Using nimh in clocks and tempeature meter

I started to use nimh batterys on every device if it uses AA or AAA batterys. I got tired of replacing equipment becouse alcaline leak damage.

I just thinked how low voltage drops in analogue clocks before clock stops working? Nimh batterys dont like used to below about 1-0.9V. So what voltage they usually stop to work. I have some old wall clocks and alarm clocks and i dont remember what voltage they stop working when i used alcalines. They are using ikea ladda LSD batterys and they still run okay without need for recharge so i need to know is it safe to use nimh batterys to that point when clocks stop working or not?

I have one DCF-77 radio controlled wall clock too with one AA nimh battery. Its supposed to stop second hand to 12 position when battery needs replacing (in my case recharging) does someone know what voltage they do that so i dont kill my nimh cells by undervoltage? User manual is no help and i just buyed this clock about half year ago so i dont have any idea yet about low battery warning voltage.

Also i use nimhs in one very old wired tempeature meter without low battery alert. When battery is empty screen stops working. I think this meter uses battery so low before it stops working that it is maybe better to recharge nimh about once a year before meter shuts down. Or is there any ideas of their voltage when meter stops working... As i said before i dont want to destroy my nimh cells becouse of undervoltage. I have SkyRC MC3000 so i can refresh them to get cells working again but still they get some damage by using them belov 1-0.9v.

Only place where i still use non-rechargeable batteries are smoke detectors. I tried to use nimh batterys in wireless detectors but they start to chirp in 2 weeks even cells are still allmost fully charged so i use varta lithium cells instead in detectors to avoid alcaline leaks.

Any ideas?

I've never had an issue with NiMH voltage on any device. I use Eneloops in everything. Alkalines have a working voltage range from 1.0v to 1.6v. So, devices usually use around 1.0v as the dead battery alert. Though, they might trigger a warning before that, say around 1.2v. But that is the low-end of the working NiMH voltage range, which is around 1.2v to 1.4v.

So, any device which is designed for alkalines, should work fine with NiMH. But you probably won't get a low-voltage alert until your NiMH is almost drained. NiMH will still work down to 0.9v, but they will die quickly once they're below a voltage of 1.2v, so you won't have a lot of time (perhaps a couple of weeks to change the battery).

To save hassle with batteries running down, I simply recharge the Eneloops once every year or two, whether they need it or not. Some clocks require every 6 months.

Whatever you do, make sure to use low-self-discharge NiMH batteries, such as Panasonic Eneloops. "Old style" NiMH batteries self-discharge too quickly, and you'd need to charge them every couple of months. Too much hassle for those kinds, IMO.

WalkIntoTheLight said:

I've never had an issue with NiMH voltage on any device. I use Eneloops in everything. Alkalines have a working voltage range from 1.0v to 1.6v. So, devices usually use around 1.0v as the dead battery alert. Though, they might trigger a warning before that, say around 1.2v. But that is the low-end of the working NiMH voltage range, which is around 1.2v to 1.4v.

So, any device which is designed for alkalines, should work fine with NiMH. But you probably won't get a low-voltage alert until your NiMH is almost drained. NiMH will still work down to 0.9v, but they will die quickly once they're below a voltage of 1.2v, so you won't have a lot of time (perhaps a couple of weeks to change the battery).

To save hassle with batteries running down, I simply recharge the Eneloops once every year or two, whether they need it or not. Some clocks require every 6 months.

Whatever you do, make sure to use low-self-discharge NiMH batteries, such as Panasonic Eneloops. "Old style" NiMH batteries self-discharge too quickly, and you'd need to charge them every couple of months. Too much hassle for those kinds, IMO.

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Yeah i know voltage of nimh to be lower than alcaline. I just dont want to lower my nimh batterys life by over discharging them. Ikea Laddas are LSD batterys.

You could swap them out and charge them when you go into and out of daylight savings.....they probably won't over discharge and it doesn't hurt NiMH's to charge them before they go dead.

I've had issues with nimh on plenty of devices and it has been frustrating as lithium primaries don't perform much better in them vs alkaleaks and in clocks/thermometers that get about a year on alkaleaks and maybe another half year on lithiums and half a year on nimh I've gone to using alkaleaks on some of them to save me about $15 a year replacing batteries as I have 2 wall clocks and 4 digital thermometer clocks with 2 remote sensors. I use lithiums in the remote sensors and a lithium in one wall clock that stay out in the garage all year. If the clocks would maintain their settings and time for a few minutes between battery changes I would use LSD nimh but having to reset the 3 of the 4 digital thermometer clocks 2 times a year for DST plus a third for batteries having to do that another 1-2 times a year more for use of nimh batteries isn't. Alkaleaks cost about 50 cents each to buy or so and I have extras that have piled up when I switched to LSD nimh and lithium primaries on all my lights and some devices that don't constantly drain them (clocks) that also aren't voltage sensitive.
I've also had caller ID boxes that don't last half as long using nimh and with 3 of them in series have ruined a few batteries from overdischarge when they were not close enough to the same capacity.
If lithium primaries didn't cost me about 2-3 times as much and lasted equivocally longer in use for the cost vs alkaleaks I would put them in all my clocks but over 5 years I figure I've saved about $50 or so on batteries not using them which is enough to replace a clock or so.

satelite said:

Yeah i know voltage of nimh to be lower than alcaline. I just dont want to lower my nimh batterys life by over discharging them. Ikea Laddas are LSD batterys.

