396XT use of battery while plugged in to power supply

[novascotian]

When I use my 396 as a handheld I charge the batteries in an external charger. I have two sets of AA cells so the worst part of doing this is the feeling that sooner or later I am going to break something or wear it out, due the frequent opening and closing of the back, and taking the cells out and replacing them. However that is not the issue I am asking about here. I also use this scanner in the car, and when I do I plug in a power adapter. Due to the fact I do not charge the cells inside the scanner I have the switch set to the non-NiMh setting.. can't recall the title of the setting at the moment.

My assumption has been that when I plug in the power adapter, the battery supply gets taken out of the circuit and the scanner is only powered by the adapter. But all of a sudden I realized that when I turn off the key in the car (which shuts off the adapter), the scanner still is working, meaning that the battery pack is supplying power... soooooo does this mean that when the adapter is operative the scanner is receiving power from both the adapter and the battery pack... I seem to recall that the battery pack did run down when I had the scanner in the car and connected to the adapter. My opinion is that both are supplying power. When I take out the cells the scanner operates perfectly well off the adapter alone, as one would expect, so the adapter is working okay. I have now begun to take out one cell when I hook this up in the car, so I can make sure the battery pack is not being used up... anyone got any ideas,, or am I doing the only thing possible to prevent use of the battery pack in the car???

 

[IdleMonitor]

It means that while u have it plugged in in the car. It is charging the batteries at the same time. If you dont want to charge them while in the radio then take them out. THE NON-NIMH setting is for alkaline batteries.

 

[wtp]

well...

if you take out a battery of course they do not charge.
if you set the switch to alkaline they do not charge.
if you see some self discharge on the batteries this is normal.
if you see a lot of discharge the battery(ies) could be bad.
if you see 4.00 volts in the morning (8am) and they are not used or charged and they are dead 3.5 volts at 8 pm that is a battery(ies) problem
i have also seen them go from 3.49 to 3.55 volts if i turn off the radio for like an hour !
i always tell my kids "you have to be more specific time and voltage that is
enjoy

 

[novascotian]

Okay, so just to clarify... are you saying that the non-NiMh setting is nothing to do with preventing a charger or adapter supplying power to the cells, and is for some other purpose such as to keep track of remaining charge or something to do with the difference in voltage between a NiMh and an alkaline for example?? I am more used to GRE type scanners that had different holders.... yellow for rechargeable and black for not... in the latter case preventing the charger from sending power to the battery pack.. Obviously this switch in the Uniden is not doing the same thing, according to what you are saying.

 

[novascotian]

Sorry wtp I hadn't seen your post when I replied.... you are saying that switching to alkaline prevents the cells from receiving any current, but the power from the adapter does power the scanner. That is what I had expected, so how is it that when I turn off the key and the adapter goes off, the scanner is still being powered from the cells. It sounds like the cells do not receive a charge but are not cut out of the circuit otherwise and are still being used.

As for my cells I have what I understand to be good ones.. .Immedions... low self discharge... and I use a Maha external charger. The cells should not lose anything at all in a day in terms of self-discharge, but I don't think that is a factor, seeing as how the scanner is apparently being powered by the cells, at least partly, whether or not the power adapter is plugged in, turned on by the key or not. Sort of looks like a shared powering of the scanner when the adapter is on, whereas I want the adapter to take over and the cells not be used up.

 

[wtp]

diode

a diode would allow the power to the radio and not "back " to the batteries

battery->power->radio

the switch would bypass the diode and let the power go to he battery also. hope it makes sense now.

 

[UPMan]

To be clear, the first reply you received was incorrect. If you set the switch to alkaline, the batteries will not be charged (but will still power the scanner in the absence of another power source).

 

[jaspence]

396xt batteries

Are you unplugging the car adapter first? In both my cars, the power plug is still live for 15 minutes after the ignition is off. In my last car, one of the plugs was always live.

 

[bear780ks]

Nov.

I'v been running at times my 396 with no batteries in it when I use it at Home and would do the same when i use it in our Truck but since there is No car charger that comes with the scanner when you buy it which I can't configure :roll: why it would be left out my guess it was done because you can Run it on it's batteries. but if I had the adapter I would run it that Way.. one thing to Note I run mine with the switch set to Alkaline which in the Display reads charge off and when i power it up the upper corner number reads 0.00

I'll add I also have the Means to rotate my batteries as well as one's have seen my post's on the batteries that I have and the chargers but i kind of feel the same way you do about rotating batteries through it's compartment I wonder when the day will come that i will wear out the Contacts.

