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a few battery questions Answered

i got 2 questions

1st. i was shopping at target today and noticed that the big energizer rechargeable "D" size batteries has the same mAh rating as the smaller "AA" rechargeable energizers i have at home (2500 mAh) can any one explain this?

2nd. i've seen some pics around the site of custom "D" sized "AA" battery holders that hold 4 "AA's" in a "D" sized space ( https://www.instructables.com/id/SA59T0CFB11L31B/ ), but i haven't seen any instructions on how to make them. can some one make an instructable about this? (preferably one that can be made to hook up the" AA's" in parallel)

Discussions

I want to put a battery powered, (AA) CLOCK in a inaccessible place and I would like to have the battery/power source last as long as possible.. Years maybe? Will multiable AA batteries soldered in parallel work? Would a D last longer? Which "type" would be best.

it does not make sense to use rechargeable batteries in such application batteries degrade over time. after few years they wont hold charge well and youll need to replace them anyway you can place the battery in accessible place and connect it to the clock with long wires

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westfw

10 years ago

For your first question, it's because battery vendors and consumers are both cheap, and they make the D-sized batteries out of mostly empty space with what is essentially an AA-sized cell inside. Going to more niche battery suppliers, you can get D cell batteries up to about 12000mAh, but they cost about $10 each (5 times the capacity at 5 times the price; go figure...) For a lot of applications, the smaller capacity rechargables work fine because they can supply as much current as a larger alkaline battery, and after all; they ARE rechargeable.

Not all battery technologies are easy to connect in parallel; minor differences in cell voltage in paralleled NiMH or NiCd batteries will result in the lower voltage
cell discharging the higher-voltage cell. Li-ion happens to work OK in parallel, but I think it's the only common technology that does work that well.

10 bucks for that much capacity! thats a steal! one 4,000 mAh D cell from radio shack cost that much dose that super capacity D cell work with energizer chargers or am i going to by a special charger

You'll need a special charger unless you're willing to wait "a long time" for the charge to complete. You have to assume that the engergizer charger is designed for a "2500mAh charge", so it will take about 4x the normal time to charge a 10Ah battery. Assuming it doesn't have a timer cut-out. There was some recent discussion of the issues in A CandlePower Forums thread.

You might also want to consider:
  • Sanyo is supposed to be coming out with 5AH "eneloop" D batteries; low self discharge (and apparently a compromise on price vs capacity.)
  • NiCd D cells (from good battery suppliers) are also about 5AH and half the price of NiMH. They apparently also have lower self-discharge, though I've never had much luck with NiCds...

i checked the charger i have available to me it out puts 1.4v to 8.4v and 0.04A to 0.5A depending on the battery it has holders for AAA, AA, C, D, and 9v sized batteries i'm making a big battery pack for a nokia 6010 for three reasons 1st i don't like having to frequently recharge my phone so i wanted to make a pack that could power the phone on standby for weeks 2nd i like to rebel against increasingly small phones so beefing up my phone and transforming it from a candy bar into a brick is my way of being different 3rd i want take as much stress off the cellphones original battery as possible because it would be the least likely to find a replacement for in the future i had at first bought a D cell battery holder (with space for 4 the forth cell will be a blank) but then i found the truth about D cells and now i'm trying to find a way to salvage my project with out buying a new battery holder. so if i buy the super fancy D cell and plug it in to the energizer charger is there a greater risk of explosion? whats self discharge?

. 1st: I don't know, but westfw's explanation sounds good and he usually knows what he's talking about. . 2nd: all you need is two metal disks. Put your AAs into a bundle and place one disk on the top terminals and the other disk on the bottom. Use something (rubberbands?) to hold everything together. Make sure all the batteries are pointed the same way, ie, all the pluses together.