Bummed out by batteries.

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Bummed out by batteries.

Once DHL get their shit together, I’m about to take delivery of a shit-ton of LEDs for my wearable project for the Burn this year. I’d thought of the clever idea of running a bunch of external iPad batteries in parallel to get the ~20A I’d need. But according to a response by Anker (http://www.ianker.com/product/79ANS1052-BA — search for “How do I get a 3E to output 3A?”) that’s not a good idea.

@Ashley_M_Kirchner_No , you said you’re running your poi off 3.7V Li Ion cells without a boost circuit, but that’s for LPD880x chips, not WS2812Bs. Anyone got experience with doing that? Even if the Li Ion chemistry did produce enough voltage at every point along their discharge curve to light them up, do the really macho RC car packs which claim to be ok at 40C have an under-voltage cut-out?

I want my setup to be as foolproof as possible, and coming home in the afternoon to find my hexayurt on fire doesn’t count.

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I use Li-Ion Power Cells, which are different than regular cells. Power Cells have a high discharge rate. And since the LPDs continue to work down to 2.7V, it works well. The LEDs I’m using with it have a low voltage drop, so they too continue to work at that low a voltage. I have a software cut-off at 3.0V.

For the WS2812B, its datasheet says an absolute minimum of 3.5V … because the green and blue channels have a dropout of 3.4V! That’s huge. So you’re going to need at least VCC+0.7V to drive them, so a minimum of 4.2V.

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Right. So I’m condemned to either a couple of kilos of NiMH or 7.4V+ of temperamental Lithium chemistry and a buck converter.

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Not necessarily condemned … there’s always beer somewhere. :slight_smile:

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I’ve powered 60 ws2812’s from a protected 14500/18650 li-ion batteries.

The 18650 will run 60 pixels for about 2-4 hours. In my setup.

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@Larry1 , at the standard 3.7V terminal voltage?

(Eeeyand I’m not talking 60 pixels. More like 1200 :-P)

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Yeah I figured you were talking about A LOT more. That’s at the standard voltage. The battery has a built in pbc that cuts off at 3.2v I believe. But the lights stop working slightly before that

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I’d also like to note I have little to no clue as to what I’m really doing. I’m just connecting wires and hoping for the best. :wink: I would be somewhat more cautious if I was wearing thr lights.

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need 20A on a wearable getup? thats going to be pretty stellar setup! You could use those ipad batteries to power segmented sections perhaps. Ive used a 10000 one for some of my wearable stuff. lasted all weekend for mine.

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20A is roughly 333 RGB LEDs at 20mA per channel. Not too shabby. Or a lot more if you’re not triggering all of them at the same time!

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Are you going to be able to wear this thing and be outside? My LED shoes and hat get rather warm after a little bit of operation.

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That’s the intent, yes.

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I run all my 2812 pieces on single cell lipos. No boosts. You get max efficiency. Also connect the data line directly to the uC (atmega328 running on same lipo source, no boost, also beaglebone w ~2v io, no level convert)

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Also would like to note that all my lipo packs have protection pcbs to prevent over discharge. And as @Larry1 mentioned the led output begins to turn red and “glitch” for a bit before the PCB shits it all down. So you have a heads up on battery change.

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Hmmm, never had either a PCB or battery itself “shit down” … smirk

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I think the choice of words was apt.

@Erik_Johnson1 , can you give us a link to the packs you use? You can get enough current out of a single cell do a nice plasma rainbow pattern?

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A typo i didnt feel needed correction :wink: LiPos i don’t source from china direct, this is a vendor local to me but they also seem widely used. I have a couple of these for the poncho http://www.batteryspace.com/high-power-polymer-li-ion-cell-3-7v-10-ah-9759156-5c-37wh-50a-rate-----ul-listed-un38-3-passed-3-0.aspx
And PCBs are recommended(you can wire in parallel for more current): http://www.batteryspace.com/PCB-for-3.7V-Li-Ion-Battery-8.0A-limit.aspx

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You’re making your own “packs”?

How many LEDs in the poncho, btw?

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Well if you consider 1S a pack, sure. But I do make 2S ones as well for my truly 5V needs (with UBEC step down converters)… All my cells and their PCB are from batteryspace and I get my HX conns for balance chargers and some random cheap locking connectors for the strips’ power from digikey. It’s currently only 2022 pixels - I do want more to fill in the sides, pants, sleeves…

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I’ve been thinking of similar battery packs for my playa bike. Does anyone have personal experience with these kinds of lithium ion battery packs? https://www.adafruit.com/products/1566