What do we do with old lithium-ion batteries?

Go to it malcolm !! with you all the way.

Totally agree. Is this not something that Which? should be pressing for? And should not the market be open to third-party batteries instead of only factory-installed OEM units.

A battery is just a power source – it should have no influence over the software in the device.

I agree. Third party batteries are not necessarily inferior. When I bought an Olympus camera I bought a spare battery and was sent a third party one, which I had not expected. It has proved just as good as the Olympus battery and was probably cheaper.

Once we have standard designs of battery then it will become more attractive to sell third-party products, and competition will help bring down prices.

I would agree that battery standardisation would be good (and as said elsewhere, user-replace-ability almost essential), but there are of course several technical problems (there would be wouldn’t there?!). Not saying they can’t be overcome, but most solutions would stymie technological development, and some be quite compromising to safety.
One of the biggest risks to Li-Ion (and-any battery with Li I’ve seen for that matter) is charging too far or too fast. Discharging too fast is also a risk. Violating any of these risks fire and explosion. We saw it when Samsung pushed one of the boundaries too far and had to recall a load of phones a year or so ago.
To that end, a modern Li-Ion battery connected wrongly – or even a mixed batch for series charging – is a strictly forbidden option. Furthermore, one cannot rely on terminal voltage alone to determine state of charge. Battery age, temperature, number of charge cycles – and a little bit of luck – all play a part in the charge/discharge vs terminal voltage curves. It follows that bespoke charging regimes are required which need to be reset when a new set of batteries are put in (often done automatically with a detection of open circuit and a “limp charge” mode and deep discharge learning curve, with the user instruction to leave the phone plugged in for several hours).
Furthermore, to take advantage of evolving technology, battery charging is re-optimised for the later developments – and if the revised regime(s) are deployed on an older version of the battery, the latter could go bang. It follows that, for safety, a different connector (or another foolproof means to determine the revision of battery) is essential. In that way, charging regimes *which evolve as battery development evolves* can be designed in concert to get the best compromise of
a) maximum longevity
b) longest discharge time in use
c) longest discharge time in stand-by
d) fastest recharge rate
All consistent of course with absolute safety.

With the above in mind, I can understand how making battery removal not for the faint hearted has evolved – but the competent should be permitted to do it and without the need to break glue lines and the attendant use of ozone-depleting chemicals. However, much as I’d like to be able to have batteries standardised, this would stymie development of performance improvements.

It’s well worth looking at these issues because if used wrongly, lithium batteries make rather effective incendiary devices. I take your point that standardisation of batteries could impede advances in the technology but I wonder if this could be accommodated in some way, for example allowing only the latest batteries offering highest energy density and/or faster charging capability to take advantage of more rapid charging.

Years ago, I learned that lithium-ion batteries must not be fully discharged to avoid wrecking them and have seen some evidence of this with batteries that have been stored in a discharged state for an extended period. Do you know if this is still the case, Roger, and if this is controlled in the battery or the device it powers?

I have no inside knowledge. However, I do know that batteries with a particularly high power discharge density – those used in drones e.g. – should be stored at ~55% charge – and refreshed every so often – to have maximum life. They should be brought to full power only an hour or so before they are needed to avoid irreversible degradation. I expect a similar problem occurs if left flat too long too.

Development in the battery technology is still very much on the fast part of the curve.

Yes, and for long term storage it’s sometimes recommended to store lithium batteries partially charged. Searching for information I have seen plenty of reference to circuitry to prevent over-discharge of lithium-ion batteries. It appears that this can be used within the battery housing as well as inside equipment.

With NiCd and NiMH batteries consisting of two or more cells in series, damage is caused when the weakest cell discharges first and then is reverse-charged by the other cells in the battery, which soon leads to the battery becoming useless. I presume that the same would apply with a lithium battery.

This is the case with a lot of plant, Malcolm – and to tradesmen in the know, it is so inside a lot of domestic equipment too. Case in point, the innards of several different manufacturers’ dishwashers, ovens and washing machines do actually have common pumps, valves, elements etc. However, those badged XYZ cost more…