Rechargeable Alkalines?

[tooki]

So… because Apple has strong brand loyalty (which, I will add, may be the result of their design decisions, not because of fanaticism), it gets held to a higher standard than its competitors?!? 

Where did I write that?  I just wrote that their high brand loyalty allows them to take more liberties when it comes to building in obsolescence through software.  You can argue whether it is moral or not independently of that.

Well it is what you argued in the original criticism. How come you criticize Apple for only providing 7 years of phone software updates, when everyone else struggles to deliver 3 years? That is a huge double-standard.

Perhaps those 7 years of support are a reason Apple has such brand loyalty.

[Siwastaja]

Yes, I've had similar problems. I have a smoke alarm which starts beeping when the voltage is just below 8V.

Are you sure and how did you measure?

Smoke alarms use integrated circuits that do ESR analysis on they battery, basically with short current pulses every now and then. This is crucial to their operation because the only thing which really consumes power in a smoke alarm is the alarm itself, and it only activates in real emergency, and it has to work. But batteries have two orthogonal aging mechanisms, capacity fade and ESR increase. In very low power application like smoke alarm the ESR increase dominates. But open-circuit voltage of the cell is relative to loss of capacity, you can't see the ESR increase with the 10Mohm or 1Mohm input impedance of the multimeter. You need to measure under load to decide if the battery is decent for the smoke alarm. And this is exactly what smoke alarms do.

I found this out 20 years ago as a smoke alarm started beeping low battery alarm and instead of just replacing the 9V battery, I measured it with a multimeter and it was reading more than 9 volts, so I was quite confused first. Yet, replacing with a new battery fixed the issue. Took some thinking to figure out what is happening.

You really need to measure under load to see what is the actual voltage at which the device stops working.

[tom66]

So… because Apple has strong brand loyalty (which, I will add, may be the result of their design decisions, not because of fanaticism), it gets held to a higher standard than its competitors?!? 

Where did I write that?  I just wrote that their high brand loyalty allows them to take more liberties when it comes to building in obsolescence through software.  You can argue whether it is moral or not independently of that.

Well it is what you argued in the original criticism. How come you criticize Apple for only providing 7 years of phone software updates, when everyone else struggles to deliver 3 years? That is a huge double-standard.

Perhaps those 7 years of support are a reason Apple has such brand loyalty.

I didn't criticise Apple for providing 'only' 7 years of updates because it was not a criticism!!    I simply pointed out that some companies have very high brand loyalty and this allows them to build other forms of obsolescence into their products, like not supporting new features on hardware that can support them, because they don't sell iOS. 

[ejeffrey]

- Another problem, both NiCd and NiMH have memory effect.  (NiMH has less of it, but still has some memory).  Unless they are fully discharged once in a while, in practice they might have a much shorter running time than expected.

Memory effect is overblown.  Yes, it technically exists, but it wasn't a major problem except after many cycles with equal discharge depths.  The problem with NiCd batteries and incomplete discharge was that at the time they were popular, the cheap charging circuits that most home users bought were slow chargers that were strictly timer based. They would charge at something like C/10 for 8 hours then reduce to a maintenance trickle charge at C/50 or something like that.  If you didn't discharge fully before putting them back in the charger, they would overcharge.  At these charge rates, NiCd batteries are more tolerant of overcharging than other chemistries in that they won't explode, but it does cause degradation.  That's why the advice was always do to a "complete" discharge, to avoid capacity loss from overcharging on cheap chargers.

NiMH battery chargers by contrast almost always use peak voltage detection and/or temperature rate of rise.  This allows accurate charge termination, and in turn both faster practical charge rates and avoids dependence on the starting state-of-charge.

- Yet another problem for rechargeable batteries is the temperature.  In cold weather they behave very poor (high internal resistance, lower than nominal capacity).  The device they try to power might not even start at freezing temperatures.

Alkaline batteries also lose performance when cold.  In both Alkaline and NiMH, performance starts to degrade at 0C and has lost significant performance at -20 C.  It's not really a significant difference.  If you want cold weather performance, lithium primary cells are generally better. 

- And yet another (sideways) problem might be the self-discharge rate.  Where alkaline batteries might need replacing once a year or even rare, a rechargeable might need to be recharged every 3-6 months, depending on its self-discharging rate.

