Carson Magnifying Visor w/Lamp: NiMH batteries?

[TimeBandit]

I have this Carson magnifying visor:

https://carson.com/product/cp-60-head-worn-magnifier/

The LED headlamp takes three AAA batteries. Unfortunately, it goes through them pretty fast--especially when I forget to turn it off. 

So I was thinking of using Eneloops instead of alkalines. But according to the owner's manual, "Rechargeable batteries not recommended" and when I asked a Carson customer service rep if it was ok to swap in NiMH batteries, he said the following:

If you use your visor all the time and they don’t sit around. It’s very dangerous for rechargeable batteries to sit in any product and not being used.

Is this a case of CYA on the part of Carson, or is there a legitimate danger here?
 

[coppercone2]

Perhaps your call was rerouted to 1975 and they were thinking of NiCAD batteries

It might be a little dimmer and cutoff somewhat sooner with secondary batteries then with primary cells because the voltage is slightly lower.

I actually got a little irritated with my wall clock running on eneloops, I think it ran longer on alkaline AA, or at least kept time better or drifted less. I changed it to nimh and I notice I am doing with it more then I remember. Hard to tell if maybe the mechanism went bad or something though.

I also have a adjustable clip on light that uses 2x AAA batteries and I feel like alkaline gives more stable performance, the nimh batteries seem to decrease light output by alot and then recover if you leave it alone, I think its circuit dependent.

[TimeBandit]

Thanks. The possibility of lower light output with the NiMH batteries was one of my concerns. I may just stick with the alkalines.

[mag_therm]

My head magnifier is worn out and broken, the one on your link looks good. Does it stay in up position?
I saw video where it would slowly creep down all the time. Don't know if video is real or not.
Thanks

[coppercone2]

Don't get me wrong, if you just look at the curves/math.. it looks like the rechargeable should perform really closely, but basically what I see with my wall clock is unstable operation. It seems to gain and lose time with the rechargeable, but with primary cells I feel like I had a good feeling of how much it would drift when it was getting low to the point where I could ignore the fact that batteries were low because I had trust in its behavior (my brain was capable of compensating the error for quite a while so long I Had an idea of what it should say that week), but with rechargeable I basically gotta deal with it as soon as I notice it because the error gets funky. Actual measurement on something like that is too annoying/trivial to deal with. Like I almost swear I started to notice 'monotonacity' problems that disappear on the next day when I switched it to NiMH, but usually I only deal with this clock in the morning and forget about it later. I don't want to try to study it because its too simple to just revert back to the alkaline battery.

But for the headlamp I stick to NiMH batteries because I burn through them too quick and it gets expensive so I just deal with the reduced capacity also.. And in general I just keep alkaline around because doing the whole NiMH upkeep thing all the time sometimes feel imposing so its like a 'cheat day' where I pay for the luxury of not having to deal with the chargers, so I get to it a month later and then have charged NiMH on hand. Maintaining operations is nice if you are tired.

[TimeBandit]

My head magnifier is worn out and broken, the one on your link looks good. Does it stay in up position?
I saw video where it would slowly creep down all the time. Don't know if video is real or not.
Thanks

It does stay up (at least for me, on my head). Overall, I've been happy with it. The interchangeable lenses are nice too. My only complaint would be the battery consumption, but that wouldn't be so bad if I would remember to turn it off.

[TimeBandit]

Don't get me wrong, if you just look at the curves/math.. it looks like the rechargeable should perform really closely, but basically what I see with my wall clock is unstable operation. It seems to gain and lose time with the rechargeable, but with primary cells I feel like I had a good feeling of how much it would drift when it was getting low to the point where I could ignore the fact that batteries were low because I had trust in its behavior (my brain was capable of compensating the error for quite a while so long I Had an idea of what it should say that week), but with rechargeable I basically gotta deal with it as soon as I notice it because the error gets funky. Actual measurement on something like that is too annoying/trivial to deal with. Like I almost swear I started to notice 'monotonacity' problems that disappear on the next day when I switched it to NiMH, but usually I only deal with this clock in the morning and forget about it later. I don't want to try to study it because its too simple to just revert back to the alkaline battery.

But for the headlamp I stick to NiMH batteries because I burn through them too quick and it gets expensive so I just deal with the reduced capacity also.. And in general I just keep alkaline around because doing the whole NiMH upkeep thing all the time sometimes feel imposing so its like a 'cheat day' where I pay for the luxury of not having to deal with the chargers, so I get to it a month later and then have charged NiMH on hand. Maintaining operations is nice if you are tired.

I may still give the NiMH batteries a try at some point, but for now I'll keep using the alkalines (just bought a 24 pack of AAA, so we'll see how long those last). Part of the problem is that the three LEDs in this headlamp are already relatively low-output, even with fresh AAAs, so going dimmer with the NiMH batteries would almost make it not even worth turning on. I may sub in different, higher lumen LEDs in the future and retrofit the power supply if needed.

[mariush]

Well ... if it takes 3 AAA batteries then it should work with up to 1.65v x 3 = 4.95v but 3x1.5v = 4.5v is a safe bet.... 

AAA batteries are around 44mm x 10 mm diameter, so you should have around 44mm x 30mm room there in the battery compartment.
You could easily add a lithium battery with a small battery charge pcb there and maybe cut a hole in the plastic to get a microUSB or usb type c to recharge the battery.

For example 10$ for 1100mAh 40mm x 30mm x 8mm tall : https://www.digikey.com/en/products/detail/tinycircuits/ASR00012/9808769

With charge port, you could also attach a power bank to your belt or have it in your pocket, and have a usb cable go from the powerbank to your light without annoying you in any significant way