Schematic approval

[Forgetful Jedi Knight]

Hedgehog, I just wanted to say that your earlier wiring diagrams are a most imaginative solution to running a LEDEngin with the NB. Splitting the battery pack is not the sort of thing I would have ever considered.

I'm still trying to wrap my head around how to hook in a recharge port. Maybe after a good night's rest...

SS, you mean recharge ports.

[hedgehog1]

I think the issue of cell balancing is the limiting factor for non-removable LiPo installs in sabers. It appears that LiPo packs do no have the balancing/safety circuit board the Li-Ion packs are built with. This little board allows the Li-Ion charger to charge the cells in parallel and the cells stay balanced. The LiPo cells are built with the idea that all these functions are performed outside the pack.

It makes sense from an R/C point of view. These packs are always charged after removal from the car, boat or plane. For a saber we tend to build Li-Ion into a saber, so we carry the extra circuit board in the pack itself.

I think to use built-in LiPos, the packs need to be built like Li-Ion packs with the circuit board built in.

[Ari-Jaq Xulden]

The battery you linked would take up the entire inside of a 5 inch DF, leaving only the threads of the MHS and room to pass only wires while producing 14.8v @1100 Mah. The 7.4v 18650 setup that HH diagrammed is smaller, meaning it will allow more to fit in the same area, has a mounting solution already employed, and as the current is more than doubled at 2700-3000 Mah it will still run longer than your setup literately sucking the current out twice as fast with a seriallell setup as suggested. This is actually not the first time this has been suggested or discussed.

Again I'm not shooting your idea down, but given the title of your thread it would imply your seeking approval. However as this is a community that shares, the reason the options that exist in the store are prevalent is because they have proven to be the best options. As I said in my OP, try it out, if you think you have found a better way let us know.

[hedgehog1]

A little math just to keep apples to apples comparisons:

Four LiPo Cells in Series: 14.8v @ 1100ma
Four LiPo Cells in Series/Parallel: 7.4v @2200ma
Four LiPo Cells in Parallel: 3.7v @4400ma

Four Li-Ion 14650 cells in Series: 14.8 @ 1050ma (these are closer in size to the LiPo above)
Four Li-Ion 14650 cells in Series/Parallel: 7.4v @ 2100ma
Four Li-Ion 14650 cells in Series/Parallel: 3.7v @ 4200ma

The four LiPo would take a less space then the four Li-Ion. There is still the cell balancing issue to deal with if the LiPo pack is not removed for Recharge.

Two Li-Ion 18650 cells in Series: 7.4v @ 2600ma
Two Li-Ion 18650 cells in Parallel: 3.7 v @5200ma

The 18650 packs are very long; but their shape does leave room for the sound boards to be mounted next to the pack.

Two Li-Ion 18500 cells in Series: 7.4v @ 1400ma
Two Li-Ion 18500 cells in Parallel: 3.7 v @2800ma

The 18500 pack takes about the same space in the hilt as the LiPo pack shown above.

[hedgehog1]

I was reading the RC posts on using LiPo cells in parallel. It turns out that using them in parallel solves the cell balancing issues - they will naturally balance themselves when charged in parallel:

http://www.rcgroups.com/forums/showt...=360273&page=2

Of course, this limits you to 3.7 volts.

[mikeclem]

Ari-Jaq Xulden,

OK, lets take this unit:
http://shop.ehobbyasia.com/systema-1...x-mad-max.html

The dimensions are: 120mm x 18mm x 10mm per unit which are stacked on top each other giving dimensions of:
120mm x 18mm x 20mm = 14.8v @ 1400 mAh or 7.4v @ 2800 mAh

Dimensions of 2 X 18650:
130mm x 18mm = 7.4v @ 2600 mAh

So, similar size with similar run time BUT no option to utilise 14.8v. I agree 7.4v could be used in my proposed setup, I guess I am merely pointing out that LiPo is a suitable alternative with the potential advantage of generating 14.8v if required. As I pointed out though back in my first post it is not the issue of LiPo vs Li Ion which I was asking about but I'm happy to share my experiences of using them.

HH - you could have a recharge port and keep the battery internal - you just need some way of accessing the balancing cable as well. Ideas that come to mind would be to have the connector underneath a switch box (like on a Luke ROTJ) with a removable top, or to have a panel which you can take off (like are often used to show off a crystal housing).

Mike

[hedgehog1]

Mike,

As long as access to the balancing cables is made part of the design, then I would agree from a power-to-space-used ratio the LiPos are viable. I don't know about impact resistance - but I know when my grandson and his friend drove my (then unscratched) RC car they hit everything there was to hit - at full speed. Based on the crash-testing they did, I will assume that the impacts in a saber hilt are no worse than those. I never did get the scratches out of that car body, come to think of it... And the steering servo has never been the same...

Space wise, the Lipos are a square (viewed in the hilt) where the Li-Ions are round, so they net a little less side-by-side space. But they LiPos are shorter.

I think the need to balance the cells (assuming the Li-Ion PCB Pack boards cannot be used with Li-Po packs for sabers) makes me prefer the Li-ions. The cost of rechargers is also less for Li-Ions.

If I had a saber design where the flat pack LiPos cells would help the build, then I would be inclined to give it a whirl and try the Li-Ion PCBs to automatically balance the cells.

In a cubic-centimeter-pert-watt ratio, the LiPos offer very little additional benefit for saber use. For RC motors with high amperage draws, then the LiPos are the hands-down winners. But that ability to do a very high amperage draw means a short run time - which is fine (even desirable) for an R/C car in a race timed to last about 'one-battery-pack' long.

Back to the real issue - Making Earths Brightest Saber:

Test a GGGG LedEngine and a GGG tri-rebel in your workshop using a fully charge LiPo pack. When you know how far you can drive them, then that will tell you the right wiring layout.

As for using the NB - I think you can pull 3.7 off of one pack using the balancing wiring OR use a voltage regulator (it won't get too hot as the NB draws little power).

I do have a third drive option to protect the NB from the higher voltage/current. I will post it shortly.

[hedgehog1]

Here is my proposed schematic that will protect the NB:



It uses the dimable buck puck with the additional Ref and Ctrl connections. The Tech Data Sheet for it is here: BuckPuck.pdf

The Ref pin provides 20 ma of 5 volt power. The Ref Dims the LED when it goes to 5 volts. Whenever the NB goes to ground, the Ref is pulled to ground as well and the LED lights up. When the NB goes to cut-off (no current flow) the ref floats back to 5 volts and shuts off the LED.

This way, the NB is handling only 5 volts at 20ma MAX.

[hedgehog1]

Here is a link to my stunt saber design using this method to get a simple 'blade pulse' without a sound card:

Cheap Blade Pulse

It uses the current flow changes of a blinking LED to alter the current flow to the blade LED.

[Silver Serpent]

Hedgehog, when your flicker technique gets widely known, I'm predicting a run on dimmable buckpucks.