7.4v Battery with Prizm v5.1

Hey guys, apologies if this has already been answered somewhere else. I've spent the last 2 or 3 hours playing with various Advanced Searches to find the answer and can't find anything specifically answering it.

So I'm brand new to both electronics and saber building. I'm working on pricing out and planning for my first build. I've decided on a Prizm 5.1 and have started reading through the manual. Based on what I've read in the manual and product page for the Prizm on the Plecter Labs website, the recommended battery is a 3.4v single cell battery pack such as a 18650 and specifies a "5.5v MAX" for the card. I had accepted this as law and was planning on just picking up a single cell 3.4v 18650 and calling in a day. However, since then I've seen mentions of other builds where people were mentioning 7.4v batteries with their Prizm sound cards or one in particular mentioned setting up the Bluetooth RICE capability (something I think might be cool if it's not getting in over my head) required a 6.something voltage which would exceed the 3.4v my battery would be putting out...

Not sure if everything has made sense, but are there significant advantages to using a 7.4v battery pack over a 3.7v one? If so, is it possible to use a 7.4v battery with a Prizm 5.1?

Finally, does the fact I'm having to ask these types of questions suggest I shouldn't be making my first build with a $115 sound card regardless of the fact I'm PRETTY sure I can pull it off? Considering the money I'll be putting into my first build it seems silly to save some money by going with a PC and limit what I'm able to do as far as saber functionality with the intent of going back later, spending the same $115 dollars anyway, undoing the work I did to wire in the PC just so I can replace it with my shiny new Prizm. Am I wrong there or is there some logic to that thought process?

Unless you want RGB and RICE, a NBv4 would be a better suggestion than a PC. The Prizm is only marginally more difficult of an install vs the NBv4, if youre not using ALL of the extended features. If you want to use a 7.4 battery, youll need to resistor it prior to the sound card AND have to use larger resistors for the LED's.

Even with the NBv4, you can color mix using the sound fonts if you go RGB on the chip. However, if youre only gonna use a dual color die, no point in the Prizm if you dont want to color mix OTF say RBW for purple main and white FoC. But again, you can use the fonts to change on the NBv4.

The first PRIZM 3.5 sound card was a derivative of the Petit Cruton 3.5 Sound card.

They are, separate models of Sound Cards with direerent specs.
(You’ve referred to PRIZM and PC in you post, and I do not quite follow)

ALL PRIZM versions thu and including 5.1 have a power supply MAX of 5.5 volts. Typically you would use a SINGLE 3.7 volt li-ion battery (say an 18650 which typically has longer capacity and run time than an 18500 or 14500 sizes), though other battery solutions are possible (though probably not as efficient as an 18650 li-ion).

The Petit Cruton and Crystal Focus Sound Cards are designed with power supply ranges of 5.5 to 11 volts. Typically you would use a 7.4 volt battery pack (made up of two 3.7 volt li-ion batteries), though you can perform a hack on those boards to use a single 3.7 volt battery.

For Bluetooth RICE capability, it involves an additional Bluetooth card to be wired to the sound card, and there is a plethora of Bluetooth modules available, with various operating specs. I’m sure you could find one with an input voltage under 3.7 volts.

If you are comfortable with your soldering skills, and knowledge of the electronics you are assembling, then you should be ok with this as your first build.

BUT, if you wanted to start out “simpler” (depending on what functions you want you saber to have), you can always make a saber with a Nano Biscotte to get the “feel” for saber smithing, and make the next project the PRIZM one!

One advantage to doing a double battery installation is you get more run time. One disadvantage is the amount of space the darn thing takes up. The battery will eat more space than anything else. My first saber used a crystal focus. I bought it because at the time I thought I would only make one saber and I wanted the best. Perceived value thing. If I had it to do again I would have bought a nano biscotti because I really didn't take advantage of any of the features the crystal focus offered above and beyond the NB. If you are going to run multiple (read more than a single accent and a av switch) accent lights and maybe a bar graph then you want a more advanced sound card. Otherwise you are best off with a NB.

