Hi, Kev
The 30% to 70% is just a guesstimate. The problem is no hearing aid app or device that I know of actually measures a battery percentage. It’s all by LED lights ON or OFF. The ReSound charger and Smart 3D app shows 5 LED lights each representing a 20% charge RANGE. Looking at the Lumity manual, there are only 4 LED lights on the RL charger, presumably each representing 25% of range.
So, once you drop to one LED light in the app or on the ReSound charger, that’s just indicating you’re somewhere BELOW 20% charge - and you have no idea where. Also, in charging, once four LED lights go on on the ReSound charger, you’re charging somewhere over 80%, but you have no idea how far. So the “safest” thing to approximate the roughly 20% to 80% range without going too far in either direction and having to watch the Smart 3D app or the charger like a hawk is just wait until you notice you only have 2 LED lights on in the Smart 3D app (or the iOS widget says “40%” charge - same deal on % range). Then you know that you’re charge has dropped somewhere between 20% and 40% - so I picked an average of 30%. Same pyschology in charging. Don’t have to watch Smart 3D app or charger like an hawk. You get a sense of it’s going to take about xx minutes. “Alexa, set a charging timer for xx minutes.” In xx minutes, you see that 3 LED lights have come on. That means you’re somewhere in the 60% to 80% range (but you don’t know exactly where). So, I picked an average of 70% charge.
On average a 40% charge range with ReSound is 30 hours on a full charge x 0.40 = 12 hours. That’s usually more than enough to get me through the day. I’m lazy about putting on my HA’s in the morning and don’t care if I take them out an hour or two before I go to bed since it’s annoying to have them on when I floss my teeth, etc. If I want more charge, 10 min in the charger gives me 4 more hours or so of runtime. There are no battery doors to mess with. Just plop them in the charger. They charge. Take them out, they stop charging. I tell Alexa to set a timer. I do other things while they’re charging.
I imagine I could do the same with the Lumity but since it has a shorter runtime per % charge and there is no buffer LEDs below the 25% LED light or above the 75% LED light, it might be harder to be sure one is staying within the 20% to 80% range as my scheme approximates.
P.S. The narrower the charging range the more equivalent full-charge cycles you get out of the lifespan of a Li-ion battery.