Rechargeable Li-ion Battery Maintenance

[pvc]

This is partially reproduced here from aDIY School Hearing Aids PDF file named (Rechargeable Li-ion Battery Maintenance) because not everyone likes to receive information from cloud storage PDF files. Also, this forum-topic-version is open to comments, questions, and discussion. Though, for the long term it is best to read the DIY School complete version which is also maintained and kept up-to-date.

Rechargeable Li-ion Battery Maintenance:​

Simply charge your hearing aids in the charger at night, and then wear your hearing aids the next morning. That’s all there is to it! Right? Well, Yes. However, there are other considerations.

In general, Lithium ion batteries (Li-ion) should not be stored for long periods of time, either uncharged or fully charged. Thus, new rechargeable hearing aids (when unboxed) are only partially charged, and also turned off. Placing new rechargeable hearing aids in their charger will turn them on to get the hearing aids ready for use, but they will not be fully charged. Therefore, you (or your audiologist) may want to leave new hearing aids in the charger until the hearing aid leds turn green indicating they are fully charged.

Checking Battery Charge Levels:​

You can use your hearing aid Phone App to read the battery charge levels. You can also use the hearing aid fitting software to read your battery charge Levels. Though, using the fitting software requires a basic understanding of adding a client to your database and connecting to that client’s hearing aids.

Storing Rechargeable Hearing Aids:​

At some point you may have a need to store your rechargeable hearing aids as a backup pair. It bears repeating that, in general, Lithium ion batteries (Li-ion) should not be stored for long periods of time, either uncharged or fully charged. So don’t do it;

• Don’t fully deplete the batteries and then put them in storage
• Don’t fully charge the batteries and then put them in storage

You can do an Internet search for “how to store li-ion battery”, and you will find many sets of instructions. I think that the Internet instructions are not an exact science. But you can get a good idea about how to store your batteries by reading some of the Internet instructions. My guess is to store at room temperature (partially-charged (50% or 60%) and perform a full charge every 3 months, before storing again at (50% or 60%) charge.

Using your hearing aid Phone App to read the battery charge levels and then adjust the battery charge levels to approximately (50% or 60%) by partially charging or partially discharging the batteries. Then turn them off until:

• you are ready to be start using them again, or
• once every 3 months, recharge to 100% before storing again at (50% or 60%) charge

 

[Volusiano]

Great write-up as always, @pvc ! I appreciate you pulling it out from the DIY School v2.1 PDF file into a thread for more attention and discussion.

I'd like to add just a couple of small items to this. If you have a rechargeable pair of hearing aids and the batteries can be removed with a simple tool and small effort, I would probably recommend that you remove the rechargeable batteries from the aids before storing, after ensuring that the batteries are at 50% state of charge. This is simply to prevent the possibility of the aids draining the batteries sooner because even if the aids are put in the OFF state, there's a possibility of a very small amount of current (called leakage current) still being drained from aids to maintain it in a "sleep" or "Stand-by" mode so that it can be "woken" up more easily. We just don't know exactly what each manufacturer does while their aids are in the OFF state with the batteries still connected, so it's best to disconnect the batteries altogether if possible and if it's easy to do.

Even with the batteries are not connected to the aids at all, there's still a small amount of self-discharge over time, so that's why you can't just leave them be unconnected and it's all good. As instructed in @pvc 's notes above, it'd good to recharge them back to full 100% every 3 months and let them run down back to 50-60% before putting them back into storage. I would even go as far as checking to see what state of charge they're in after 3 months of storage to know so that I can adjust this 3 month maintenance more properly. For example, let's say after 3 months of storage, you check them in the aids and they show only 10% of charge, then maybe I would shorten the 3 month maintenance cycle to 2 months to see what state of charge they'd be after 2 months. Conversely, let's say if their state of charge is 40% after 3 months, maybe I can go a little longer than 3 months before I need to refresh them. I'd say the ideal maintenance interval is when your battery's state of charge has gone done to 30% before you should want to refresh them. And you can refresh by charging them up to 100% then drain them down to 50-60% then store. Or you can just time your charge until they're at 50-60% then stop, instead of going up fully to 100% then you'd have to drain them down again back to 50-60%.

