Should I change my UX battery ?

[fatice]

I find that my battery life drops a lot after fully charge, so I ran a battery test:

PEG-UX50
S/N:
--
INCOMPLETE
--
Brightness: 50%
--
40 minute(s)

Minute Voltage Percent
0 4.20 100%
1 4.20 100%
2 4.20 100%
3 4.20 100%
4 4.17 94%
5 4.16 93%
6 4.13 87%
7 4.12 85%
8 4.10 80%
9 4.09 78%
10 4.08 77%
11 4.08 77%
12 4.05 70%
13 4.05 70%
14 4.01 63%
15 4.01 63%
16 4.01 62%
17 3.98 57%
18 3.98 57%
19 3.98 56%
20 3.96 53%
21 3.96 53%
22 3.95 50%
23 3.93 47%
24 3.93 46%
25 3.91 42%
26 3.90 40%
27 3.90 40%
28 3.88 37%
29 3.88 37%
30 3.88 37%
31 3.87 34%
32 3.85 30%
33 3.85 30%
34 3.85 30%
35 3.84 28%
36 3.81 23%
37 3.81 23%
38 3.81 22%
39 3.80 20%

I know, my battery life sucks. So what is the normal UX battery test result looks like ?

If I were to change my battery, what battery should I get ?

Like the ones selling on ebay ?
http://search.ebay.com.au/search/search.dll?sofocus=so&sbrftog=1&fstype=1&from=R10&satitle=UX50+battery&sacat=-1%26catref%3DC6&fsop=1%26fsoo%3D1&coaction=compare&copagenum=1&coentrypage=search&floc=1&sargn=-1%26saslc%3D2&sadis=200&fpos=6102&ga10244=10425&ftrt=1&ftrv=1&saprclo=&saprchi=&so=Show+Items

The capacity is a myth. Lots of cheating labels and sellers.
e.g. 3.7v 850mAh = 4.2v 750mAh.

Could anyone give me a suggestion ?

Thanks