BCD436HP/BCD536HP: Internal AA charger MEASURED

[nanZor]

You want numbers? Here it comes.

What this is NOT is a rehash of the hundreds of internal vs external chargers. It is *mainly* about the internal charger, a teeny bit of nimh info for us nerds, and yes maybe a quick mention of an external charger to accomplish a specific purpose.

I picked up a recent model 486HP to replace my trusty 396xt, and am thrilled. So thrilled I picked up another. So I have time to play these charger games now. Long-time battery geek, with an eye for practicality vs lab-perfection.

Instead of a super-long TL;DR type of monologue, I'll try to keep it as short as possible and break it up just a little. Jump in anytime!

 

[nanZor]

What we know already:

The internal charger is a simple timed charger where you can change your hours of charge up to 14 hours max.

When charging from the 5v mini-usb port, it pulls about 300ma. That means most standard 500ma usb ports should have no trouble charging the 436. And it also means that if you decide to use say a li-ion cellphone type power bank, and are going to need 14 hours to recharge the AA's, then say a 5000mah or more fully charged power bank will be needed.

I measured the current actually used to be charged to be about 280ma. I did this with the help of a Maha Powerex MH-C9000 analyzer using only 1 hour of charge from fully depleted batteries inside the Uniden, and then discharged on the analyzer. More below on batts. Those who want to put their Flukes into the device are welcome to do so. I took the ultimate battery-nerd solution.

The charger incorporates a thermistor or other temp-sensing device to help shutdown the charge if you put trash cells into it. Try not to do that.

LVD - Low Voltage Detect shutdown:
After all the alerts go off, if you ignore them, the Uniden timed charger does the right thing - it writes to the card, and then shuts down at nearly 3.0 volts at the "pack level", which under perfect circumstances, would mean that batteries are only being depleted to 1 volt apiece.

Nimh cells are actually designed to be fully discharged down to 0.9v on an individual basis without harm. However, in a series configuration, small differences in manufacturing quality means that setting it just a tad higher to 1v (3 volts overall), gives you some real-world wiggle room to accommodate the slight differences, without driving one or more cells below 0.9v.

Of course this means using high-quality batteries that are closely matched for both capacity and internal resistance so they "reach the bottom" at the same time. If they are very different, say old crusties from your frs radio, one from a baby swing, and another from your 75xlt scanner, then you are going to have problems.

Where to start charging:
Other than maybe a short "opportunity charge" of a few hours, when I use the internal charger, I do so from when it shuts down from low voltage on it's own. Past the alerts. I set the alert voltage for the lowest level possible and ignore it. Thats the only real way of getting into the ballpark of using the hour-timer. Otherwise, you may run the chance of unnecessary overcharge from not knowing where you are in regards to capacity left when you start recharging.

 

[nanZor]

Uniden (Corun) oem AA batteries

The batteries I received were the classic 3-pack of orange/green 2300mah rated nimh cells. They were dated 19/07 which I assume was pretty fresh.

When measured with a Maha MH-C9000 for both capacity and internal resistance, they met their goal.

All three cells were cycled three times to wake them up a little, although today, most nimh don't need the kind of cycling that cells used to need 20 years ago. I'm not sure if they are "low self discharge" or not, but the numbers say they are good for testing and use internally - at least for now.

How did the capacity / resistance test:
I used the Maha MH-C9000 to fully charge the batts. Unknown to many users, this also included a mandatory 2-hour additional time on the charger after they signify they are "done". This charger uses not only standard -dv EOC detection, but also a proprietary mix of algos which makes them just a *tad* conservative when the "done" indicator first lights up. At this time, it applies a 60mah charge each hour for 2 hours, and then drops to a 10ma benign TRUE trickle. I removed the batts rather than leave them on the dinky 10ma trickle.

This provides the most accurate discharge capacity termination, which I did at a slighly less than normal 300ma.

Also, cells were charged in slots 2/3/4 only. Over time and hard use, slot-1 of the MH-C9000 tends to go slightly out of cal, and is also a signal for me to get a new one. Anyway...

Corun AA Capacity Results:
Cell 1 2287 mah
Cell 2 2282 mah
Cell 3 2315 mah

Safe to call them all "2300mah" as rated.

Corun AA Impedance/Resistance Results:
Cell-1 1.44
Cell-2 1.43
Cell-4 1.44

What? Another unknown to most users is that the Maha MH-C9000 provides a *relative* internal impedance measurement once, and ONLY once upon immediate insertion into a slot upon charge. This very first value looks suspiciously similar to a voltage, but it is NOT. The second time you see numbers, it will be the actuall cell voltage from then on.