There is some advantage to the "charge back to 100% then drain back to 50-60% again" method, though, even though it's a little more involved maintenance each time. The actual full capacity of a battery may diminish over time. For example, when brand new, let's say a battery has 1000 mAh capacity (100% health). Let's say after repeated use for 3 years, by the time you want to store them, their health has diminished by 30% (they only have 700 mAh full charge capacity left). Usually the diminished full charge capacity would not be known accurately unless the battery has gone through a full charge cycle from a low state of charge to 100% SOC, so the device would know how much current has been pumped into it until it becomes "full". Computers and smart phones usually keep track of this data, and that's why they can tell you your battery's health level (its current max capacity, usually as a percentage of the original fresh max capacity). I don't know if hearing aids have this smart in it or not. I do know that the Oticon More and Real do keep a statistical history of their battery usage, and that's why when you change to fresh battery, you need to reset this in Genie 2 so it knows that fresh batteries are now in place. This will give them more accurate estimate of the actual battery capacity as its health is diminished.

Anyway, back to the original point in the previous paragraph, by fully charging to 100% then discharge back to 50-60% every 3 month cycle, this may help the aids give you more accurate estimate of the battery's actual max capacity.

I know I've ended up writing a very long post here when originally I said I just wanted to add a couple of small points. I'd say that all in all, if you want to keep it simple, follow the instruction as outlined by @pvc. The salient points I made above is simply just for more insights in case anyone is interested in knowing more details behind the scene and want to get even a more accurate maintenance cycle out of their storage process. But they are still minor points. The most important thing is to know and be mindful about is that storage for Lithium-ion batteries is not simply a store-it-and-forget-it process.

 

[pvc]

Thanks @Volusiano for your insight.

This DIY School Hearing Aids PDF file named (Rechargeable Li-ion Battery Maintenance) also has an Appendix which describes Oticon’s battery protection mode as Puffery. imo> Maybe that's what it is?? Though, maybe I am missing something? If we find out different, then I can change the PDF docoment to reflect our current knowledge.

Appendix:
Don’t get confused by puffery, for example Oticon’s battery protection mode which is described in this getting-started-with-more-brochure.pdf (and clip below). What does Battery protection mode actually do (aside from turning your hearing aids off)? Here’s a -> link to the end result of a testing effort and you will need to scroll up if you want to see the previous testing results. As far as I can tell the (Tools/Set battery protection mode) does nothing except to disable the hearing aid On switch? Pffft!

Note that forum images may appear as icons (not full size) until you are Logged in as a forum member.

 

[pvc]

HMm; I'm not sure that I fully understand Oticon's BATTERY HEALTH/Maximum capacity, which you can find in Genie2/END FITTING step by selecting Batteries in the left Pane, and then Mouse-Hover over Battery Health;

• Last night (after a full day's use and charge level=22%) my maximum capacity was 87%
• This morning (freshly charged to charge level=100%) my maximum capacity is 89%

I also wonder how much time (months) before my maximum capacity will reach the replacement threshold of 84% from it's current capacity of 87% or 89%? Here's a clip;

The HELP files for BATTERY HEALTH says;
This section indicates the general condition of the batteries. Point your mouse to the graph to see the current maximum capacity and the threshold for recommended replacement.

At the threshold, a full charge supports approximately:

• 21 hours of daily use without streaming.
• 18 hours of daily use in combination with 4 hours of streaming (TV, ConnectClip, etc.) and 1 hour of smartphone streaming.
• 16 hours of daily use in combination with 8 hours of streaming (TV, ConnectClip, etc.) and 1 hour of smartphone streaming.

 

[pvc]

OIC; I checked again and one of the batteries has BATTERY HEALTH = 87% and the other battery has 89%. So you have to check both batteries.

 

[Volusiano]

Thanks for sharing this. I wonder if this is THE warranty criteria before Oticon would be willing to replace the battery under warranty or not? Obviously they're not making this feature available to the users themselves via the ON app and only the HCP with access to Genie 2 can find this out.