Please share your experiences with rechargeable 9v batteries.

[NoNotAgain]

Home Depot sells a smoke detector manufactured by Code One that uses a sealed in place lithium Ion battery that they warranty to still be functional for 10 years.

Quite a few municipalities are changing their fire code regulations to require this type of detector ONLY.

A lot of cities with high populations of poor people used to hand out smoke detectors every year. The fire department would come back the following year to find that either the detector was chirping or the batteries were removed.

I personally like the sealed in battery approach and toss the unit at 10 years. The ionizer is usually toast anyway and the manufacturers recommend replacement anyway.

 

[WalkIntoTheLight]

Home Depot sells a smoke detector manufactured by Code One that uses a sealed in place lithium Ion battery that they warranty to still be functional for 10 years.

It must be a very efficient smoke detector. In my detectors (the ones I'm testing), alkalines would be almost drained after about a year. Lithiums don't have 10x the capacity of alkalines. Maybe double?

(I doubt they're lithium ions being used, they're likely lithium primaries.)

 

[NoNotAgain]

It must be a very efficient smoke detector. In my detectors (the ones I'm testing), alkalines would be almost drained after about a year. Lithiums don't have 10x the capacity of alkalines. Maybe double?

(I doubt they're lithium ions being used, they're likely lithium primaries.)

Direct quote from the Home Depot description.

"10-Year Lithium Ion Battery Operated Ionization Smoke Alarm"

http://t.homedepot.com/p/Code-One-1...ted-Ionization-Smoke-Alarm-21009992/203728679

 

[WalkIntoTheLight]

Direct quote from the Home Depot description.

"10-Year Lithium Ion Battery Operated Ionization Smoke Alarm"

http://t.homedepot.com/p/Code-One-1...ted-Ionization-Smoke-Alarm-21009992/203728679

Well, I still don't think they're using a lithium-ion battery. That doesn't make much sense for a long-duration throw-away device. Lithium primary makes a whole lot more sense. Probably a mistake in Home Depot's listing.

 

[SaraAB87]

I am sure that my alkalines last more than a year in the smoke detectors at least. They are just off the shelf duracells, energizers and ray o vac. I have never had a leak.

Usually when the detector starts beeping we find the alkaline in there has an expired date.

We have a guy who comes every year and checks the smoke detectors, provided by the city since we have an elderly person in the house.

The thermostat is another story, they recommend changing it every year, it's only 2 alkaline AA's so it's cheap to maintain. I am sure those batteries in there would last a long time, but it seems to be more voltage sensitive than other stuff so it needs to be replaced at least once a year.

 

[WalkIntoTheLight]

I am sure that my alkalines last more than a year in the smoke detectors at least. They are just off the shelf duracells, energizers and ray o vac. I have never had a leak.

Yes, most smoke detectors last well over a year on alkalines. The ones I'm testing just seem to be very inefficient (cheap ones bought at Costco), which is good for testing because I won't have to wait several years for the results. But yes, the ones I'm using really are abnormally inefficient.

The thermostat is another story, they recommend changing it every year, it's only 2 alkaline AA's so it's cheap to maintain. I am sure those batteries in there would last a long time, but it seems to be more voltage sensitive than other stuff so it needs to be replaced at least once a year.

I use Eneloops in my furnace thermostat. I charge them once a year, and they still have about two-thirds their capacity left.

I think every manufacturer of smoke detectors, thermostat controls, etc., all say to change the batteries once or twice a year. It's CYA stuff. If the batteries suck or you forget for a couple of years, it'll still work.

 

[TinderBox (UK)]

What is the highest real capacity low discharge/pre charged 9V battery , I have a couple of Vapex instant 200mah 9v and they seem to work fine.

I would not trust ni-mh 9v battery`s in a smoke alarm as rechargeable battery can suddenly go flat and you might miss the low battery warning, if you are out, I much prefer Alkaline or Linthium , both have approx the came capacity, but Alkaline chokes under high loads and you only get a percentage of the capacity, when lithium works much better and will last longer, but only in high drain appliances.

I have mains powered smoke alarms in my home, they have an lithium backup battery in case of power failure.

John.

 

[MidnightDistortions]

The only problem i have with 9V cells now is that there are not many chargers out there for them to test their capacity and so far i just have the Tenurgy kit. One option for 9V NiMH's is to replace the cell every 3 years with a fresh one. I don't trust the built in lithium ones. They could die before the unit goes bad and you'll just be throwing away a perfectly good unit. I'd rather have a user replaceable battery along with a user replaceable ionizer so you can keep the unit and replace the non functioning part.

 

[WalkIntoTheLight]

One option for 9V NiMH's is to replace the cell every 3 years with a fresh one.

That's fine if you're using them in moderate-drain devices and charging them several times per year, you still get your money's worth. But NiMH 9v costs about 4x more than a quality alkaline. For a smoke detector, you'd better get many years out of a NiMH 9v, or it's more cost-effective to just use alkalines.

