Not able to add ether in my private network's account

Question

1. I have created a small ethereum private network. I opened launched the private network from terminal 1, launched the geth console from terminal 2, and opened mist browser in terminal 3. Once mist is launched, I created a new account (Eherbase) which has currently 0 ether. Now, when I do miner.start(), it gives null and "INFO [03-04|10:49:12] Commit new mining work number=1 txs=0 uncles=0 elapsed=777.632µs", on other console, but the balance for the account is still zero. How can I add ether to my account?

2. I started again with new genesis.json file with a account already having some ether, but I am now not able to see that account in my mist browser? what should I do?

OS - Ubuntu 14.04
geth- 1.8.1-stable-1e67410e
mist - 0.8.10

commands that I used: terminal 1-
Created private network # geth --datadir=./chaindata/ init genesis.json
launch network # geth --port "35555" --datadir=./chaindata/
terminal 2-
open geth console # geth attach ipc:/address_to_geth.ipc
terminal 3-
open mist # mist --rpc /address_to_geth.ipc

genesis.json file

{

"config": {

"chainId": 15, 

"homesteadBlock": 0,

"eip155Block": 0,

"eip158Block": 0

},

"difficulty": "0x20",

"gasLimit": "2100000",

"alloc": {

"7df9a875a174b3bc565e6424a0050ebc1b2d1d82": 
    { "balance": "300000" },

"f41c74c9ae680c1aa78f42e5647a62f353b7bdde": 
    { "balance": "400000" }

}

}

Answer 1

I started again with new genesis.json file with a account already having some ether

since you can't add ether to an account in the first place, then where is this account getting its ether? An account with ether on the public network can't be transferred to a new private network.

First start the private network, then create an account in that same private network, copy the address of that account to the genesis.json file or specify it as the etherbase for mining and restart the network. Open mist on the private network with a backup copy of that same account and your problems should be resolved.