From: William Hermans <[email protected]> Reply-To: <[email protected]> Date: Wednesday, May 28, 2014 at 11:19 AM To: <[email protected]> Subject: Re: [beagleboard] Re: Can the BBB get damaged due to a hard power down?
> Batteries can be had that have a lifetime of 5+ years. Depending on the type > of battery you use. Flooded lead acid ( for RE use ) can have a much longer > life. Especially if the batteries are conditioned / charged properly. You can buy Tadiran batteries that last 10 years, but they are expensive. They aren¹t real batteries either, they are a type of hybrid battery. http://www.tadiranbat.com <http://www.tadiranbat.com/> > > > I've personally bought, and used 10,000 aH D Cells that have lasted 3 years, > but failed eventually, because I was using them in a Maglite flashlight, and > had dropped it many times. The point is, where there is a will, there is a > way. > > Also, perhaps I am remembering wrongly, but I seem to recall reading that > super caps have a limited lifetime as well. Something about only having so > many charge cycles similar to a battery. Not true. As long as you do not exceed their maximum voltage, supercaps charge cycles are 100x that of batteries and their life expectancy is >10 Years. You can also charge and discharge them much faster than batteries. Regular Lithium Iron are good for about 1,000 charge cycles and <3 year capacity is less than 80%. > > > > On Wed, May 28, 2014 at 11:06 AM, Dr. Michael J. Chudobiak > <[email protected]> wrote: >>> asked anyone at TI if it is OK to use the PMU like this? Perhaps you >>> should post a question on E2E. >> >> From http://e2e.ti.com/support/power_management/pmu/f/200/t/185514.aspx >> <http://e2e.ti.com/support/power_management/pmu/f/200/t/185514.aspx> : >> >> "The battery charger should work fine with a supercap. You'll need to make >> sure the TS (battery temp sense) pin is at a proper voltage to allow >> charging. If the supercap does not have a temperature sensor, you can simply >> put a 10k resistor from TS to GND." >> >> >>> If you are charging at 440mA, it will take 50 Seconds to reach full >>> charge. What happens when the power fails before that 50 Seconds? I would >>> recommend that you monitor the supercap voltage and wait until it is fully >>> charged before opening any files. >> >> That is why I use full data+metadata journaling on the filesystem. >> >> If an unclean shutdown happens before the supercap is charged, the next >> boot-up will be delayed for several seconds as the filesystem is repaired >> using the full journal. That is annoying, but it is a minor cost for >> robustness. Mostly, the supercap is there to eliminate the need for the >> repair delay. >> >> >>> It is an interesting concept, but I'm still skeptical if this can really >>> work. >> >> Well, I do use it, so that's one data point. >> >> The other main alternative for bullet-proof power-fail robustness is to rely >> on on something like unionfs to provide a mix of read-only and read/write >> filesystems, but that's not so simple either. It's complex and not very well >> supported in general. >> >> Batteries have a fairly limited lifetime, so I don't consider that a >> practical solution (for me). >> >> I'm interested to hear how other people prevent corruption on power loss, >> though. >> >> >> >> - Mike >> >> -- >> 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] >> <mailto:beagleboard%[email protected]> . >> For more options, visit https://groups.google.com/d/optout >> <https://groups.google.com/d/optout> . > > > -- > 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/d/optout. -- 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/d/optout.