 

[WalkIntoTheLight]

Time for the 6-month update on the use of 9v NiMH rechargeables in smoke detectors:

- An unused Tenergy Centura (LSD, claims 85% charge after 1 year, 70% after 2 years): currently 9.05v
- The used Tenergy Centura: 8.77v
- The used Energizer Recharge: 8.78v

Very little voltage drop in all samples since I last checked 1.5 months ago. Both the low-self-discharge and regular NiMH battery are doing the same. I'm not sure if the Tenergy Centura really does retain 85% charge after 1 year, since I doubt the unused battery still has that much in it after just 6 months, but I have no way to know for sure. OTOH, the Energizer, which doesn't claim to be LSD, seems to be holding up just as well as the Tenergy.

 

[Kurt_Woloch]

I've also done some self-discharge tests in the last months (mostly on AA batteries though). From your tests so far, the unused Tenergy battery still has a higher voltage now after 6 months than the used one had after 80 days. If the unused battery keeps dropping at the same rate it did in the last 45 days, it will take another 7 months to reach 8,91v, at which point it will have self-discharged to the level the used battery reached after 2 months. We don't know how many mAh this corresponds to /we probably won't find out until the first used battery is depleted), but if the self-discharge takes 13 months to get to the same point as the regular discharge in 2 months (chances are it will actually slow down further), this would mean that the self-discharge is about 15% of it and the regular discharge combined. How much the actual self-discharge level will be is yet to be determined... I'd propose that if the used batteries get depleted, the unused one should continue to sit until it reaches 8,91 V on its own so we at least know how long this takes.

Your batteries are already holding up for a unusual long time (50% of the runtime of an alkaline although they have maybe 35-40% of its capacity), and it doesn't seem like they reach their end yet.

 

[WalkIntoTheLight]

I've also done some self-discharge tests in the last months (mostly on AA batteries though). From your tests so far, the unused Tenergy battery still has a higher voltage now after 6 months than the used one had after 80 days. If the unused battery keeps dropping at the same rate it did in the last 45 days, it will take another 7 months to reach 8,91v, at which point it will have self-discharged to the level the used battery reached after 2 months. We don't know how many mAh this corresponds to /we probably won't find out until the first used battery is depleted), but if the self-discharge takes 13 months to get to the same point as the regular discharge in 2 months (chances are it will actually slow down further), this would mean that the self-discharge is about 15% of it and the regular discharge combined. How much the actual self-discharge level will be is yet to be determined... I'd propose that if the used batteries get depleted, the unused one should continue to sit until it reaches 8,91 V on its own so we at least know how long this takes.

Yes, I'll try that. I have no way to determine actual capacity or relative capacity of 9v batteries, since I don't own any device that can discharge at a fixed constant rate in a reasonable amount of time.

Your batteries are already holding up for a unusual long time (50% of the runtime of an alkaline although they have maybe 35-40% of its capacity), and it doesn't seem like they reach their end yet.

Yes, what surprised me most is how little the voltage has dropped on all batteries in the past 1.5 months. It's really started to plateau. They are holding up pretty well compared to my past experience with alkalines, however, those alkalines were probably not fresh, as I tend to buy in bulk and I think they may have sat around a few years before I used them. So, perhaps it isn't a fair comparison.

 

[WalkIntoTheLight]

Time for the 8-month update on the use of 9 volt NiMH rechargeables in smoke detectors:


- An unused Tenergy Centura (LSD, claims 85% charge after 1 year, 70% after 2 years): currently 9.00v
- The used Tenergy Centura: 8.77v
- The used Energizer Recharge: 8.74v

The change in voltage over the past 2 months is almost nil. I'm beginning to wonder if estimating charge using voltage is much use at all. I know it's not too accurate even in good single NiMH cells, but I thought I'd be seeing a steadier voltage drop in these 9 volt NiMH batteries over the past few months.

If I estimate charge based on voltage, full charge should be about 9.24v (1.32v per cell), and empty about 8.40v (1.20v per cell). But it seems these batteries lose voltage more quickly at first, and then very slowly later. So, I'm not sure what the discharge curve looks like.

In any case, they seem to still be working fine; the smoke detectors are triggered about once a week.

 

[Rick NJ]

I did a review of the Tenergy Centura 9V and TN141 (charger) mini review. It is not a comprehensive review but it still has info that you may find useful.

I do not have long term voltage info in my review, but I have some detail about discharge characteristics and energy delivery characteristics graph there.

You can see it here:
http://www.eevblog.com/forum/reviews/tenergy-centura-9v-and-tn141-mini-review/

 

[WalkIntoTheLight]

I do not have long term voltage info in my review, but I have some detail about discharge characteristics and energy delivery characteristics graph there.

Thanks. Your slow discharge graphs explains why the voltage on my batteries has been hanging around the 8.7v level for so long.