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All the wall clocks I have, use a single AA battery. You don't have to worry about over-discharging a NiMH battery if it's used in a single-cell device. Reversing the polarity is impossible with a single cell.

You might drain it down to 0.5v, or maybe even less. No problem. I wouldn't leave it that low for months, but you'll know if it's drained when the clock stops. Depending on the clock (I have a few), they seem to last anywhere from 6 months to a couple of years on an Eneloop.

I've actually measured the cut-off voltage on electronic clocks and indoor/outdoor thermometers. They've pretty consistently quit at about 0.9V. While lithium AA & AAA cells don't have more capacity than alkies, they work much better for sub-zero temperatures, maintaining a greater, more stable, voltage. I like them for remotes too, especially because they can last for many years and don't leak. Why tie up a more expensive LSD NiMH cell, which is better for high drain uses, for several years?

jayflash said:

I've actually measured the cut-off voltage on electronic clocks and indoor/outdoor thermometers. They've pretty consistently quit at about 0.9V. While lithium AA & AAA cells don't have more capacity than alkies, they work much better for sub-zero temperatures, maintaining a greater, more stable, voltage. I like them for remotes too, especially because they can last for many years and don't leak. Why tie up a more expensive LSD NiMH cell, which is better for high drain uses, for several years?

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I've measured alkaleaks and on some clocks they start having issues around 1.25v where nimh still have some power left and alkaleaks have a fair amount of power. Lithium primaries (unltimate energizers) have a little more capacity than an average alkaleak about 10-15% more power especially longer runtimes where alkaleaks and nimh get cut off due to voltage dropping lithiums run down to 1.6v before failing.
I don't see putting alkaleaks in devices that take 5 years to drain them as the leak chances are way way too high over that period but I don't see using lithiums in devices that drain them in a year or less if the weather isn't a factor the cost over 10 years over the leakage cost has to be considered. It used to be you could get a good LSD nimh for about the same price as an ultimate lithium cell but that has changed they are about twice as much now if you buy them in bulk about $2.50 or more for LSD nimh and $1.35 or so for lithiums at Sam's club.

Battery Junction has an interesting AA from ipower. Its a Li battery (so higher internal voltage) but appears to include a DC - DC converter inside for a stable 1.5 volt output.

https://www.batteryjunction.com/ipower-aa-lithium-polymer-battery.html

It might be that I find it interesting because I use a similar method on van conversion electrical work. Some nominal 12 volt devices are very sensitive to the "actual voltage", so I use 24 and 48 volt battery packs and a DC - DC converter to make a stable 13 volts.

HarryN said:

Battery Junction has an interesting AA from ipower. Its a Li battery (so higher internal voltage) but appears to include a DC - DC converter inside for a stable 1.5 volt output.

https://www.batteryjunction.com/ipower-aa-lithium-polymer-battery.html

It might be that I find it interesting because I use a similar method on van conversion electrical work. Some nominal 12 volt devices are very sensitive to the "actual voltage", so I use 24 and 48 volt battery packs and a DC - DC converter to make a stable 13 volts.

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Those USB AA batteries typically use a 14500 and a buck circuit to drop to 1.5v and even though theoretically that should allow them to maintain voltage till the cell is almost depleted depending on the circuit itself you may get less runtime using the cells as the circuit itself consumes power and takes up space that additional cell chemicals could be placed thus reducing the capacity.
One other issue with these converter cells is that the circuitry uses a DC-AC-DC conversion, yes a DC-DC converter does convert to a rough AC type voltage to run through a crude transformer type circuit to boost or buck the voltage then converts back to DC.
These circuits can introduce noise and RF interference that can make them useless in some applications as they either are near and interfere with things or inject noise into circuitry itself and cause issues.
Essentially these would be good for two reasons: for devices that cut out way before nimh batteries are mostly depleted due to lower voltage, and to replace alkaleaks with a usable rechargeable option.
On very low drain applications most likely they won't last nearly as long as alkaleaks due. IMO in rarely used remotes lithium primaries is the way to go while often used LSD nimh is a good choice.
One other way to get 12v stable voltage is to boost unstable 12v voltage up and buck it back down and use a regulator to keep it at the right voltage.
If you have more than one device you can use a voltage divider circuit off a higher voltage source to get what you need for lower power uses it is easier to make but since it consists of resistors at higher currents it would probably have unacceptable power losses.

