Author Topic: 3.6/3.7 v lithium cell memory effect  (Read 1651 times)

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dnix71

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3.6/3.7 v lithium cell memory effect
« on: October 23, 2014, 03:00:07 PM »
I have heard that there isn't one, but I'm beginning to wonder. I have a Virgin Mobile 3G/4G Hotspot that uses the Sieera Wireless "W-1" battery rated 3.7v and 1800mah. The VM Hotspot was so well known for overheating when usb tethered that it was replaced by a much larger unit.

After a while the unit refused to fully charge the original battery so I bought 2 more off eBay. Radio Shack sold the VM Hotspot but refused to sell replacement batteries  :o. After a couple of months, both the newer cells were also rejected by the unit. Even if I plugged the unit into a usb powered hub and set it to charge, it wouldn't.

I checked the battery voltage and all three were about 3.85v, which is marginal for that cell. Thinking that all 3 cells couldn't be duds I got out a cell phone battery charger that has a clip-on adapter plate with lots of pins and if you can get 2 pins to line up it will autodetect polarity and trickle charge *any* 3.6/3.7/7.2/7.4 v lithium cell/pack.

After cycling all three cells a few times the finish voltage came back up to 4.1 - 4.14. [35ma @ 4.2 fixed voltage charging].

Now the Hotspot treats the cells as if they were fully charged and they all give long normal life untethered. The Hotspot still doesn't really like being usb tethered. In the mean time I went out and ordered 2 more cells from eBay for $5.50 each.

I only have this thing so I don't have to use the company's guest network. $25/month for 1.5GB isn't a great deal for the data I use on the Hotspot, but it works on 3G which is all I can get where I work. If my neighbors' open Comcast router happens to be offline at home I can use the Hotspot there, too, instead of having to stop at BKing or MickieD's to leach off of their open network.

My neighbor doesn't know I use his router. It was open with no password, so I put one on and left it open. I also upgraded the firmware just to be nice. He has only powered cycled once in years, so I've only had to password protect it twice.