A couple observations on designing a Li-Po (or general power supply cape, no matter what the power source)....
1. the charger can be separate and it makes the design much easier. RC Li-Po packs are plentiful as are the chargers for them just build a cape that allows running off one of those. 2. Current measurement could be useful and is a good idea. Possibly via i2c or maybe via simply using one of the analog pins. 3. the input voltage for such a cape ought to be roughly 9-(15-20) volts. the low end covering a reasonably well drained 6 cell lead acid car battery and the high being above 15 for the charging voltages sometimes seen in the same type of battery then rounded up from there to whatever pack voltage is for a fully charged number of Li-Po cells in series with a voltage higher than 15 or so. that would cover many if not most applications I can forsee. Eric On Tue, Jan 14, 2014 at 6:41 AM, Mike Bremford <[email protected]> wrote: > Hi Ron > > Did you cater for inputs above 14V? If powering from 12V lead-acid > batteries, they typically charge at 14.4-15V but I'd certainly expect spikes > of higher and I wouldn't want to plug in anything that couldn't take up to > 16V safely. I see you have a 15V zener on there so the regulator won't > receive more than that, but if this was sustained presumably your polyfuse > would go soon after, correct? > > Second, your chosen regulator will put out 2.25A - are the components sized > to deliver all of that, and could I tap some of it to power a USB hub? Say > by using the 2.1mm power socket on the beaglebone as a power source for the > hub? If yes to both of these then you might have a customer if my board > doesn't work when it turns up from oshpark next week... > > Finally, if you're looking for other ideas, how about current measurement > through I2C? Nice to have rather than essential, but if you're redesigning > the board a spot to solder an INA219 (or something like it) wouldn't go > amiss. If you haven't got some way to signal the BeagleBone yet that it's > running on LiPo, this part will also tell you about input voltage so you > could probably deduce it from that. > > > > On 14 January 2014 04:22, Ron B. <[email protected]> wrote: >> >> Sorry for the late reply on this thread but it just popped back to the top >> of the list and caught my attention. >> >> I've been powering my BeagleBone from RC batteries for some time now. The >> most versatile method that I've been using is a buck/boost power "bar" that >> attaches to the expansion connections and provides a stable 5V from a >> 3-14VDC input. It isn't fancy, but it's (relatively) inexpensive and >> doesn't cover up the console port or I2C pins. I've released all of the >> files for anyone who wants to build one here. >> >> I'm also working on a proper Li-Ion PowerCape that incorporates charging >> and power control circuitry. This allows for operation as a "mini UPS" or >> as a battery-powered "node" that can power itself up and down. I just built >> up the first full prototype yesterday and will post some pictures on the >> blog later this week. I'd really like to get feedback on the PowerCape, >> especially with regards to the connectors and placement that I've chosen. >> >> -Ron >> >> >> On Tuesday, January 22, 2013 4:20:49 PM UTC-6, Eric wrote: >>> >>> I'm trying to better understand the issue with the creation of a LiPo >>> cape for the bone. Here's my thinking: >>> >>> With a nominal cell voltage of 3.7v it would take a 2 cell LiPo pack to >>> light up the 5v rail no matter what you do. At this point you have 7.4v. >>> Use a buck converter and produce 5v from 7.4v (or possibly a 6-13.8v source >>> making it a rather useful general power supply cape useful for powering the >>> bone in your car as well) with decent efficiency and feed that into the 5v >>> line on the expansion connectors the same way that the battery cape does >>> now. As for charging the lipo pack I'm not sure I'd really worry about that >>> much, rather I'd simply supply a connector on the cape for a standard RC >>> type lipo pack and optionally a decent sized cap for continuity when >>> changing batteries. The user could then choose the type and size needed for >>> the desired runtime. when it comes to charging, just disconnect the LiPo >>> pack and plug it into a standard RC charger available from any decent hobby >>> store where the pack was sourced from. How does this vary from the >>> approaches previously looked at for a LiPo cape? What problems might I have >>> missed? >>> >>> Eric >>> >>> >>> >>> Eric >>> >>> On Tue, Jan 22, 2013 at 6:33 AM, Andrew Bradford >>> <[email protected]> wrote: >>>> >>>> On Mon, 21 Jan 2013 20:53:16 -0800 >>>> Eric Fort <[email protected]> wrote: >>>> >>>> > Just a thought.... A large lithium pack for the bone would rock! >>>> >>>> Regarding the lithium battery pack idea, it's a good one except for one >>>> little issue with the bone where a rework is required in order to power >>>> down into TPS65217 OFF or SLEEP modes when a battery is connected due >>>> to SYS voltage staying present and the way 3.3V_EXP is generated. So >>>> long as you don't want to power off with the battery still connected >>>> there's no issue, though. >>>> >>>> The existing battery cape doesn't have this problem as it's 4 AA cells >>>> with a regulator and that feeds into the 5V line on the expansion >>>> connectors. >>>> >>>> -Andrew >>> >>> >> -- >> For more options, visit http://beagleboard.org/discuss >> --- >> You received this message because you are subscribed to the Google Groups >> "BeagleBoard" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> For more options, visit https://groups.google.com/groups/opt_out. > > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/groups/opt_out. -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. 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