TenergyCentura 9V NIMH Rechargeable Batteries, 200mAh Low Self-Discharge Square Battery for Smoke Alarm/Detector, 4 Pack

We have 10 wired smoke detectors with battery backup. Wanted something economical so got these. They are lasting 1 year on a charge, they probably would last longer but I recharge them every fall. Just passed the two year mark and no issues. They fit into the smoke detectors with no problem. Using a Bonai charger.

I have a clock radio that uses a 9v battery for backup in case of power failures. When the power goes out the clock display shuts off to save power but the battery allows it to still keep time and if your alarm is set it will go off as usual. The clock has a low-battery warning light to let you know when to replace (or in my case recharge) the battery.I was using one of the first old style NiMH 9v batteries that was not low self-discharge that had a 150mah capacity and I think around 7.2v output. When it was fully charged and I put it into the clock radio it would take literally 3 or 4 seconds for the low battery light to come on. Obviously the battery didn't have a voltage above the threshold of the warning light so it came on immediately and stayed on. The battery did have enough power to run the clock if we lost power which was good, but it was annoying that I didn't have any way to know when the battery was drained. I found out through trial and error that the battery would only last about two or three months due to it self-discharging over that time. And that was without any power outages.So I went with this new low self-discharge 9V battery to see what would happen and couldn't be happier. It has a higher voltage so now the low battery light stays off (at least so far). I ordered these along with the Tenergy TN141 2 Bay 9V Smart Charger for NiMH 9V Rechargeable Batteries and gave the battery a quick charge to top it off before use. It has been about a month now and I just picked up the Delkin Devices DD/BATTEST MULTI RoHS AA/AAA Battery Power Tester and checked the charge level and it's still showing a full charge which is excellent, the old battery would have already been down to around 50% charge at this point. I will use the battery tester on it again when the low-battery light comes on, I may be able to use it for a while after the light comes on depending on it's charge level at that time.Over time as my other 9v alkaline batteries fail in my smoke detectors and other devices around the house I will definitely be replacing them with these. There really isn't any reason to stay with standard alkalines batteries over these new low self-discharge type of rechargeables anymore, with a few exceptions where rechargeables just aren't a good option for a particular device. But for the majority of our devices these are the way to go, saving us a lot of money over time. Using these batteries is most likely going to eliminate having to ever buy alkaline 9v batteries again since each one can be recharged up to 1000 times. That's a nice chunk of change saved right there. For each of these new 9 volts you bought you would be saving 1000 times the cost of a 9v alkaline, which even if they sold for only a dollar apiece you would save $1000! That's absolutely ridiculous. In a "I really like that" ridiculous kind of way!These modern low self-discharge NiHM batteries are another small but helpful innovation that makes our lives just that much easier. Highly recommended.*** Update Sunday, June 10, 2012This discussion got me wondering, when using NiMH low self-discharge batteries, just how long would a smoke detector give you low battery warnings, until the batteries discharged completely and the warnings stopped?I had a Kidde NightHawk combination smoke/CO2 alarm that I could test with and like a lot of newer alarms it takes AA batteries, so I tested some Imedion AA low self-discharge NiHM batteries (three). I discharged the batteries until they were down to about 25% full, put them in and then had a long wait until I heard the first low battery warning. The alarm manual stated that using alkaline batteries the low battery warning would last at least seven days. I figured that the way these batteries discharge quicker than alkalines at the end of their life that the warning time would definitely be shorter than seven days, maybe around 2 to 5 days. However, what I found was the complete opposite! To my great surprise I actually ended up stopping the test myself before the batteries were completely exhausted. Why? Because the alarm gave me constant low battery warnings FOR THREE FULL WEEKS. I really didn't need to see just how much longer they were going to last past that.So apparently the low voltage cutoff point that triggers the warning was high enough that the NiHM LSD battery still has sufficient voltage to keep the warnings going for a long time, before it hits the steep (and quick) drop off point. So maybe a NiHM LSD 9V battery like this Tenergy might last longer than you would think as well, depending on the device used. Maybe we'll hear about how a 9V battery fares from someone in the future, either on Amazon or posted elsewhere.

