Battery options

[Jedi-Diah]

I'm trying to decide what battery pack to use with my vintage Graflex conversion. (I've read most of the battery threads)

So far my options are:

A) 2x18650 LiIon inline stick like Erv uses= 7.2V, 2400mAh (5" long but narrow and great capacity)

B) 2x14500 Ultrafire or Trustfires like Yoda uses in some of his chassis = 7.2V, 900mAh (great on space but don't know how long it would last)

C) 7.2V NiMH, 2600mAh from TCSS but "out of stock" (seems like great capacity and would still fit in the hilt just fine. I also already have a NiMH charger for a 4.8V, 2600mAh pack and I wouldn't have to buy another charger)

I'm planning on using the new CF 4.1 or USB 2.0 (I'm getting both) and was planning on using a blue Lux Rebel, P4 or a LedEngin but I'd like to be able to try a Lux V or K2 as well. I was thinking about mounting the CF on the battery in the lower part of the hilt.

I think higher capacity is better but Yoda uses the Ultrafires with the Lux V. I'm just wary of the 900 mAh.

What is the general rule on battery runtimes and performance if the led I'm using is similar to a blue or green Lux III (like the Rebel or P4)? Let's say for example it requires around 3.8 fV and 1000ma max. How long would the 2x14500 last compared to the 2x18650?

[xwingband]

The 14500's would be like 1 1/2 hour and the 18650 certainly double and more.

There isn't a super right answer for this situation. Obviously for runtimes the 18650 stick is going to offer you the most time. Personally, I like to use an 8.4V NiMH pack or higher with a V, but you'd only be able to get in an AAA pack easily in a graflex.

[Novastar]

...What is the general rule on battery runtimes and performance if the led I'm using is similar to a blue or green Lux III (like the Rebel or P4)? Let's say for example it requires around 3.8 fV and 1000ma max. How long would the 2x14500 last compared to the 2x18650?Well, the general rule is exactly the idea based on the numbers the manufacturers will publish for the "mAh" of a cell.

For example, if the "mAh" (milli-ampere hours) of a cell is rated for 2400mAh... the cell should last about 2.4 hours based on a consistent 1A draw from the cell.

Obviously, only rough estimates can be made, since most of the time:

* People draw varying currents (i.e. sometimes 1A, sometimes 700mA, sometimes anything in between)
* Battery charges vary
* Driver boards vary
* Even if you are technically "drawing 1A", there may be other components drawing small amounts of current within the circuit (such as little LEDs, motors, speakers, etc.)
* Only a "real world" test produces the runtime a battery will ACTUALLY have

Myself, I always recommend the 18650s for many reasons (one of which has to do with the battery chemistry and just the general stability of this style of cell vs. others), but you can use whatever you like, and sometimes--certain cells are prohibitive for your design specifications.

So, ultimately--you have to make the choice! :) As it always is with sabers! Uh... and most things in life! :)

[Jedi-Diah]

Thanks guys. I appreciate the feedback. I remember Erv saying something to the effect that he likes the mAh to be twice the draw. So, I should try to get something like a 2000mAh battery if I have a 1000ma led which leads me to the 2400mAh or 2600mAh batteries.

Novastar, I understand the idea that 2400mAh should last 2.4 hours at 1A draw or 2400mAh should last twice as long as 1200mAh but what happens if you increase the battery voltage -- say from 4.8V to 7.2V or to 8.4V (all still 2400mAh capacity)? Will they all last 2.4 hours or does increasing the voltage size increase run times (I assume it does but don't know why)?


Well, the general rule is exactly the idea based on the numbers the manufacturers will publish for the "mAh" of a cell.

For example, if the "mAh" (milli-ampere hours) of a cell is rated for 2400mAh... the cell should last about 2.4 hours based on a consistent 1A draw from the cell.

Obviously, only rough estimates can be made, since most of the time:

* People draw varying currents (i.e. sometimes 1A, sometimes 700mA, sometimes anything in between)
* Battery charges vary
* Driver boards vary
* Even if you are technically "drawing 1A", there may be other components drawing small amounts of current within the circuit (such as little LEDs, motors, speakers, etc.)
* Only a "real world" test produces the runtime a battery will ACTUALLY have

Myself, I always recommend the 18650s for many reasons (one of which has to do with the battery chemistry and just the general stability of this style of cell vs. others), but you can use whatever you like, and sometimes--certain cells are prohibitive for your design specifications.

So, ultimately--you have to make the choice! :) As it always is with sabers! Uh... and most things in life! :)

[MoonDragn]

Btw, if you are going to make your on Inline 2x18650 sticks, don't do what I did and order the 7.4v board with the fuel gauge plug from Battery space. The board they sent me was HUGE. It was as wide as two sticks side by side and will never fit into the space I need to put it in. I have to go reorder another one of a different type :(

Also, looks like Batteryspace has these Lithium Iron Phosphate batteries too. They are only about 1400 maH but apparently are safer than Li-ion or Li-Polymers and will not ever explode. It has almost double the temperature tolerance of the other batteries too.
They also sell an inline 2x18650 version of these with the same dimensions.

