NimH AAAs

[ef37a]

The ones in my BT VOiP phones don't seem to last long so I have been looking for replacements. The claimed mA/hr capacity does not seem to correlate with price. Duracells are 850mA/hr but some much cheaper brand is rated at 1100mA/hr

I don't mind what I pay I just want the longest life. Suggestions welcome (but keep it clean)

Dave.

[Hugh Robjohns]

I use Panasonic Eneloop Pro which are 930mAh. Available from Amazon. Not the cheapest, but larger capacity than most and seem to last a long time.

[resistorman]

Eneloops here too

[ef37a]

Thanks chaps, pack of 4 ordered.

"I love it when a p............."!

Dave.

[ajay_m]

Eneloops also have very low self discharge, which can be a problem with NiMH cells. This ensures equipment not used regularly still has a charged battery.

[ef37a]

Eneloops also have very low self discharge, which can be a problem with NiMH cells. This ensures equipment not used regularly still has a charged battery.

Ah, handy! Coz I have 3 handsets and often one gets buried in crap on the sofa for a week and then takes yonks to get a full charge.
BT must fit some really cheap **** cells since I can find no brand on them bar "China".

Dave.

[N i g e l]

check that your phone setting is NiMH rather than NiCd, if thats a thing.
The phone might be giving up too early based on voltage.

[James Perrett]

check that your phone setting is NiMH rather than NiCd, if thats a thing.
The phone might be giving up too early based on voltage.

I'd be surprised if anything that uses VOIP is old enough to use NiCd cells.

I use GP Recycko and Amazon Basics cells here with a GP intelligent charger.

[N i g e l]

check that your phone setting is NiMH rather than NiCd, if thats a thing.
The phone might be giving up too early based on voltage.

I'd be surprised if anything that uses VOIP is old enough to use NiCd cells.

I use GP Recycko and Amazon Basics cells here with a GP intelligent charger.

I have recent equipment released in 2022 that gives a battery choice menu.

I also use GP Recycko. Lowest drain app is in an MSF wall clock

[DGL.]

Personally I just use the LIDL ones when they have them in, less than £5 I think for the 8 x AAA 1Ah ones I brought last week.

[merlyn]

It's worth noting that battery capacity is measured in Amp-hours (Ah), not Amps per hour (A/h). It's a measure of charge. 1 Coulomb is 1 Amp-second. 1 Amp passing a point for one second is 1 Coulomb of charge. 1 Amp-hour is then 3600C. Ah is a more user-friendly unit, like kWh instead of Joules for energy.

I think the 1100mAh batteries you're talking about are Lloytron. They probably aren't 1100mAh. I have Lloytron AAs and they're fine for what I use them for, which is a portable recorder.

Most NiMH batteries these days are low self discharge. Any batteries sold pre-charged obviously have to be.

[ef37a]

check that your phone setting is NiMH rather than NiCd, if thats a thing.
The phone might be giving up too early based on voltage.

I'd be surprised if anything that uses VOIP is old enough to use NiCd cells.

I use GP Recycko and Amazon Basics cells here with a GP intelligent charger.

I have just gone through Settings and there is nothing about battery type but then as you say, not likely and they came with NiMH anyway. I remember as well that my very old analogue Panasonic DECTs still came with NiMH.

Dave.

[ajay_m]

NiMH and NiCd cells both have the same nominal load voltage, 1.2V, although a fully charged cell will be over 1.3V.
You can charge NiCd cells with a NiMH charger though not the other way around, because NiCd cells are very rugged and will generally tolerate brute force charging approaches like continuous trickle on 1/10C (where C is cell capacity in mA/hr). A NiMH charger may, theoretically, undercharge a NiCd cell but it will not damage it. So there would normally in equipment be an alkaline (1.5V) and NiMH/NiCd (1.2V) setting only.

[ef37a]

NiMH and NiCd cells both have the same nominal load voltage, 1.2V, although a fully charged cell will be over 1.3V.
You can charge NiCd cells with a NiMH charger though not the other way around, because NiCd cells are very rugged and will generally tolerate brute force charging approaches like continuous trickle on 1/10C (where C is cell capacity in mA/hr). A NiMH charger may, theoretically, undercharge a NiCd cell but it will not damage it. So there would normally in equipment be an alkaline (1.5V) and NiMH/NiCd (1.2V) setting only.

