[Server-devel] external batteries
I didn’t find the batteries I saw before, but this looks pretty good. http://www.amazon.com/AmazonBasics-Portable-External-Battery-Charger/dp/B00LRK8JDC/ref=sr_1_22?s=wirelesssrs=10112675011ie=UTF8qid=1425048233sr=1-22 weighs 8 oz. check my math, but at 10K mAh that should power a 3W 5V device for 16.67 hours in a perfect world. this one has two usb outs, so for devices with portable hdd there is a supply for the device and another for the hdd. some of these take awhile to charge, so two smaller ones might be better, though more complicated. not sure if you can charge and use at the same time, but input is separate from output.___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] [XSCE] external batteries
I've experimented with several of these class of device. They are a 3.7V Lithium battery with a charging and discharging circuit attached. Like the high current power adapters, the outputs are not always 5V; sometimes they are somewhat higher, so that at high current charging the voltage at the other end of the cable remains good for the smartphone or tablet. I wouldn't let them near any USB HDD until I'd checked the voltage and ripple; to avoid harm to the input regulators on the USB HDD. Some of them cannot be charged at the same time they are being discharged, so they are useless as a DC UPS. Some of them continuously run the discharging circuit, so they lose capacity rapidly after being charged. This is because they don't detect the USB plug, or don't have a power switch. Their end to end efficiency isn't great. Because they are being sold by capacity, more of the battery capacity is used. The cycle life seems to be around 1000 full charges, about half what would be expected from a product that optimises for lifetime. -- James Cameron http://quozl.linux.org.au/ ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] [XSCE] external batteries
excellent, better than the one I found From: George Hunt Sent: Friday, February 27, 2015 9:56 AM To: Tim Moody Subject: lithium battery I'm excited about our discussion yesterday. Based on your research, what do you think of: http://www.amazon.com/gp/product/B00F4U49M6/ From the comments, I suspect that there is really a 3.7v battery inside, so that there is enough headroom to actually charge the thing. Then they must do a dc-dc conversion back up to 5v output I think our application will be gentle on the electronics, compared to mainline usage. I like the idea of lcd capacity indication. The comments suggest that output reading is not reliable, but hopefully it will be repeatable.___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
