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<body class='hmmessage'><div dir='ltr'>quote If you over discharge them then they can lose capacity in a real hurry<BR><BR>
at a chemistry lecture the clue to this was the statment<BR>
<BR>
"when anion and cations combine in a solution they form an inert substance)"<BR>
<BR>
not the same but understands why discharging a lifepo4 battery below a safe voltage they just die and cant be revived <BR> <BR>
<DIV>> Date: Fri, 17 May 2013 11:56:09 +1200<BR>> To: chchrobotics@lists.linuxnut.co.nz<BR>> From: markaren1@xtra.co.nz<BR>> Subject: Re: [chbot] LiPo batteries<BR>> <BR>> How timely.<BR>> <BR>> I am pretty sure that Li Ion and Li Po have similar issues:<BR>> <BR>> Been given a small pile of Li Ion batteries, and <BR>> bought some http://www.ebay.com/itm/260841670123<BR>> <BR>> Briefly, if you over charge them they do occasionally explode<BR>> <BR>> If you over discharge them then they can lose capacity in a real hurry<BR>> <BR>> There is a difference between 4.1V and 4.2V <BR>> cells, beware - this is absolute max terminal voltage.<BR>> <BR>> The boards above have 5V in, 5V out and cell <BR>> protection, so the cell is taken out of circuit <BR>> of over-charge or over-discharge imminent. I do <BR>> plan to run one of these up carefully and see how they behave.<BR>> <BR>> Li Ion can deliver large currents, so an in-line fuse is mandatory.<BR>> <BR>> From Wikipedia<BR>> Li Ion specific energy 100–265 Wh/kg<BR>> Ni Mh specific energy 60–120 Wh/kg<BR>> Ni Cd specific energy 40–60 Wh/kg<BR>> <BR>> The good news is there is a lot in a lightweight package<BR>> <BR>> The bad news is that there is a lot in a lightweight package<BR>> <BR>> If treated with respect, they behave well -- these are not for the unwary.<BR>> <BR>> In terms of burning your house down, you probably <BR>> already have lots of these units in your phone, laptop etc. already.<BR>> <BR>> If you have concerns about safety, stick with <BR>> NiMh the older types have self discharge <BR>> problems, but I don't think they will blow up (a <BR>> function of internal resistance and available energy).<BR>> <BR>> Mr Harris is one of (or The) resident expert, and <BR>> I await comments from him on this brain-dump.<BR>> <BR>> -Mark<BR>> <BR>> <BR>> At 11:17 a.m. 17/05/2013, you wrote:<BR>> >How safe is it really to have LiPo batteries around the house?<BR>> ><BR>> >I was thinking of using some of the 1-cell hobbyking offerings as backup<BR>> >for some microcontrollers. Then I read the reports of what these<BR>> >batteries do to people, like burning the house down, but I don't fancy<BR>> >having the chemical smoke of one of them's guts in the house either.<BR>> ><BR>> >What would people consider to be safe handling precautions in terms of<BR>> >charger, charge location and storage? What about charging them<BR>> >in-circuit?<BR>> ><BR>> >Thanks,<BR>> ><BR>> >Volker<BR>> ><BR>> >--<BR>> >Volker Kuhlmann<BR>> >http://volker.dnsalias.net/ Please do not CC list postings to me.<BR>> ><BR>> >_______________________________________________<BR>> >Chchrobotics mailing list Chchrobotics@lists.linuxnut.co.nz<BR>> >http://lists.ourshack.com/mailman/listinfo/chchrobotics<BR>> >Mail Archives: http://lists.ourshack.com/pipermail/chchrobotics/<BR>> >Web site: http://kiwibots.org<BR>> >Meetings 3rd Monday each month at Tait Radio <BR>> >Communications, 175 Roydvale Ave, 6.30pm<BR>> ><BR>> >When replying, please edit your Subject line to reflect new content.<BR>> <BR>> <BR>> _______________________________________________<BR>> Chchrobotics mailing list Chchrobotics@lists.linuxnut.co.nz<BR>> http://lists.ourshack.com/mailman/listinfo/chchrobotics<BR>> Mail Archives: http://lists.ourshack.com/pipermail/chchrobotics/<BR>> Web site: http://kiwibots.org<BR>> Meetings 3rd Monday each month at Tait Radio Communications, 175 Roydvale Ave, 6.30pm<BR>> <BR>> When replying, please edit your Subject line to reflect new content.<BR></DIV> </div></body>
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