Question regarding Eneloop rechargeables & C/D adapters

[Will91]

Hi everyone:

I'm going to take the advice I got here a while back to purchase a set of Eneloop rechargeable batteries and a battery charger. I notice that some of the kits come with a C and D size adapter. I didn't realize that what this means is that one slips a AA battery into the C or D sleeve and presto, you can apparently use it in a device that uses C or D batteries.

I have some older 2D, 4D and 5D flashlights. I just called Maglight and they say as long as the output voltage is 3,6, and 7.5V respectively, it should work. I see this is simply 1.5V times the number of batteries. However the datasheet for the Eneloop AA battery says the nominal voltage is 1.2 V. Will the Eneloop's put out enough voltage for my Maglite D flashlights??

Thanks!

 

[Justin Case]

The Eneloops work fine in C and D Mags. To my eye, incandescent output looks identical for Eneloops vs alkaline C or D cells.

The main issue is that the C and D adapter shells use the AA cell itself to make the negative electrode connection. The problem is that the AA cell has a small bottom plate diameter, while a C or D cell's bottom plate is far larger. You will probably have to do some minor, though judicious, bending of the top coil of the Mag tailcap spring to make ground contact to the AA Eneloop.

 

[Will91]

Thanks Justin Case:

Good point about the tail cap spring. I had not thought of that.

1.2V vs. 1.5V doesn't sound like much of a difference but for a 5D Maglite, we're talking 6V vs. 7.5V so I thought I would ask the board.

 

[piojo]

This is simply 1.5V times the number of batteries. However the datasheet for the Eneloop AA battery says the nominal voltage is 1.2 V. Will the Eneloop's put out enough voltage for my Maglite D flashlights?

My meager understanding is that the nominal voltage for a rechargeable or lithium cell is the voltage that it will usually have under a load, while the given voltage for an alkaline or "heavy duty" battery will only be achieved under perfect conditions (i.e., very low current draw). Rechargeables and lithiums are just much better at taking a high load.

Additionally, the voltage of an alkaline battery drops steeply as its capacity drops, while NiMH and Lithiums are somewhat more constant--so a 1.5V alkaline battery will become 1.2V or lower long before it is used up. In flashlights, 1.2V rechargeables tend to do better than 1.5V alkalines (based on runtime graphs I have looked it).

 

[chmsam]

This topic probably belongs in the flashlight electronics/batteries section but I'll add another consideration while it's still here and that's the capacity of the cells. Alkaline D cells have 12,000 mAh or more while rechargeables have 2,800 and usually less. Expect run time to suffer a lot with AA's.

 

[Justin Case]

I tested my Eneloops in 2C, 3D, and 4C Mags and noticed zero difference in incandescent output vs using alkaline cells.

I measured around 1/2 amp tailcap current draw in my old 3D Mag. Looking at the alkaline battery shootout data for D cells, it looks like alkaline Ds at that load will dip to 1.4V pretty quickly and then spend a lot of time between 1.2V and 1.4V.

Looking at the AA Eneloop data, it looks like the Eneloops will drop rapidly and settle in at around 1.3V for most of the cell's running life.

Yes, you'll get about 12 Wh for an alkaline D vs 2.4 Wh for the Eneloop. A fair tradeoff IMO, especially since you can recharge the Eneloop. The Eneloop also has much better high current performance than the alkaline D.

 

[HKJ]

This topic probably belongs in the flashlight electronics/batteries section but I'll add another consideration while it's still here and that's the capacity of the cells. Alkaline D cells have 12,000 mAh or more while rechargeables have 2,800 and usually less. Expect run time to suffer a lot with AA's.

Some rechargeable D cells has just as low capacity, you really has to check the capacity when buying C and D cells or you will get small cells packed in C or D containers.
Some adapters for D cells can have more than one AA cell in, this helps on the capacity.

 

[Will91]

Thank you everyone for all this excellent input. I think the route to go is to purchase "real" D sized rechargeable batteries. I found some 10000 mAh Tenergy D cells at all-battery.com. Are they any good?

Now I recently learned the newer Sanyo charger that comes with the Eneloop AA batteries charges batteries in pairs and there is some discussion by Amazon buyers that this can lead to overcharging of a battery if you pair a more fully charged battery with a more depleted battery because the charger just senses the pair rather than individual batteries. Hopefully I can find some recommendations for premium chargers in the Stickies that work with the Eneloops and sense the individual batteries.

 

[ElectronGuru]

One extra note. What makes eneloops special is LSD. AccuPower makes C cells that are true LSD, with double the mah of AAs.

 

[TakeTheActive]

...I think the route to go is to purchase "real" D sized rechargeable batteries. I found some 10000 mAh Tenergy D cells at all-battery.com. Are they any good?

Unless you really NEED and thus will consistantly USE all of the available Capacity of "real" 10,000mAh D cells, IMO, it's a bad choice.

Buying a 10,000mAh non-LSD D cell and only using 20% of it's Capacity on a regular basis is like buying five 2000mAh non-LSD AA cells (i.e. not Eneloops!), using one and putting four in the drawer. The chemicals inside a rechargeable battery need to be 'cycled' on a regular basis or they begin to go bad. And the non-LSD cell will 'Self Discharge' MUCH faster than the Eneloop.

