# Power from a PPE 9v battery

Discussion in 'The Projects Forum' started by stevy123, Mar 9, 2008.

1. ### stevy123 Thread Starter Active Member

Nov 19, 2007
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Hi All

I have a circuit which i am powering from a 9V PPE battery. The circuit is drawing 300mA, how long should i expect the battery to last?

Anyone know the formula to work this out?
How much longer would i get if i was using 8 AA 1.5 batteries to give me 12V?

Steve

2. ### hgmjr Moderator

Jan 28, 2005
9,030
214
What is the meaning of PPE?

hgmjr

3. ### SgtWookie Expert

Jul 17, 2007
22,182
1,728
I think Steve is talking about PP3 9V "Transistor" batteries.
How long the battery will last depends upon the construction of the battery.
Typical Capacity
(mAh)
565 (alkaline)
400 (carbon-zinc)
1200 (Lithium)
120 (NiCd)
175 to 300 (NiMH)
500 (Lithium polymer rechrg)

Let's say you use a lithium cell. 1200/300 = 4 hours - not long.

You could use six 2500mAh AA batteries to get just over 8 hours of operating time.

4. ### hgmjr Moderator

Jan 28, 2005
9,030
214
If you are referring to PP3 then based on the mAh (milliamp-hour) ratings that sgtwookie has provided then you can estimate the duration of an alkaline type 9V battery with a load of 300 milliamps to last approximately 565/300 = 1.88 hours or 113 minutes.

The same means of calculation can be used to estimate the duration of for each of the battery types that sgtrwookie has listed.

hgmjr

5. ### Audioguru New Member

Dec 20, 2007
9,411
896
Why not look at the datasheet of a 9V battery like Energizer's alkaline battery. www.energizer.com
1) Its voltage does not stay at 9V, It drops quickly to about 7.2V then drops slower to nothing.
2) Its capacity with only a 25ma load is 625mAh but then its voltage has dropped to 4.8V.
3) With a 300mA load, it reaches 6V in a little less than 1 hour.

Here is its voltage curve with a 250mA load.

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Nov 19, 2007
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