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Old Feb 06, 2013, 07:42 PM
kad
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Question
Initial Charge on Sanyo Eneloop TX pack

I'm looking to get a 2000mAh Sanyo Eneloop pack for my Auroa 9 TX and I'm seeing two conflicting initial charge methods.

Radical RC says no more than 100mah for 28 hours, that any higher rate will damage the pack.
http://www.radicalrc.com/category/Tx...-NiMH--NiCd-20


Batteries America, on the other hand, says to charge it at a minimum of 200ma for 14 hours.
http://www.batteriesamerica.com/newpage8.htm
http://www.helifreak.com/showthread.php?t=208590

What method have others used (successfully) for the initial charge with these packs?

-K
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Old Feb 06, 2013, 07:52 PM
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Radical RC knows what they're talking about. I personally recommend 50-100mA for several days for the initial charge. I have been using my ~50mA Hitec wall chargers for over 6 years with my Eneloop transmitter packs and they provide well over 10 hours of transmitter time. 200mA charge current is far too high and completely unnecessary in my experience.

Mark
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Old Feb 06, 2013, 08:13 PM
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^ What Mark says.

mw
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Old Feb 08, 2013, 04:59 PM
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What Mark/mw sez +2
200mA may be C/10 for that capacity pack, but a bit much for AA size cells.
Pete
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Old Feb 08, 2013, 06:52 PM
Pro Bro #1963
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Not to change the thread but I just got a Fut. 8FG Super. It comes with a 6cell 1700mah NiMH pack. The manual says to use wall charger (included) and do initial charge for 12hrs @ 170mah (which the wall charger puts out). I did this and am now doing the first discharge cycle on my Triton charger at 300mah. Should I use my Triton instead and do more like 100mah charge rate? The 8FG manual mentions nothing of this of course. How many cycles should O do to form this pack?
Thanks!!
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Old Feb 08, 2013, 07:17 PM
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The 170Ma charge rate the wall wart puts out is a forming charge.
As a rule, transmitter really don't need their batteries cycled as you would receiver packs, since you can watch the voltage as you use the radio.
Now, your 8FG (great radio) has a system on timer at the top of the display, to the left of the voltage display. You can easily reset that timer every time you charge the battery, I do this every charge. This way you know how much run time you're getting out of the charge. Now I bet you have a lot of learning to do with the programming and time needed to setup your models. You should get better than 6 hours on the timer before the battery gets too low. The 8FG battery is better than the average Tx pack, since it's not made with AA cells, but rather 4/5th A cells. Shorter and fatter than AA cells and more robust.
Best of luck with the 8FG. Mine is 3 years old now, and still rock solid!
Pete
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Old Feb 10, 2013, 08:58 AM
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Quote:
Originally Posted by flygilmore View Post
Not to change the thread but I just got a Fut. 8FG Super. It comes with a 6cell 1700mah NiMH pack. The manual says to use wall charger (included) and do initial charge for 12hrs @ 170mah (which the wall charger puts out). I did this and am now doing the first discharge cycle on my Triton charger at 300mah. Should I use my Triton instead and do more like 100mah charge rate? The 8FG manual mentions nothing of this of course. How many cycles should O do to form this pack?
Thanks!!
Nearly all manuals will tell you to charge for ~14 hrs before use ... and many will not mention subsequent charges assuming you will basically continue to use supplied charger.

For standard NiXX batterys - 1/10th rate is accepted cahrge rate .. so the 170mA is fine for first and subsequent charging.

Many 3rd party peak detect chargers actually charge at higher rates ... my Prolux is near 1A when charging full rate ... but I only use it when Tx / Rx packs are really low ... usual charger I have are 50mA older chargers ... Tx packs are 2300mAh.

Nigel
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Old Feb 10, 2013, 10:22 AM
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Quote:
Originally Posted by mrforsyth View Post
Radical RC knows what they're talking about. I personally recommend 50-100mA for several days for the initial charge. I have been using my ~50mA Hitec wall chargers for over 6 years with my Eneloop transmitter packs and they provide well over 10 hours of transmitter time. 200mA charge current is far too high and completely unnecessary in my experience.

Mark
I have always read C/10 was a standard charge/balance rate for NiMh chemistry 12/16 hrs as the high cell will vent while the lower ones catch up until i suppose they are all venting and in balance,which in this case is 200mah,so where did you hatch that one from?Agreed there is nothing wrong with charging it @50mah for 3 days.Just a question.
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Old Feb 10, 2013, 10:38 AM
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Venting?
NiMH cells after being fully charged just turn all the excess charging energy into heat. If the charge rate is low enough (like 1/10C), the cell will dissipate the heat to the atmosphere without venting. If the heat is not released fast enough the internal pressure will increase to the point that the cell will vent.

From http://www.ka7oei.com/nicds.html

Quote:
Overcharging:

As the name implies, this happens when you continue to dump energy into the cell - even after it is fully charged. When this happens, the energy has to go somewhere. The most obvious effect is heat. If you are "Slow" charging cells and they become even slightly warm, they are already overcharged!