Back in 2002, BEFORE I learned better by reading the Archives here, I bought 4500mAh C and 6000mAh D non-LSD NiMH cells to replace the ???mAh C and ???mAh D NiCD and 2200-2500mAh 'fake' NiMH D cells I was using at the time. My usage was 'Speak & Spell', 'Frogger', miscellaneous flashlights, and one FM Radio / CD player (Boom Box). Except for playing the CD player for hours on end, the batteries usually 'Self-Discharged' in the other devices before I got anywhere near their rated Capacity out of them.

I made the same mistake with a B&D Dustbuster - I replaced the original sub-C NiCD cells with MUCH higher Capacity NiMH cells. And, since I hardly use their full Capacity (and don't like to leave them 'Tricke Charging' for weeks on end), they too 'Self-Discharge' all the time and have gone bad prematurely.

If your D cell flashlights sit around doing nothing for days / weeks on end and then you want to randomly pick one up and use it for an hour now and then, you'll be MUCH happier with 'Charged' 2000mAh LSD AA cells than 'Self-Discharged' 10,000mAh non-LSD D cells.

Click on my Sig Line LINK and read about 'Storage Box Queens'.

 

[Will91]

Thanks:

I think you have convinced me to stick with Eneloop AA's and find some D shells that will work with the tail cap spring on my Maglites. In fact, I rarely use my 4D and 5D Maglites anymore so perhaps I can keep a set of D shells on hand for when I do want to use it. Mainly I use my mini Mag. Does anyone have a recommendation for a quality D shell?

 

[Justin Case]

The Eneloop D shells work well. Tenergy D shells also work well.

If you have a new model D Mag with the variable rate spring (tight coils at the ends, open coils in the middle), then you don't have to bend the end loop tighter. Instead, you can wedge a coin (I used a copper penny) in-between the last and second-to-last turn. The coin will be securely trapped.

With the old Mag spring with the uniformly spaced coils (I think they have the yellowish cadmium plating, instead of the newer chrome plating), then you'll have to do the bending to make that last turn smaller in diameter to contact the bottom plate of the AA Eneloop.

I can post a photo later.

I have an old Maha C401FS that has 4 independent charging channels. On slow charge, it's a good charger. Fast charge is probably too fast and heats up the cells too much.

 

[Justin Case]

New version DMag tailcap on the left. Old version CMag tailcap on the right (I have an old DMag from the 1980s with the same tail spring design -- it just wasn't in-hand when I took the photo). Both Mags have the "C" and "D" letter in the serial number. The DMag was purchased very recently, while the CMag was obtained several years ago.

Note that without the penny wedged into the spring, the bottom of the AA Eneloop is too small to make contact with the DMag's conical tail spring.

For the CMag tail spring, I bent the end of the wire spring inward so that the coil diameter is smaller than the AA Eneloop.

 

[thedeske]

Thanks for the pic Justin. I have a newer Mag tail in a 3D. Guess I'll give it a bend or try the penny trick until I finally take the antique out of service. The Eneloop sets look like a good deal even if the charger is basic.

 

[Justin Case]

Use a pre-1982 penny if you want 95% copper. The new pennies use a zinc core with a copper plate.

 

[mdocod]

Accupower sells 10AH D cells that are low-self-discharge just like eneloops, they have been tested and used by CPF members and are great performers, this is what I would recommend as rechargeable alternatives for D cell flashlights, they also have a 4.5AH C cell that is LSD. You can get the cells from thomasdistributing.

 

[Justin Case]

I agree that when considering just the battery performance, an LSD Accupower C or D NiMH is a better way to go. But when you factor in the fact that many may have a boatload of AA Eneloops or regular AA NiMH and zero C/D NiMH, the equation changes. Do I really want to spend $100 on yet more NiMH batteries for my C and D Mags? I already get 1.5h run time from my Eneloops in my 4C P4 Mag. So what do I really gain -- 4.5h run time? If that's something I really need, that would be one thing. I'd be all over it. But I have spare AA NiMHs everywhere, extra C and D alkalines, 123A lights, extra CR123A cells, extra RCR123A cells, extra 17670 cells, .... The AA NiMHs and CR123A cells are also fairly common camera batts.

Plus, you also need a way to charge the C or D NiMH Accupower cells. I really don't want to buy yet another charger. To charge C/D NiMHs (assuming I decided to get some), I would probably use some C and D battery holders, solder some alligator clips to the wires, and attach the wires to my Maha AAA/AA charger.

 

[Black Rose]

Plus, you also need a way to charge the C or D NiMH Accupower cells. I really don't want to buy yet another charger. To charge C/D NiMHs (assuming I decided to get some), I would probably use some C and D battery holders, solder some alligator clips to the wires, and attach the wires to my Maha AAA/AA charger.

Here is what I did for my Rayovac Hybrid C and D cells.

I've tweaked it slightly now in that I sandwhich the ring terminal between two rare earth magnets to get a very solid connection.

 

[Justin Case]

Thanks, nice workaround. I have some crimp connectors I could use, although I do prefer soldered connections. But I suppose if I end up using spring contacts in a battery holder and alligator clip connections to the charger, soldering on the clips might be moot.

 

[Black Rose]

Not sure which charger you have, but I did consider using aligator clips originally with the C9000, but there isn't any way to connect an alligator clip to the positive charge contact on the C9000, so I went with a wooden dummy AA cell and pressure fit ring terminals in the charger.

The ring terminals on the battery end are soldered to the 18 gauge wire.