BCD396XT Battery Switch - Low Battery Alert Question

[Arizona_Scanner]

OK, so my apologies if some feel this has been covered, as I would say it has "sort of" been covered, but not fully.

I understand that the switch either turns the charging circuit on or off, and that it is not supposed to do anything more than that per our resident Uniden expert. I understand that it is NOT supposed to impact the timing of the battery alert (icon / sound).

Now here is the thing I don't get and am wondering about. Doesn't this create an issue when using NI-MH batteries with the switch set to alkaline (for external charging only)?

On the PSR-500 and PRO-106, there are adjustments in the menu for alkaline vs. NI-MH, and you can play with the thresholds. These thresholds are clearly quite different. Without different thresholds for the very different battery types, how does this not create a situation where the icon cannot possibly come on, flash, etc., at the correct time for BOTH types of batteries since they have very different discharge curves? I would suspect that on one type of battery, the icon would come on and stay on far too long before the batteries were truly low enough to require replacement. Sure, an hour (or whatever it would be) of alert is only an annoyance, but I'm just curious.

It would seem to me that the switch only does what the two different battery holders do for the GRE units, so how do GRE scanners get / need the different / adjustable thresholds and the Uniden scanners don't?

Is anyone using the above method (NI-MH batteries in the scanner with switch set to alkaline, external charging only) currently and if so, what are your experiences?

Thanks.

 

[One13Truck]

Very rarely have I used regular alkalines in my 396XT so I never really changed the setting over to that. Maybe tomorrow I'll give the NiMH batteries a fresh charge and test it out to see the difference.

Not really answering your question but that battery display is one of the very few things I really dislike about the 396XT. It's the best scanner I've ever owned but the battery level meter drives me crazy. I wish there was a way to change it to the battery icon displaying instead of the meter. Or at least change it to give an approximation of the % of charge left in the batteries. I'm not a fan of the Low Batt warning going off at 3.49 or whatever it usually is. Give me the battery icon or a display saying 15 or 20% or whatever it may be instead. The rest of the display can be customized with the different options. I wish this could too.

 

[nanZor]

With nimh, it is real hard to give an approximation of charge, since for most of it's life, the voltage stays stable and then drops off the cliff.

However, you may find the voltage display useful to see if a cell is going bad, or an external charger is not doing it's job properly.

Fully charged, a 3-cell unit should 3.84v or so - about 1.3v per cell. So you pop in some newly recharged cells, and quickly check to find 3.6 or even lower voltage. Something's wrong! Time to take the voltmeter out and check those cells, or find that the charger has gone bad on one or more cell compartments. Either that, or the cells are poor-quality to being with. For us battery geeks, that voltage display is kind of handy, even if it is more of a voltmeter than a gas-gauge.

This assumes that you are keeping all three in related "packs", and not sharing them with remote controls, toys, etc which will guarantee a bad balance.

 

[sylkwood]

As far as I know the switch is there to prevent you accidentally trying to charge alkaline batteries by mistake. By switching it to Alkaline even if you should plug in the charger it will have no effect.

 

[RickLeb]

Give me the battery icon or a display saying 15 or 20% or whatever it may be instead.

That would be ideal, but in order to do that the scanner would need to know the battery chemistry, and the mAh rating of the battery. That type of display is common in Cell phones and Laptops because the manufacturer know what type of battery is going to be used.

The switch in the 396XT appears to do nothing more than stop the charging of the batteries, and doesn't change any thresholds for the low battery alarm. As a result the scanner cannot display a % remaining value, and it simply flashes the low battery alarm as the voltage approaches the value the scanner can no longer keep running.

Since alkaline batteries have a more linear discharge curve, the low battery warning will last longer before the scanner shuts down. With NiMh batteries the warning period is often only a matter of minutes because of the sharp voltage drop at the end of their discharge curves.

 

[One13Truck]

I get WHY they have the voltage display instead of a % display or an icon. I just wish there was an option to change it out. I'd take an imperfect display over the voltage. It's just one of the few thing that bugs me about the scanner. I can't really explain why. I just don't like the display that way.
I'll blame my OCD for it. To my OCD the alarm should be going off when the meter is close to 0 and the unit shut off at/near 0. With this I usually see it go off around 3.5 or 3.49. It just doesn't seem "right". Weird, but just a peeve of mine.