Rechargeable AA batteries

[victorzamora]

C-rating is fairly standard jargon with batteries. I haven't seen C-ratings be mentioned in any products other than the packs themselves. Different chemistries have different max C-ratings both charge and discharge. Different chemistries also have different "preferred" charge and discharge ratings. Max C-ratings are tied to the internal resistance of the cells. There are some lithium packs that are capable of something obscene like 100C constant discharge rates. That means it'll drain, from full, in 1/100 of an hour, without any permanent detriment to the pack.

 

[fmerkel]

OK, OK. Let the folks chew on this.

C rate [https://en.wikipedia.org/wiki/Battery_(electricity)]
The C-rate is a measure of the rate at which a battery is being discharged. It is defined as the discharge current divided by the theoretical current draw under which the battery would deliver its nominal rated capacity in one hour.[32] A 1C discharge rate would deliver the battery's rated capacity in 1 hour. A 2C discharge rate means it will discharge twice as fast (30 minutes). A 1C discharge rate on a 1.6 Ah battery means a discharge current of 1.6 A. A 2C rate would mean a discharge current of 3.2 A. Standards for rechargeable batteries generally rate the capacity over a 4-hour, 8 hour or longer discharge time. Because of internal resistance loss and the chemical processes inside the cells, a battery rarely delivers nameplate rated capacity in only one hour. Types intended for special purposes, such as in a computer uninterruptible power supply, may be rated by manufacturers for discharge periods much less than one hour.

 

[fmerkel]

There are some lithium packs that are capable of something obscene like 100C constant discharge rates. That means it'll drain, from full, in 1/100 of an hour, without any permanent detriment to the pack.

Which is complete BS. Generally the wires would melt.

 

[tbone1004]

@fmerkel yeah, so with what you just posted, how on earth does that translate to your post #26 where you said a 2000mah battery is 2.0a so it is 2C?

the comment about 100C is not complete bs, but yours is. in .01 of an hour, or roughly 35 seconds, there isn't a lot of time for heat to build up to melt the wires, and there is nothing saying that you couldn't size the terminals and wire appropriately to handle that kind of draw, and because your statement in post #26 was completely wrong, you have literally no basis to make that statement because 100C does not correlate to any amperage, so you have no idea how big the battery would have to be. 100C out of say a 3400mah 18650, is 340a draw, roughly that of a starter motor in a v8 or high compression engine. They use fairly small wire, typically 6awg which is actually typically rated at 150a, but because it is for such a short duration, they can get away with thinner wire. If you wanted to maintain that amp draw for 100% duty cycle, you would only have to go to 1/0 cable, but that is completely overkill because 30 seconds isn't very long....

You also don't know how long the leads are which goes to heat buildup due to voltage drop which increases the amp draw since watts drawn remain constant. Hint, this is why the UK uses 230v instead of 120v, smaller wires=cheaper, or why airplanes, hybrid cars, and industrial motors use much higher voltages. Keep the amps down keeps the heat down which keeps the cost and weight down

they make 5 4/0 welding cables that can sustain 1500 amps at a 100% duty cycle. To maintain that for 30 seconds is nothing and won't lead to much heat buildup.

please stop making incorrect statements because you clearly have 0 understanding of what C rates are and how they are applied in the real world



if you are going to simplify, please do it with factually correct statements instead of complete fallacies.

simply put, C rate=charge or discharge rate divided by the battery capacity
that's it, it is literally impossible to simplify that any more
2a draw or charge divided by a 2a battery=1c
2a draw or charge divided by a 4a battery=0.5c
2a draw or charge divided by a 1a battery=2c

end of discussion. if you can't understand that, please don't participate in this thread

 

[muzikbiz22]

Eneloop is a brand name. The brand was originality owned by Sanyo but Sanyo was bought by Panasonic (2009 or 2010?). Due to antitrust issues the Sanyo battery stuff was then sold off to Fujitsiu. Maybe...
The Evolution of eneloop and Fujitsu Rechargeable Battery | Famcart News BLog

Wow, I didn't know there was THAT much to the story. Thanks for this !!

 

[victorzamora]

Which is complete BS. Generally the wires would melt.

I'm sorry, but you're showing a pretty dramatic misunderstanding of C-rating. The pack that I'm talking about has been proven repeatedly at 100C continuous.

Getting back to this to try to clear it up: Just knowing what C-rate the discharge is occurring at doesn't tell you anything. You don't know the gauge of the wire or the current draw through those wires. C-rate is simply the charge or discharge rate normalized to the pack's capacity.

 

[sunnyboy]

Well, I *do* have an Ikelite DS51, and I've had it since Mar 2014. When I bought it, I also bought 2 x 4 packs of the Energizer 2300 mAh rechargeable batteries (8 total). I also bought a fancy charger that allows me to set the max charging amps among other features. I alternate the sets of 4 so that each set 'rests' for a dive while the other is in use. I also charge the batteries as soon as the housing has been rinsed and dried using the 1000mA rate.

I've used these batteries in my previous camera (Canon A570) and I've found a set lasts about 3 years, then doesn't hold a charge for a whole dive. They are inexpensive enough that buying a new set every 3 years is not bad.

With the DS51 I bought the two sets to see if alternating them results in them lasting longer. However, as it's just coming up 3 years on both sets, I really can't say yet how my experiment has worked. So far both sets run a full dive without any issues, and my dives are routinely 70+ minutes in colder waters off Vancouver Island. I also dive year round so the batteries get used almost every week.

 

[stuartv]

I also have a number of Energizer 2300mAh batteries.

Energizer Rechargeable NiMH AA Batteries Pack Of 8 by Office Depot & OfficeMax

They actually test (on my Opus charger/tester) at around 2300. And they seem to work fine in my Inon z240 strobes.

Oh, and I don't normally worry about shelf life. I charge my batteries usually the night before I'm going to dive with them. That just seems prudent, regardless.

 

[Doby45]

I also have a number of Energizer 2300mAh batteries.

Energizer Rechargeable NiMH AA Batteries Pack Of 8 by Office Depot & OfficeMax

They actually test (on my Opus charger/tester) at around 2300. And they seem to work fine in my Inon z240 strobes.

Oh, and I don't normally worry about shelf life. I charge my batteries usually the night before I'm going to dive with them. That just seems prudent, regardless.

Those are the exact batteries that I use and yes, they test out to approx 2300mah.

 

[Charles2]

simply put, C rate=charge or discharge rate divided by the battery capacity
that's it, it is literally impossible to simplify that any more
2a draw or charge divided by a 2ah battery=1c
2a draw or charge divided by a 4ah battery=0.5c
2a draw or charge divided by a 1ah battery=2c
[/USER]

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