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My wife has an exercise bike that uses 4 C-Cells for the display. These last about 2 months and cost $7 for 4 at HD. I can get 36 AA batteries for $15. I Thought about drilling a short piece of 1" dowel for this project (that makes is SS) but opted for the quick, easy fix.

db5 wrote:My wife has an exercise bike that uses 4 C-Cells for the display. These last about 2 months and cost $7 for 4 at HD. I can get 36 AA batteries for $15. I Thought about drilling a short piece of 1" dowel for this project (that makes is SS) but opted for the quick, easy fix.

Please let us know how this works out?

AA batteries do not equal D batteries. Yes they are both 1.5 V but the mAh capacity is significantly different. The mAh capacity is the determining factor on how long the battery lasts. I am using alkaline cells (Duracell) numbers in this case which appears to be what you are using. The mAh capacity of AA cells is just over 10 times less than D cells. AA cells will cost you significantly more. So by my calculations AA cells will cost you over twice as much as D cells.

36 AA cells approximately equals 4 D cells and you are paying twice as much for the AA cells.

I did all the calculations in my head so if I missed something please correct me as I know you will.

You missed the pesky 'detail' that he was using "C" cells before.

JPG wrote:You missed the pesky 'detail' that he was using "C" cells before.

Oops, I hate it when that happens. OK, the numbers scale fairly linearly. So approximately 16 AA cells equal 4 C cells. That means the cost is about the same regardless of which battery you use.

Have you considered picking up a 6v DC wall wart and using it instead? Check around your house, you might already have an extra one laying around from old junked electronic equipment.
If you use a wall wart, you can simply plug it in the wall when needed and umplug it when done. And, you never buy batteries again.

Another idea is to get rechargeable AAs and a charger, $20 for 8 and a charger: https://smile.amazon.com/EBL-Battery-Ch ... th+charger. For a while, I used some AAs in D cell adapters for an exercise bike; sure, they didn't last as long, but since they were rechargeable I didn't have to throw them out when done.

I am still using some batteries that are well over 10 years old.

I went to this website http://www.allaboutbatteries.com/Energy-tables.html and decided it was worth experimenting since AA and C cells are the same length. D cells are longer so you can’t do that with them. I also got a cost comparison from HD because that’s about the cheapest place I can get C cells and it is known as a source by everyone on this forum. I usually get AA batteries at Costco and they run about 27 cents each vs. $1.50 for C cells. Best case I’ll save quite a bit and if not, worst case I now have a kit to create a C cell when I don’t have one. I’ll let you know how this works out in a couple of months – or less.

Picture is v 1.1 battery pack for bike.

roy_okc wrote:Another idea is to get rechargeable AAs and a charger, $20 for 8 and a charger: https://smile.amazon.com/EBL-Battery-Ch ... th+charger. For a while, I used some AAs in D cell adapters for an exercise bike; sure, they didn't last as long, but since they were rechargeable I didn't have to throw them out when done.

I have a charger and bought some of those batteries (as pictured) two years ago. They are about played out. I might do that or, since I have a box full of power supplies, adapt that if I can figure out how to wire it in.

Both good recommendations. Thanks.