# I need help regarding short time boosting current

Discussion in 'The Projects Forum' started by Stevelee1982, Jan 21, 2016.

1. ### Stevelee1982 Thread Starter New Member

Jan 21, 2016
7
0
I am creating a circuit to boost the amp from 25A to 35A for few seconds

My supply is from a battery using 48V dc 25A

I need to learn how to short boost the amp to 35A
I did some research but still got no idea

Thanks a lot for the help

2. ### Dodgydave AAC Fanatic!

Jun 22, 2012
5,144
769
You cant get 35Amps from a 25Amp battery, simple physics NO...

Jan 21, 2016
7
0
4. ### Dodgydave AAC Fanatic!

Jun 22, 2012
5,144
769
Thats converting AC to DC, like in a switchmode psu, you might get an increase in current but the voltage will drop, you can't get more out than you put in.

5. ### mcgyvr AAC Fanatic!

Oct 15, 2009
4,787
973
Explain EXACTLY why you think you need to boost the current..

6. ### Stevelee1982 Thread Starter New Member

Jan 21, 2016
7
0
I need to boost motor
And the load is around 1000watt

7. ### ErnieM AAC Fanatic!

Apr 24, 2011
7,436
1,625
What you need do is get some storage device that can hold 10 amps at a steady voltage for these few seconds, then be recharged.

The best device for this is another battery.

8. ### Stevelee1982 Thread Starter New Member

Jan 21, 2016
7
0
You mean like a small battery to hold that power ?Is there any idea ?

9. ### strantor AAC Fanatic!

Oct 3, 2010
4,302
1,989
How do you know that your battery can only supply 25A? Does your motor stall or what?

How do you know that 35A is the value that you need to achieve?

10. ### Stevelee1982 Thread Starter New Member

Jan 21, 2016
7
0
It's just written on the battery and the controller will power cut if the battery supply does not supply enough for the initial start
So i am thinking of a way to let it have enough for the start so once the Motor Start moving it does not really cut off and the extra load is not needed

11. ### strantor AAC Fanatic!

Oct 3, 2010
4,302
1,989
It still isn't clear whether you've actually experienced the situation where your battery does not provide enough amps.

The reason I ask is that 48V * 25A = 1.6HP. This sounds like a traction system; maybe a small scooter or ebike, or even a high power RC car. In systems like that, the battery is often spec'd in terms of continuous discharge amps and peak discharge amps (sometimes expressed as a "C" rating). If your battery is rated for 25A continuous output, then it almost guaranteed to be capable of outputting much more than that (like 10X, 250A, or more or less) for brief periods (you wouldn't need to add or change anything at all). I suspect that is the case here, going on what limited info you've provided.

However, if your battery is rated 25A max discharge rate, then in all likelihood it is already undersized for the job. If your battery has 25A max output, and you're going to demand 1000+W from it continously, it's going to drain faster than a brand new toilet.

12. ### marcf Member

Dec 29, 2014
149
20
I am a little confused. Seems like the strategy for starting a DC motor is to limit it's initial current draw.

If no steps are taken to limit the initial starting current, there will be a lot of it with possible adverse effect upon the motor.

See:

http://www.ni.com/white-paper/14921/en/

13. ### #12 Expert

Nov 30, 2010
16,671
7,314
There is nothing in your link that says the motor will commit suicide if given its proper voltage. There is nothing written about limiting its initial current. Trying to give the motor more current is exactly the opposite of limiting it's starting current. The link says the fuses usually blow because of a start current of 20 to 30 times the running current. Giving the motor even more current only makes the fuse problem worse.

Dec 29, 2014
149
20
15. ### #12 Expert

Nov 30, 2010
16,671
7,314
That certainly helps. It establishes that a DC motor can hurt itself if you apply the recommended running voltage when it is not moving because too much current is the result. Now we consider that the Original Poster, Stevelee wants to add even more current than the usual amount...or maybe he read the labels, doesn't know what they mean, and thinks a battery of 25 amp-hours capacity can not deliver more than 25 amps.

I think this is another case of a person asking for what they want instead of what they need. A belief in the absolute value of a label, entirely misinterpreted, leads the questioner to want the opposite of what he needs.

Stevelee1982 and strantor like this.
16. ### strantor AAC Fanatic!

Oct 3, 2010
4,302
1,989
That's what I suspect as well, and I was trying to chase the devil out of the dearth of details.

I have \$5 that says OP's battery can supply more than ample current, and his controller is more than sufficient to limit starting current. He doesn't need anything at all and is the victim of nameplates.

Stevelee1982 and #12 like this.
17. ### Stevelee1982 Thread Starter New Member

Jan 21, 2016
7
0
Ok thanks a lot every one after some research I finally know what I really need

I need to open a new topic or do I need to edit here ?

18. ### ErnieM AAC Fanatic!

Apr 24, 2011
7,436
1,625
If you don't start a new thread people will still wander by and answer your original question.