# What type of battery would this required?

Discussion in 'Electronics Homework Help' started by Nick90, Dec 1, 2012.

1. ### Nick90

7
0
Dec 1, 2012
Hey there,

Ok so I'm a total beginner when it comes to electronics, as I'm a product designer at university, but in one of my projects I have an air pump and have to be able to justify if my product will be mains powered or battery powered.

So if someone could basically explain to be how I would calculate what size of batteries it would require and how long they would last it would be greatly appreciated.

I bought a generic pump online and one of those electronic readers and it seems to be averaging about 5-6W, 0.025A and 240V.

Sorry if that doesn't make sense, I'm not very experienced as i said.

2. ### Harald KappModeratorModerator

11,443
2,628
Nov 17, 2011
That sounds like the pump is driven by AC. A battery delivers DC. You can use a DC/AC inverter to generate the necessary AC from a battery. But unless using a battery is mandatory (e.g. for portability) I would not recommend that venue.

Be careful when handling 240 V. If in doubt, get expert help from someone who knows how to deal with that stuff.

3. ### Nick90

7
0
Dec 1, 2012
Thanks for the reply, yes I'm almost certain that I think be running the product from the mains, not battery, I just need to put this into my project to show I've taken into consideration every possible option.

Ok say i got my hands on a DC air pump instead, what would the equation be to calculate how long the battery would last at a constant drain?

Thanks

4. ### davennModerator

13,812
1,945
Sep 5, 2009
Hi there Nick
welcome

well we cant answer that till you actually get a pump and tell us what its spec's are

cheers
Dave

5. ### davennModerator

13,812
1,945
Sep 5, 2009
Hi there Nick
welcome

if the pump is say 12V and requires 1Amp, then you need to consider how long you want it to run for 2 hrs, 10 hrs etc etc and get a battery with the Amp-hour rating to suit with a bit extra
An example a 12V battery with a 7A/H rating and if it was 100% efficient ( it wont be) you could get a 7 Amp drain for 1 Hr or 7 hours at 1Amp / hour.
In practice that doesnt happen, as with time the battery voltage drops off and it looses its ability to continue to supply the required current. I would expect somewhere around 5 hours of life from a 7A/H battery contineously drawing 1 Amp

that will give you a reasonable approximation... it will also be determined by things like the quality and type of battery of the battery. eg sealed lead-acid, NiMH, LiPO etc

cheers
Dave