# How to calculate cost of AA accumulator charge? [closed]

I would like to calculate how much it will cost to change AA accumulator. Is it really cheaper than usage of batteries (don't consider ecology question as of now)?

Let's say I have the following

1. accumulator: GP Rechargeable NiMH AA HR6 270AAHC 2700 series (2600 mAh);
2. battery charger 1: GP PowerBank Smart 2 (GPPB14, pdf)
3. battery charger 2: Technoline BC700 (pdf).

In accordance with BC700 data, accumulator currently is in the following condition (?): 200 mA, 1.26V.

The cost of electric power is 3.18 per K.W.H..

1. Is there any difference in terms of cost (besides time of charging) which battery charger is used and in which mode?
2. How to calculate cost of charging?
3. How to calculate possible cost of accumulator refresh (=recovery)? Believe, it will depend on number of charges and discharges.

## closed as off-topic by jinawee, Waffle's Crazy Peanut, Kyle Kanos, Pulsar, Brandon EnrightDec 30 '13 at 19:13

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "This question appears to be about engineering, which is the application of scientific knowledge to construct a solution to solve a specific problem. As such, it is off topic for this site, which deals with the science, whether theoretical or experimental, of how the natural world works. For more information, see this meta post." – Waffle's Crazy Peanut, Kyle Kanos, Pulsar, Brandon Enright
If this question can be reworded to fit the rules in the help center, please edit the question.

• I don't think this is on topic here - it's not about a physics concept. – David Z Dec 30 '13 at 11:02
• @DavidZ, which stack exchange site would you recommend? Haven't found anything more suitable... – LA_ Dec 30 '13 at 11:41
• Maybe Electronics.SE is a better home for this question? – Ali Dec 30 '13 at 12:17
• As a cheap estimate, look at the back of the charger to see its wall-plug current rating & multiply that by the time it takes to charge. If the cost of electricity is even 5% the cost of a new AA battery I'll be shocked (pun intended) – Carl Witthoft Dec 30 '13 at 13:21
• As Carl and John point out, the electricity cost is negligible, so you don't need to worry about prices. – DumpsterDoofus Dec 30 '13 at 16:55

## 1 Answer

I agree with David that the question is a bit off topic, but there is a physical principle that you have to take into consideration so it's worth a brief answer.

The capacity of the battery is an amount of energy and the KWhour is also a unit of energy, so to calculate the cost of charging you just need to calculate the battery capacity in KWHours. The capacity of your battery is 2600 mAh, which means it can provide a current of 2.6A for one hour. The voltage of an AA NiMH battery is $1.2\,V$, so the power $W$ is voltage $V$ times current i.e.

\begin{align} W &= V\cdot I \\ &= 1.2\,V \times 2.6\,A \\ &= 3.12\,W \\ &= 0.00312\,kW \end{align}

This is the power the battery can produce for an hour, so the energy is simply 0.00312 KWHours, and the cost is therefore $0.00312 \times 3.18 \approx 0.01$ currency unit. In practice charging a battery is not 100% efficient, but even so the power used will be a tiny amount. You don't say what the units of currency are, but unless you live in a country with a very unusual currency the cost of charging the battery is likely to be negligable.