LDS NiMH (which are almost all the cells on the market now) last for several years.  They still don't have the shelf life of an unused alkaline cell (7+ years), but it's enough to not really be a problem for the vast majority of cases where there is any significant load.  I even use NiMH batteries in remote controls.  There are still a few non-LDS cells on the market.  However. they are now the specialty item targeting high power devices like camera equipment.

[Halcyon]

LDS NiMH (which are almost all the cells on the market now) last for several years.  They still don't have the shelf life of an unused alkaline cell (7+ years), but it's enough to not really be a problem for the vast majority of cases where there is any significant load.  I even use NiMH batteries in remote controls.  There are still a few non-LDS cells on the market.  However. they are now the specialty item targeting high power devices like camera equipment.

I've replaced all my batteries from AAA through to D cells completely with Ikea AAA and AA NiMH cells (for C and D size applications, I use Panasonic battery adapters; Part No. BQ-BS2E8SA and BQ-BS1E8SA respectively). To charge, I have a Powerex MH-C980.

[IanB]

I've replaced all my batteries from AAA through to D cells completely with Ikea AAA and AA NiMH cells (for C and D size applications, I use Panasonic battery adapters; Part No. BQ-BS2E8SA and BQ-BS1E8SA respectively). To charge, I have a Powerex MH-C980.

I found those battery adapters to be of less use than I expected, since many devices taking C and D cells expect the full size positive button of a regular D cell, rather than just the smaller AA size button. Some spring contacts slip right over an AA button without touching it.

There are, however, genuine NiMH C and D cells, from Tenergy, for example. I have bought their Centura brand and found it to work reliably. The downside is that it takes a long time to charge an 8000 to 10 000 mAh D cell (charging current is limited to about 3.5 A, if you even have a charger that can do that).

[Halcyon]

I've replaced all my batteries from AAA through to D cells completely with Ikea AAA and AA NiMH cells (for C and D size applications, I use Panasonic battery adapters; Part No. BQ-BS2E8SA and BQ-BS1E8SA respectively). To charge, I have a Powerex MH-C980.

I found those battery adapters to be of less use than I expected, since many devices taking C and D cells expect the full size positive button of a regular D cell, rather than just the smaller AA size button. Some spring contacts slip right over an AA button without touching it.

There are, however, genuine NiMH C and D cells, from Tenergy, for example. I have bought their Centura brand and found it to work reliably. The downside is that it takes a long time to charge an 8000 to 10 000 mAh D cell (charging current is limited to about 3.5 A, if you even have a charger that can do that).

These particular adapters have their own terminal to mimic the size of the D cell. (the C-cells don't, they literally just "pass through" the terminal on the AA cell itself, via a hole). The AA positive terminal connects internally to the D-cell adapter itself.

The only reason I went with adapters was because: (1) I only have one product that uses C cells (that's a kitchen scale). I don't have any use for D cells at the moment, so rather than holding onto batteries, might as well just have adapters on-hand. (2) I don't have a charger capable of charging C or D-size cells, and I probably won't buy one anytime soon as their use is rare.

[IanB]

These particular adapters have their own terminal to mimic the size of the D cell. (the C-cells don't, they literally just "pass through" the terminal on the AA cell itself, via a hole). The AA positive terminal connects internally to the D-cell adapter itself.

That's interesting. I might have to look at them again.

The only reason I went with adapters was because: (1) I only have one product that uses C cells (that's a kitchen scale). I don't have any use for D cells at the moment, so rather than holding onto batteries, might as well just have adapters on-hand. (2) I don't have a charger capable of charging C or D-size cells, and I probably won't buy one anytime soon as their use is rare.

I don't have a charger for C or D cells either. What I do is put them in series and charge with a constant current from a bench supply. If I use a low enough current I can just leave them for several hours and watch the voltage until they are charged.

I bought the C and D cells to use in lanterns in case of a power outage, for which the high capacity is a definite advantage.

[Halcyon]

I bought the C and D cells to use in lanterns in case of a power outage, for which the high capacity is a definite advantage.

That's the obvious trade-off, particularly if you're in an area where long power outages occur, the higher capacity might be worthwhile. However, you could also argue that buying more AA batteries would give you the same capacity, but whilst they are not being used for emergency power, you can cycle through them in other devices.

I have 2 containers, one which contains fully charged cells, and another for used or depleted cells. Once I need to change batteries, I go for a fresh set and the empty ones go into the box for charging once I have accumulated enough to throw them on the charger. That way everything eventually gets used and exercised.