What's going on with these D cell NiMh battery capacities?

[Trashman]

So, we've got a newborn, now, and a baby swing which gets a lot of use. It's crossed my mind a few times that I might want to buy some rechargeable batteries for the swing, so I started looking around and noticed that there is a HUGE difference in advertised battery capacities. I see some Energizers rated at 2500mAh, some 2900mAh Rayovacs and then, over at Battery Junction, I see these other brands, like Tenergy and Titanium listing capacticities of 12000 and 10000mAh! What's going here? Are they rating their batteries in a different manner? I mean, Energizer and Rayovac are no slouches with it comes to the manufacturing of batteries. How can it be that there are other companies making the same size battery, but with 4 times more capacity? Are these ratings bogus or, perhaps, calculated differently?

 

[Lynx_Arc]

The 2500 and 2900 nimh are not complete batteries they either have a subC battery or maybe a AA in them instead of being ALL D nimh. The 12A and 10A are fully nimh cells with no padding at all in them.

I wouldn't waste money on the 2500/2900 nimh Ds instead use a AA adapter that takes one or even 2AAs in parallel and AAs as they are cheaper and AA chargers are plentiful and fast and cheaper.

 

[Mr Happy]

The potential mAh capacity in manufacturing is approximately proportional to the internal volume of the cell. So a NiMH AA cell, when its volume is fully utilized, can have a capacity of 2000 - 2500 mAh. A D cell has a volume more than four times as large as an AA cell, so when its volume is fully utilized you get NiMH capacities in the 10,000 - 12,000 mAh range.

However: when Energizer and Rayovac make NiMH cells in the C and D sizes, they don't use the whole volume. What they do is put a small cell about the volume of an AA cell in the middle and surround it with a big shell.

There might be practical reasons for this. The reality is that very few budget priced consumer chargers can do a good job of charging a 10,000 mAh cell. Either they would need more expensive electronics to charge at 2 amps or more, or they would need to take 24 hours to complete a charge at a more common 500 mA. So the mainstream manufacturers avoid the problem and deliver C and D cells with the same capacity as AA cells, so that Joe Average consumer doesn't get confused by the expensive chargers or really long charging times.

 

[Trashman]

Ah ha! Thanks guys. I've got plenty of AA rechargeables, but no D adapters. I wonder, though, how long they'd work in a big ol' baby swing with music, lights, and a motorized mobile? (they also power the swing) The alkaline D's are doing pretty well, so far, and they're pretty cheap at Big Lots (Fuji brand, $1.49 for two!). I've got a feeling AA's won't be powering the swing for very long, so I guess the 10000+mAh cells would be the ones I'd need. Anybody have an idea what the capacity range of Alkaline D cells is?

 

[Lynx_Arc]

I am clueless to the current demands of what you have. Is it portable needing batteries? How long does it run on D cells and how many does it use? The reason I ask is because nimh D cells are rather costly if you need more than 4 of them you could shell out more than you realize at $8-$15 each for D cells plus shipping AND having to buy a charger on top of it all the AA adapter thing may be very attractive or other alternatives.

 

[lctorana]

Anybody have an idea what the capacity range of Alkaline D cells is?

At low drain rates, Energizer claims 20Ah.

 

[JimmyM]

I had the exact same dilemma as you when we had our first child. The swing was killing batteries constantly. I bought a big wall wart at the Rat-Shack and wired in a power jack to the battery compartment. Now it doesn't need batteries at all, but I can use them if I want. I've saved myself the cost of the AC adapter many times over.

 

[Niconical]

Just my personal opinion, but I don't think it would be worth your while investing in D sized nimh and a charger for them. The little guy is only going to get bigger and grow out of the swing, and soon I don't suppose you'll get any use from the batteries.

However, it doesn't feel right to write a post only advising to not buy something, so, option 2...., find a good D cell lantern that you could then use with the nimh cells after the swing is finished with.

 

[mdocod]

Just my personal opinion, but I don't think it would be worth your while investing in D sized nimh and a charger for them. The little guy is only going to get bigger and grow out of the swing, and soon I don't suppose you'll get any use from the batteries.

However, it doesn't feel right to write a post only advising to not buy something, so, option 2...., find a good D cell lantern that you could then use with the nimh cells after the swing is finished with.

Genius!

oh- and with that future lantern in mind, make it a set of AccuPower LSD cells
Eric

 

[phenwick]

However, it doesn't feel right to write a post only advising to not buy something, so, option 2...., find a good D cell lantern that you could then use with the nimh cells after the swing is finished with.

Niconical, You know your guilty of enabling another flashaholic.