Unfortunately when I tried to put them in my order and calculate shipping, it says shipping is not available to my area. Looks like UPS will only ship to some places because these are considered hazardous material. Not sure how I would go about getting one of these to test.

[Donnovan Sunrider]

The issue I keep finding is that 18650s appear to be too big to fit in an MHS section side-by side. Nearly all of the packs I find are 1.45" wide, so they don't fit. It's either that or get a stick over 5" long down the tube.

I have a good handle on pretty much all the aspects of my CF sabre build except for how I'm going to power the thing.
Are there other good long-running options that fit better in an MHS hilt than the 18650s? There are so many options it's hard to suss out the best ones without spending a lot of cash on experimenting. :???:

[Jedi-Diah]

I only have 1.4" max ID in the Graflex and 18650 side by side is out. The pre-made stick is good but kinda long.



The issue I keep finding is that 18650s appear to be too big to fit in an MHS section side-by side. Nearly all of the packs I find are 1.45" wide, so they don't fit. It's either that or get a stick over 5" long down the tube.

I have a good handle on pretty much all the aspects of my CF sabre build except for how I'm going to power the thing.
Are there other good long-running options that fit better in an MHS hilt than the 18650s? There are so many options it's hard to suss out the best ones without spending a lot of cash on experimenting. :???:

[Donnovan Sunrider]

The internal of an MHS piece is 31.56MM (1.2425") wide (according to info on the forum), which makes a battery pack that's shown as 1.4" just too big unfortunately.
I think I'm stuck with half my hilt devoted to battery space, but I'm hoping that someone has other ideas for a rechargeable solution.

[MoonDragn]

You could try a inline 2xAA holder and use 2 trustfires sold in the TCSS store. Or you can just use 2AA holder thats back to back. That will save space and fit in the graflex. Thats what I'm using.

[Jedi-Diah]

But with 2x14500 you get 7.2V at only 900mAh and if you use a LuxV, you are using 7.2V and either 700mA or 1000mA (overdriven) so you should get about an hour more or less.

Do the runtimes change if you us a led that requires less voltage (but same mA)?



You could try a inline 2xAA holder and use 2 trustfires sold in the TCSS store. Or you can just use 2AA holder thats back to back. That will save space and fit in the graflex. Thats what I'm using.

[MoonDragn]

But with 2x14500 you get 7.2V at only 900mAh and if you use a LuxV, you are using 7.2V and either 700mA or 1000mA (overdriven) so you should get about an hour more or less.

Do the runtimes change if you us a led that requires less voltage (but same mA)?

It depends on how efficient the LED is. But yes a led with less voltage and same amperage does use less power, so will last longer on the same battery.

For example, 1000 mA at 7.2V is 7.2 watts, but 1000 mA at 3.6V is only 3.6 watts.

Even though both draw the same current, the Amp/hr draw is different between the 2 LEDs. The 2nd one will run 2x as long as the first if we were to use the SAME battery setup.


The calculation goes something like this: lets say the forward voltage of the LED is 6.9 V, at 700 mA. That means it is drawing a max wattage of 5.04 Watts.

Lets assume we are driving the LED directly with a 2 lithium Ion batteries rated at 2400 mAh each without resistors or a driver board for a total of 7.4 V. The actual amperage drawn would be 5.04/7.4 or .68 A or 680 mA. That means with a total of 4800 mAh, it will take 4800/680 or 7.05 hours for those batteries to run down.

Things get more complicated with a resistor, a driver board, or a buckpuck.

A buckpuck keeps the current constant. So a 1000 mA puck will draw 1000 mA all the time. It will then theoretically take the battery 4.8 hours to run down with the same setup. Almost the same calculation with a driver board. But since the buckpuck has a voltage minimum to activate, that number may be even less because the voltage on a battery will start to go down after usage. Once past a certain point the buckpuck will shut off.

A resistor however actually lowers the current draw, expending the extra current in the form of heat. Depending on the resistor value, you would have to calculate the draw of the LED + resistor to get the actual run time.

[Jedi-Diah]

So for sake of example, let's say I had a stunt saber that used a 12V, 900mAh battery pack and a 1A buckpuck. A green Lux V should last around 2 hours and a green Lux III should last around 4 hours (rough estimate)?

So, a 7.2V 2400mAh with a green Rebel/Lux III/P4 should last around 5 hours (and Lux V half of that)? Am I thinking right?



It depends on how efficient the LED is. But yes a led with less voltage and same amperage does use less power, so will last longer on the same battery.

For example, 1000 mA at 7.2V is 7.2 watts, but 1000 mA at 3.6V is only 3.6 watts.

Even though both draw the same current, the Amp/hr draw is different between the 2 LEDs. The 2nd one will run 2x as long as the first if we were to use the SAME battery setup.