Lynx_Arc said:

Those USB AA batteries typically use a 14500 and a buck circuit to drop to 1.5v and even though theoretically that should allow them to maintain voltage till the cell is almost depleted depending on the circuit itself you may get less runtime using the cells as the circuit itself consumes power and takes up space that additional cell chemicals could be placed thus reducing the capacity.
One other issue with these converter cells is that the circuitry uses a DC-AC-DC conversion, yes a DC-DC converter does convert to a rough AC type voltage to run through a crude transformer type circuit to boost or buck the voltage then converts back to DC.
These circuits can introduce noise and RF interference that can make them useless in some applications as they either are near and interfere with things or inject noise into circuitry itself and cause issues.
Essentially these would be good for two reasons: for devices that cut out way before nimh batteries are mostly depleted due to lower voltage, and to replace alkaleaks with a usable rechargeable option.
On very low drain applications most likely they won't last nearly as long as alkaleaks due. IMO in rarely used remotes lithium primaries is the way to go while often used LSD nimh is a good choice.
One other way to get 12v stable voltage is to boost unstable 12v voltage up and buck it back down and use a regulator to keep it at the right voltage.
If you have more than one device you can use a voltage divider circuit off a higher voltage source to get what you need for lower power uses it is easier to make but since it consists of resistors at higher currents it would probably have unacceptable power losses.

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I agree that there are potential challenges, but it might be a viable path for applications where NiMH voltage is not enough and normal Li battery voltage is too high.

The reason that I chose the buck only circuit vs a combo buck boost is that typically the efficiency is higher and complexity is lower. Most of the applications that I use are only 200 - 400 watts for 12 volt (12 volt refrigerator for example) so it works.

The higher battery pack voltage also benefits the efficiency for feeding a 2000 watt inverter and for allowing smaller wires. You would be amazed at how long the round trip wire runs can be in a 24 ft van.

HarryN said:

I agree that there are potential challenges, but it might be a viable path for applications where NiMH voltage is not enough and normal Li battery voltage is too high.

The reason that I chose the buck only circuit vs a combo buck boost is that typically the efficiency is higher and complexity is lower. Most of the applications that I use are only 200 - 400 watts for 12 volt (12 volt refrigerator for example) so it works.

The higher battery pack voltage also benefits the efficiency for feeding a 2000 watt inverter and for allowing smaller wires. You would be amazed at how long the round trip wire runs can be in a 24 ft van.

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I agree that much power the actual resistance and voltage drop in wiring can be an issue for sure buck converters tend to be more efficient than boost converters due to the lower current needed. Too bad you can't just find a 24V inverter instead as that may be even more efficient.

Lynx_Arc said:

I agree that much power the actual resistance and voltage drop in wiring can be an issue for sure buck converters tend to be more efficient than boost converters due to the lower current needed. Too bad you can't just find a 24V inverter instead as that may be even more efficient.

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What's the problem in finding 24v inverter? At Europe where we use 230v 50hz you can find 24v inverters like 12v ones becouse they are used in lorries. I just installed one to my friends lorry becouse old one stopped working.

satelite said:

What's the problem in finding 24v inverter? At Europe where we use 230v 50hz you can find 24v inverters like 12v ones becouse they are used in lorries. I just installed one to my friends lorry becouse old one stopped working.

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I've never looked for one myself but I'm guessing either they are sold where aircraft parts are sold or have to be ordered as our vehicles here are 12V not sure if tractor trailers are 12v though could be 24v perhaps but I'm guessing they have 12v outputs for use with devices such as chargers and GPS and tablets and stuff.

Lynx_Arc said:

I've never looked for one myself but I'm guessing either they are sold where aircraft parts are sold or have to be ordered as our vehicles here are 12V not sure if tractor trailers are 12v though could be 24v perhaps but I'm guessing they have 12v outputs for use with devices such as chargers and GPS and tablets and stuff.

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Yes they have 12v outputs too in lorries but you can use inverter for like coffee machine or microwave

satelite said:

Yes they have 12v outputs too in lorries but you can use inverter for like coffee machine or microwave

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And fridges too, I know someone that is a truck driver and he bought a tv and blu-ray player that was 120v to use the built in inverter
I have an 800watt inverter that I rarely use as I've invested in 12V native chargers and device adapters.

I routinely use 24 and 48 volt DC input inverters, although 12 VDC input is more common in the RV / conversion van world. Sold world wide as heavy duty trucks and marine are commonly 24 volt, and off grid homes and the entire telecom infrastructure is mostly 48 volt.

There are many other DC input voltages available as well.

Unless there is a really good reason, usually the inverter DC input is matched to whatever battery pack is being used.

DC - DC converters are used when the end customer has devices that either could not be purchased in 12 volt or they had already purchased some items and we just deal with it using a converter.

The kind of interesting thing about these conversion vans and RVs is that even though the DC refrigerators use relatively little power at any given time, they tend to be the largest total power load on the system. Especially in coastal areas, it can take 300 watts of solar panels to keep up with just the refrigeration load on a high efficiency DC refrigerator.

Sorry for going off topic, but my point is the same. No matter what the battery internal voltage is, sometime you just have to be clever and do what it takes to obtain the voltage that the end device requires. This isn't always a perfect match.

Goal zero found this out the hard way when none of their pricey little power units could power a 12 volt refrigerator. Of course their answer was to sell another expensive add on product rather than fix the original problem.

I have made the experience that eneloop lite cells dont have any issue when they get discharged down to 0V. In my case they always got back up to notmal capacity. I used them without any issues in old clocks on the wall.