Battery Q and more

[whacker]

I've got an old Uniden BC 100XL that was my first handheld scanner, that I still use for dedicated VHF & UHF freqs when there's an event that uses just that nearby. It works like a champ, and is built like a brick! Slightly more sensitive in the UHF band than my BCD396T, but very hissy audio.

Any way, like most radios of its time, as far as rechargeable batteries, it came with 1000 mAH ni-cads (x6), which were replaced once or twice. More recently I replaced them with 2000 mAH NiMH batteries, as ni-cads are harder to find now and a don't perform as well.

But I've never found a comfortable recharge/usage cycle with them. The original batteries would give a good 6-8 hours run time (IIRC) after a 14-16 hr. charge in the radio. This is not the kind of radio you want to pop the batteries out of to put into an external charger, as you have to unscrew the bottom plate to remove them, and the memory is volatile, so you generally avoid that.

The current NiMH batts in the unit only seem to run 3 hours or so. Correct me here, but, if a set of 1000 mAH cells needs ~14 hrs. to charge, then wouldn't a set of 2000 mAH cells need roughly double that with the same charge current? I just want to figure this with some accuracy, and be able to get a full charge out of them. Otherwise I might try to find some ni-cads again, which I'd rather not do. I've never seen NiMH cells with a lower rating than 2000, but what do I know.

Another issue: I've got an old BC 200 XLT that hasn't worked for a long time, that needs a repair and a battery pack. Does anyone still repair these? I know Uniden probably doesn't. I used to rebuild my own battery pack from Radio Shack AA NiCads with the bare leads on them, but I'm not doing that anymore. Any info on that would be appreciated

 

[EMTLJB]

Try a local Batteries+ for a replacement battery pack or rebuild service. Batteries Plus battery store - All your battery needs for Laptop, camera, cell phone, camcorder, SLA, batteries recycling and much more

 

[benbenrf]

Whacker

If a 1000mAh battery needs 14hrs to charge, then a 2000mAh battery will need 28hrs to charcge - Yes/No?

Well - it could be either - I'll explain.

If the charger that is been used was designed to charge originally the 1000mAh batteries and you are now using it to charge 2000mAh batteries, it may well be timing out before the 2k batteries are fully charged.

Why? - because many dedicated chargers (i.e. chargers that come with particular battey types - as often is the case with consumer products) have in them, as part of the overall charge cycle control program, a timer in one of the charger IC's, which times out after a certain time period - deliberately so to prevent damaging the battery. If your charger has such a time-out built in, and it was designed/setup by the manufacturer to charge 1000aMh batteries, what in effect is happening is that after 14hrs it has only managed to replace 50% of the charge before it times out from the constant current cycle and drops to trickle charge cycle, if it is now been used to charge a 2000mAh battery.

Sometimes it's not the charger that has a timer built into it - take apart a Sony cell-phone battery and in many of them you will find a small IC, about 1/3 to 1/2 the size of a finger nail. That has software embedded which "comes to life" the moment the phone is connected to a charger, and runs a log against charger output and remaining battery current, to determine for how long the charger should be allowed to dump constant current into the battery, before the trickle charge cycle kicks in.

The charge timer may also be built into the receiver (often the case if the manufacturer is supplying a simple wall plug in AC/DC power supply type so-called "chargers").

As well, different battery and cell manufacturers use slightly different chemistries for the NiCads and NiMHs they manufacturer. While they will still all be constant current type initial charge cycles, variations in chemistry between manfuacturers leads to different cells and batteries of the same ratings coming off production floors with different C ratings e.g. C, C2 .....C4, C5, C6 to keep the batteries in peak condition over repeated recharging.

C is:
the current necessary to nominally charge for example a 10-ampere-hour battery from zero to full charge in 5 hours (2 amperes per hour) is referred to as the battery's C/5 rate.

In theory is can make a diff, but in reality it tends to so small that against what you have described I think it unlikely.

I think what is happening here is either you have a damaged cell in the battery pack (which means a cell that is either not charging correctly or is not holding its charge corretcly), or your charger has a time out (or there is a time out somewhere - could be in the receiver or the battery pack its self) and is timing out for 1000mAh batteries, leaving your 2000mAh rated pack/cell effectively 50% or thereabout short-changed.

Those are my ideas on it

 

[whacker]

I kind of doubt this vintage of a scanner has a timer for the recharge; just a hunch. Unlike the BCD396T, which has a very well defined charge timer that tells you when charge is complete, and turns it off. I have the original box and instructions, and IIRC it seems to indicate you just plug it in and go for 14-16 hours. It also seems to encourage you to go ahead and leave it plugged in if you're going to be at the "base station", so it would appear there's no warning regarding the possibility of overcharging. I'll have to investigate further, but more replies are welcome. Thanks Benbenrf.

 

[benbenrf]

Okay ..... then that leaves a faulty cell in the pack as the most likely culprit.

Would it be practical to open the pack and check/test each cell individualy?

 

[NotSoFast]

My BC346XT has a 800mA charger. That means it will charge at a 800mAH rate. So if I have a 2000 mAH battery set in my scanner I need to charge it for 2.5 hours per battery, or a total of 7.5 hours. So I would set my charge for 8 hours if I had a fully discharged battery in order to fully charge it. However, if I had 1000 mAH batteries installed, I would then only have to charge it for 3.75 hours, or a sertting of 4 hours.

And that is if the scanner is off during that charge. Figure on longer if it is on while you charge. (I'm assuming here that the timer starts counting from the time external power is applied and not from the time the scanner is turned off.

By the way, don't mix battery charge ratings. You can damage the batteries if you discharge them past the Amp hour rating of the smallest rated battery.

 

[whacker]

I will probably take out the cells and put them through a discharge/charge cycle in my LaCrosse charger, at its lowest (200 mAH) rate, and see how they do after that.