Using AA in C or D cell applications

Hello folks. I've read a little bit about folks using AA batteries where C and D batteries are supposed to be used. I see people asking questions like where to get an 8AA to 2D holder and statements about using 8AA to replace 6C cells. I wonder how you do this, and if maybe some of you can show pictures of how you do it.

Right now, as an example only, we have a baby swing that uses four C batteries. I put 1AA battery into a NexCell C cell adaptor and put four of them in the swing and it seems to work fine. Now I know the batteries won't last nearly as long as a C cell... but I am using the same setup with a toy that uses four D cell batteries.

I also realize that using four AA cells provides only 4.8V to the toy where 4 C cells provides 6V. So am I hurting anything by doing this?

Ultimately I'm trying to use AA rechargables (eneloops) in anything and everything I can (including my Fenix L1T and L2T just to keep this post somewhat on topic )

In the 8AA to 2D holder you mentioned, they are used to run 8 AA batteries in series in the same space as 2 D batteries. Doing this supplies higher voltage to be able to drive higher power bulbs for brighter lights than the stock host light.

"I also realize that using four AA cells provides only 4.8V to the toy where 4 C cells provides 6V. So am I hurting anything by doing this?"

No. because realistically under a full cycle of discharge, the voltage drop from alkaline cells under load is quite a bit more than with the NiMH cells. The working voltage of the NiMH cells is only a little bit below the constantly sloping-off working voltage of the alkaline cells.

The only concern to use of 2 or more NiMH cells in series is to pay attention in use to avoid a deep discharge or even voltage reversal. The manufacturers often spec the capacity of a NiMH down to about 1v per cell. voltage reversal usually reduces the life of the cell.

Only in the case of some applications, such as paint-ball guns and wireless mikes is the lower voltage from a NiMH cell vs an alkaline cell potentially a problem. If you have the usual motorized toys, just use the NiMH cells and save a lot of money and landfill space.

If the application stacks up a lot of cells, ie, more than 4, then there may be an issue with the stacked voltage from NiMH cells. An example is the "standard" 9v cells. In this case, there are batteries for sale that add another cell. ie: the usual NiMH 9v cell actually is a nominal 8.4v. The manufacturers recognized this and squeezed in another cell to reach a nominal 9.6v. Items such as wireless mikes function much better with the proper voltage, arguably with a fresh charge on the NiMH 9.6v battery, an overvoltage. The catch with the 9.6v cells is that they need a different charger.

FWIW, I have tried out upsizing an AAA to a C or D - not really worth it since the capacity is rather low. The AA upsizing to a C or D is generally worth the bother of the more frequent battery changes. The operation with the somewhat lower current supply capacity of AA cells is noticeable, but only if you know what happens with fresh D cells.

Here are some locations for battery upsizers:

http://www.greenbatteries.com/battery-adapter.html

http://www.starbatteries.com/baad.html?gclid=CKya5rm7pIcCFRI8SAodwkpt5A

Tim

Thanks a lot for the replies folks!

@moldyoldy: I actually purchased 3 each of the same nexcell C and D upsizers from Thomas Distro with my charger. I also just purchased eight of the upsizers that will accept 1 to 4 AA batteries into a single D cell from www.eastgear.com to extend the runtime.

I find the adapters that came with the BC-900 difficult to use because they are so large. The NexCell adaters are difficult because the spring usually slips off the bottom of the AA when installing... and the "button" protrudes in a strange way and cant usually slip into the device wlike a normal D. I think the upsizer (1-4AA to D) adapter looks like it will work better, although at a higher cost. I really liek the idea of using any numebr of AA's though.

I will pay attention not to over-discharge the AA's

Hello Rob,

I use adapters to enable me to use AA cells in some of my 3 D lights. The light becomes a lot lighter which makes it easier to carry.

The adapters I have came with my La Crosse BC-900 charger. I have been able to pick up extra ones from people that were about to throw them away.

Mine are "nesting" types. The AA cell goes inside a C size adapter, that then fits inside a D size adapter. All of these connecting surfaces must be kept clean to keep the resistance down. I have seen adapters that separate with only one connection at the top of the AA cell. They utilize the bottom of the AA cell for the other contact. These come in one size for C and another size for D. The nesting ones take up less storage space, but the dedicated ones should perform better.

