I just bought this light and only used a few times. I noticed that on a 20W option the highest capacity battery NP-F970 only lasts 90minutes, is that the average or my battery is drained out? Also, is there a higher capacity battery than 970?
Thanks in advance.

I have the HVL20 and power it with one of two NPF960 batteries. They used to be main power for my PD150 camera, but when I went Z1 I got two 970 batts as a bonus.

I can't think of a time I went through a light battery while doing an event. But 90 minutes is realistic.

Considering it is an onboard battery, 90 minutes is pretty good as these lights go.

I have other gripes with the light, but longevity is not one of them.

90 min sounds about right. As Mark stated, this wouldn't be one of my gripes either. It's better than nothing, but there definitely better lights out there.

90 min sounds about right. As Mark stated, this wouldn't be one of my gripes either. It's better than nothing, but there definitely better lights out there.
I agree, if I was purchasing a light today, I would go LED based.
And if onboard battery power is a requirement (especially long life Sony batts) then the Sony HVL-LBP is a fantastic choice. Great battery run times, stays cool, great spread for widescreen shooting, dimmable, flip down diffuser or beam focuser, no hotspot like HVL-20 light, and runs forever on Sony NP770 battery and longer with NP970.

It's expensive and large, but a great light none the less.
http://www.bhphotovideo.com/c/product/475084-REG/Sony_HVLLBP_HVL_LBP_LED_Light_System.html

Yeah, I wish it had a low battery warning. Mine died in the middle of a Father Daughter dance!