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Re: [Gumstix-users] Goliath dead?
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From: adrian c. <adr...@gm...> - 2008-05-08 00:37:24
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Thanks, thats very helpful. I think I'll take another look at getting two AA cells into the case. Adrian On Tue, May 6, 2008 at 2:01 PM, Lawrence Harris <gu...@ha...> wrote: > There are a couple of things to be aware of with NiMH (and NiCd to a > slightly lesser extent). > > During discharge in parallel one cell will provide all the current until > it's voltage drops below the other then they will swap so you can get > overall longer running times but not increase current draw by > paralleling cells. > > During charge the normal algorithms involve looking for a 'peak' in the > charging voltage to determine when the cell is full. This is caused by > a change from absorption of charge to pure heating. In NiMH this is a > very small bump. > > When you put two cells in parallel they can often mask each other and > the charger will never see the peak and wont shut off. You then get > thermal runaway and destroy the cells if not the product. The solution > is a very slow trickle charger or separate the cells for charging. > > Similarly with the cells in series often the first cell to 'peak' stops > the charger. This leaves all the other cells not quite full. Each > cycle causes this problem to get worse, running time gets shorter until > the battery looks like it's dead. A full slow deep discharge of the > whole pack and then slow charge will revive the pack. This problem is > less of an issue than the parallel situation and manufacturers seem to > not worry about it. Usually means they sell more battery packs but > don't have to deal melted plastic cases. > > Of course none of the charging issues are an immediate problem if you > take the batteries out and charge them in wall wart style charger as > they almost universally charge each cell separately, though there are > good ones that baby the cells and bad ones that just cook them. The > ideal charger does each cell individually, monitors for the peak, has a > timer to cut off charging if the peak is missed and a thermistor to > monitor the temperature if the cell starts to go into thermal runaway. > > Lawrence Harris > > > > > adrian cockcroft wrote: > > I wanted capacity in a lower profile, so was hoping to use four AAA in > > series/parallel rather than two AA in series. The AA are also longer > > which makes the power bulge harder to fit. Are there any charging > > issues with series/parallel NiMH? > > > > Adrian > > > > On Mon, May 5, 2008 at 7:45 PM, Gordon Kruberg <go...@gu...> wrote: > > > >> The goliath board you have takes, out-of-the-box, 2 x NiMH for the charger. > >> Gordon > >> > >> > >> > >> > I have a beta Goliath board, the issues are mostly just getting the > >> > design right, there is a lot of complex stuff on the board. I've been > >> > working on a case for it, which could be adapted by anyone else using > >> > the 4.3" LCD. Latest update is that I added a power bulge/battery > >> > holders to the rear cover of the design. It takes four AAA 1000mAh > >> > NiCd. You can see it here: > >> > > >> > http://wiki.hbmobile.org/index.php?title=MyPhone_Landscape_Case > >> > > >> > I use the free version of Alibre to design this, (www.alibre.com) and > >> > I'm still working on the details of the battery holder. If anyone > >> > wants copies of the design files, drop me an email, and I'll send you > >> > the latest. When it stabilizes, the design files and STL files for 3D > >> > printing will be on the wiki. > >> > > >> > Adrian > >> > > >> > On Sun, May 4, 2008 at 11:35 AM, Jeff Sadowski <jef...@gm...> wrote: > >> > > >> >> I am curious about the status of this product? > >> >> > >> >> I'm guessing since it was having issues in reliability it was pulled? > >> >> > >> >> or was it that no cell phone service would support it being on their networks? > >> >> > >> >> Are there any other open source phone projects? > >> >> > >> >> ------------------------------------------------------------------------- > >> >> This SF.net email is sponsored by the 2008 JavaOne(SM) Conference > >> >> Don't miss this year's exciting event. There's still time to save $100. > >> >> Use priority code J8TL2D2. > >> >> http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone > >> >> _______________________________________________ > >> >> gumstix-users mailing list > >> >> gum...@li... > >> >> https://lists.sourceforge.net/lists/listinfo/gumstix-users > >> >> > >> >> > >> > > >> > ------------------------------------------------------------------------- > >> > This SF.net email is sponsored by the 2008 JavaOne(SM) Conference > >> > Don't miss this year's exciting event. There's still time to save $100. > >> > Use priority code J8TL2D2. > >> > http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone > >> > _______________________________________________ > >> > gumstix-users mailing list > >> > gum...@li... > >> > https://lists.sourceforge.net/lists/listinfo/gumstix-users > >> > > >> > >> ------------------------------------------------------------------------- > >> This SF.net email is sponsored by the 2008 JavaOne(SM) Conference > >> Don't miss this year's exciting event. There's still time to save $100. > >> Use priority code J8TL2D2. > >> http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone > >> _______________________________________________ > >> gumstix-users mailing list > >> gum...@li... > >> https://lists.sourceforge.net/lists/listinfo/gumstix-users > >> > >> > > > > ------------------------------------------------------------------------- > > This SF.net email is sponsored by the 2008 JavaOne(SM) Conference > > Don't miss this year's exciting event. There's still time to save $100. > > Use priority code J8TL2D2. > > http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone > > _______________________________________________ > > gumstix-users mailing list > > gum...@li... > > https://lists.sourceforge.net/lists/listinfo/gumstix-users > > > > ------------------------------------------------------------------------- > This SF.net email is sponsored by the 2008 JavaOne(SM) Conference > Don't miss this year's exciting event. There's still time to save $100. > Use priority code J8TL2D2. > http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone > _______________________________________________ > gumstix-users mailing list > gum...@li... > https://lists.sourceforge.net/lists/listinfo/gumstix-users > |