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Old Mar 18, 2013, 06:42 PM
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New NiMH packs from BatterySpace.com weirdness

Hi, all,

I just ordered and received some replacement packs from BatterySpace.com for my old Futaba Conquest FP-T4NBF radio. Their prices, compared to the standard Futaba pack, were incredible, and they advertised item #RA-HAA8R1HT22 as a direct replacement for the original 500mAh 9.6V NiCd pack... and it's a 2200 mAh NiMH pack, to boot! Yay, right? $16.99!! And the 4.8V 500 mAh original is now 800 mAh and NiMH! Wow!

So, here I am with my new package. The 4.8V pack is four AAA size instead of four AA like the original pack, the 9.6V pack has the wire coming out the wrong side and it's almost too short, the plugs aren't the original plugs (although they do work.. just missin' the "one way only" key in the plastic), and the pack is almost too big to fit in the radio; had to force it in, and I can just barely get the battery cover on, but I did... but OK, they were cheap and CAN be made to fit. So far, I can ignore all that.

Now, I'm trying to charge the packs. I have an AC6 charger, and am charging the packs at 1.1A for the 2200mAh 9.6V and .4A for the 800mAh 4.8V. Neither would take a charge for more than 10 minutes or so before the AC6 declared "FULL." Unusual, but hey, maybe they shipped them charged, right? Nope. The charge didn't hold. Sooo.. I tried discharging them down to .85v/cell per the reading I've done about NiMH batteries (3.4V for the 4.8V pack, and 7.8V for the 9.6V). The voltage drops steadily according to the readout of the AC6 down to about the 4V level (for the 4.8V) pack, then drops very rapidly down to 3.2V and the AC6 shuts off. When I go to charge it a few minutes later, the voltage readout STARTS at 5.1V. What's going on?!?!

I've done most of my experimenting so far on the 4.8V 800mAh pack, but the 9.6V 2200mAh pack is exhibiting the same issues; the AC6 shows full discharge down to the target voltage, then when I charge it after a 10 minute rest, it shows a much higher voltage than it had when it discharged, and only takes maybe 250 mAh of charge.

Am I an idiot? Seriously.. if I'm screwing up, tell me. Am I doing something wrong?

Thanks in advance..

Barry
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Old Mar 18, 2013, 06:54 PM
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NiXX is essentially dead at 1v. I would NOT go lower for a PACK.
To D/C you want to use no more than C/5.

NiXX pack voltage is a very poor indicator of capacity. They will rebound from essentially dead to a seemingly decent number but they have no capacity at all. Unloaded voltage is simply not accurate.

I would do a forming charge (C/10) on both discharged packs.
THEN do a C/5 D/C and try a regular charge. You may have to do some tweaking on the delta-V setting in the AC-6 to get it to work properly.

It may take several cycles to sort out, especially if the packs have been laying around a long time.
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Old Mar 18, 2013, 07:02 PM
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charge it at .1 amp and see how much you can put back
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Old Mar 18, 2013, 07:12 PM
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Quote:
Originally Posted by rcalldaylong View Post
charge it at .1 amp and see how much you can put back
Delta-V is not likely to work at that low level (even for the AAA) and the excess heat will be minimal and simply dissipate. You could leave it on there forever.
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Old Mar 18, 2013, 07:23 PM
Dude, I do fly all day long!
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Originally Posted by flydiver View Post
That's not likely to work since you could leave it on there forever.
all I know is my nice shiny eneloops won't charge at 1.1 amps without tripping after 10 mins. however, if I charge at .1 amps, it will fully charge in about 4-6 hrs depending on how depleted it is.

DX7 replacement batteries using Sanyo Eneloops (2 min 57 sec)
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Old Mar 18, 2013, 07:35 PM
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My advice - quit attempting to charge with your AC6 and simply use the wall charger that came with your Futaba to charge both the Tx and Rx packs. A long, slow charge will properly equalize all cells within each pack and avoid the false peaks that you're experiencing with your AC6. Plug 'em in and charge for a few days and then perform discharge tests.

Mark
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Old Mar 18, 2013, 07:48 PM
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Quote:
Originally Posted by rcalldaylong View Post
all I know is my nice shiny eneloops won't charge at 1.1 amps without tripping after 10 mins. however, if I charge at .1 amps, it will fully charge in about 4-6 hrs depending on how depleted it is.

http://www.youtube.com/watch?v=KkOOEt0asMk
I agree. I use the Eneloops in one of my TX. I charge them at about 0.5 when I use the AC-6. Your video does not show the charger at all.
What do you charge with and how is it set?
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Old Mar 18, 2013, 07:58 PM
Dude, I do fly all day long!
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Quote:
Originally Posted by flydiver View Post
I agree. I use the Eneloops in one of my TX. I charge them at about 0.5 when I use the AC-6. Your video does not show the charger at all.
What do you charge with and how is it set?
I use the regular DX7 wall plug. it fully charges in about 4-6 hrs...that's when the batteries starts to get warm and I unplug.

on a side note, I have used the acucell-6 set to nimh and have tested charging at various rates. If I remember correctly setting to 1 amp or above would quickly trip the full status in about 5-10 mins depending on how depleted the cells are. But if I set to .1 it does do a full charge just fine.