When charging, I find that I can just put the whole thing in the charger and charge it as a D cell.

Tom

Voltage is not a problem in general. Current draw can be high and may drain or even kill AAs, especially the higher capacity ones. Therefore, when using AAs instead of Cs and Ds, stick with 2Ah and below capacity batteries as they are more robust (in general) and can provide higher current.

AA to C in my clock (1), and doorbell receiver (4) last for ever, but then they are low drain.

Well suited to adaptors.

RobSpook said:

@moldyoldy: I actually purchased 3 each of the same nexcell C and D upsizers from Thomas Distro with my charger. I also just purchased eight of the upsizers that will accept 1 to 4 AA batteries into a single D cell from www.eastgear.com to extend the runtime.

Click to expand...

Do you like the Quad AA adapters? Do they work well? I'd love to run my Mag on say 12 Rayovac Hybrids since use of it is sporadic and I tend to forget to charge the batteries in it. Some times I use it a lot, some times it sits for 2 months.

macdude22 said:

Do you like the Quad AA adapters? Do they work well?

Click to expand...

Well, I ordered them about 10 hours ago, and they are being shipped to me in Germany from Singapore via FedEx International. I hate it that they can't ship to my APO becaus enow I have to pay customs... I'll post here to let you know how they work out.

Question - if you are using the quad AA in a D-cell holder, what do you use for the unnecessary D-cell(s)? change the bulb? some sort of a dummy cell?

Hmmm, I was assuming the carrier had some sort of "voltage step" circuit to cut it back to aprox. 1.5ish V. Forgive my terminology, I'm not that familiar with voltage regulation but it sounds like it must have something as they explain it as a drop in solution.

I use those with AA NiMH for a 2D Maglite in which I don't want to leave alkaline cells because of possible leakage (shelf queen). I still have a lot of alkaline D cells for this light in case I need them.

macdude22 said:

Hmmm, I was assuming the carrier had some sort of "voltage step" circuit to cut it back to aprox. 1.5ish V. Forgive my terminology, I'm not that familiar with voltage regulation but it sounds like it must have something as they explain it as a drop in solution.

Click to expand...

I just assume it connects 2-4 AA batteries in parallel. This explains how it will work with 1, 2, 3 or 4 AA's and not reuire dummy cells. Also wouldn't require voltage regulation, because EMF's in parallel circuits are equal (approx 1.2 v in this case eh?)

RobSpook said:

I just assume it connects 2-4 AA batteries in parallel. This explains how it will work with 1, 2, 3 or 4 AA's and not reuire dummy cells. Also wouldn't require voltage regulation, because EMF's in parallel circuits are equal (approx 1.2 v in this case eh?)

Click to expand...

Yea thats how they work, I need this very thing but in a 4 cell series, I'm betting though that I could mod those to my needs. I'm glad I clicked this thread and in this big o'l planet we live on I just know there is that very holder in a series set up as opposed to parallel but I'm sure get tired of trying to find them. Glad I clicked on this thread and actualy I need those too, those are just a no lose buy with the new Low Self-Discharge NiMh. I'm going to call them tommorow and see if they can contact thier suppier to see if they have the very ones I want and buy two of the parallel

Well, I got the 4AA to D adapters today and let me tell you, it's a great idea, and a quality product... HOWEVER... You'll have to modify them to make them work with most of your batteries!

They are made by "Grandcell" and apparently their batteries have a smaller diameter positive button than my Eneloops, Energizers, and Rayovac Alkalines...

There is a flat piece of plastic with four holes for the buttons to snap into, so I just used my dremel with an appropriate attachment to slightly increase the diameter. I wedged a large flathead screwdriver between the plastic piece with the holes and the contact surface so the drill would ride on it. It was somewhat difficult because the holders won't dissasemble...

Anyway, now that i got four of eight done, they seem to work great. Just make sure you make the holes big enough so that there's NO DOUBT all batteries ALWAYS make contact.

Rob