jayrob
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I field quite a few questions along this subject...
I'm sure there are several posts that cover this. But I don't know where they are. So I'm making a brief post that I can just refer people to.
Please post your input for good information to be learned by others!
Li-Ion Batteries:
Most Li-Ion batteries have the claimed capacity stamped on them. But the only way to know for sure is to run them and time it.
(as far as I know)
Of course, it will depend on what current draw they are at.
FlexDrives are a boost driver. So it's tricky to get completely accurate estimates. Because the current draw on the battery will normally change as the battery drains and voltage drops.
It's because the driver uses extra current to boost diode voltage demand.
For instance, if you have a blu-ray diode, which is asking for 5 volts, then your FlexDrive will boost the needed voltage from a single 4.2 volt Li-Ion by using extra current. The driver does this very efficiently.
Now the tricky part. As the battery drains, and the voltage starts to drop. The driver will use more and more current to keep the diode at what ever voltage it asks for.
So as your battery drains, it must keep supplying more and more current as it drains.
That is why you need a high quality battery like AW brand. Or an IMR Li-Ion... (with a high current build - low current builds can get away with lesser quality batteries)
For 445 builds. The voltage of the diode is closer to the battery voltage. (Li-Ion) Around 4 volts. So the difference is not as bad as with a blu-ray build.
But still, the battery is probably at maybe 3 volts by the time it needs to be charged. So the 'boosting' is still needed even with a 445 build...
Anyway, you can just kind of estimate what is going to be the run time for your battery.
You can get a pretty good idea if you understand what is going on with the way it works.
If you have a linear driver, such as a DDL, or the FlexModP3 that I use in my Maglite builds, it is a different story.
The current to the diode is the exact same as the battery current draw when using a linear driver.
So your math is easy to figure. Example:
If your battery is exaclty 2900mAh's capacity, and your current is 1450mA's with a linear driver, then your battery will last for 2 hours. (if it is truly 2900mAh's capacity)
Batteries 'in parallel' vs 'in series':
This is also kind of basic, but good to be mentioned for those who do not know. Or perhaps never really thought about it.
When you have more than one battery, and they are connected in parallel (negatives together, and positives together), this will be a battery pack with the same voltage as a single battery. But multiply the capacity.
On the other hand, if you have more than one battery, and they are connected in series (positive to negative), this will be a battery pack that will have the same capacity as a single cell. But multiply the voltage.
I'm sure there are several posts that cover this. But I don't know where they are. So I'm making a brief post that I can just refer people to.
Please post your input for good information to be learned by others!
Li-Ion Batteries:
Most Li-Ion batteries have the claimed capacity stamped on them. But the only way to know for sure is to run them and time it.
(as far as I know)
Of course, it will depend on what current draw they are at.
FlexDrives are a boost driver. So it's tricky to get completely accurate estimates. Because the current draw on the battery will normally change as the battery drains and voltage drops.
It's because the driver uses extra current to boost diode voltage demand.
For instance, if you have a blu-ray diode, which is asking for 5 volts, then your FlexDrive will boost the needed voltage from a single 4.2 volt Li-Ion by using extra current. The driver does this very efficiently.
Now the tricky part. As the battery drains, and the voltage starts to drop. The driver will use more and more current to keep the diode at what ever voltage it asks for.
So as your battery drains, it must keep supplying more and more current as it drains.
That is why you need a high quality battery like AW brand. Or an IMR Li-Ion... (with a high current build - low current builds can get away with lesser quality batteries)
For 445 builds. The voltage of the diode is closer to the battery voltage. (Li-Ion) Around 4 volts. So the difference is not as bad as with a blu-ray build.
But still, the battery is probably at maybe 3 volts by the time it needs to be charged. So the 'boosting' is still needed even with a 445 build...
Anyway, you can just kind of estimate what is going to be the run time for your battery.
You can get a pretty good idea if you understand what is going on with the way it works.
If you have a linear driver, such as a DDL, or the FlexModP3 that I use in my Maglite builds, it is a different story.
The current to the diode is the exact same as the battery current draw when using a linear driver.
So your math is easy to figure. Example:
If your battery is exaclty 2900mAh's capacity, and your current is 1450mA's with a linear driver, then your battery will last for 2 hours. (if it is truly 2900mAh's capacity)
Batteries 'in parallel' vs 'in series':
This is also kind of basic, but good to be mentioned for those who do not know. Or perhaps never really thought about it.
When you have more than one battery, and they are connected in parallel (negatives together, and positives together), this will be a battery pack with the same voltage as a single battery. But multiply the capacity.
On the other hand, if you have more than one battery, and they are connected in series (positive to negative), this will be a battery pack that will have the same capacity as a single cell. But multiply the voltage.
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