BCD396T extremely warm when recharging?

[gregmoss]

Has anyone else experience their BCD396T getting extremely warm or hot when it's recharging? Will this harm the radio? Or limit it's life expectancy, performance, etc? I normally recharge the batteries outside of the scanner. I hate too keep taking them out, also worried about damaging the battery post/connectors

 

[firescannerbob]

Sounds like the early BC-250D's that got so hot they burned up the digital cards...

 

[W4KRR]

Has anyone else experience their BCD396T getting extremely warm or hot when it's recharging? Will this harm the radio? Or limit it's life expectancy, performance, etc? I normally recharge the batteries outside of the scanner. I hate too keep taking them out, also worried about damaging the battery post/connectors

Yes, excess heat will shorten the life of the batteries, and possibly damage the scanner. I take mine out and charge them in an external charger, a Maha MH-C401FS. It will charge from one to four AA batteries in a few hours. I also have a spare set of batteries always charged, so I just swap them.

 

[UPMan]

It is very normal for NiMH batteries to get warm while charging. Unlike NiCd, which only get hot during overcharge, NiMH batteries are exothermic during the entire charge process.

 

[Codeman]

It is very normal for NiMH batteries to get warm while charging. Unlike NiCd, which only get hot during overcharge, NiMH batteries are exothermic during the entire charge process.

As long as NiMh cells don't exceed about 115°F, no damage will be done. Although I haven';t gotten my DDM/probe out to measure the cells temps in the 396, I pretty sure it doesn't gets that hot.

If one or more cells does/do get that hot in the 396, I would suspect them of being defective.

 

[khvfdff]

Mine also gets hot. It doesn't get hot enough that its unbareable to touch. I have also noticed that on my scanner, when it is charging it goes all the way up to about 4.35 on the battery voltage and then when the charge is complete it goes down to about 4.10-4.15 but the batteries last only about 8-10 hours, all depending on the activeness of the channels. I have also had to stop using my priority channels because to me the priorites seem to keep running the battery down quicker like in 6-8 hours. Is there a way to correct this or not. I only had one channel as priority which is the main dispatch channel for our county and my fire department. Should priorities be running the batteries down like that. My county is active but you only hear the dispatch center talking because we are on an 800 system that cant be trunked with a scanner right now. So I leave the 800 frequencies off right now because the 800 frequencies are too active.

 

[Codeman]

The voltage meter is simply reading the voltage across all threee cells. During charging, that voltage is increased by the presence of charger's current. The readings displayed when the charger is not connected are more accurate in regards to the batteries themselves. Unless the 396's voltage meter takes into account that charger's applied voltage. Given the sudden change in voltage when connecting/disconnecting the charger, I doubt that it does take it into account.

Fully-charged cells should read about 4.5V total, but the life of NiMh cells is increased by only charing them to about 95%, which would translate to around 4.3-4.4V total.

If you can hold the cells by your fingertips for a few seconds, they probably aren't reaching 115°F - it just feels that way. Of course, that assumes no nerve damage.

 

[khvfdff]

The voltage meter is simply reading the voltage across all threee cells. During charging, that voltage is increased by the presence of charger's current. The readings displayed when the charger is not connected are more accurate in regards to the batteries themselves. Unless the 396's voltage meter takes into account that charger's applied voltage. Given the sudden change in voltage when connecting/disconnecting the charger, I doubt that it does take it into account.

Fully-charged cells should read about 4.5V total, but the life of NiMh cells is increased by only charing them to about 95%, which would translate to around 4.3-4.4V total.

If you can hold the cells by your fingertips for a few seconds, they probably aren't reaching 115°F - it just feels that way. Of course, that assumes no nerve damage.

I know that it reads across all three cells. When I put regular alkaline batteries in I get 4.6V on the voltage reader. I can get about 12-14 hours out of those batteries. With the NiMH batteries I only get 4.35V when its in the middle of charging and then when its completely charged it reads 4.10-4.15V on the voltage reader. It even does this with the scanner turned off. That is why I am thinking there is something wrong with my batteries. My father is telling me though its not my batteries. I only have 74 channels running and they are not that active at all. I know part of it was with my priority being turned on. The only channels that have the most activity on them are the main fire dispatch channel for my county, and a county that we mutual aid to at times. Their tone channel and TAC-1 channel are active. The only other time that I have more than 74 channels running at a time is when I have Gainesville F/R and Alachua F/R 800 turned on or the Jacksonville F/R 800 turned on. Sometimes I have my FM Broadcast or TV Broadcast channels turned on but not that much. I also use the CB Band Channels but that is only if I am away from a CB radio. If I do have the TV or FM Broadcast channels on I usually leave it on the plug so it doesn't wear down the batteries.

