1.5v AAA Alkaline Batt. question

[Hank Zudd]

Not for a flashlight, but my wife just got a Bodybug (excersise/weight loss gizmo) and it uses 1.5v AAA alkaline batteries. The tech support guy told her not to use rechargeable batts, but I call BS.

What NiCad would work in this application? What's the diff. from a 1.2v NiCad & 1.5V alkaline? thanks

 

[kuksul08]

I think some equipment is designed to work at 1.5 volts and based entirely around that voltage. NiMh's and NiCd's are 1.4V fully charged then settle down to 1.2V. I have found that 99.9% of stuff runs just as well or better with rechargeable NiMHs though.

 

[Marduke]

NiMH would probably work just fine.

 

[Arrkhal]

Some cheap electronic devices rely on the very high internal resistance of alkaline batteries to limit current. NiXX batteries have a short circuit current (flash amps) about twice that of the same size alkalines. A cheap, unregulated, low-resistance device may cook itself if you try it with batteries it's not designed to take.

I stuck a NiCd 9-volt in something once which said "alkalines only" on it (before noticing the sticker) and got away with it (the warning on that particular device was probably due to the fact that it doesn't handle low voltages well, and rechargable 9-volts are sometimes actually 7.2 volts, and always have absolutely pathetic capacity), but I've also heard of people frying stuff. YMMV, and be prepared to replace the Bodybug whatsit if something goes wrong.

 

[VidPro]

the device costs some $250, its a microcontroller type of gadget.
that is a lot of money to toss if they void the warrenty on you or something. soooo, i disclaim my answer based solely on its price and the manufactures suggestions. no $25 worth of alkalines would be worth the $250 , when not following manufacture recommendations, or if ever needing warrenty service.

but
i would use some regular ni-mh on it , and see how it goes, it is unlikly that it will damage the device, and i cant see how it could effect the calibration of it. but it Could suffer from not enough voltage.
in a device like this it could require (for 2X example) ~2.6v minimum to operate correctally, and WITH such a low drain from the device, it could run off of alkalines for a long time before dropping that low in voltage, unlike a higher drain device.
with ni-mh (or ni-cd) it may suffer from not enough voltage.

now there ARE situation where not enough voltage could cause a problem beyond not running, a microprosessor stalls , a mosfet half closed, a regulator having a fit. but so too would the alklaine reach that voltage in eventuality.

i would assume if there was ever a problem, it will be from to low of voltage in this situation.

that would be the biggest difference, the alkaline would start out at ~1.5v , and given a LOAD it would drop down in voltage , but small gadgets dont have a big load. so it stays at ~1.5v for a long time then wanes down slowly to ~1.0-.9v before it is pretty much dead.
a Ni-Mh AAA would start with a max voltage of about ~1.4v and decline quick to ~1.2v and hold that ~1.2v for a long time then get to about ~.9v as it was dying.

if it is a 4xAAA device, then you might have the issues of reverse charge , when the battery set is allowed to discharge to far down, that CAN be another reason why a certian battery is defined by the manufacture, just so the care and feeding of the device is simplified.