Battery Discharge role

[sysysy]

hi,

recently i'm doing a project and need to buy a lipo battery.
I found that a discharge rate is always include for in the battery spec and it affect the battery price?

but what i dun understand is how the discharge rate affect the battery performance?
higher or lower discharge rate will give a better performance?

Because i found that more higher discharge rate, more expensive the Lipo battery.
for example( 20C vs 30C) discharge rate.

Hopefully, can get some knowledge from u guys.

Thanks.

 

[OlPhart]

I'd recommend looking into the basics of energy storage. See how the parameters affect performance & suitability for a given application. <<<)))

 

[kpatz]

What's the current draw of your application and the mAh rating of the battery?

 

[audioguru]

I use Li-Po batteries in my electric RC model airplanes and helicopters. Some people have tested many brands and find that some Chinese manufacturers lie about their max discharge ratings. You should look for tests of the batteries that you use.

A max discharge rating is exactly what it says. Its the max allowed discharge current without too much voltage lost or too much heat being made in the battery. The higher the better.

Now I use Thunder Power batteries that are assembled in the US. They have a high max discharge current (25C) that allows my airplanes to climb vertically and go very fast at full power. Each flight lasts longer than other batteries. They can have many charge-discharge cycles. They are 4th generation.

Before I got Thunder Power I used another more expensive brand that has low max discharge current (14C) and the batteries take only a few charge-discharge cycles before they are useless.
My friend bought some cheap Li-po cells from China for a very low cost. He gave me one. It had low power (a low max discharge rate) and it lasted for only a few flights.
The poor batteries are 3rd generation (2 years old technology).

 

[sysysy]

What's the current draw of your application and the mAh rating of the battery?

1800mAH and my max current less than 10A, let assume 10A
is it with the 25C discharge rate,

mean the maximum current draw in this battery is 1.8 x 25 = 45A

does it mean like this?

 

[audioguru]

The battery might produce 45A for a moment with a high voltage loss but a continuous current of more than 15A will probably cause a fire.
The connector might melt at 15A continuously but might survive 45A for a moment.

 

[sysysy]

The battery might produce 45A for a moment with a high voltage loss but a continuous current of more than 15A will probably cause a fire.
The connector might melt at 15A continuously but might survive 45A for a moment.

Why the continuous 15A current will cause the fire?

May i know the further reason?

 

[kpatz]

1800mAH and my max current less than 10A, let assume 10A
is it with the 25C discharge rate,

mean the maximum current draw in this battery is 1.8 x 25 = 45A

does it mean like this?

On paper, yes. In real life, resistance of the connectors/wires and heat generation will become a factor at such high currents. Also, at 45A, you'll drain the battery in under 3 minutes.

But, if your circuit draws a max of 10A, you can get by with a battery that has a max discharge rate of (10/1.8) = 5.6C.

As long as your circuit stays under the max discharge rate, the battery will survive.

 

[audioguru]

Why the continuous 15A current will cause the fire?

May i know the further reason?

I am just guessing since you didn't post the datasheet for the battery.
Some of my Li-Po battery cells are only 120mAh. Their max current rating is 14C which is 1.68A. When the plastic cover breaks off the connector and the contacts short together then there is enough current to create a spark, melt and shorten the contacts.