Unlike other analyzers I have which show actual milliohm values, they are not consistent due to slight differences in contact resistance etc, leading to skewed conclusion. It is the MH-C9000's "consitant relativity" that has never failed me.

CHART:
Up to 1.60 = brand new very good cell
1.80 = middle age - impedance starting to rise
2.00 = old age - possibly abused. About to be rejected by most chargers that look for this.

In other words, the Uniden-supplied Corun AA's are perfectly fine to use for the next set of tests.

 

[nanZor]

Is a 14 hour time charge enough or too much?

We're about to find out. Given that I didn't pry apart my new toy and put the Fluke to it, I estimated the charge current based on the 1 hour charge and discharge with the Uniden and the Powerex. So it may not be 280ma, but perhaps something closer to 230 or 250ma. We'll see.

After a 12-hour charge in the Uniden, I'll discharge with the Powerex, at the same 300ma rate as before, and see if it meets the baseline capacity figures for the Corun AA's from the previous test.

NIMH batteries *will* accept a certain amount of overcharge, and "LSD or low-self-discharge" less so, but still, they are designed to do that for *limited* amounts of time. This is accomplished by not having the anode and cathodes being the exact same capacity - oxygen recombination can now take place because of this.

** WARNING **
I noted that in my excitement to get my new toy up and running after fully charging / balancing them in an external charger which charges each cell individually, there is the chance that one can man-handle the cells and force them in with the wrong-polarity.

Don't do that, or you'll make the weasel go pop.

I'll let you know how it goes when the somewhat laborious charge and discharge test is done.

The gist of this is that I want to get a better handle on it, since I intend to use lower-capacity Panasonic Eneloops (1900mah measured typically) with the 436 as well. Later on those.

 

[pb_lonny]

That is an interesting article and some great information.

 

[nanZor]

Thanks - I'm trying not to go off the deep end, but once I get rolling it's hard to stop.

 

[nanZor]

Basic handling notes

While we're waiting for the 12 hour timed charge / discharge test to complete, a few notes about battery handling ...

Most AA's are pretty robust mechanically. But have you ever dropped one to a tiled kitchen floor or cement? I have.

Depending on how they land, they should be considered suspect for damage. Although cracking or shorting the anode / cathode structure is a possibility, the bigger possibility comes from if it lands on the anode (positive terminal).

Even if you don't see any physical damage, landing on the anode can weaken the pressure-cap and it may vent - ever so slightly - at lower pressures when the cell goes into the oxygen-recombination mode (gassing internally like it is supposed to). This loss of electrolyte means that the cell will lose capacity, and not truly recharge properly. Now you have an unbalanced "pack" in regards to the series connections in the Unidens.

"Skinned Wrappers"
If you are in the habit of pulling cells from other devices, like tightly-fitting flashlights, and the wrapper is "skinned" or thinned out to expose the case, you may introduce another problem.

Despite some tight space tolerances in the Uniden, for the most part it looks good. But some battery brands may have fatter thicknesses, and with shoddy manufacturing, very thin wrappers. If the cases of the cells touch each other - that's not good. Or, looking at the compartment, I see that under extreme circumstances, fat "skinned" cells pulled from a flashlight may conduct from the cell casing to the metallic sd-card lock mechanism. Don't do that either.

In other words, while the Uniden design is sound, consumer-level mistreatment may force an unforeseen issue.

... twiddling my thumbs while the 12 hour test continues ...

 

[nanZor]

12-hour Uniden charge results are in:

After taking the OEM Uniden AA's (Corun) down to 0.9v, and recharging with the 436 set for 12 hours time charge, a discharge with the Maha MH-C9000 was performed at the same discharge rate of 300ma like the earlier test:

Cell1 - 2292 mah
Cell2 - 2306 mah
Cell3 - 2328 mah

These are actually just a tad bit better than what the initial charge (after 3 cycles of break in) of the Maha itself recorded. Since this is not lab equipment, and subject to room temperature changes, I'm not too surprised.

But what it tells me is that 12 hours is totally sufficient, rather than using 14 hours for these nearly-new cells. Even though cells are designed to handle short amounts of overcharge, there is no need to extend these overcharge times longer than necessary. Over successive cycles, unnecessary overcharge adds up, and contributes to raising the internal resistance little by little with secondary reactions. Which then takes more time to charge. And charges hotter and the vicious cycle starts.

My *gut* feeling is that I could probably achieve the same with only a 10-hour charge. We'll try that next and report back.

So if you are using 14 hours on good quality cells that don't seem to be giving you any trouble, roll that back to 12 hours, and see if you incur shorter run times.

