"Batteries for dummies"

mjn

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I know I can't be the only one that is new to all this stuff. I can look thru threads for hours on end, and maybe get the information I'm looking for... but many of you speak in a language I don't understand; ie; "modern electronic speak."

I started this thread to jumpstart my own feeble brain, and to help others like me that have recently been bitten by the flashlight bug.

Those of you who would like to contribute something to this thread please do so. That way, some of us dummies might actually learn something! :)

Great post by angelofwar;
Correct; Primaries come in three types:
1) Lithium; more expensive, but the preferred power source:
-Lighter
-Longer Shelf Life
-Better operating range temperature wise
2) Alkaline; cheap, available, but THEY LEAK. Short shelf life, poor operating range
3) Lead Acid; Heavy and out-dated, BUT reliable.

Rechargeable:
Nickel is the safest
Lithiums provide more power to weight/size ratio, but are also more dangerous.
1) NiMh (Nickel Metal Hydride)
2)NiCad (Nickel Cadium)
-From my experience NiMh is better than NiCad and holds there charge longer, but NiCads charge faster. Also, NiCads are lighter than NiMh

Not to up to date on lithium R/C's, just know they're (for the most part) dangerous without any understanding, and should only be used by people that have read up and understnad the associated dangers.

Battery Capacity will determine how much energy a battery has, and this is measured in mAh (Amp Hours): Take the Amperage (How much a lamp draws) and divide it by the mAh (Amp Hour rating of the battery/batteries), and that will give you an approximate runtime.

Battery size is measured as such: The first two numbers are the diameter in mm's (18650's are 18mm's in diameter, and, I believe the next two numbers are their length. (65mm's).

So, an 18650 is 18mm dia, and 65mm length. not sure what the extra "0" is at the end.

That's MY understanding of the whole battery shin-dig. No expert, but that's the nuts and bolts.
 
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Mr Happy

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Battery Capacity will determine how much energy a battery has, and this is measured in mAh (Amp Hours): Take the Amperage (How much a lamp draws) and divide it by the mAh (Amp Hour rating of the battery/batteries), and that will give you an approximate runtime.
The other way round, actually (mAh / mA = h). You get a longer run time with a larger capacity or a smaller current draw.

So, an 18650 is 18mm dia, and 65mm length. not sure what the extra "0" is at the end.
The "0" at the end indicates it is a cylindrical cell ("0" for round).
 

flatline

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The "0" at the end indicates it is a cylindrical cell ("0" for round).

I'm skeptical. I've got a handful of 14505 cells that are shaped identical to a 14500 cell, so unless the '5' also means cylindrical cell, there must be another meaning to the last digit.

--flatline
 

Mr Happy

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Yes, the total length of the battery including any button at the positive end. Be careful not to short out the battery when measuring it. I just measured one of mine and the length was 50.3 mm. Maybe the "5" means button top?
 

flatline

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I randomly grabbed one 14505 and it measured 49.4mm in length.

I had always assumed that the last digit said something about the chemistry since a 14500 is Li-ion and the 14505 is a Lithium primary cell.

--flatline
 

45/70

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I had always assumed that the last digit said something about the chemistry since a 14500 is Li-ion and the 14505 is a Lithium primary cell.

The last digit is supposed to represent the shape of the cell. "0" being cylindrical. I've seen many times however, where the last digit is used to extend the measurement accuracy, eg. a "14505" cell being 50.5 mm in length. I do not believe this is proper though, but some distributors seem to do this anyway.

Dave
 

ozdavo

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Sorry to resurrect this thread, but i'm another newbie to this and thought this place would be as good as anywhere to post, save making a new thread.

I think I understand the mAh/mA=h and flipped to mAh/h=mA, so if I do understand this correctly, I have an appliance the has a propriety battery pack that I believe contains 6 x 18650 cells connected in series. The pack specs are 22.2V 1500mAh. The appliance specs state runtime will be 15minutes on normal or 6 minutes on Max power.
So:
mAh / h = mA
1500 / 15min = mA
1500 / 0.25 = 6000mA or 6A Draw on Normal.

mAh / h = mA
1500 / 6min = mA
1500 / 0.1 = 15000mA or 15A Draw on Max.

