# Lithium battery enegy

Discussion in 'The Projects Forum' started by meththas, Mar 16, 2012.

1. ### meththas Thread Starter New Member

Feb 26, 2010
16
0
Hi All,

I am trying to decide between two voltages of a battery that gives the same Ah output. The first is 14.8V and other a 11.1V battery both giving 4.4Ah (Lithium).

If I use a lower voltage how will that affect the energy and cycle life of the battery?

Currently I expect the 14.8V 4.4Ah battery to cycle through ~200 cycles of my instrument. I was told I can use a lower voltage without much affect on this number... but I don't know why. Can anyone confirm and explain this to me please.

2. ### wayneh Expert

Sep 9, 2010
11,920
2,855
The higher voltage has more power, since power is voltage x current. But your load may not benefit if it has a linear voltage regulator inside it, which simply burns off excess voltage as heat. So, more info is needed to answer the question.

3. ### ishaan3731 Member

Jun 23, 2011
43
1
please define the problem in a precise manner ie. what kind of circuit you are using that supply for.... and other important information etc. It all depends from application to application ....... Just for eg when making a robot.... u need 12 volts for the motor ....but the actual requirments to get maximum rpm from motor is the availibilty of current of around 1A.......even if ur operating the motor at 9V's....... So alll depends on ur application!!!!!

4. ### wmodavis Well-Known Member

Oct 23, 2010
737
149
The battery's energy or power is, as wayneh says, equal to voltage times current and is in no way dependent on "what kind of circuit you are using". That simply has nothing to do with your question. It does NOT depend on your application!

14.4 x 4.4 = 65.12 watt-hours of energy
11.1 x 4.4 = 48.84 watt-hours of energy
65.12 - 48.84 = 16.28 watt-hours more energy in the 14.4 volt battery.

Of course that assumes a fully charged battery capable of its full rated capacity.

5. ### meththas Thread Starter New Member

Feb 26, 2010
16
0
Thanks for all the replies.

the battery will be supplying 2 different voltage rails 5V and 3.3V that has a mirocontroller, sensor and a LCD connected to it. 5V will take around 200mA as will the 3.3V.

The instrument will be powered up for around 60seconds at a time while it takes some readings, analyses and displays.

I am using switch modes to bring the voltage down to the level required.

Using the 14.8V seems a bit wasteful to me as I do not need it to be that high. Hence why I wouldnt mind to move to the 11.1V battery.

6. ### #12 Expert

Nov 30, 2010
16,031
6,541
The 14.8 V supply "wastefulness" is almost eliminated by using a switchmode controller. The best thing about switchmode controllers is that they waste very little energy as heat...unlike a linear regulator. I wouldn't change from 14.8 to 11.1V if it only cost a single dollar, as long as a switchmode controller was in charge.