 

[nanZor]

Obsessing about internal resistance:

NIMH is "exothermic", meaning that they naturally get warmer as they charge. Warm is ok. HOT is even ok (despite decades of consumer misinformation) - but *blistering hot* is not.

A major contributor is the internal resistance of the cell, especially if aged or abused. It takes longer to charge, gets hotter during charge, and these two contribute to the internal resistance rising even more cycle by cycle pretty rapidly.

Unfortunately, the 436 doesn't detect this early on like even the lowly BC75xlt does, and you may unwittingly be feeding your scanner some real trash when you charge the cells internally. How would you know?

I fed two known totally thrashed high-resistance cells that my Maha chargers, Eneloop chargers, and a few others just kicked out and refused to charge into the 436. Instead of balking, or refusing to charge like the BC75xlt, it proceeded to charge anyway. Sure they start out cool, but later on, different story.

So I don't want to put trash into the 436. THIS is why I recommend getting hold of an external charger - even if you don't plan to use it as your primary charger - to make two very important tests that the 436 simply can't do.

1) Charge each cell individually to ensure a reasonable level of "balance" among all 3 cells when starting out, and occasionally thereafter.
2) Indicate when the internal resistance is so high, that it is better just to trash / recycle the cell instead and start fresh.

Many chargers themselves are not trustworthy - particularly those that don't charge each cell individually. Even "famous maker" battery manufacturers have chargers that to me, seemed to be designed to protect the AA alkaline market, and not charge even their own rechargeable cells properly.

Thus, get what your battery nerd friend recommends. For me, if my job depended on my boss not firing me for recommending an easy-to-use charger that accomplishes both objectives above it would be:

ANY Eneloop charger that charges cells individually. Take your pick. I prefer the slightly faster 3.5 hour charger, since it has an even tighter cell-resistance detection - or so it seems. Analyzers are a different story.

Cycle your cells in them once in awhile as a checkup if you are totally sold on charging internally.

Lets see if the 10-hour charge is sufficient....

 

[nanZor]

10 Hour Charge results ... and a better plan!

Like before, I charged in the 436 (starting from fully depleted), and measured discharge on the MH-C9000 analyzer:

Cell-1 2238 mah
Cell-2 2239 mah
Cell-3 2243 mah

Those figures a just about 50-60mah short of what an overcharged (controlled) Uniden oem 2300mah battery provides.

What this means is that 11 hours for these cells (It goes to ELEVEN!) would provide the tiny amount needed to prevent the cells from becoming unbalanced over time.

What about Eneloops with only 1900mah typical measured? I'll stick my neck out and say EIGHT hours for those. But I won't subject you to all of this over again.

The cells will tell you if you listen (feel) carefully enough!

 

[nanZor]

Field-Expedient way to set your charge time!

Forget all the analyzers. We can get close enough with just our fingers. For nearly any cell. Let THEM tell you. It's easy because of nimh's exothermic nature:

When the cells enter the overcharge phase, there is a *significant* difference in temperature from the hour before, and that's the time to stop when you can detect the temperature disparity between two consecutive hours.

Example:
You have set your charge time for 12 hours.

1) At hour 11, put your fingers on the batterie(s) and make mental note of the temp.
2) Just before the end of charge at hour 12, put your fingers on the battery again.

A) If the batteries are totally cool during both of these finger-checks, increase your time by 1 hour.
B) Likewise, if the finger check reveals warm batts at both hourly checks, decrease the charge time by an hour.
C) Repeat, until there is a distinct difference in temp between the last two hourly finger-checks.

Obviously, between changing your charge times, use the scanner until it shuts itself off when you do this. After determining the best hour length, don't worry too much if your low voltage alert is set a bit high - the cells can handle it, but tweak an hour even lower if you want to play.

Can't put your finger on the battery for even a couple of seconds? TRASH / RECYCLE them. Warm, and even *somewhat* hot is ok, but *blistering hot* where you pull back in pain is not. Since we are in a plastic case charging, I prefer warm - limited to just an hour of overcharge - to hot, and repurpose any high internal-resistance aging cells to something else and start fresh.

I think this is probably the most expedient way to do it to get real close to the ballpark - and if checked on some sort of timeline, a way to keep up with the real-world changes easily enough as the cells age.

I think I'm done testing. Honestly, for the most part I use external individual-cell chargers even though this technique is good for me on outings and trips. But the biggest reason I use external chargers, is that I just can't be down scanning for 10 or more hours at a time!

