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sell682
2009.03.14, 11:26 AM
Hello,

I have a Duratrax Ice Charger and I have a pnracing 4 AAA battery rack.

What mah setting should I put into the Charger for there 4 batteries when charging them at the same time. Should I just add the 750mah for all 4 batteries together and put into the charger that its a 4 cell 3000mah battery pack. Or should i put 750mah at the packs mah capacity?

Please help I dont want to fry these batteries. Also what charge rate and discarge rate should I use?

Thanks for your help

EMU
2009.03.14, 12:40 PM
You should put 750mah. When the pack is wired in series, or on a charging tray in series, the capacity remains the same... it is the voltage that increases. When a pack is wired in parallel, the capacity increases and voltage remains the same.

I charge my SHO 750 cells at 500ma. These cells are known for venting at higher ma ratings.

sell682
2009.03.14, 09:17 PM
Oh ok...Im using a PN Racing Battery Tray...is that in series or parrallel? Sorry for the stupid question.

EMU
2009.03.15, 01:40 AM
Series. It is essentially the same as hardwiring them as a pack. You are not charging each individual cell, but rather the entire pack. It is best to equalize the cells (discharge each cell individually to the same voltage cutoff) before the initial charge, so that you get a full charge. Then you can repeak between runs. I wouldnt discharge between every run though.

If you race once a week, you can discharge the cells individually, then give them a slow charge, a couple days before the race... I dont like to touch my batteries the day before I race with them. I allways like for them to sit at least a day.

I also only use one pack of batteries no more than twice in a day. The only exception is my practice cells, which are retired race cells. They are still fast, just not quite as fast as the ones I use for races. I would use them for a modified car, where I dont need as much punch.

Action B
2009.03.15, 02:18 AM
I charge my SHO cells with a regular energizer 15 minute charger (3 amps) just like all my other batteries. I don't know what people are doing to these cells to make them vent. Since I heard about them venting I have made what I call the "fan sandwich" to charge them now. Its where I put my energizer 15 minute charger upside down on another fan while my batteries are charging to help reduce heat. I've charged them several times with no problem with this crappy 20 dollar charger lol.

I don't have as deep of pockets as some of the guys here. I just recently was looking into a helios and the price is ridiculous. Of course, don't plan on being truly competitive without a 300 dollar or more transmitter... maybe this hobby isn't for me lol.

EMU
2009.03.15, 02:45 AM
At the KO race, a teammate used my chargers to charge his SHO cells. I have 2x Duracell 30 minute chargers. The fast charge is 1.7A, followed by a trickle to top the cells off. I had to clean them up after a few cells vented. Luckily I noticed that he put the cells in the chargers... so it wasnt on there long. At least 4 of the 8 cells vented, and not my battery terminals in the chargers are corroded. I had to sand them down a little to get my batteries to charge. I then told him to only use my 2x Lacrosse charger at 700mah, and even without a fan, no cells vented again.

I have charged my single set of SHO cells with my Duracell chargers a few times without vents... but, I guess I was just lucky, and maybe that after the cells break in a few cycles at a lower amperage, that there is less risk of venting???

The winner of todays stock class used a KT-18... You dont necessarily have to have the best transmitter. It just makes it easier to cover up setup flaws with all of the functions that are available on the transmitter. Of course, Davey G is one of the best drivers that I have ever seen, and his setups are usually flawless, but he uses a stock transmitter :eek: You can find the EX1-UR for about $200 with ASF module... Although, I do prefer the helios.

Action B
2009.03.15, 03:13 AM
Yeah, I don't think its a charge rate really. I think its all about the heat. Problem is, the faster you charge the more heat you produce. The fan sandwich is really effective at heat dissipation. I touch the batteries occasionally to see how hot they are getting.

I understand what your saying about some people using a stock transmitter, especially for stock class. Though, I still think it makes significant difference. I wouldn't expect to see a single stock transmitter at PN nationals or anything. That tells you something. Right now I can't even afford the 2.4 conversion for my car.

EMU
2009.03.15, 03:30 AM
I dont think its a heat issue. The cells did not get hot when the vented. It is just like overclocking a computer chip... as you go up in voltage, you get more heat, but even if you use phase change cooling, you can still fry the chip. Keeping it cool helps, but damage can still occur even when the batteries are cool.

