The economy of rechargeable batteries

[Lithp]

Can someone please explain how rechargeable bateries are, in the long run, more economical?
I understand that you only have to buy one battery and recharge it. However, doesn't the cost of charging them outweigh the cost of buying new ones? Plugging a charger into an outlet costs money. Does it cost the same amount as plugging in a hair dryer for example?
Clearly I do not understand electronics and electricity. Can someone please explain how it is more affordable to buy rechargeables. In laymans terms please.

Thank you

 

[LEDSmith]

With Respect to flashlights on this forum, most are powered by CR123 cells. Typical cost of a CR123 lithium is $1 per cell.

Investment in rechargeable CR123's is $50. This includes the charger and 2 batteries. each battery is good for 500 uses. So 2 batteries equals 1000 uses.

So if you do the math, The long term cost of non-rechargebale cells is $1000. versus $50 for rechargebles.

Power required to charge the bateries is negledgable.


Above is the simple explaination, not factoring in the differences in cell capacity.

 

[ledy]

This is a quote from: http://www.gaiam.com/retail/gai_content/learn/gai_learnArticle.asp?article_id=1430


So throwaway batteries are wasteful and a health hazard. They're also surprisingly expensive. Alkaline cells cost around $0.90 to $2.20 per battery, depending on size and brand. Use it once, and then throw it away. In comparison, rechargeable nickel-metal hydride cells - including the initial cost of the battery, a charger, and two or three cents worth of electricity - cost $0.04 to $0.10 per cycle, assuming a very conservative lifetime of 400 cycles. Chargers outlive batteries, so these rechargeable cost figures err on the high side. Typically, throwaway batteries cost $0.10/hour to operate, while rechargeable batteries cost only $0.001/(1/10 of one cent) per hour.

 

[evan9162]

Electricity costs are almost nil.

Consider:

Let's say a charger is only 30% efficient. That is, 30% of the power consumed by the charger can be released by the battery while discharged.

So, let's take a AA NiMH cell, 2000 mAh. When charged, the cell contains 2.4 W-h of energy. So to charge that cell takes 8 W-h of energy. Lets call the life of the battery 500 cycles, which are all full cycles. 8 * 500 = 4000 or 4kWh. Around here, 1kWh of electricity costs about 6c, so a single cell will use 25c of electricity throughout its useful life.

Let's assume you will use it in an application where you get roughly the same battery life per charge as you would a regular alkaline cell. So, to get the same use from alkalines would require 500 alkaline cells. If you get them for 25c each, that's $125 of batteries.

Lets say you require 4 batteries, and get them and a charger for $30 (a reasonable price). 500 battery changes will cost you $30 (cost of batteries + charger) + 4 * 0.25 (cost of electricity to charge 4 cells 500 times) = $31.

Now, 500 battery changes of 4AA alkalines will cost you $500. ($125 * 4)

So, to get the same battery usage costs $31 with recharagbles, and $500 with alkalines.

That's how they're more economical.

 

[jtr1962]

Even at current NYC rates of $0.18/KW-hr the electricity to recharge a 2000mAH NiMH cell over its lifetime only costs about $0.75. The cells themselves can be had for as low as $1. You have $1.75 versus $125 for alkalines (assuming alkalines can be purchased for $0.25) over the life of the cell (not to mention that you have 499 less cells in the landfill). About the only use for alkalines is in low-drain applications like wall clocks where self-discharge is a factor, or any other intermittant use where batteries might go a year or two between changes. For high-drain applications, and especially for children's toys, they make absolutely no sense. My sister's in-laws have three kids and spend $30 a week on batteries. This is beyond stupid. In fact, since low-drain applications use either AAA or AA cells, I don't think C or D disposible cells should even be allowed to be sold any more. They're only used in high drain applications better served by rechargeables. It's no big deal to buy a few chargers and sets of batteries so a fresh set is available when the set in use is exhausted.

BTW, I've yet to see Cs or Ds with the same volumetric capacity as AAs. This would mean 7000 mAH Cs and 13500 MAH Ds. I'm sure though that despite this current production NimH Cs or Ds outperform alkalines in high drain applications even though the alkalines allegedly have greater capacity.

 

[Lithp]

Interesting. Thank you all for your input. I didn't realize that charging a battery was so inexpensive and therefore so economical. Your explanations have clearly answered my questions.

Thank you.

 

[cobb]

The only down side, if the device needs batteries to use in an emergency or a smoke detector, your better off with non recharagables as they self discharge over time without use. But for stuff you use daily or uses batterys fairly quick like a digital camera, RC car, high power flashlight, etc you break even and come out ahead if you take care of them.

FYI, the ccrane company sells a solar powered battery charger for regular batteries and maybe nimh, do not beleive they have one for lithium, but I doubt it would be that hard to wire one up to a standard charger.