Likewise, while heat is a normal by-product of "quick charging" a cell, when the energy is no longer being chemically converted (as in the charging process) the cell will suddenly start to warm up even more: One of the indications of full/overcharge is a sudden rise in cell temperature.

If charging persists even after "full charge" is reached, not only is heat produced, but gases can be generated as well. Small amounts of these grasses are normal, and may be reabsorbed into the cell's chemistry. If gas production is too high, pressure will build up and safety vents built into all types of cells will allow the excess gas to escape. Because this gas is derived from the cell's electrolyte, venting implies that some of the cell's capacity has just escaped into the air. If one particular cell vents more material than another, then it can become the "weakest link." As you will read below, this is bad.

Another effect may be present when the cell is in a continuous state of "slight" overcharge. Normally, when charging, the grasses that are produces (one of which is oxygen) are re-absorbed by the cell's chemistry. Oxygen, however, is an extremely corrosive element and may contribute (along with the elevated temperature) to breakdown of portions of the cell's internal structure - including the plastic (usually polypropylene) separator. When this separator starts to fail, self-discharge can greatly accelerate. All of this can happen even if out gassing has not occurred.
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Old Feb 10, 2013, 11:12 AM
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Thanks for the correction on venting my bad ok it's heat i was'nt thinking,i suppose if it's venting it's shot,however a suggestion that a 1/10 charge rate is too high sounds rather odd based on what little i have read or know about NiMh most recomend 1/10 C as a standard charge rate.So fill me in delta peak fast charging must be crazy to do.
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Old Feb 10, 2013, 12:14 PM
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Quote:
Originally Posted by The Tug View Post
I have always read C/10 was a standard charge/balance rate for NiMh chemistry 12/16 hrs as the high cell will vent while the lower ones catch up until i suppose they are all venting and in balance,which in this case is 200mah,so where did you hatch that one from?Agreed there is nothing wrong with charging it @50mah for 3 days.Just a question.
I hatched this from the voices in my head. e.g. - Personal experience, common sense, and reported observations from others.

I have voiced my disagreement with the universal and oft-quoted "1/10C for 14-16 hours" on many occasions. Reasons as follows:

1/10C for 14-16 hours was initially recommended by battery manufacturers for NiCd cells that have significantly lower capacity than today's NiMH cells. A typical AA NiCd is ~600mAh. The 1/10C charge rate would obviously be 60mA. This rate is low enough to prevent excessive heat build-up and resultant damage when the cell reaches full charge.

Applying this same recommendation to a 2000mAh AA NiMH cell gives a 200mA charge rate. Since all of the charge current is dissipated as heat when the cell reaches full charge, this 200mA charge current will be dissipating over 10 times as much power as the 60mA in the NiCd example. A 2000mAh NiMH AA cell is more sensitive to heat than an 600mAh NiCd AA cell, further compounding the problem.

In my experience, initial forming charge should be based on cell form factor (physical size) rather than capacity. I personally would never charge any AA cell above 100mA without the benefit of peak detection, capacity cut-off, or a thermal feedback mechanism that will terminate charge upon excessive heat rise. I use 50-55mA and have never had an issue, nor would any be expected at this low current.

I have seen many reports of trashed NiMH transmitter packs from charging at 1/10C for an extended period of time which support my concern of the antiquated 1/10C recommendation.

Mark
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Old Feb 10, 2013, 06:58 PM
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Quote:
Originally Posted by The Tug View Post
I have always read C/10 was a standard charge/balance rate for NiMh chemistry 12/16 hrs as the high cell will vent while the lower ones catch up until i suppose they are all venting and in balance,which in this case is 200mah,so where did you hatch that one from?Agreed there is nothing wrong with charging it @50mah for 3 days.Just a question.
I was told this by a Battery Tech - who's job it is to know ! ..... If a rechargeable cell Vents or gets Hot - it's being damaged and that damage is accummalative.... ie every time it happens, it adds to the previous damage. Warm is OK ... Hot is not. Venting is a sure sign of overstress of the cell.

When we used to charge up NiCD's on electric cars ... we fast charged in less than 15mins ... 6 cell C packs .... BUT we had fans running over them to try and cool them down while charging. Life expectancy ? Serious racing ... maybe 10 races ... after that used for practice.

Nigel
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Old Feb 11, 2013, 10:39 AM
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mforsyth, your post (#11 above) makes lots of sense, I never thought of the heat problem with the newer high capacity cells. What you say seems very practical and probable. I have always been an advocate of the 0.1C charge rate but will be more careful and watch the heat rise as well now when charging the high capacity cells. As most of us know, excessive heat is the most common culprit for ruining cells. Once a Nixx or LiPo vents, it is ruined.
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Old Feb 11, 2013, 10:52 AM
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Quote:
Since all of the charge current is dissipated as heat when the cell reaches full charge, this 200mA charge current will be dissipating over 10 times as much power as the 60mA in the NiCd example.
P=VI
Voltage is the same on both packs so the difference in power =200/60= 3.3 times, not >10.
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Old Feb 11, 2013, 11:03 AM
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Thanks for the clarity on that one Mrforsyth i just wanted to know the reasoning behind it.
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