15 minute battery charger for C and D size?

[Sam]

There are several 15 minute battery chargers for AA and AAA batteries. But I could not find one for C and D. Do they exist? Is there a technical limitation preventing its existence?

BTW, the 15 minute battery charger for AA and AAA is wonderful. I keep one in my car and I never have to worry about battery for my camera, GPS, or my kids' MP3 players.

 

[TromboneAl]

I've also wanted a C or D charger for NiMH batteries.

What types of batteries are you talking about? I've had good luck with no-name brand NiMH batteries from Ebay. The disadvantage is they self-discharge at 30% per month, so you can't just leave them in a box. You can put them in the freezer, and they hardly discharge at all, but you must defrost them before use.

I've used them in walkie-talkies, clocks, CD Walkmen, even remote controls.

 

[Sam]

I only use NiMH batteries. For AA and AAA I use RayoVac brand, because RayoVac was the only one selling a 15 minute battery charger 3 or 4 years ago. Except for 9V, all batteries used at home are rechargeable. I guess I save at least $100/year. I use a regular RayoVac charger for C and D. It takes about 12 hours to charge them. OK for now, but I really want an "instant" charger.

I made it a requirement that any new battery operated "toy" must work on standard size battery, AAA, AA, C, or D. No more silly, expensive, odd sized battery. Except, of course, my laptop. Wonder which PC maker will "revolutionize" the industry with this simple change?

 

[cute fuzzy bunny]

Most laptop batteries when broken open reveal AA size lithium ion rechargeables.

I could have sworn that somebody had a bunch of pop open cases for most major laptops that you could populate with your own NIMH or LIION AA cells.

 

[Sam]

I've had good luck with no-name brand NiMH batteries from Ebay. The disadvantage is they self-discharge at 30% per month, so you can't just leave them in a box. You can put them in the freezer, and they hardly discharge at all, but you must defrost them before use.

The self-discharge problem does not bother me much yet, as I have a good supply of batteries and chargers.

You might want to consider Hybrid NiMH batteries. They are supposed to retain charge much longer. I have not tried them yet.

http://www.rayovac.com/recharge/hybrid_products.shtml

 

[wabmester]

D-cell adapter.

link

 

[samclem]

Is a rapid charger for C and D cells impossible due to problems dissipating the heat of recharging? There's a lot less surface area per unit of volume in a C or D cell compared to AA or AAA. The bigger cells are also a lot less popular, which might also be a reason.

Any EE types out there? I'd think you could recharge a C or D cell using an AA cell rapid charger, just jumper, say, two "+" leads from two compartmernts on the AA charger to the "+" lead on the C cell, and do the same for the "-" side. The voltage would be right, and the charger would still automaticaly cut off when the voltage of the cell reached the right point. The only issue would be the aformentioned heat dissipation problem.

BTW, did you ever notice that the colume of a "C" cell is much smaller than a "D" cell, but the disposable ones are almost always priced the same per battery. C cells are a ripoff.
Also, last time I checked, rechargeable NiCd D cells were rated at the same amp/hour capacity as the NiCd C cells. Basically, each D cell was just a C cell with a spacer around it so it would fit in the designated device. I don't know if things are the same with NiMH cells.

 

[Sam]

I too suspect that heat is the problem.

About identical C and D capacity, I'm pretty sure it's not true with NiMH. The D has at least twice the capacity of the C.

 

[TromboneAl]

Sam, could you give me an example of how you use the 15-minute charger? If you need a new battery for your walkman, for example, do you put a battery in the fast-charger, then wait 15 minutes?

I tend to always have four batteries in my charger. If I need two, I take them from the charger, and put two others in their place. The charger consumes 4 watts (about $5 per year).

The main disadvantage is that for, say, a clock or remote control, I have to replace every few months rather than every few years. Do you use yours for apps like this?

 

[mb]

Most laptop batteries when broken open reveal AA size lithium ion rechargeables.

Actually it is the so called 18650 size. (18mm diameter, 65 mm high.) Close to a 4/3A. Diameter of an A cell but 4/3 as tall.

 

[Sam]

TromboneAl, the 15-min charger is most valuable to me when I'm away from home. In my car, I have a GPS (2 AAs), 2 cameras (6 AAs), 1 mp3 player (2 AAAs), and a flashlight (2 AAs). I usually keep 2 extra AAs and 2 extra AAAs fully charged. But sometime, more than one device runs out of battery at the same time (my bigger amera takes 4 AAs). The most I have to wait is 15 min to get fresh batteries.

At home, I'm pretty much like you in term of usage. I'm not sure how often I change the battery of the clock or the remote controls. My guess is twice a year?

I have never measured the power consumption of the charger (need to buy that Kill-A-Watt). But at home, the big slow charger is always populated with batteries, up to 8 AAs or AAAs, or up to 4 Cs or 4Ds, or a mixture of all sizes.

 

[HFWR]

I prefer boobs in a C or D size...

 

[Sam]

I don't think you're alone.

 

[samclem]

About identical C and D capacity, I'm pretty sure it's not true with NiMH. The D has at least twice the capacity of the C.

I overcame my laziness and checked at Harbor Freight's site: Both the C and D cell NiMH have 1500mAH capacity. At least the price is the same: $6.99 for two. These are really junky batteries--they have less capaity than high-quality NiMH AAA cells.

Better-quality cells (by Maha, etc) are actually "full," with C sizes rated at 5000mAH and D cells at 10,000mAH. Though a 2-pack pack of C cells cost $16, they are still a much better buy than the Harbor Freight "cheapies."

 

[cute fuzzy bunny]

Actually it is the so called 18650 size. (18mm diameter, 65 mm high.) Close to a 4/3A. Diameter of an A cell but 4/3 as tall.

Theres quite a variety of cell sizes in use. About 80% of the apple laptops, almost all of the compaq laptops, and many dell units until recently were manufactured using liion AA cells. Quite a few were made with weird little rectangular batteries as well.

Examples:

 

[Sam]

Why not take one step further, and make the circuitry transparent to the user, so all one has to do is simply swap the batteries.

 

[Nords]

I too suspect that heat is the problem.

Maybe the 15-minute C&D-cell charger has to be used in the freezer...

 

[Sam]

Believe it or not, I am about to try that as soon as I find a C or D cell battery that can be recognized by the RayoVac proprietary charger.