 

[evan9162]

Good point cobb (jtr hinted as well) - for devices which only need battery changes every year or so, regular batteries are the way to go, as you likely won't ever break even, and the alkalines will work better.

 

[Xrunner]

For me rechageables isn't all about cost. While the savings ($ and environment) are nice, the big factor is that I can always have them ready to go. After using a light for a while, I can charge up the cells, knowing that next time they will be back to 100%.

-Mike

 

[Dukester]

Though I am not as scientific as the above post I simply put it this way. If you use your lights every night than rechargebles are the way to go. I use rechargeables because they get used nightly to run my dogs on 40 acres of mostly wooded property. If I only had Lithium Powered Lights i'd be in the poor house....

 

[Lynx_Arc]

In many devices nimh outlast alkalines several times over, buying two sets so you have one set fresh while the other is recharging saves you time and gasoline making that special trip when you unexpectedly find your batteries dead with no spares. Time and Gasoline are two commmodities rechargeables save no one thinks about. If you stocked up 4 sets at a time that would be 125 trips to the store of which perhaps at least 20-25 were for batteries alone.

 

[cy]

I use li-ion not because of cost, although savings is always nice.

primary reason for using li-ion rechargables is performance.

 

[Lynx_Arc]

Another advantage of rechargeables is with car cord based chargers you can be out camping etc and oooops I need to drive 300 miles to get batteries, just plug in that fast charger and an hour later or so you are good to go again.

One note.. you can recycle your disposable batteries instead of throwing them away, think about saving them up including nicads and dead nimh etc batteries and taking a box in once in awhile to your local recycling center. Be a responsible flashaholic.

 

[TORCH_BOY]

With lots of battery powered things around the house I was always going shopping for batteries, now I use rechargeable batteries, this over a short period of time has not only saved
me alot of money but also time.

 

[Lynx_Arc]

One other nice thing about rechargeables.. you don't feel guilty for accidentally leaving something on and draining them dead nor using them a lot more than just necessary. I sometimes just play with my lights because I know they don't cost me anything to recharge the batteries. Anything I have rechargeables for I use whenever I *FEEL* like it instead of just *NEEDING* to use it.

 

[cobb]

As an example would be my palm m125. I used it to read webapges of line, take notes, read text from my digital books and a set of alklines only lasted 2 weeks. SO, every month I needed 4 aaa batteries for my palm. I saw on a furm they can use nimh batteries, they were inexpensive and the palm has a feature to adjust its battery meter for them. I then bought a set for ten bucks, another ten bucks for a charger and keep one set charged, while another in the palm. So I then instead of buying a set of aaa each month for my groceries, I just swapped out the batteries and recharged them. I do use regular batteries like alklines in my tape less tape recorder as it uses a pair every few months, but for high drain stuff they are a must if you plan on using it a lot.

 

[jayflash]

To reiterate what was mentioned. One must evaluate the frequency and extent of use to determine whether rechargeables are a worthwhile investment. Sometimes primary cells are a better choice.

For my usage level, regular, primary, CR123 cells are cheaper than L Ions because, if I understand correctly, rechargeable lithiums only last about two years or so. If that's accurate, then they'd die of old age before I'd break even. However, for heavy, frequent, use, rechargeable cells are definitely the way to go.

 

[ledy]

Why do rechargeable lithiums only last a year or two? The one in my laptop (2 year old now) is still going strong. I must admit that I use the battery around once a month, other than that, I just take the battery out and leave it in the bag (lighter laptop). So it's not all about the length of time.

 

[Kiessling]

I absolutely have to chime in here to cure some of you from your delusions about those *rechargeable* /ubbthreads/images/graemlins/icon15.gif batts ... /ubbthreads/images/graemlins/evilgrin07.gif /ubbthreads/images/graemlins/grin.gif

some disadvantages of rechargeables:
- they need care, I do not have that time nor the will
- I do not like chargers runnnig in my home with potential risks associated, especially when I am not at home
- I'd like to be able to change batts "in the field"
- if the batts are empty, I'd like to replace them, not wait for a recharge
- travelling with rechargeables is uncomfortable and you need more luggage
- I'd like to be sure to have top performance with a new load, and not degrading rechargeables
- it will take a long time to pay for the expensice Li-Ions and their charger compared with now cheap CR123s
- rechargeables are potentially dangerous, especially Li-Ions and when used in series
- rechargeables represent one more variable that can go wrong in an already complex system, making diagnostics harder
- Li-Ions have an expected life of 2-3 years indipendent of usage

... and all this just to avoid a few bucks per week for fresh batteries .... no way. And I really like fresh battereis ... ya know ... maybe something Freudian ... /ubbthreads/images/graemlins/naughty.gif

maybe I would talk differently if I were to use my lights heavily in my job, but alas no, and so ... rechargeables are BANNED ! /ubbthreads/images/graemlins/smile.gif

bernie

 

[evan9162]

I take it you don't own a digital camera?