Unity Network - How to send a float value from cliento to server

hello, I have a problem sending values from a client to a server in unity network.
I have a class that sends the percentage of the battery in the client and that will be updating in the server but when I run client-server, the server does not receive data and the client shows me that:

Trying to send command for object without authority.
UnityEngine.Networking.NetworkBehaviour:SendCommandInternal(NetworkWriter, Int32, String)
BatteryInfo:CallCmdSendBatteryValue(Single)
BatteryInfo:Update() (at Assets/Scripts/BatteryInfo.cs:17)

this is my code:

Code (CSharp):

1. using System;
2. using System.Collections;
3. using System.Collections.Generic;
4. using UnityEngine;
5. using UnityEngine.Networking;
6.  
7. public class BatteryInfo : NetworkBehaviour {
8.     [SyncVar]
9.     public float valorBateria;
10.  
11.     private void Update()
12.     {
13.      
14.         if (!isServer)
15.         {
16.             valorBateria = (SystemInfo.batteryLevel) * 100;
17.             CmdSendBatteryValue(valorBateria);
18.         }
19.      
20.     }
21.  
22.     [Command]
23.     public void CmdSendBatteryValue(float b)
24.     {
25.         RpcUpdateBaterry(b);
26.     }
27.  
28.     [ClientRpc]
29.     public void RpcUpdateBaterry(float b)
30.     {
31.         valorBateria = b;
32.     }
33.  
34. }
35.  

Am i using using the commands and RpcClient wrong?
I am usin unity 2017