That's interesting, the battery for an old Makita drill was a borked NiCd but the replacement was NiMH. I have the correct charger for the drill and it lists both chemistries, must be a compromise somewhere? It lists charging to 14.4V for a nominal 12V battery.

Dave.

[merlyn]

... (where C is cell capacity in mA/hr).

Oopsie.

[N i g e l]

It lists charging to 14.4V for a nominal 12V battery.

Dave.

"12v" is just a moniker. Even a new, fully charged car battery is over 12.6 and charges @ 13.4

[Acoustic Landscape]

NiMH? these are the best I've used, and those who have done exhaustive test comparitors on You tube

Rechargable: EBL lowest standing discharge rate.
Non rechargable: Varta, they have three types dependent on the power drain requirements, yours are probably the 'Power' variety or the one up from that 'max power'.

Prior to that it was Hybrio by Uniross, but they seem to be on the way out now, some of ours are still charging up to 2500mA after seven years! ..Smart charger.
High current battery chargers will always fry batteries, shortening their life.

There is another factor here, most rechargeable batts are 1.2V many devices will show a low battery warning or simply not function when it sees these kind of voltages, standard 1.5V batteries will be necessary. EBL have recently introduced a 1.5V Lithium rechargeable quoted 3Ah for AA. I have no experience of those yet.

The other notable thing, get a smart charger, AccuPower difficult to better. Your batteries will last longer and can be brought back from the dead, e.g. in very low power, long use/ cold applications, though if severely discharged, they may need a 'kick start'.

[ajay_m]

... (where C is cell capacity in mA/hr).

Oopsie.

Yeah that was a touch illiterate, I meant of course mAhr (properly I think mAh) or milliamp-hours not milliamps per hour. i.e for a cell with 850mAh capacity (i.e can deliver a current of 850mA for one hour), then the safe charging current at 1/10C would be 85mA but for NiMH cells a charger should not generally trickle charge at that rate but taper off down to zero as the cell voltage comes up to the full charge endpoint voltage. As I understand it, NiCd cells will happily tolerate being constantly trickle charged at 1/10C but this isn't ideal for NiMH cells, though if you charged them overnight in an NiCd charger and popped them out in the morning, I'm not clear you'd be doing any significant harm.

Confusingly some manufacturers are representing battery capacity in mWh as well.

These 1.5V lithium rechargeables are interesting; I think they have an inbuilt buck convertor to convert the intrinsic 3V cell voltage to 1.5V, and then the special charger they come with provides, I'm guessing, an input voltage that bypasses the convertor and charges the cell directly, probably via some kind of 'ideal diode' circuit based on a p-channel mosfet or something like that.

Of course these cells will die very abruptly when their discharge capacity is reached, hence you'd have to monitor active hours carefully, you're not probably gonna get a low battery warning first. How reliable they are, I don't know, but an ingenious solution for sure. I'd also be dubious that the buck convertor would handle high current drains without thermal issues, given the small size of the package, and as for what might happen in the event the cell terminals are ever shorted, even momentarily, I don't know, though a lot of convertors now have pretty decent current limiting protection.

[merlyn]

... Confusingly some manufacturers are representing battery capacity in mWh as well. ...

In some ways that's better as it takes the voltage into account. Say we have a lithium battery designed to replace a 12V lead-acid battery. A lithium-ion cell produces 3.7V. That's a nominal figure and the voltage comes down from 4.2V as the cell discharges. 3.7V is in the middle of the discharge curve somewhere.

To get 12V, Li-ion cells are wired in series, probably parallel too to get more capacity. There may also be a switched-mode voltage regulator.

Sometimes the capacity in specs is given as the capacity at 3.7V, making lithium batteries seem to have ludicrously more capacity than the battery they are replacing. What's relevant is the capacity at 12V.

mWh = mAh * voltage

Another way to make specs comparable would be to say "2000mAh @ 3.7V" or "617mAh @ 12V" = 7400mWh.

I still think in mAh out of habit, and it is a unit of charge, but mWh can clear up how capacity is measured.

[DGL.]

One thing you also have to take account of with batteries is capacity vs. current draw. Batteries can have a different capacity dependant on the amount of current a device is drawing.
It's why alkaline batteries were generally crap in digital cameras but Ni-Mh batteries were fine, even the lower capacity Ni-Mh AA's were far superior than Alkalines when used in my 1st digital camera (a 5mp. praktica of some description) even though on paper the Alkaline batteries had a higher capacity.