 

[Codeman]

I...
With the NiMH batteries I only get 4.35V when its in the middle of charging and then when its completely charged it reads 4.10-4.15V on the voltage reader. It even does this with the scanner turned off. That is why I am thinking there is something wrong with my batteries....

The point I was trying to make earlier is that if you see 4.35V with the charger connected, then it drops when you disconnect the charger, that difference is due to the current being sent through the batteries during the charge. Sorry if I misunderstood you.

Is the 4.10-4.15V reading, when the charging is completed, is that with the charger still connected? If so, then your batteries may be nearing the end of their usefulness. Or, the 396 has terminated the 14-hour charge period, and the lack of a charging current is the cause of the voltage drop.

I would keep using the cells, but if the time they last drops, then I'd have to say the cells are about at the end of their usefullness.

8-10 hours could be about right, depending on the capacity of the cells, how much you use the backlight, volume, etc. Do you know the capacity (mAh) of your cells? If they're in the 2000-2200 range, then 8-10 hours sounds about right.

I'm using relatively new Energizer 2500mAh cells. With either no backlight, or backlight on squelch only, they last 10-12 hours. That implies an average draw of 250mA/hour. So, with some 2000 mAh cells, I would expect them to last 8-10 hours.

Sorry to ignore the effect on your scanning habits in regards to battery life. I don't know how those impact it. In general, though, I wouldn't think just the number of systems/freqs that you're monitoring would have much of an impact. Switching between different types of systems would probably have a larger impact, since different circuitry is being used for the different types of systems.

 

[khvfdff]

The batteries that I have came with the unit. They are 2300mAh. I don't mess with the volume unless I am in a vehicle with the window rolled all the way down. I think my dad just does that to make me mad. I then have to turn the scanner up to the maximum volume setting. Which makes it then sound like crap. The point that I was trying to make earlier is that when the scanner is charging it goes to 4.35V usually, then as it is finishing the charge complete, it drops to about 4.10-4.15V. Yes that is with the scanner still plugged in. I know that when I unplug the scanner the voltage is going to drop anyway. But is it normal for the scanner to do this especially that far lower when its doing the charge complete. It won't go to the 4.5V like its supposed to then go down to 4.4-4.3V.

 

[UPMan]

NiMH have terminal rated voltage at 1.2 volts nominal, not 1.5 nominal (which would be the correct voltage for Alkaline). 3 x 1.2 = 3.6V (not 4.5). In real life, fully charged NiMH batteries will show higher than 1.2V per cell, but not as high as 1.5V per cell when not under charge.

Also, NiMH have a very flat discharge curve that starts dropping only when the cells are near depletion (unlike Alkaline, which have a fairly constant downward discharge slope). You cannot reliably estimate the battery life remaining in a NiMH battery by using voltage alone.

Priority should not adversely affect battery life (unless the scanner is normally left holding on a single conventional channel).

Your scanner sounds like it is operating normally -- battery life of 8-10 hours (while near the low side of normal) isn't unreasonable, depending on backlight use, volume setting, reception activity, etc.

Alkalines have about 2600 mAh of useable energy (typically), so, getting 10-20% longer run time out of the alkalines is pretty normal, too.

 

[khvfdff]

Ok UPMan,

You are the expert. I trust your knowledge. So now I understand it.

 

[MacombMonitor]

NiMH batteries can be safely charged at a rate that would make them hot enough to be very uncomfortable to hold you your hand. That being said, I think you might prolong the life of your scanner by charging them elsewhere. Or you could consider setting up a small fan to blow air over the scanner while charging, to help cool it down several degrees. At the very least, make sure there is adequate ventilation around the scanner, and keep it out of direct sunlight while charging.

 

[Codeman]

NiMH have terminal rated voltage at 1.2 volts nominal, not 1.5 nominal (which would be the correct voltage for Alkaline). 3 x 1.2 = 3.6V (not 4.5). In real life, fully charged NiMH batteries will show higher than 1.2V per cell, but not as high as 1.5V per cell when not under charge.
...

Yeah, that was a bit of a brain phart earlier with my mention of 1.5V. Thanks for the save, UPMan. My bad...

When I charge the Energizer 2500mAh cells in the 15min Energizer charger, I'm seeing 1.45-1.47V right when they top off. Voltage does drop some as the cells rest, but they're consistly at 1.38 - 1.40V, even after a 24-hour rest.