maximum current for 5 mins?

[george88b]

hello..

i have a motor which is 1.2 KW and 100 A. I want to connect it with a battery car. with what criterias i will select the battery? and if my Ahr of the battery is 42, and I20=2.2 how much is the max current for 5 mins??

thnx very much

 

[(*steve*)]

If the Ahr rating is 42, and you want to discharge it in 1/12 of an hour, what do you think the current would be?

Is this a question from a school assignment?

If not, then the answer in practical terms, is not so simple.

 

[george88b]

If the Ahr rating is 42, and you want to discharge it in 1/12 of an hour, what do you think the current would be?

Is this a question from a school assignment?

If not, then the answer in practical terms, is not so simple.

yeah..is from school assignment..will be 3.5 amps..but i read a lot about this and is confused me..so the right answer is 3.5 amps?

 

[(*steve*)]

How did you get 3.5 amps?

What does an Ahr rating mean? How is that number arrived at?

 

[george88b]

is mean that gives 42 Amper per hour--> in 5 minutes will give the 1/12 of 42..is that not right?

 

[davenn]

is mean that gives 42 Amper per hour--> in 5 minutes will give the 1/12 of 42..is that not right?

not quite try again, with this hint a 42 A/H battery will give 42 Amps for 1 Hr (under ideal conditions), thats it, then its flat

so what do you think its capable of supplying for 1/2 hour (30 mins) ?

or if you only draw 21 Amps, how long do you think it will last before going flat ?

Dave

 

[george88b]

so..for only 30 mins will pass 84 amps?..?
i know that if i have 100ahr will pass 5 amps in 20 hours and 20 amps in 5 hours.. so in my case will pass 84 amps per 30 minutes..

 

[george88b]

so..for only 30 mins will pass 84 amps?..?
i know that if i have 100ahr will pass 5 amps in 20 hours and 20 amps in 5 hours.. so in my case will pass 84 amps per 30 minutes..

i think that time i m right! and for 5 mins will pass 504 amps..if i m right;p

 

[(*steve*)]

The figures seem right.

The wording isn't quite right though.

A 100 amp hour battery can power a 20 amp load for 5 hours. A 100 amp hour battery will be drained in 20 hours if the load draws 5 amps.

you don't "pass 5 amps in 20 hours", you pass (not my preferred word) 5 amps for 20 hours.

 

[george88b]

ok..thnx a lot..!!!!!!!!!!!!!!

another one question pls?

i have 1200 W power and 100 Amper
how can i choose a car battery? i have to find a car battery which have 100 amper?

 

[(*steve*)]

The real answer is to check the datasheet for the battery you want to use.

However, if this is a theoretical question, you might like to use google to find out what current is required for car starter motors. You could also look at the "cranking current" that car batteries are rated for.

Ahr clearly allows you to determine how long a given load can run from the battery. (How long --- in theory -- would this 1200W motor run from your 42Ahr battery?)

There are other ratings which indicate the maximum current you can draw from the battery (without damaging it)

 

[george88b]

The real answer is to check the datasheet for the battery you want to use.

However, if this is a theoretical question, you might like to use google to find out what current is required for car starter motors. You could also look at the "cranking current" that car batteries are rated for.

Ahr clearly allows you to determine how long a given load can run from the battery. (How long --- in theory -- would this 1200W motor run from your 42Ahr battery?)

There are other ratings which indicate the maximum current you can draw from the battery (without damaging it)

the problem here is that i dont know if the 42 ahr i used is correct. i have 1200 w motor which want and 12 v battery..from this informations i can find the ahr or the CCA?

 

[(*steve*)]

Get the make and model of the battery and google it, or call the distributor of those batteries.

If you don't have a battery, determine the ratings you require and go find a battery specialist who will recommend an appropriate battery for you.

 

[george88b]

i dont have battery my friend..if i maltiply my ampers by 24 hours i will find the Ahr? (90 A x 24) ?
my question is can i calculate the Ahr from the informations i have?(my informations is 90 A, 1200W, 12V)

 

[(*steve*)]

Take that information along with the time you want the motor to operate to a battery specialist and get their recommendations. Remember that you need to allow time for the battery to be charged, and that you never want to discharge a lead acid battery too far. You may want to limit the discharge to 50% (or even less).

A battery specialist should be able to help you.

 

[Resqueline]

I have 1200 W power and 100 Amper
how can I choose a car battery? i have to find a car battery which have 100 amper?

A battery is not spec'd in Amperes (well, Cold Cranking Amperes maybe, but that's a different matter not to be considered here).
Being a school task, given that you have learnt about Ohms law and all that, what other (two) units can you calculate from those two units given?

 

[george88b]

A battery is not spec'd in Amperes (well, Cold Cranking Amperes maybe, but that's a different matter not to be considered here).
Being a school task, given that you have learnt about Ohms law and all that, what other (two) units can you calculate from those two units given?

hello my friend..i m studying mechanical eng.. i learn in uni just the basics for electronics..i know that i can calculate the C (C=P/V), R and Volts

 

[Resqueline]

Well, my guess is that the question is about the battery voltage needed to get 1200W at 100A.

 

[george88b]

Well, my guess is that the question is about the battery voltage needed to get 1200W at 100A.

the batteries specifications are giving the CCA, Ahr, and volts.