LED battery charge level mod

[Guitar_modder]

I am modding a rock band guitar by ripping out the guts and putting them into a squire strat body. I am installing a new 4.8v rechargable battery pack into the body, and want to be able to check the remaining charge on my batteries by pressing a button and having a row of LEDs light up, more LEDs lighting the stronger the charge. I tested running 6 2.1v LEDs with varying resistances with bad resuls, so I thought maybe running multiple LEDs with different vf specs instead. Is this a good way to go about this? 3mm LEDs are preferable, but 5mm will work too. Thanks.

Ps. I know that the nimh battery pack has a less than optimal power curve, but I just need a ball park indication of battery life.