Economy/feasibility of using LSD AAA in low drain application

[ekincam]

The remote control for my car alarm typically lasts about 3 months using 1 alkaline AAA cell. It's a 2-way remote so it's constantly checking for signal from the car. The remote will start beeping if the car alarm goes off and I am in range of the transmitter from the car for example.

I bought the Eneloop pack from Costco so I have a bunch of Eneloop AAA cells that I really don't have a use for. Is it feasible to use these in my remote so that I wouldn't have to buy any more alkaline cells? The alkalines are not expensive in any way, a big pack from Costco is pretty cheap and it would last a long time. However, using LSD rechargeables would seem marginally more economical.

I took some measurements with a DMM yesterday and when the remote is transmitting and then beeps as confirmation that the car received the command, the current is approx 120mA and this lasts maybe 1-3 seconds. At other times, the current is 0 but it blips to about 40mA every 10s or so. It might be more or less because my DMM might not be able to measure fast enough. The open voltage on the cell was approx 1.3V meaning the cell is almost dead, or should be dead in some applications. I know that NiMH cells typically have open voltage of 1.2V and I don't think it'll be a problem.

The remote does warn me that my cell is dead, or near dead with a sequence of beeps, but the cell has an open voltage of 1.0V or less. I don't remember the exact value though. One concern is whether I could potentially damage my AAA cells by running them all the way down to 0.9 volts or less.

Does this seem like a good application for LSD NiMH cells?

 

[Power Me Up]

I'd say that you should be fine to use Eneloops for that application.

I use a set of 4 Eneloop AAA cells in my Harmony 520 universal remote and they work fine - they last about 3 months in it - about the same as a set of alkalines, so I'd suspect that the Eneloops would also give you similar performance for your car remote.

0.9 to 1.0 Volts is the recommended cutoff point for discharging NiMH cells, so that's also fine. (Of course, you can recharge them sooner as well)

 

[bfg9000]

Go for it if you can remember to recharge them before they go dead, or carry an AAA light with a spare. As Power Me Up pointed out the cells won't be damaged, but the problem is you will probably get little to no warning when the NiMH battery is about to die, due to the sharper rolloff at the end of their flatter discharge curve.

On the bright side, this means operational range of the remote is likely to be much more consistent right until the end.

 

[kitelights]

Personally, that's an application that I would use Energizer lithiums for, because of the weight. An alkaline cell weighs 12 grams, Eneloop 14 grams, and the lithium is <9 grams. I hate bulk and weight in my pockets.

It would be interesting to see how much longer the lithium cell would last than the alks that you're currently using - my guess is substantially longer. It would be worth the additional $2-4 a year for me for the weight factor.

 

[Brock]

I would use the enloops and just change them out once a month. Then you don't have to worry about over discharging them and don't have to worry about them running dead when you're not expecting it. You might even be able to go every other month, but I find changing them monthly in low drain devices work better since I don't have to remember which month it is

 

[Marduke]

I would use the enloops and just change them out once a month. Then you don't have to worry about over discharging them and don't have to worry about them running dead when you're not expecting it. You might even be able to go every other month, but I find changing them monthly in low drain devices work better since I don't have to remember which month it is

Or choose odd numbered months to top off AAA cells (AAA = odd number, 3), and even numbered months to top off AA cells (AA = even number, 2) in semi-frequently used devices.

 

[MorePower]

Personally, that's an application that I would use Energizer lithiums for, because of the weight. An alkaline cell weighs 12 grams, Eneloop 14 grams, and the lithium is <9 grams. I hate bulk and weight in my pockets.

It would be interesting to see how much longer the lithium cell would last than the alks that you're currently using - my guess is substantially longer. It would be worth the additional $2-4 a year for me for the weight factor.

Using lithium-iron disulfide cells would net you a savings of 4 grams or so (11.5g Energizer alkaline vs 7.6g Energizer lithium), but you'd likely not see any change in how long you could go between battery changes. If an alkaline AAA lasts 3 months in this application, that means it's a very low discharge rate, so the lithium cell would have no benefit whatsoever. For example, at 25mA continuous discharge, both cell types have a capacity of 1200mAh

Also, as a point of reference, the weight difference of ~4g is less than that of a US nickel. With no added bulk, do you really think carrying the weight of a nickel around would be noticeable? Just playing devil's advocate...:devil:

 

[radellaf]

Of course then you have to remember which semi-used devices you have, and which have the NiMHs in them.

I have been looking for weeks for what thing I put two hybrid AAs in. There's just too many.

Oh, the lowest drain device is my alarm clock with two AAs. Would way over-discharge a NiMH...and an alkaline. No low batt warning, even the 2-sec LED backlight works OK, when the batts are so low that they're leaking. That wasn't fun to find.

The only warning, if you can call it that, is that the alarm fails to go off maybe one time in 10. So occasionally that I figured I was just turning it off in my sleep.

So, what, change them every christmas? Dunno what would be least likely to leak.

 

[Mr Happy]

I have to say, I have never seen or had an AA alkaline cell leak on me in 25 years. In fact, when alkalines were first being marketed as a better replacement for zinc-carbons, one of the selling points was that they were unlikely to leak. It puzzles me to hear about these leaking stories from others.

I wonder if it is down to manufacturing shortcuts in these super-cheap cells that you can get now? Has any one had a genuine Duracell leak on them?

 

[Brock]

I personally have never had or seen a Duracell leak and we go through LOTS of them, on the order of 1000 a year. I have had Energizers leak and a couple of other off brands, but not Duracell... yet... We do use Procell's though.

 

[Marduke]

I have to say, I have never seen or had an AA alkaline cell leak on me in 25 years. In fact, when alkalines were first being marketed as a better replacement for zinc-carbons, one of the selling points was that they were unlikely to leak. It puzzles me to hear about these leaking stories from others.

I wonder if it is down to manufacturing shortcuts in these super-cheap cells that you can get now? Has any one had a genuine Duracell leak on them?

I've had several Duracell leak, and Energizer too.

 

[shadowjk]

I've had duracell AAA leak on me, it was a fully discharged cell that I was storing on a shelf because I was too lazy to go to recycling centre just for a few cells.

 

[TorchBoy]

... I was too lazy to go to recycling centre just for a few cells.

Look at it this way - you were saving the planet by not unnecessarily polluting it with vehicle exhaust. It's not your fault the battery leaked while you were saving the planet. :thumbsup:

 

[ekincam]

I have used alkalines to the point where they reverse polarity and have not yet had one leak. Maybe I don't go through enough of them.

Thank you for the replies. I will try the Eneloops in my remote once the current one is expended. It's reading approx 1.3V ATM.

 

[Jackson]

I've had many experiences with finding leaking batteries in battery powered toys when I was growing up. Usually the situation involved leaving the batteries in the toy for a long time and forgetting about it (though the toy was shut off.)