But as long as what i'm doing is safe for the scanner I will run it at times this way.. As it's a little easier than rotating batteries) one thing i dislike doing this method the scanner seems to be a little more echoey but I'm trying to work that out.. Ra


I wanted to add I heard something that i thought was kind of neat on the Oldies channel: have a Listen

The Irish Rovers - The Unicorn Song - YouTube

 

[novascotian]

First off bear780ks, by coincidence, the Irish Rovers were just here in Halifax last week on their farewell tour. The Unicorn certainly was their biggest hit in their career.

Back to the battery situation. My 12v outlet shuts down when the key is turned to off in my car, so there is no more power coming out of the adapter. I do have the radio set to alkaline so when it is turned off there is that message Charge off, which to me implies that no current is going to the cells from the adapter when the radio is off, but one has to wonder if that is also the case when the radio is turned on. If so, then the suggestion above about the diode is a good one, except that I am not really willing to modify the radio. At this point I think I am just going to have to accept that regardless of the switch position, the cells will be powering the radio (and of course discharging) along with the adapter, so I will continue to remove one cell when I go mobile.

 

[UPMan]

He wasn't suggesting a modification. He was explaining what the ALK -- NIMH switch does.

 

[IdleMonitor]

To be clear, the first reply you received was incorrect. If you set the switch to alkaline, the batteries will not be charged (but will still power the scanner in the absence of another power source).

Regardless if they're nimh or alkaline if there's batteries in the compartment and you plug it in its still gonna try and charge No? And charging non rechargeables is a definite no no and can ruin the radio.

I wouldn't even attempt trying to test the theory out on nonrechargeable batteries.

Bottom line if you don't want to charge batteries while plugged into the adaptor then take them out. Especially non rechargeable batteries.

 

[UPMan]

Regardless if they're nimh or alkaline if there's batteries in the compartment and you plug it in its still gonna try and charge

That is not a correct statement. If the battery switch is set to ALK, the batteries will not be charged, regardless of the actual battery chemistry.

If you don't want the scanner to charge the batteries when plugged into an external power source, set the switch to ALK. If you accidentally leave the switch set to NiMH and put alkaline batteries in the compartment, the scanner will register a charging fault within about 2 minutes and abort charging (long before the current going to the alkalines could cause a problem). This method works well enough that we have removed the ALK--NIMH switch in new models.

 

[IdleMonitor]

And btw im just going based in a 396t scanner. Maybe the 396xt model is different.

And also. I've been swapping out rechargeable batteries in my 396t for the last 5 ot 6 years on a regular basis and no effect on the battery compartment cover either. Still in tact and closes no probem.

 

[IdleMonitor]

That is not a correct statement. If the battery switch is set to ALK, the batteries will not be charged, regardless of the actual battery chemistry.

If you don't want the scanner to charge the batteries when plugged into an external power source, set the switch to ALK. If you accidentally leave the switch set to NiMH and put alkaline batteries in the compartment, the scanner will register a charging fault within about 2 minutes and abort charging (long before the current going to the alkalines could cause a problem). This method works well enough that we have removed the ALK--NIMH switch in new models.

Interesting to know and thanks for the clarification. When I put alkaline batteries in its set to alkaline. If its nimh then its those batteres that are in. I've never crossed them to see what happens because...well sometimes ya just don't know and I never wanted a burntout radio so I never attempted.

 

[W4ELL]

It works as I would expect it to...

I use my 396XT the same way. I have NiMh batteries, my charge switch is set to alkaline so they won't ever charge, and I power it via car adapter while in the car. While the scanner is plugged into the adapter, my batteries don't get used at all. If I unplug the adapter, my scanner stays on because the batteries take over. In fact, on some occasions when this happens, I can hear an almost instantaneous blip in the audio when the batteries take over.

On a couple of occasions, my adapter has come unplugged from the lighter socket without my knowledge and, in turn, my batteries would take over and eventually die.

I have never noticed any abnormal draining of my batteries while the scanner is powered via car/home adapter and the charge switch set to alkaline.

- W4ELL - Posted from my secret underground lair. now Free

 

[UPMan]

396T has same switch, same operation.

 

[bear780ks]

Good Info

Hey Paul thanks for the good info, much appreciated.. I wished i could seen this kind of help on another forum I'm member on)

All i see on it most of the Time in it's threads is a Cat chasing it's tail and when you try to help you either get slapped on the hand by a Community Leader or you get moderated..

 

[N8IAA]

This method works well enough that we have removed the ALK--NIMH switch in new models.

Which new models Paul? My 125 has the same switch as my 396XT. Or, are you talking about the new digital scanners being announced next month?
Larry

 

[davidmc36]

....I've been swapping out rechargeable batteries in my 396t for the last 5 ot 6 years on a regular basis....

Same here. I got a xt basically the day they were released and swap nearly daily, cover and contacts are just fine.