View Full Version : Double Capacity?!?!
2009.03.18, 07:00 PM
I picked up a case of orion 900hv batteries last weekend. Ive hade lots of these cells in the past with no weird issues. Through the course of the week I have been discharging and charging the batteries to see what the capacity of each cell is, all of them were normal except one.
I am discharging at 1 amp down to .9 volts and charging them on a Maha C9000 at 1 amp. All of the other cell charged between 50-55 min. and up to between 890 and 970 mah, however one cell charged for 136 min and the mah got up 2065, well over double the capacity of the cell. Has anyone had this happen before or know why it could have happened. Thanks in advance.
2009.03.18, 07:17 PM
I've had that happen with some cheap Energizer 950's, about 4 of them, in just the last few weeks.
All of them charging for more than 2 hours and the mah capacity between 1800 and 2100.
And they were charged with the Maha....I don't remember what amperage I was charging at though.
I think maybe the peak wasn't getting detected ?
Strange, too....all of them got very hot, but didn't vent.
Just find 3 more like it, and enter an endurance race :p
What are the numbers on the cell when discharging?
I had that happen to me with an Orion 900... kind of frieked me out a bit, but now the cell is fine and has numbers similar to the rest in its pack. Try not to let it over charge if you see it over its capacity. If you see it over 1000mah, pull it and discharge... then charge it again. It cant be good for the cell...
2009.03.18, 09:16 PM
It's a curiosity with the MAHA C9000. I have this charger and every so often I get a cell that just won't stop charging. It may have to do with the peak-detect not functioning correctly; Also it may have something to do with the condition of the cell. When a cell(Pack) sits too long or is exposed to extreme heat and/or cold, the chemicals inside the cell can become deactivated to some extent. This is discussed in the MAHA C9000 manual, and is why the MAHA has a "Break-In" mode. "Break-In" gives the cell a kick-start and awakens the ingredients :) I've noticed that if I am charging a cell at low Amps (say 0.5A) then this runaway-charging happens slightly more often, especially with new cells, or cells that have been sitting for a long time.
EMU is right, if you see a cell go to 120+% of its rated capacity (For Orion 900's that'd be 1080mah), to be safe pull the cell off and discharge it. Be sure to discharge the cell at 2.0A to 3.0A(3A is preferable) to "exercise" the cell. If the cell is new then most likely after a few charge cycles it will begin performing and charging to a normal peak-cap unless it is flawed out the factory.
Just a note, sometimes I have cells peak at over 120% their rated capacity. For example, with brand-spankin'-new Intellect 750's, with some packs I've consistently got 950mah+ out of all four cells per pack. These cells are definitely undamaged and fresh - It isn't a certainty that you'll get fresh cells from the factory. But 950mah is roughly almost 130% rated capacity (750mah), and I've had a few go to just a hair under 1000mah. Anything over 1000mah however with Intellects, and I'd pull the cell off the charger.:eek:
2009.03.18, 11:39 PM
Sounds to me like they are missing the peak, hopefully your charger backed off the amperage and didn't kill them. I had this happen once or twice, sometimes you just get those oddball packs. I always watch the first charge and make sure it doesn't go past a 1/2 hour on my Duracell 30min chargers... I usually do a discharge and then charge one more time. I haven't had an issue with my Duracell chargers, but my old Lacrosse did this to me a few times with new cells. One set heated so much the whole side of the charger's chassis melted a bit.
Someone told me that charging with a fan on the cells can cause this issue too. I used to charge my 10th scale cells on a fan and I think that may have caused some premature cell death because the peak would definitely flatten out when I did this. I thought the more mah in the better, but I now know this isn't the case.
2009.03.19, 09:30 AM
Capacity on charge is not capacity on the cells (cell capacity is discharge ) charging capacity just shows how must energy is pumped into the cell . Waste energy is the heat generated by the cell. High IR cells genrate more heat(waste energy),overcharge past the peak ( this case ) is the same thing the cell stops accepting power and generates heat. If it generates to much heat quickly It can blow the cells seals.
2009.03.19, 12:19 PM
waste charge! that happens when your terminals are not clean enough & the delta v peak detect is set too high with a low amp charge rate.
your cells will "never" accept more capacity than what is physically possible.
always clean your terminals, both on the battery & the charger.
this happens to us everyday, but the discharge MAH does not change.
just my .02 :)
2009.03.19, 04:46 PM
I've run the cell through a discharge and a charge once more and everything is fine now. Seems to be no damage to the cell and the charger has not done this with any other cells. I am still going to keep a close eye on that cell and the charger it was in, I have two Maha's and it was the oldest one that the cell was in when it happened. Thanks everyone for your advice and tips, I'm not a battery expert so this little problem left me confused and looking for answers.
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