The calculation goes something like this: lets say the forward voltage of the LED is 6.9 V, at 700 mA. That means it is drawing a max wattage of 5.04 Watts.

Lets assume we are driving the LED directly with a 2 lithium Ion batteries rated at 2400 mAh each without resistors or a driver board for a total of 7.4 V. The actual amperage drawn would be 5.04/7.4 or .68 A or 680 mA. That means with a total of 4800 mAh, it will take 4800/680 or 7.05 hours for those batteries to run down.

Things get more complicated with a resistor, a driver board, or a buckpuck.

A buckpuck keeps the current constant. So a 1000 mA puck will draw 1000 mA all the time. It will then take the battery 4.8 hours to run down with the same setup. Almost the same calculation with a driver board.

A resistor however actually lowers the current draw, expending the extra current in the form of heat. Depending on the resistor value, you would have to calculate the draw of the LED + resistor to get the actual run time.

[MoonDragn]

Well in the case of a buckpuck, your current draw is always constant (Assuming the load is constant and does not burn out, and that theres no loss in efficiency). So you're going to draw 1 amp no matter what size LED you use. If you use a 1 A buckpuck on a 12 V 900mAH battery pack (3 batteries), that battery will be drained in less than approx. 2.7 hours.

In the case of the Luxeon V, its been driven normally, but the Lux III will be overdriven.

For the 7.4V 2400 mAH pack, it would be drain in less than approx 4.8 hours.

[Jedi-Diah]

Ok. I'd rather get 4 hours than one hour so I'll probably go with 7.2V 2400mAh.

Now the question is do I go with the 2x18650 5" stick or maybe even the NiMH Tim sells (but not in stock)?

http://www.thecustomsabershop.com/72V-AA-2600mAh-NIMH-Rechargeable-battery-pack--P173.aspx

I assume this should fit in a Graflex since it fits in MHS hilt sections. It is only 4" long. Plus I already have a NiMH charger for another NiMH pack I got from TCSS (4.8V 2600mAh).

Can someone make a compelling argument why I should use a LiIon pack instead of NiMH (same V and mAh)? I know already that the LiIon discharges more evenly (flatter) over the life of the charge but we're talkin 4 hours. Plus space shouldn't be an issue either.




Well in the case of a buckpuck, your current draw is always constant (Assuming the load is constant and does not burn out, and that theres no loss in efficiency). So you're going to draw 1 amp no matter what size LED you use. If you use a 1 A buckpuck on a 12 V 900mAH battery pack (3 batteries), that battery will be drained in less than approx. 2.7 hours.

In the case of the Luxeon V, its been driven normally, but the Lux III will be overdriven.

For the 7.4V 2400 mAH pack, it would be drain in less than approx 4.8 hours.

[Novastar]

...Can someone make a compelling argument why I should use a LiIon pack instead of NiMH (same V and mAh)? I know already that the LiIon discharges more evenly (flatter) over the life of the charge but we're talkin 4 hours. Plus space shouldn't be an issue either.Um, this is really personal preference to a certain extent. Although, in a way, you're answering your own question (flatter discharge rate, better voltage per cell, better energy density per cell).

Somewhere around here (in "new technologies"?) I made some Li-Ion post that lists the benefits. I'm too lazy to dig it up. You guys know me... I'm *LAZY*!!! :)

But anyway, some other good things about Li-Ions is that the PCB is added safety/control of the cells... you'll probably never accidentally short circuit the pack. Also, better for the environment when disposal time comes (so I ALWAYS advocate that, since every little bit to the environment helps).

It's true though that things that are "X+1" wide won't fit in things that are "X" wide... .... ... ... that's pretty obvious. So, when people have space issues with them... sure, I understand. Not every hilt part is made to fit the 18650s, duh. Just like you can't fit a super-pimped out CF setup in a 7" hilt, lol.

[MoonDragn]

I think in your case you should probably use the NiMH packs if you already have a charger. The shape of the 18650s are just all wrong for it to be efficient in MHS.

In my saber, I have a 5 inch long tube in the middle thats only 1 inch in diameter. Perfect for 2 18650s.

[Jedi-Diah]

Do the LiIon last longer than NiMH (after many charges)?



Um, this is really personal preference to a certain extent. Although, in a way, you're answering your own question (flatter discharge rate, better voltage per cell, better energy density per cell).

Somewhere around here (in "new technologies"?) I made some Li-Ion post that lists the benefits. I'm too lazy to dig it up. You guys know me... I'm *LAZY*!!! :)

But anyway, some other good things about Li-Ions is that the PCB is added safety/control of the cells... you'll probably never accidentally short circuit the pack. Also, better for the environment when disposal time comes (so I ALWAYS advocate that, since every little bit to the environment helps).

It's true though that things that are "X" wide won't fit in things that are "X+1" wide... .... ... ... that's pretty obvious. So, when people have space issues with them... sure, I understand. Not every hilt part is made to fit the 18650s, duh. Just like you can't fit a super-pimped out CF setup in a 7" hilt, lol.