I did see a couple KT-18s at the KO race last week (the biggest Mini-Z race that I have been to). The guys were fast too. One that I can remember was in the A main for Expert stock I think, he was TQ (fastest in qualifying).

Action B
2009.03.15, 03:44 AM
Well, many people charge batteries at high amperage exclusively. Christian for one has stated that he only charges at 2.5 Amps and has never had a cell vent. Neither have I. I'm not saying they don't. I guess I'm just not cursed with cell-venting syndrome.

At the myrtle beach event I went to. I dont recall even one of the pro class racers having a stock transmitter. Heck, most of the sportsman didn't.

Action B
2009.03.15, 03:56 AM
This article of a patent from a guy who probably knows a lot about batteries seems to support the idea that heat is what causes battery leakage. He explains that overcharging is the number one killer of batteries because any charging beyond its peak charge is translated into heat. Of course, I don't really care what it is so long as my cells don't leak..which they dont... yet...

It would be nice however to know the truth behind venting, for all of us here.

http://www.freepatentsonline.com/7405538.html

I'm open to other suggestions. The processor analogy isn't so good for me because quite frankly I don't know that much about processors.

TheRinger
2009.03.15, 07:39 PM
I had 750 orions, intellects, and 1100 orions vent on me in different chargers. I do believe heat has something 2 do with it. The intellects I had vented in my old lacrosse charger even charging them at .5 amp. After that I cleaned the charger, made a fan that sits on top of it and it put more of a charge in the batteries, so much that it charged my duracell 1000's at 1.7 volts, 1500mahs with that set up. But charging them like that will greatly decrease the life of the battery and charger so I moved on 2 maha chargers and don't charge them higher then there rated with the exception of my 8 cell maha charger which can only do fast, soft, and recondition which I use 4 race day. I charge my 750 orions with my superbrain 989 or 960 charger or ice charger with a atomic charging tray so if they vent all it will ruin is the charging tray.

EMU
2009.03.15, 08:26 PM
I think the 8 cell Maha charges at 700ma fast, and 350ma slow...

Cherub1m
2009.03.16, 10:41 AM
I think the 8 cell Maha charges at 700ma fast, and 350ma slow...

MH-C800S (grey colored one) 1.0A (Standard mode) / 0.5A (Soft mode) rapid charge

MH-C801D (black colored one) For AA batteries it's 2.0A (Rapid mode) / 1.0A (Soft mode) rapid charge. For AAA batteries it's 0.7A (Rapid) /0.35A (Soft) rapid charge.

MH-C9000 WizardOne Charger-Analyzer is programmable from 0.2A to 2.0A in increments of 0.1A

All are great chargers the instruction does say not to charge batteries in rapid mode if rated lower then 800mah for the MH-C800s and for the MH-C801D if rated below 700mah dont use rapid charge. I've charge most of my batteries at 1000ma that includes 700 to 900 never had a problem, however I've never tried the orion 750 SHO that people seem to be having problems with.

EMU
2009.03.16, 12:54 PM
This is the data for the MH-C800s
Fast Charge Current: 1000mA (AA), 700mA (AAA)
Soft Charge Current: 500mA (AA), 350mA (AAA)

doug01n
2009.03.16, 03:23 PM
I believe that the more you increase the current, more damage to the cells.

The competition cells have a fenomenal punch after a 1.5 or 1.8A charge, but it really damage it. Right now, I'm charging my Sony cells with 0,1A current.

@ 0,2A, my 900mAh cells took 992mAh, and the 800mAh will take about 930mAh... It will be charging overnight. It will have an excelent run time, but less punch.

And last, I think that cooling the battery tray whille charging may change the chemical balance of redox reactions inside the cells, making them overcharge and consequently vent.

Action B
2009.03.16, 07:41 PM
And last, I think that cooling the battery tray whille charging may change the chemical balance of redox reactions inside the cells, making them overcharge and consequently vent.

With all due respect, why?

doug01n
2009.03.16, 08:06 PM
Whell...

