Convert $/Ah to $/kWh: Simple Explanation

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Discussion Overview

The discussion revolves around converting the price of battery cells from $/Ah to $/kWh, specifically for a 2.8-3.0 Ah battery cell at an assumed voltage of 3.6 V. Participants explore the underlying principles of this conversion, including the relationships between amperes, volts, and energy in kilowatt-hours.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant expresses difficulty in understanding the conversion process and seeks clarity on how to convert $0.76/Ah to $/kWh.
  • Another participant explains that to convert Ah to kWh, one would multiply Ah by the voltage (V), noting that Ah is a measure of coulombs.
  • A different participant points out that the voltage is not constant at 3.6 V and emphasizes the importance of considering discharge curves and the specified discharge rate of the batteries.
  • Another participant discusses the practical implications of amp-hours in relation to battery capacity and cost, suggesting that the cost of energy from batteries can be compared to commercial AC supply.
  • One participant humorously acknowledges a mistake regarding the "kilo" factor in the conversion, indicating a common source of confusion in the calculations.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and confusion regarding the conversion process, with no consensus reached on a definitive method or outcome. Multiple viewpoints on the implications of voltage variability and discharge rates are presented.

Contextual Notes

Participants note that the voltage of the battery is not constant and that the Ah rating is dependent on specific discharge conditions, which may affect the conversion to kWh.

km011
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It has been years since my college physics class and I'm struggling to get an answer that makes sense. I'm trying to convert the price of battery cells from $0.76/Ah (for a 2.8-3.0 Ah battery cell) assuming 3.6 V to $/kWh.

This is likely really simple, but I really want to understand how to do this.

Thanks!
 
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Amps are Coulumbs/sec (so Ah would be a measure of columbs)
Volts are Joules/Coloumb
so to get KWh (which is joules) You'd take Ah*V
 
cpscdave said:
Amps are Coulumbs/sec (so Ah would be a measure of columbs)
Volts are Joules/Coloumb
so to get KWh (which is joules) You'd take Ah*V

there's an unaccounted for "kilo" in there somewhere ?
 
Also realize that the voltage is not a constant 3.6V. Look at the discharge curves for the batteries you are considering. Also, the Ah rating is at a particular specified discharge rate only. (and temperature)
 
amp hours are used for volume of a battery. ex: 9v Duracell = 500ma/hr. which only means the battery will produce 500ma for one hour. or 100ma for 5 hrs. you had dollar signs so I can only take that as what would the cost be in dc battery output compared to alternating commercial supplied current. using 500ma is too small so figure a couple 50AH car batteries. last time I checked one kwh (AC) was about ten cents a kwh. so your 100AH batteries deliver (12 x 100) = 1200 or about 12 cents per hour. By the time the trickle charge was done you probably would have spent 3 times that amount. and that doesn't account for what bigguy said about curves, drop, etc.
 
jim hardy said:
there's an unaccounted for "kilo" in there somewhere ?

Opps there is indeed :) Only off by 10^3 that's a good day for me :D
 

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