 

[palmerjrusa]

Uniden (Corun) oem AA batteries

The batteries I received were the classic 3-pack of orange/green 2300mah rated nimh cells. They were dated 19/07 which I assume was pretty fresh.

When measured with a Maha MH-C9000 for both capacity and internal resistance, they met their goal.

All three cells were cycled three times to wake them up a little, although today, most nimh don't need the kind of cycling that cells used to need 20 years ago. I'm not sure if they are "low self discharge" or not, but the numbers say they are good for testing and use internally - at least for now.

How did the capacity / resistance test:
I used the Maha MH-C9000 to fully charge the batts. Unknown to many users, this also included a mandatory 2-hour additional time on the charger after they signify they are "done". This charger uses not only standard -dv EOC detection, but also a proprietary mix of algos which makes them just a *tad* conservative when the "done" indicator first lights up. At this time, it applies a 60mah charge each hour for 2 hours, and then drops to a 10ma benign TRUE trickle. I removed the batts rather than leave them on the dinky 10ma trickle.

This provides the most accurate discharge capacity termination, which I did at a slighly less than normal 300ma.

Also, cells were charged in slots 2/3/4 only. Over time and hard use, slot-1 of the MH-C9000 tends to go slightly out of cal, and is also a signal for me to get a new one. Anyway...

Corun AA Capacity Results:
Cell 1 2287 mah
Cell 2 2282 mah
Cell 3 2315 mah

Safe to call them all "2300mah" as rated.

Corun AA Impedance/Resistance Results:
Cell-1 1.44
Cell-2 1.43
Cell-4 1.44

What? Another unknown to most users is that the Maha MH-C9000 provides a *relative* internal impedance measurement once, and ONLY once upon immediate insertion into a slot upon charge. This very first value looks suspiciously similar to a voltage, but it is NOT. The second time you see numbers, it will be the actuall cell voltage from then on.

Unlike other analyzers I have which show actual milliohm values, they are not consistent due to slight differences in contact resistance etc, leading to skewed conclusion. It is the MH-C9000's "consitant relativity" that has never failed me.

CHART:
Up to 1.60 = brand new very good cell
1.80 = middle age - impedance starting to rise
2.00 = old age - possibly abused. About to be rejected by most chargers that look for this.

In other words, the Uniden-supplied Corun AA's are perfectly fine to use for the next set of tests.

My Maha MH-C9000 charger doesn't give a relative internal impedance when I first insert a battery.
Was this a later enhancement of the C9000?

My unit must be over 10 years old and is in constant use, it's the best battery charger I've ever bought (and I have quite a few).

 

[nanZor]

Easy to miss - it's only shown when activating a charge. To avoid it scrolling to another slot and missing it, when I do the relative impedance measurement, I just stick a cell into one slot, leaving the others empty.

Either just wait, or initiate a charge. Watch like a hawk, since that value will be shown once, and only once.

When I'm done measuring resistance, I'll remove the cell, and then insert another one and initiate a charge.

I've tried catching it with multiple cells inserted, but that's pretty elusive.

Note that this works best on relatively discharged cells, or has at least had some rest and not hot off the charger - as a fully charged cell voltage might be reading 1.44 on your voltmeter. And then the *relative* reading for an impedance for a new cell might be just near that numerically, but they are two different things. Easy to confuse the two.

Example:
I just stuck in one single Eneloop and waited for it to do a default charge.
When the voltage reading showed up it was at 1.58 V !! No way! (wait for it)
Keep watching the display. The next time it rolls to volts, that exactly what it is - about 1.25v this time and will be volts every time thereafter. That first readout, even though it says "V" is not - it's the relative resistance reading.

Since values up to 1.6 (for relative resistance that is) indicates a very healthy cell, I'm happy.

Now you know why this isn't in the manual. Can you imagine the tech-support for that?

 

[nanZor]

ENELOOP charge testing:

New 2000mah white Panasonic / Sanyo Eneloops were put under the test. Non-counterfeit genuine "gen4" versions were tested like before.

Initially charged with an "individual-cell" charger to ensure balance, they were fully discharged to 0.9v individually. Similar to just letting the scanner run until it turns itself off. Ambient temp around 80F.

Recharged solely via the usb jack set for 9 (nine) hours instead of 11 as I did with the oem batts. Discharged at 300ma and measured on the Powerex MH-C9000 analyzer. Results are consistent with my experience with these:

Nine-hour charge / discharge test
Cell-1 1914ma
Cell-2 1923
Cell-3 1906

These values are consistent with fully charged good eneloops. However, due to their low internal resistance, they were stone-cold when checked every hour, and especially at the last 9th hour. Thus I'm going to run again with 10 hours and check temp again, just to make sure I've pushed them into a little bit of overcharge to let any slightly lagging cells be fully charged - since we're running in a series configuration.

