Yeah @auntpie… You open up a can of worms, by breathing new life into this thread…In truth, rechargeable aids only work mild/moderate & “Some” severe thresholds, occasionally into profound with 105db receivers… But, for most severe/profound losses, the battery drain would be very excessive, so these Super Power BTE’s (SP) or Ultra Power BTE’s (UP) aids, cannot work at present with rechargeable LifePo4 Batteries, they aren’t powerful enough yet, so 675 or 13 batteries, are the only game in town! That, I believe is about to change in the next few years… Nissan is developing “ A Lithium-Ion Solid State Battery” capable of storing “Allegedly” 4 times the energy, or 1200 miles, on a 10 minute charge, these batteries are much denser than Lifepo4, and might, if successful, see the demise of the “Automobile Industry” as we know it? I am almost certain the major hearing aid manufacturers, will be developing their own type, solid state or whatever? Personally, I am Pro rechargeable everything, but only if they are fit for purpose, at the moment rechargeable doesn’t cut the mustard for my loss, we are not there yet, but I think and hope that is about to change… LifePo4 batteries have a couple other drawbacks, when they short circuit, they can cause a fire, water damage is usually the main enemy… The fumes are highly toxic, I was reading a report last week on e-cars, it would appear, electric cars are becoming a major problem for the UK Fire Service, as they become more popular, any e-car fire, is a major hazard, toxic fumes are one problem, the other is it’s extremely difficult to put a battery fire out, the preferred method is to let it burn, but it takes about 4 hours or so to burn out, and the fire can restart at any time, so waste disposal companies will not look at them, and refuse to accept them! Not to mention, it’s time consuming for a busy Fire Service! Rechargeable hearing aids have a BMS (Battery Management System) they will cut out in subzero 0-C temperatures, this happened twice to me, in challenging circumstances out in the sticks, with rechargeable aids, the aids will not reboot until placed in the charging dock! I would imagine, once these new batteries are developed, 4 or 5 days runtime might be feasible for under an hour charge? At present there is no perfect solution, one size doesn’t fit all, rechargeable is a reasonable solution for the vast majority, and as the battery technology becomes better, hopefully we shall see a vast improvement on hearing aid runtime & charge time… As always, YMMV… Cheers Kev 