Is a 11.1v 2200 mah battery pack - the equal to (3) 3.7v cells at 733 mah each? Or is that 2,200 each cell ?
The battery is 2.2Ah (no need for thousands of millis, that's marketing vanity, like saying a minute is
60,000 milliseconds!)
It has a capacity of 2.2 ampere-hours from its terminals. Since its a series connected pack
the same current and charge flows in all the cells.
A parallel connected pack would have the capacities of the cells sum, but the voltages wouldn't.
DocStein99:
Is a 11.1v 2200 mah battery pack - the equal to (3) 3.7v cells at 733 mah each? Or is that 2,200 each cell ?
Each cell is 2200mAh. They are connected in series so only the voltage add up (3 x 3.7V).
If the same cells were connected in parallel the capacities would add up but not the voltages so it would be 3.7V and 6600mAh.
Steve
Ok, thank you.
MarkT:
The battery is 2.2Ah (no need for thousands of millis, that's marketing vanity, like saying a minute is
60,000 milliseconds!)
It has a capacity of 2.2 ampere-hours from its terminals. Since its a series connected pack
the same current and charge flows in all the cells.A parallel connected pack would have the capacities of the cells sum, but the voltages wouldn't.
I wouldn't call it vanity, but consistency. Keeping the same measurement in the same unit is normally a good thing, because it'll require less mental calculations when you're comparing it to something else.
The lead batteries are labeled in amp hours. Its all the lithium batteries that are milliamp hours. Maybe more people could get confused if a battery is labeled "900 MAH" next to one that was "1.3 AH".
900 mega ampere henries would indeed be confusing. 8)
M = mega
m = milli
µ or u = micro (u is a cop-out really, but its not always easy to find µ on a random keyboard)
Small cells such as AAA's, PP3s, AA's, LR44's and so forth are typically quoted in mAh
because they have values in the 100's to a 1000 or so, and its not completely unreasonable (although
Ah would be perfectly fine for all but button cells like CR2032).
Then someone makes a larger capacity cell like a D-cell or a LiPo and thinks than calling it 4Ah sounds
smaller than the AA cell's 1500mAh, and thus we get stupidty like my 10,000 NiMH D-cells for bike lights,
they are 10Ah, in the same way a 12V power supply is not a 12000 mV power supply!
The Panasonic NCR 18650B batteries labeled "3400 MAH", I measured on my tool take between 2,800 and 2,950 for each of the (6) brand new cells I bought, from 2 different vendors. It's not perfect, but a whole lot more fair then the "SUREFIRE" brands, that I can barely get enough time to drive flashlights with. I am going to round up to 3,000 mah - to simplify.
The lead batteries that run my rechargeable lawnmower, are 18 AH each. I did not measure the charge on one of those cells yet. If I were to replace one of those cells, with Panasonic 18650's. I calculate 3-cell packs = 12.6 (or 11.1) volts at 3,000 mah. It would take (6) cell packs of (3) cells, (18) 18650 batteries total, to give the equal 18 AMP hours. Is that right?
With all my shopping, lowest cost per 18650 cell is $5.00, (18) cells is $185. Compared to the $28 lead battery, is definitely a waste of money. The lithium equal is only 1.7 pounds of weight - versus 10 pounds of lead.
I've been comparing cells from laptops, tablets, R/C hobby cars & planes, and so far at $5.00 - for each 3,000 mah cell, the winner of efficiency at cost is that Panasonic NCR battery.
LiFePO4 cells are interesting, they have a really good endurance (1000's charging cycles I think),
much safer than other lithium chemistries too. If you factor lifetime of battery into the cost analysis
you'll see that lead-acid isn't as cost-effective as you might think for deep-cycle use.
MarkT:
Small cells such as AAA's, PP3s, AA's, LR44's and so forth are typically quoted in mAh
because they have values in the 100's to a 1000 or so, and its not completely unreasonable (although
Ah would be perfectly fine for all but button cells like CR2032).
I think one problem is that people really don't like decimals, particularly below zero. My tiny 0.03Ah Lipos would be tricky to read. But I agree that once you get much above a couple Ah that's the easier measure and to be fair quite a lot of lipo sellers are now at least including that on the packaging, so "3.3Ah / 3300mAh" is not unusual.
Steve
MarkT:
LiFePO4 cells are interesting, they have a really good endurance (1000's charging cycles I think),
much safer than other lithium chemistries too.
i havent looked into LiFePO4 yet, but I will now - thank you.
I haven't had problems with any of my lithium cells yet. I am not abusing them or anything else, just charging and testing on scooter and flashlights so far.