So yeah, unlike the 2300mah oem's, the eneloops will provide generally about an hour less of scanning runtime. BUT, because of their low internal resistance, larger internal quality cell materials at only 2000mah, that means less heat (stone cold in this case) in a plastic-bodied, enclosed, and slightly cramped battery charging compartment when charging via usb.

We'll see what the 10 hour run will bring and we'll report back.

 

[nanZor]

10 hour signal for Eneloops detected

Definitely got the signal - stone cold at 9 hours, and at 10 hours the cells were very noticeably warmer. Warm, but not hot. We're done charging - no need to go further.

The actual discharge amounts are undergoing the test in the analyzer and will provide results sometime tomorrow.

 

[nanZor]

10 hours for Eneloops

Results are in. 10 hours was enough to fully charge the cells, and provide a little bit of overcharge to make sure they are balanced:

Cell 1 - 1930 mah
Cell 2 - 1955
Cell 3 - 1967

So there you go. From full discharge 10 hours for eneloops. For the oem Uniden 2300's, 11 hours was sufficient.

I suppose if you want to, remove the battery door before charging to allow heat to escape during that last hour.

While I personally won't use the timed charger each and every time, I have no issues with doing so for weekend trips, short vacations, or just a few hours of "opportunity charging" from time to time.

But, if you mismatch cells, throw in some cheap junk budget cells they may *start* out looking ok, but give them a year and their internal resistance goes through the roof. Put it this way - I'm still using 1st-gen Eneloops from 2006 without them getting hot in the 436 too as a test.

For now, I'll run with the OEM Uniden cells, and keep an eye on their internal resistance over time and cycles, and report back if anything unusual crops up.

 

[pb_lonny]

More great results, I love reading about this.

 

[nanZor]

Your path to nimh enlightenment for consumer batts begins or ends at the Fujitsu FDK nimh plant (formerly Sanyo) in Takasaki, Japan. Whether wrapped as Eneloop or Fujitsu lsd's, that's the cream of the crop.

It's too easy for me to get tangled into a battery thread, so I'll just say if you want to know more, visit the Candlepower forums dealing with batteries. It's where the Sanyo engineers, in conjuction with the Maha/Powerex engineers solicited feedback from users, and actually implemented quite a few suggestions when creating the MH-C9000 analyzer specifically with Eneloops in mind, but also other nimh as well. Also the home of the "protected" li-ion cell. Take a 2 week vacation, roll the threads back to about 2003, and start reading.

Here, instead of providing anecdotal evidence, I've tried to provide a way for others to easily duplicate the tests for themselves. I have charger recommendations depending on whether you want to get all analytical, or just stuff them in and walk away, but will save that for those threads.

 

[palmerjrusa]

Your path to nimh enlightenment for consumer batts begins or ends at the Fujitsu FDK nimh plant (formerly Sanyo) in Takasaki, Japan. Whether wrapped as Eneloop or Fujitsu lsd's, that's the cream of the crop.

It's too easy for me to get tangled into a battery thread, so I'll just say if you want to know more, visit the Candlepower forums dealing with batteries. It's where the Sanyo engineers, in conjuction with the Maha/Powerex engineers solicited feedback from users, and actually implemented quite a few suggestions when creating the MH-C9000 analyzer specifically with Eneloops in mind, but also other nimh as well. Also the home of the "protected" li-ion cell. Take a 2 week vacation, roll the threads back to about 2003, and start reading.

Here, instead of providing anecdotal evidence, I've tried to provide a way for others to easily duplicate the tests for themselves. I have charger recommendations depending on whether you want to get all analytical, or just stuff them in and walk away, but will save that for those threads.

Is the 0.5X battery capacity for charging capacity valid for making sure the -delta V algorithm for complete charging works?

 

[nanZor]

Yes 0.5C is the minimum recommended to get a significant enough dv from the battery to signal the charger to go into a top-off mode believe it or not. It is *not* truly the end of charge - it just means like a yellow traffic light "be prepared to stop". This is why the Maha MH-C9000 stops the high current charge, and does a two-hour 60ma / hour top off without you knowing. There are other factors involved other than dv, like slope detection and other proprietary methods I've tried to pry from them without success.

This is all good stuff, but there are some out there that forget these are consumable products, and can obsess over them like they are living beings.

You know what - I'm going to break my attempt at not recommending a charger. I should probably put it elsewhere, but don't want to leave any thread readers hanging...