Chemically, the NiMh battery consists in a chemical oxidation / reduction ballanced equation. When you apply a current, you are unballancing this equilibrium state, making it charges. The eletrons pass from one pole to the other, being there until you close the circuit again (with a motor or a short-circuit) and the eletrons comes once again to the lower potential diference point. Occurs that all the oxidation / reduction reactions generattes and are affected by the heat, as a catalizer, or a "stopper", changing the point of equilibrium of the reactions.

So, if you change the equilibrium point of the redox reaction, you may get a overcharge, damaging the cells, or if you overheat with a high current, the inside substances just boill and leaks out of the battery.

Of course, if i'm wrong, I really appologize, 'cause my innorganic chemistry classes ended a long time ago. But i'm now stimulated to search for some scientific papers about the NiMh batterys. :)

Sorry about the bad english too... I'm trying to write correctly!

Action B
2009.03.16, 11:08 PM
Whell...

Chemically, the NiMh battery consists in a chemical oxidation / reduction ballanced equation. When you apply a current, you are unballancing this equilibrium state, making it charges. The eletrons pass from one pole to the other, being there until you close the circuit again (with a motor or a short-circuit) and the eletrons comes once again to the lower potential diference point. Occurs that all the oxidation / reduction reactions generattes and are affected by the heat, as a catalizer, or a "stopper", changing the point of equilibrium of the reactions.

So, if you change the equilibrium point of the redox reaction, you may get a overcharge, damaging the cells, or if you overheat with a high current, the inside substances just boill and leaks out of the battery.

Of course, if i'm wrong, I really appologize, 'cause my innorganic chemistry classes ended a long time ago. But i'm now stimulated to search for some scientific papers about the NiMh batterys. :)

Sorry about the bad english too... I'm trying to write correctly!
Again, this is damage from heat from overcharging right? The rest of the oxidation and redox reactions are just details. You just stated what I stated more technically. "Additional charging after peak charge has been reached will be converted to heat, which causes leaking due to expansion"

Let me know if I"m missing something here.

Also, I was thinking that regular chargers made for general public usage might result in less venting. Since an 80% charge is sufficient for 99.9% of the population, its highly possible that the chargers used by hobbyists may be getting dangerously close the the critical fully charged point, a fine line that when crossed results in venting. Its doubtful that my 15 minute charger is really attempting to get the most out of the battery. Why would they design it to come so close to that limit. For a mass produced product like this its merits would be pretty slim when compared to the risk and lawsuits.

EMU
2009.03.16, 11:20 PM
The problem is that there is heat inside the cell, and cooling the outisde of the cell causes it to peak late... causing overcharging. That is the reason why the fast chargers only fast charge for part of the charge, then they trickle to top off the cell. When the light turns green, that means that the fast part of the charge is finished, but the cell is not fully charged. It still needs to trickle to reach full capacity. I am guessing that the fan stays on until either the cells are cool (via temp sensor), or when the cells are fully charged. I have not figured that one out yet.

Fast charging the SHO cells, even with fans will not prevent venting. As I stated, the Duracell 30 minute, which fast charges at a little more than half the rate of the Energizer 15 minute, and has a fan, still vented the cells. They were new, so that could be another factor... but I have charged my SHO cells in the Duracell charger without any venting a few times.

I honestly did not notice any decrease in power charging the SHO cells at 700ma compared to the 1.7a that the duracell has. They had just as much punch, and had a longer runtime, probably because the peak detection is better in the Lacrosse charger than the Duracell.

I actually prefer the charge my batteries at a lower amperage without a fan, than a higher amperage needing a fan. They seem to run just as fast, and dont drop off as much midway through the race. I only use my 30min chargers for racing, and use the Lacrosse for practice and battery cycling.

doug01n
2009.03.17, 06:46 AM
I totally agree with both (Action B and EMU). These "flex" chargers are the way to get a quick charge without too many risk.

Welll... I'm really curious about what is happening here on my desk right now. As I posted yesterday, my Sony 800mAh (the white ones, that hold charge for more than an year), are on my turnigy accucell-6, charging @ 0,1A. Right now, the charge is during more than 20 hours, and the cells have already 1684mA, and the voltage is 6.08V stabilished, rising so slow...

I ask you: WTF is happening here??? :D