5V Boost and Lipo/Li-ion Charger

So without a doubt I would like to come up with a 'shield' to allow this, unless someone else does.

My main interest is extending the prop shield to allow at least 120 LED, APA102/WS2812 strip to be used. Which means about 5A current output. But It should work as a stand alone extension that provides 5V and portability with lipo/li-ion batteries as well.

There's 2 ideas I've been playing with. One is to simply use a battery charger IC, and a boost converter IC capable of at least 5A output at 5V.

The other is to allow additional boost modules to be stack-able by setting the boost converter output to about 5.5V, which is then connected to a rectifier diode with a voltage drop of .5. We should be able to connect the output of the rectifier diodes together. So in theory additional boards can be stacked on (with additional Lipo/Li-ion batteries) each would allow an additional 120 LEDs to be used. However this stack-able approach results in a straight loss of efficiency for those who only want to use ~120 LED's with no benefits. Would that even matter? Which seems more appealing?

One horse has done some work on Teensy format battery boards
https://www.tindie.com/products/onehorse/lipo-battery-charger-add-on-for-teensy-31/
there was another design but not finding it at the moment.
Targets a different use but may be worth a look, and maybe try and get in touch for any things that didn't work.

With stacking modules there are complications there around what happens if one fails. If each powers a strand it's just that the strand goes out, but if they are OR'ed via diodes then your failure modes can be more exciting. For WS2812 LEDs a possible design is to skip the Teensy mount and instead have a PCB that can mate directly to the end of the LED strip housing battery boost circuit (minimal wire lenght) and 3.3->5V level converter.

GremlinWrangler said:

One horse has done some work on Teensy format battery boards
https://www.tindie.com/products/onehorse/lipo-battery-charger-add-on-for-teensy-31/
there was another design but not finding it at the moment.
Targets a different use but may be worth a look, and maybe try and get in touch for any things that didn't work.

With stacking modules there are complications there around what happens if one fails. If each powers a strand it's just that the strand goes out, but if they are OR'ed via diodes then your failure modes can be more exciting. For WS2812 LEDs a possible design is to skip the Teensy mount and instead have a PCB that can mate directly to the end of the LED strip housing battery boost circuit (minimal wire lenght) and 3.3->5V level converter.

Click to expand...

The closest thing I've seen is this boost converter+ charger from Adafruit https://www.adafruit.com/product/2465 but an output of 1A wouldn't even power 1 meter of LED strip. I'm not sure I see the issue with the failure of 1 boost converter module...

On second thought, this dilemma can be solved using some cut/solder pads to bypass the diode and configure the boost converter.

With multiple OR'ing of power supplies you can have issues both where one PSU dies and you get a cascade of failure and restart amongst the rest and wildly swinging voltages, or where the PSU design has a very flat output V vs I stability and then whichever PSU has the slightly higher output V will carry all of the current and the others will just coast. Good load sharing means you actually need a fairly steep slope on the output voltage so the partners can pick it up.

Certainly can and is done, just would be careful assuming a given IC+design can 'just work' without some research and testing.

GremlinWrangler said:

With multiple OR'ing of power supplies you can have issues both where one PSU dies and you get a cascade of failure and restart amongst the rest and wildly swinging voltages, or where the PSU design has a very flat output V vs I stability and then whichever PSU has the slightly higher output V will carry all of the current and the others will just coast. Good load sharing means you actually need a fairly steep slope on the output voltage so the partners can pick it up.

Certainly can and is done, just would be careful assuming a given IC+design can 'just work' without some research and testing.

Click to expand...

The best solution would likely involve feedback based adjustment for each power supply. However this way with ORing diodes is simple and low cost. Presumably the IC would have a current limit clamp. A scenario where the power supplies are 'taking turns', as they hit the max current output and shut off, may cause them to operate at the lower end of the efficiency curve, but it should still work. Of course there will be some testing to do. So far I have not seen prior tests done that says this simply will not work, so I will give it a go.