DIY Li-Ion rechargeable battery pack

[Novastar]

Great explanations, Eastern. And lol @ the Nova-quote, hahahh. It seems we're running into this a lot lately--the whole "debacle" of mA vs. mAh. Oh well. In perspective, I certainly did not understand this for a LONG time until Corbin explained it to me back in 2005. You can hardly expect people with ZERO electronics experience to understand quickly though... so... if anyone understands... I do.

One other note...

I have been told by someone who is pretty darn "expert" in the Li-Ion industry that using individually protected cells (keyword: individually...) to make 7.4v packs or 11.1v or whatever... can lead to long-term problems.

Now... I have NEVER seen an issue with this as of yet--even though I don't make 7.4v packs with individually (keyword: individually...) protected cells. But I see them being used ALL the time (Yoda does so with his Graflex Chassis setups, and many many folks use the 2 x 14500 "AA"-style cells in little AA spring packs, which are wired up for the voltage).

I'm not sure what that means, since... it's obviously conflicting with the guy I know (who works for a very well-known high tech company which I cannot say).

Additionally, it's also fairly common thought that cells that go into packs are supposed to be metered/tested in ways that show they should go together. What do I mean? Well, I mean to say--like LEDs and "binning"... no two are created totally identical. Some are closer together as "matches" than others. In this case--the cell chemistry, inherent resistance, discharge rates, TRUE capacity (down to the last little bit)... is supposed to match darn well.

Unfortunately, you can't really determine this on your own when you have two cells in front of you. Hopefully those cells are from the same company, bought at the same time... and GOD FORBID you buy 2 cells from differing companies at differing times with differing mAh capacities... and then throw a 7.4v PCB on them and call it good!! O.O This could be dangerous... or simply just cause problems later on.

Again, I don't know what the long-term effects of putting together "pre-protected 3.7v" cells... but I figured I should just say... mise en garde.

BOTTOM LINE = It's a good standard practice for building Li-Ion packs to use (initially) unprotected cells... and then throw on the correct PCB for 7.4v, 11.1, 14.4, blah blah blah... and don't mix brand types, nor "mAh" types... and don't use one cell you got in 2006 and one from 2009. I know, it's pretty obvious. heheh

LINK TO VIDEO TUTORIAL (7:24):
Although it's near the end of the video (7:24)... .... --> http://www.youtube.com/watch?v=DNcc2oZWmO8

[Matt Thorn]

Great information, Novastar. Thanks. I had wondered vaguely about the PCBs for Li-Ion packs (e.g., Why are unprotected Li-Ion batteries sold at all? Why are 7.2V PCBs sold separately?). Maybe one of our electronics pros (Erv? Eandori?) can shed some more light on the issue.

And if my record with wrapping my head around the "mA ≠ mAh" concept is any indication, I may actually be able to grasp the Li-Ion PCB issue in roughly two years.

[Jay-gon Jinn]

Great information, Novastar. Thanks. I had wondered vaguely about the PCBs for Li-Ion packs (e.g., Why are unprotected Li-Ion batteries sold at all? Why are 7.2V PCBs sold separately?). Maybe one of our electronics pros (Erv? Eandori?) can shed some more light on the issue.

And if my record with wrapping my head around the "mA ≠ mAh" concept is any indication, I may actually be able to grasp the Li-Ion PCB issue in roughly two years.

Unprotected cells are sold so that a hobbyist can make a custom pack to suit their individual needs. You just need to make sure that when you add a pcb to your custom pack made with un-protected cells that it matches the pack you've made.

[Maurnick]

How could one recharge a pack like this if it weren't being set up in-hilt with a recharge port?

[Shadar Al'Niende]

How could one recharge a pack like this if it weren't being set up in-hilt with a recharge port?

you wouldn't?


seriously though, You would have to do some dangerous wiring...

[Matt Thorn]

Yeah, a charge port is pretty much a must.

[eastern57]

no there are ways. You can put a quick disconnet on your battery, and another on an adaptor for the charger, you can do it that way. Buy two QDs: one set for the saber guts to the battery pack and an extra connection for a charger adaptor.

You will have to cannabalize one of the charger adaptors, but it's an option... I've done it before.

[Matt Thorn]

no there are ways. You can put a quick disconnet on your battery, and another on an adaptor for the charger, you can do it that way. Buy two QDs: one set for the saber guts to the battery pack and an extra connection for a charger adaptor.

You will have to cannabalize one of the charger adaptors, but it's an option... I've done it before.

I did think about that possibility before responding, but I couldn't imagine a scenario in which that would actually be preferable. Another possibility, if you really don't want to have a charge port visible on your hilt, is to hide the port inside the pommel, and pull it out for recharging. I'm pretty sure I've seen photos of just this sort of set-up. Either way, you would still need a Tenergy-style smart charger.

[Lan-Ja Hamil]

I did think about that possibility before responding, but I couldn't imagine a scenario in which that would actually be preferable. Another possibility, if you really don't want to have a charge port visible on your hilt, is to hide the port inside the pommel, and pull it out for recharging. I'm pretty sure I've seen photos of just this sort of set-up. Either way, you would still need a Tenergy-style smart charger.

I saw in one of Novastars videos he hides the recharge port inside the pommel of the saber. Just unscrew the pommel and there it is.

[eastern57]

I did think about that possibility before responding, but I couldn't imagine a scenario in which that would actually be preferable. Another possibility, if you really don't want to have a charge port visible on your hilt, is to hide the port inside the pommel, and pull it out for recharging. I'm pretty sure I've seen photos of just this sort of set-up. Either way, you would still need a Tenergy-style smart charger.

If you have an Ultrasound or a CF - where there's battery draw, even while the saber is off - you'll need some method to cut battery power entirely. A recharge port does that... or just a separate power switch.

I use a battery/QD on the this set-up, because I had wired in a separate power switch, and a recharge port wasn't necessary.

http://forums.thecustomsabershop.com...ead.php?t=8948