 

[Trashman]

Well, so far, we're still on the first set of alkaline batteries, so, amazingly, it lasts much longer than I would have thought (on 4 D batteries.) She's less than a month old, though, and doesn't seem to be quite so entertained by the music or mobile movement, so we've mainly just been using the swing function, and a little bit of the fluctuation and color changing light. Maybe, in a couple of months, she'll be more distracted by the other battery eating functions and we'll start going through batteries more quickly. Again, though, we've been using the swing for more than 3 weeks on the same set of batteries and they're still working fine, plus, it's only $3 for 4 more. I've been thinking, though, that she's bound to get more toys in the future that need D batteries, so they'll probably come in handy, eventually (maybe). I may be jumping the gun, though, since the first set is still running fine and don't know how long it'll be until she outgrows it. Hopefully, that won't be till a while. I guess, I'll just have to wait a little longer until I need to make the first battery change and weigh my options. I do already have a charger capable of charging D batteries, but it's a really old one (20 years old?) and won't have an option for a faster charge rate--I can always let them charge for 24+ hours, though, right?

 

[phenwick]

If the charger is timer based, it may shut down before the cell is at capacity, requiring multiple cycles. Something that old was probably designed for lower capacity cells of the time.

 

[jerry i h]

Well, so far, we're still on the first set of alkaline batteries, so, amazingly, it lasts much longer than I would have thought...

So, you are liking those alkys, are you?? Just wait until you switch to rechargeables to save money . D alkys, even those cheap-o generic ones from W*lgreen's, are rated at 20AH. Even under ideal circumstances (expensive NiMH's and a sophisticated charger going for almost a c-note), the state-of-the-art D rechargeables are rated at 10 or 12 AH. So, assuming you buy the best-of-the-best, your rechargeable D cells will last, at BEST, 1/2 the time of cheap-o alkys.
OTOH, you just stick 'em into the charger overnight, and they are good to go the next morning, so maybe they are not THAT bad...:shrug: ??

 

[Norm]

Congrats on the new addition Trashman, my daughter used AA to C adapters with eneloops in a Fisher Price swing worked very well.
Norm

 

[Trashman]

So, you are liking those alkys, are you?? Just wait until you switch to rechargeables to save money . D alkys, even those cheap-o generic ones from W*lgreen's, are rated at 20AH. Even under ideal circumstances (expensive NiMH's and a sophisticated charger going for almost a c-note), the state-of-the-art D rechargeables are rated at 10 or 12 AH. So, assuming you buy the best-of-the-best, your rechargeable D cells will last, at BEST, 1/2 the time of cheap-o alkys.
OTOH, you just stick 'em into the charger overnight, and they are good to go the next morning, so maybe they are not THAT bad...:shrug: ??

The thing about the different battery chemistries is that their lasting power depends on the application. Put an alky in a digital camera and you'll get 1/5 (roughly) of the shots you can get with a rechargeable, despite the alkaline being of a higher capacity. I'm not sure which is better for running a motor, though. The music function would probably benefit from the rechargeables, but I'm not sure about the actual swing. But, in actuality, a 10mAh NiMh can actually last longer than a 20mAh alkaline, in the right application. For high draw, quick burst situations, like a camera flash, rechargeables will definitely outperform alkys.

Thanks for the congratulations, Norm!

 

[Essexman]

Congrats on the new addition Trashman,.
Norm

I can't believe it took 14 posts until one of us said that!

Sorry I don't have any input to give on your D cell question.

Just wanted to say congratulations to you and your family.

 

[mdocod]

Hello jerry i h,

As Trashman pointed out, the AH ratings on cells can be very misleading.

The alkaline cell has substantially higher internal resistance than a NIMH cell, so more of the available more is converted to heat before it ever escapes the cell under higher loads. There are VERY FEW consumer applications where the higher AH rating of the alkaline cell actually holds true in use, those applications are pretty much limited to clocks and remotes. If it has a motor, a speaker, a bulb, etc etc, you can almost guarantee that a NIMH will outlast it.

Eric

 

[NA8]

Keep it simple.

These batteries:

http://thomasdistributing.com/shop/...html?SP_id=&osCsid=j9mt5l70ejoehfod07hlg9hsv2

This charger:

http://www.thomasdistributing.com/maha-mh-c808m-battery-charger.htm

P7 Maglite mods ? Just an added bonus.

 

[metlarules]

If your looking for a less expensive alternative to the above check out these batteries and this charger.
http://www.batteryjunction.com/r1ed-gd7000.html

http://www.batteryjunction.com/v1ec-bc2hu.html

 

[Lynx_Arc]

I've been thinking, though, that she's bound to get more toys in the future that need D batteries, so they'll probably come in handy, eventually (maybe). I may be jumping the gun, though, since the first set is still running fine and don't know how long it'll be until she outgrows it. Hopefully, that won't be till a while. I guess, I'll just have to wait a little longer until I need to make the first battery change and weigh my options. I do already have a charger capable of charging D batteries, but it's a really old one (20 years old?) and won't have an option for a faster charge rate--I can always let them charge for 24+ hours, though, right?

First off most toys these days are going to AA batteries and higher drain ones are coming with rechargable packs. I would hold off on buying any D cell recharagables based only on the future as LSD rechargables should improve more and more now they are becoming mainstream and you will have more choices and hopefully better chargers for them. No, your old charger is not recommended for charging NIMH D cells.. get one designed for them as the cells are not cheap enough to want to ruin to save money on a charger.