And both methods, (DX7 wall charger/Acucell-6) are acceptable and after a full charge on either method, the I get a good 8 hrs or more.

that's kind why I think the OP should try it at .1 amp. I'm sure his batteries are fine...it just doesn't like the higher charge rates.
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Old Mar 18, 2013, 08:19 PM
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Thanks... and still confused

Thank you all so much for the quick replies. I've got to admit, I'm even more confused than ever. Before bothering you folks, I did the usual 'net searches and found out what I could about the best way to treat NiMH batteries. The consensus seemed to be that what was best was to charge them between .5C - 1C, and that trickle charging was a big no-no. That was from more of a pure tech related forum rather than R/C folks. Pretty heated, long thread discussion on that topic, actually. One of the members posted a bunch of .pdf documents from all the major manufacturers of NiMH rechargeables, and most of them agreed that 1C was the way to go. Here's the thread...

http://www.candlepowerforums.com/vb/...NiMH-Batteries

Then I found the following chart...

http://www.onlybatterypacks.com/up/p...STRUCTIONS.pdf

That, of course, further confused the issue. Talk about some SEVERELY high discharge rates! Plus, it seemed to advocate trickle charging, despite the other forum's strong advisement against it.

Here, most of you are suggesting doing a forming charge at C/10 or using the stock charger that came w/ my radio (which would equate to a C/44 charge for the 9.6V pack and a C/16 charge for the 4.8V pack). The advice I've read, if I've interpreted it correctly, seems to be treating NiMH packs exactly the same way that NiCd packs are treated. Most of the reading I've done is counter to that, and suggests treating NiMH differently due to the higher heat buildup, much smaller delta -V, etc.. I won't throw out anymore terms, because I don't pretend to understand them yet.

Having said that, since I've read the initial replies here, I've had the 4.8V on my charger at a ..2A rate, and it's hovering at 5.6V but slowly building up capacity; it's taken an additional 230 mAh in the past 73 minutes, and the pack is just slightly warm, a bit above room temperature. So far, so good, so you must be right.

The 9.6V pack ran the radio for about an hour without any input before crapping out, so I guess I've got to do a long charge on that, too. I'll try it at .3A (unless one of you chimes in and tells me to knock it down to .2A.. my charger won't do anything in between) and see what happens.

Thanks so much. I'm surprised that there's so much difference of opinion in a topic that one would think would be pretty much by the numbers, scientifically.

Best to all,

Barry
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Old Mar 18, 2013, 08:33 PM
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United States, CA, Bear Valley Springs
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You'll ruin Eneloops at a 1C (2 amp) charge. Most of us use no more than a 1 amp or .5C for fast charging them.
Otherwise, use the wall wart charger. They like that much better.

mw
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Old Mar 18, 2013, 08:48 PM
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Quote:
Originally Posted by musechaserpilot View Post
most of you are suggesting doing a forming charge at C/10 or using the stock charger that came w/ my radio (which would equate to a C/44 charge for the 9.6V pack and a C/16 charge for the 4.8V pack).
^^^ Do this ^^^ and you can eliminate a lot of confusion and worry and you will not be disappointed.

Many of us who are highly experienced have been doing precisely this for many many years and with 100% success. The NiMH Eneloops in my transmitters are over 5 years old and still provide over 10 hours of Tx time and are almost exclusively charged using the 50mA wall chargers that were supplied with the Tx.

Mark
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Old Mar 18, 2013, 10:38 PM
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It maybe of note that the 'stock' eneloop charger is 500mA.
These ultimately are consumer cells, NOT power cells. Power cells can (and should?) be charged a lot faster.
OTOH power cells probably are not going to have a lifespan measured in years.

I charge my own eneloop packs with the stock wall wart which is a very slow rate given it is only 110mA.
I did make up a 400mA wall wart I'll use sometimes, and if I'm in a hurry I'll pull it and put it on a upper end Duratrax.
About once a year I'll pull the individual cells and run them through a high end single cell charger. I guess I doubt it's very critical but it makes me fill good and obsessive.
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