Replacement Battery for Polycom SpectraLink 8400, 8440, 8450, and 8452 Phones | 2350 mAh | 8440 VoWLAN handsets | Replacement for OEM 1520-37215-001 and RS658

Pros: Fits the 8440 like a glove, and is completely at home in both positions of the charging cradle. Runtime is *way* better than the stock battery.Dislikes: none. This battery is somewhat thicker than the standard-capacity one, which takes a bit of getting used to, but that's not really an issue after using it a few times.For $50-ish, this was a cheap way to keep a perfectly functional wireless SIP handset running, and with a significantly longer runtime than it had when it left the factory. Time will tell as to cell life, but it is recommended.

I have used this for a week now, and I have been able to get 2-3 days per charge, and I do turn it off when I leave work each day, but only charge back when I get a low battery indication on the phone. I don't talk a lot on the phone, but I have it available when someone calls. This battery is double the capacity of the originals in the phone. My originals failed in just a few months of use, so I am hoping this unit is more durable. So far, so good.

Ordered regular and extended batteries. Both work great and hold a charge well!

the battery works just as good as factory battery at half the price

Battery works as advertised. A great replacement for the old battery.

Works perfectly!

Works as expected so far.

Works just as well as the OEM battery. I would recommend.