Four out of Five Good - Battery Changes Difficult
344404
Our new house had five of these in it when built about five years ago.  Four of them have worked fine.  One has given occasional problems.  It would randomly start making a continuous cricket like sound, not the every thirty second chirp, more like a field full of crickets!  Changing the battery didn't solve the problem.  Even after turning off the circuit breaker, it would take an hour sometimes for the noise to stop.  I have replaced this one.

There is one thing I don't like about these, and may be the same on other USI detectors.  The battery can be difficult to change.  I found that the little release tab usually would not work for me.  I would end up having to wedge a screw driver next to the little tab to release the battery.  Most of the tab's have broken off for me.  So, now I have to use a screw driver to release the battery's.
3836328
Mine are kinda fussy. The batteries seem to get sucked up really fast, and if you forget to turn them off one night, they are toast. After replacing batteries 3 times in each over a couple months, I gave up on them.
523474
<div id="video-block-R2ICDR63FJAGWV" class="a-section a-spacing-small a-spacing-top-mini video-block"></div><input type="hidden" name="" value="https://images-na.ssl-images-amazon.com/images/I/A1kj9CavkrS.mp4" class="video-url"><input type="hidden" name="" value="https://images-na.ssl-images-amazon.com/images/I/71e0l2Rv1zS.png" class="video-slate-img-url">&nbsp;Worked well until the batteries needed changing.  Battery carrier is stuck and will not come out.  So I can not change batteries.
2638147
Doesn't give the low battery warning as well or long as others I've had
1809997
battery are not really fit well, so it usually reset itself. After that, I figure it out by put some paper to make it fit.
3473313
Overall good, but needs to be removed for changing for access to memory card and battery, as well as USB port.  Minor inconveniences.
3649951
It is not as easy as it looks to change them out and the instructions aren't the best.  That's why only 4 stars.  So far working fine after I finally was able to change everything over.  You be to move the ear piece, camera and home button over to the new one.  I think some if this has to do with it being a 6s.  Anyway would recommend to a friend.

I changed from a 4 to a 2 after using for several months.  Saved some money but it freezes not and I will push one letter and it inputs one next to it. Very unreliable.
3253233
They are not exactly the same,with the old ones I could turn the battery off
by turning the button battery to the right. With the new batteries I have to take them out of the
collar to avoid draining the battery.
1780350
I was able to install the battery using the tool and instructions available online, however removing the connectors and reattaching them was a bit of a chore and for awhile, I thought I would not be able to get my Nook to work again but persistence paid off. The Nook connectors are removed and reinserted by lifting them up (and pressing them down to reinsert them) rather than my original assumption that they were slid in and out.
4970510
3 of them worked just fine, very reliable, and I use rechargeable batteries which last a long time.  The fourth one won't shut off so had to ditch it.
4085909
Unusual key placement gave this neat gadget too steep of a learning curve. I found it less of a hassle to simply use the onscreen keyboard after a while. The case is also difficult to remove, and doing so resulted in cracked housing the third or fourth time.
The battery being seperate was a nice change of pace.
658480
love them but a bit inconvenient that you have to keep the switch in the off position or it kills the battery just as fast as if on.  If you can remember to do this...they are great!
3243344
The battery clicked in but for some reason they were a slight bit wider than the other battery so I had a difficult time getting it to fit in with the battery cover to snap shut. I finally did get it but had to rig it up a bit.
2107253
Works great until the four oddball batteries need to be replaced. Who has all of these batteries around?  Triple A's would be nice.
3013234
The Kastar battery, a substitute for the Sony BP-U60, meets expectations for service life, on a rating of 5800mAh. The green display LEDs for battery remaining are nice and bright, far brighter than other non-Sony BP-U60s that I have been using (e.g. Wasabi, Watson).  I have now put the Kastar through about five cycles of discharge-charge, using a Sony factory charger instead of the Kastar charger that was packaged with this purchase. The first charger that arrived was electronically defective, with a display screen that failed to show any alpha-numeric information. It lit up, but was blank.  No charging action took place, regardless of the slide switch settings that I thought might "re-set" from a fault of some kind.

The replacement charger that a cheerful Kastar representative shipped Priority Mail has mechanical problems but it charges correctly.  The problem with this one is a small, spring-loaded cover that slides from the left to the right over the deck (or tray) where the battery sits. Its sole purpose appears to be that of covering the two metal contacts that connect the charger with the battery.  The problem is that the springset overpowers the simple friction-fit that the battery relies upon to stay in place.  The springs push the battery to the right and disconnect the battery.  A small, very flexible bit of plastic on the right half of the deck is inadequate to rise up and click into the matching groove of the battery, so it does not help retain the battery against the spring cover.

These problems persist regardless of whether trying to mount a new Kastar battery, or a very worn Sony factory battery. Separately, as other reviewers have mentioned, certain batteries fit very tightly in the slotted grooves along the rails of the deck, requiring two hands and a significant push to install and remove from the charger.

In a telephone discussion with the Kastar representative who answered the toll free number, the manufacturer was described as very receptive to customer feedback. I described the problem like I have done here, and suggested some ways to improve the design, hoping for changes that will make their way eventually back to to the product.  I am keeping the charger, after I found a way to defeat the spring-loaded cover. That was a matter of binding the cover to the main housing of the charger when preparing to charge a battery, so that the cover cannot push the battery out of position.
3344339
Battery fits fine. Had to find insteuctions on youtube to install. Tricky to line the battery up - it is held in place by double-stick tape so it can't be moved around after its plugged in. Screwdrivers included were worthless - had to buy a set to disassemble phone.
Job took close to an hour  and a half, including time spent watching videos and ordering screwdrivers. Uses T5 and T4 torx drivers. Battery working well. Took 3 charge discharge cycles to get close to proper life. Not quite as good as original phone battery when new, but still over 24 hours standby and use time.
Will update this review in a few months.
2759362
some of them work fine, but others are hard to turn off and the batteries just run out. they're cheap enough it's not that big of a deal but still worth noting.