These batteries work well for recharging many times. They are medium quality and will charge over and over for a good amount of time. They don't last as long as more expensive batteries.

Muy buenas

I bought these for multimeter s and it works fine.I own Tenergy 10,000mAh D cells, 5000mAh C cells, 2500mAh AA and AAA cells and now the 9v.Out of 8 D cells one wouldn't take a charge and (The Battery Superstore) replaced it immediately.I just mailed the one bad battery and and I received another 2 days after they got the returned one.All the others I bought after that. 32 AAs I use for radio controlled trucks and controllers.It saves a lot in the long run. I have recharged the AA cells a dozen times or more and they actually hold more the more you use them like .25 to or more.New they were around 1.355 to 1.36 some now are 3.95 volts.I check them every time I charge them.The C cells I used for a cordless drill battery pack. The original pack had 14 ni-cd for 18volts I used 15 batteries for the new one.I taped it up with black tape so it don't look great but will bury 3 inch deck screws for quite a while. It's a whole new drill.The AAA cells I soldered into 5 packs to replace 4 AA on board RC trucks.Only one bad one out of more than 75 and that one was replaced.Decent product,very good vendor!

they work well

I bought my first of these a long while back. And I wasn't impressed initially. The battery felt light for a 9v, materials felt cheap. But happily a long while later, I've been pleasantly surprised.These rechargeable batteries hold a charge for a long time. I originally bought them for Rocksmith. I don't play the game much but had bought a cheap acoustic electric to do so. The pickup like most of them do require a 9v battery. I popped it in and even over a year later, the charge was good. I recently had an issue with a smoke detector. The 9v Duracell batteries I'd bought for them originally-- by the time I had to use them, they were long expired and like 3 years old. It didn't occur to me that they'd run out of juice before I even got a chance to use them. I pulled the battery from my guitar which hadn't been used but three or four times and was months... think like 18 months since I last recharged. They held the charge well enough that it's been over a week in my smoke detector and it's still not beeping low battery. I've long since charged a backup but it may be a long while before I have to swap them. I'll be using these as my replacement and backup 9v batteries from here on out. Even if they run down in between 3 or 4 year swaps, I can recharge them-- and I just don't believe they would take longer to drain than sitting inside the smoke alarm/detector.

I have 12 of these for use in smoke detectors. Two won’t charge in the Tenergy charger. When I contacted customer support, they argued the my battery tester was not accurate. How about the fact that they make the smoke detectors chirp and the battery charger throws an error? Absolutely terrible customer service.One other thing to note, six of my batteries are 10 years old. They still charge fine and seem to last in the smoke detectors for about one year before needing charged. Our detectors are hardwired with battery backup. These batteries don’t have as many amp hours as others but work fine.Product is is pretty good. Customer service is awful.PS - I never had an issue with the battery tester.

Es una excelente compra, aquí conseguía otras baterías casi al mismo precio y solo 2 y me duraban 3 meses y eso que eran recargables, estas pilas eran 4 y duran mucho.

Por su precio están bienDuran al rededor de 4 horas

They were fully charged and ready to go.Used for a carbon monoxide alarm

I tested these at a constant current draw of 50mA, discharging to 6.3V, and....drum roll.....they slightly exceeded their specification!! :) I measure approximately 210mAH, which exceeds the specification of 200mAH. THANKYOU Tenergy for being honest with your specifications.This is an initial review - I will update later if I have anything more to add, after I have used them.

These cost about 4x as much as regular (disposable) 9v batteries, but will pay for themselves if you use them in anything that requires them to be recharged just 4 times. Being low-self-discharge, they should last a year in low drain devices. I'm using them in smoke detectors, and they are working well. I'll recharge them every 6 months or so, since I was going through alkalines about every 6-12 months. I expect these batteries should last about 10 years, based on previous 9v rechargeables I've used, so in the long-run I'll save money.