How to slove voltage drop ?

[Sudhakar.R]

Hello,

I'm using bldc motor. Battery Voltage is 40.4V. I run the motor on no load the battery voltage is 40.4V and when I apply the load the voltage is dropping.

load(current) is 1A & voltage is 40.3V

load(current) is 2A & voltage is 40.2V

load(current) is 3A & voltage is 40.1V

load(current) is 4A & voltage is 39.9V

how to slove this problem if any one know help me.

[Peter BENSCH]

Well, every voltage source has an internal resistance at which voltage drops as the load current increases. The wiring from the voltage source to the load also has an additional ohmic resistance. This inevitably causes the output voltage to drop as the current increases.

Does this answer your question?

Regards

/Peter

[LCE]

And these values don't look too bad.

It's only about 1% voltage drop at 4 A.

[Sudhakar.R]

again I test, this time

load(current) is 1A & voltage is 40.1V

load(current) is 2A & voltage is 39.6V

load(current) is 3A & voltage is 39.1V

load(current) is 4A & voltage is 38.8V

how to slove this pratically?

[Peter BENSCH]

If you are concerned about some voltage drop, you should connect a more powerful power supply with lower internal resistance. Or change the wiring. Or both.

Since we don't know what you have connected where and how, we can't say much more.

Regards

/Peter

[Sudhakar.R]

The motor is connecting to battery. The battery voltage is 40.5V and i measure the voltage on no load and load.

[Peter BENSCH]

We understand that.

And as I said, the voltage at the terminals of the battery will inevitably collapse under load, which is caused by the internal resistance, also called output impedance.

[Sudhakar.R]

hi @Peter BENSCH​ ,

I want to display the State of Charge(battery Percentage) on cluster. this changes affect the SOC.

how to solve this in softwer. I don't know where i made the mistake. if you know help me.

[Peter BENSCH]

Your mistake is that you cannot reliably measure the status of a battery when it is under load. For this purpose, a pause is usually used during which the battery is briefly without load.

No one will be able to help you here because no one knows your system design and the presence of the loads over time. You should therefore thoroughly revise your concept again.

Regards

/Peter

[Sudhakar.R]

thank you for your comment.

[Sudhakar.R]

our System Design,

I'm working on EV Two wheeler Cluster. I measure the voltage from battery using voltage divider method.

the battery voltage (31 - 40.5) is convert into battery percentage(0 - 99).

In driving time, the voltage is dropping depends on the load. the load is 4A that time the battery is 20 percentage decreas. this is affect the SOC.

[LCE]

For a really good evaluation of battery charge status, you need more than the voltage.

At least know the capacity (Wh), constantly measure voltage and current over time.