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Originally Posted by minorhero

One advantage to doing a double battery installation is you get more run time. One disadvantage is the amount of space the darn thing takes up. The battery will eat more space than anything else.

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Yea and if you have the room for dual batts, you could always use a switch to isolate and flip to the other battery for extended run time :)

Two batteries in series = more volts
Two batteries in parallel = longer run time

Be very careful with using li-ion in either configuration.
Batteries are not all the same and charging and discharge characteristics vary from battery to battery, and can cause issues if not managed properly. (There are protection circuits old in the store if you want to wire two cells in series).

If you want the space of a single cell, but the additional run time, make your single cell removable, so you can just swap in a fresh battery as needed (do your charging outside the hilt. Saves the complications of wiring and protectiting two cells in parallel OR saves the complications of a switch between 2 batteries).

Thanks for all the advice guys. Sorry it took me so long to reply to all of these. In regards to what I WANT, I'd like to be able to use both RGB and RICE. The reason being that I know myself and know that I'm going to want to fine-tune the exact colors I want for the blade in the most efficient way possible. I'll get frustrated going back and forth with the SD card. I'm a very visual person, so I'd like a sort of live-preview as I'm tweaking the various settings. I came up with a new idea for the chassis that makes the Bluetooth RICE receiver unnecessary as a port should do just fine.

That being said, trying to get a 7.4v battery to work with the Prizm seems like more trouble that in would be worth, which was a big part of what I was wondering. I think I'll just stick with the 3.7 and call it a day. I'll save space in numerous ways taking that route and really don't foresee myself needing much more power than that. Honestly the lightsaber will probably sit on a shelf most of its life just waiting to be shown off. So I don't need a ton of battery life. Just wanted to make sure I wasn't going to be missing out on anything huge by not trying to make the 7.4 work.

My mentality is somewhere along the lines of where minorhero was for his first build. Theres a chance this will be my only build so I wanna do it right. Thanks for all the help!

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Originally Posted by djmehs

Thanks for all the advice guys. Sorry it took me so long to reply to all of these. In regards to what I WANT, I'd like to be able to use both RGB and RICE. The reason being that I know myself and know that I'm going to want to fine-tune the exact colors I want for the blade in the most efficient way possible. I'll get frustrated going back and forth with the SD card. I'm a very visual person, so I'd like a sort of live-preview as I'm tweaking the various settings. I came up with a new idea for the chassis that makes the Bluetooth RICE receiver unnecessary as a port should do just fine.

That being said, trying to get a 7.4v battery to work with the Prizm seems like more trouble that in would be worth, which was a big part of what I was wondering. I think I'll just stick with the 3.7 and call it a day. I'll save space in numerous ways taking that route and really don't foresee myself needing much more power than that. Honestly the lightsaber will probably sit on a shelf most of its life just waiting to be shown off. So I don't need a ton of battery life. Just wanted to make sure I wasn't going to be missing out on anything huge by not trying to make the 7.4 work.

My mentality is somewhere along the lines of where minorhero was for his first build. Theres a chance this will be my only build so I wanna do it right. Thanks for all the help!

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If youre only wanting to tune the color and not the fonts, maybe a Pico is better? Its got RICE for that feature only.

Should point out the safety comment about wiring Li-Ion batteris in parallel. I was warned this could result in a "thermal event" when I asked about this as a possible workaround for the amperage demands for a neopixel build. Wiring Li-Ion batteris in series or parallel yourself is not recommended.

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Originally Posted by adacey

Wiring Li-Ion batteris in series or parallel yourself is not recommended.

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With this, you can safely wire two unprotected 3.7v li-ion battery cells in series to create a 7.4v pack (IF wired correctly). The pcb takes care of regulating charging of the two cells (as uneven charging can cause issues). There is also a hazard when soldiering directly to the li-ion cell, as excessive heat can lead to said “thermal event”, so that step requires caution.

I’m not aware of a DIY solution in the store to wire 2 cells in parallel, as you REALLY need “matched” cells to be safe. Betty leave that to the pros.

My personal opinion is, IF available, buy the battery solution for you needs pre made. I don’t want to take that risk.