charge rate of 100 mA for 2 hours. So, if you want a full charge using 1000 mA as the initial charge rate, it could take about 4 hours (2 hours @ 1000 mA + 2 hours @ 100 mA).

 

[Wrend]

Re: Eneloop & Charger Advice

You can also carry extra sets charged and ready to use so you don't have to wait for them to charge.

The C9000 will charge at up to 2000mA per channel, so a little over an hour or so for a full charge on Eneloop AAs. It's probably somewhat better for them to charge them at 700mA to 1000mA.

 

[Lobstradomus]

Re: Eneloop & Charger Advice

Now that it appears Sanyo has discontinued their MDU01 USB battery charger, does anyone have any recommendations for a decent USB AA/AAA charger?

 

[cdogg44]

Re: Eneloop & Charger Advice

Maha Powerex C800S, C801D and C808M each handle 8 batteries at a time.

EDIT: The C9000 terminates conservatively, stepping down at the end to a topoff charge rate of 100 mA for 2 hours. So, if you want a full charge using 1000 mA as the initial charge rate, it could take about 4 hours (2 hours @ 1000 mA + 2 hours @ 100 mA).

Other than all of the break in and cycle modes, does the C9000 offer features I am going to need over either of the 8 battery chargers if I am just going to have a stash of Eneloops and run them until they are dead in the woods and charge them back up?

Do I need the maintenance features of the C9000?

 

[Yamabushi]

Re: Eneloop & Charger Advice

Do I need the maintenance features of the C9000?

It depends on your applications.

The 8-cell chargers have a conditioning function so the analysis function is the significant advantage to the C9000.

I have 1, 2, 3, 4 and 8-cell devices and want to use matched cells in the multi-cell devices (especially the high current devices) so I use the C9000 analysis function to periodically check my cells. If all my devices were single-cell I think I would have bought a C800S.

 

[Mr Happy]

Re: Eneloop & Charger Advice

Other than all of the break in and cycle modes, does the C9000 offer features I am going to need over either of the 8 battery chargers if I am just going to have a stash of Eneloops and run them until they are dead in the woods and charge them back up?

Do I need the maintenance features of the C9000?

If you ignore all the other features of the C9000, it remains a solid and reliable charger for simple charging. It will charge 4 AA eneloops in about an hour at the fastest 2000 mA charge rate while keeping them quite cool. The price you pay for this coolness is that if you take the batteries off the charger as soon as they are done they will be charged only to 95% or so. If you use other chargers at 2000 mA that try to go all the way to 100% the batteries will get hot. Of course, charging 12 batteries on the C9000 will require you to attend to the charger once per hour or so. On the other hand, I know of chargers with 8 slots, but hardly any with 12 slots. So you either need more than one charger or more than one charge cycle, unless you are patient.

You don't need the maintenance features of the C9000, but consider them a bonus. You may find you value them once you have some experience with your batteries.

 

[cdogg44]

Re: Eneloop & Charger Advice

If you ignore all the other features of the C9000, it remains a solid and reliable charger for simple charging. It will charge 4 AA eneloops in about an hour at the fastest 2000 mA charge rate while keeping them quite cool. The price you pay for this coolness is that if you take the batteries off the charger as soon as they are done they will be charged only to 95% or so. If you use other chargers at 2000 mA that try to go all the way to 100% the batteries will get hot. Of course, charging 12 batteries on the C9000 will require you to attend to the charger once per hour or so. On the other hand, I know of chargers with 8 slots, but hardly any with 12 slots. So you either need more than one charger or more than one charge cycle, unless you are patient.

You don't need the maintenance features of the C9000, but consider them a bonus. You may find you value them once you have some experience with your batteries.

Although it would be expensive, is an 8 slot charger and C9000 pair the answer? That would give me the ability to charge all 12 at once, and still give me the C9000 capabilities if/when I ever needed them. Also just so I'm clear, these chargers (C9000 and Maha 8 slots) are smart enough that I could load them up, go to bed, and they would shut off in the night and not toast the batteries?

 

[Mr Happy]

Re: Eneloop & Charger Advice

If you are going to use the 12 batteries in the same device at the same time, then the best advice would be to charge all 12 batteries the same way on the same kind of charger. It is likely to shorten the life of NiMH cells if they are not charged and discharged evenly.

The C9000 will definitely shut off automatically without toasting the batteries. With the 8 slot charger I can't give you that perfect assurance. I don't own one and that charger works slightly differently.

Another possibility to consider when charging 12 eneloops at once, although not quite a consumer "drop in the batteries and forget it" solution, is a hobby RC charger like the Turnigy Accucel-6. If you can make up a battery harness to put 12 eneloops in series (e.g. using a cardboard tube and magnets) then you can use such a charger to charge your batteries all at once. Feel free to ignore this suggestion if it makes you feel uncomfortable, as it is definitely more of an advanced technical solution and is not quite consumer-friendly for the ordinary battery user. But anyway, just so you know it's out there.

 

[Wrend]

Re: Eneloop & Charger Advice

I have 2 C9000s to handle larger workloads and testing sessions, and because I only use up to 8 cell applications for my Eneloops. If I had need of 12 cell series sets, I'd probably pick up another C9000. I can understand that that might be considered a bit excessive to some peoples needs.

Just a side note here, but I think Sanyo/Panasonic, at least in the Eneloop on-line guide, only recommend using up to 10 cells in series. This might be due to the risk of having slightly unevenly balanced cells and the increased risk of reverse charging some of them when using that many in series. So, it is probably even that much more important to make sure that your cells are balanced, if you want to get a more long and useful life out of them.

Another option (similar to what Mr Happy suggested) my be a low rate series charge of 200mA or less for about 14 hours or so for a full charge on your Eneloop AAs. This charging method is used in hobby transmitters that use packs of NiCd or NiMH cells (and other wall wart style charging methods for things such as cordless phones), and works pretty well. It has other risks and limitations though, like taking a long time, and slow cooking your cells on the charger if you leave them charging too long. 200mA or less is a low enough rate to where you won't do too much damage to your cells if they're over charged a little, and actually, a little overcharging using this method is needed to balance them. Just don't over do it. You can tell when they're done when they start to warm up a little more. If you're using a good hobby charger for this, you can set a time, temperature, and capacity limit termination. The charged capacity limit is going to need to be significantly more than the stored capacity of the cells for a full and balanced charge. (About 1.4 to 1.6 times the amount for Eneloops.)

For charging at faster rates (700mA to 1000mA) you'll need to use the drop in voltage when full detection termination method (-ΔV) of the hobby charge and might have to play around a little with the setting for it to get it to terminate properly. Use the manufacturer's guidelines for NiMH cells.

To put the cells in series, you could also use battery holders that can be picked up at places like RadioShack and put a few of those together in series.