Firstly, is my math correct (I understand there will be losses & resistances involved that I have ignored)?
Secondly, hypothetically, could this be rebuilt with higher power cells (assuming the current ones are 1500mAh 18650's), and if so, what cells are available that can handle this discharge rate for regular use?

Thanks
 

Mr Happy

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Firstly, is my math correct (I understand there will be losses & resistances involved that I have ignored)?
Secondly, hypothetically, could this be rebuilt with higher power cells (assuming the current ones are 1500mAh 18650's), and if so, what cells are available that can handle this discharge rate for regular use?

Yes, your calculations are correct. Ignoring losses, a 1500 mAh pack can theoretically supply 1.5 A for 1 hour, or 6 A for 0.25 hours, or 15 A for 0.1 hours. (I think your device may use less current than this, assuming it has been designed with some allowance for losses and ineffiency.)

As far as "higher power cells" are concerned, there is a difference between power and capacity. High power means high instantaneous current (15 A is a very high current for small cells). High capacity means long run time. Usually you trade off one against the other. You can't easily get high power and high capacity at the same time.

So what you really want is higher capacity and longer run time without sacrificing power. Given the numbers you have quoted I don't think that will be easy to achieve.
 

ozdavo

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Yes higher mAh and consequently longer run time is what I'm after, while maintaining the 15A draw, is what I'd ideally want.
So there are not 18650's in the high 2000 mAh range that can handle 15a draw?


Sent from my iThingy using Tapatalk
 

fractal

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Slight modification to the OP.

lead acid is typically considered rechargeable. You have one in your car. I have many in the UPS's for my computers. You probably meant carbon-zink which were the common primary cells a while ago and are commonly sold as "heavy duty" batteries.

lead acid are great in the capacity / price category when large capacity is required. The capacity / weight is lackluster.
 

Curious_character

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"C" means the capacity of the cell (in mAh or Ah) divided by one hour. So "C" of a 3000 mAh cell, for example, is a current of 3000 mA.

The capacity of a cell (in mAh or Ah) is typically measured at C/10 or C/20. That is, a 3000 mAh cell should deliver 300 mA for 10 hours or 150 mA for 20 hours. However, the capacity of the cell decreases as the load increases. Consequently, you can't expect a 3000 mAh cell to deliver 3000 mA for one hour, 6000 mA for a half hour, etc. As it turns out, the capacity of quality NiMH and Li-ion cells doesn't drop a whole lot up to one C or so, but at currents greater than that (i.e., discharge times of less than one hour), it can drop considerably.

The OP comparison of NiCd and NiMH cells is a bit outdated. We now have "hybrid" type NiMH cells which self discharge very much more slowly than even the very best NiCd cells ever did. Sanyo's Eneloop cells, in particular, have gathered a very good reputation. I've read elsewhere that they're going to drop the Eneloop brand name and label the cells Panasonic, but look for "pre-charged" or "ready to use" to identify the low self discharge cells.

One last note: Even the best brands of batteries tend to be overly optimistic in specifying cell capacity. Don't expect to actually get the claimed number of mAh from a cell, even at a low current drain. And the cheap cells (for example the many "**fire" brands) are nearly always wildly optimistic, with the claimed capacity bearing no resemblance to what you can really get.

c_c
 

exSun

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I measure the capacity of my rechargeable NiMH batteries with a West Mountain Radio CBA II. I've found reputable brands (Eneloop) do give close to the rated capacity at C/10 or C/20, when they are new. However, I've found you must cycle them a few times - run them down to a safe level (I use 1V/cell) then recharge, and repeat several time. Perhaps this is forming and reforming layers within the cell, but the capacity increases - to fairly close to the spec.
 
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