[chbot] LiPo batteries

[Volker Kuhlmann]

Hi Mark,

Thanks for the good info!

Multi-cell makes it more complicated hence my plans for 1-cell. If I
find I really need 5V I'll use two (and think about the charging then).
The bigger the better for the same effort, so I was eyeing up the 5Ah
range ones, like
http://www.hobbyking.com/hobbyking/store/__18560__Turnigy_5000mAh_1S_20C_Lipoly_Single_Cell_.html
Although made for high-Amps, if it keeps a micro going for a day or two
in the next desaster that'd be splendid, so I'm looking at 0.5A very max
discharge and thus that's not the problematic aspect.

On Fri 17 May 2013 11:42:01 NZST +1200, Mark Beckett wrote:

> The cheap RC type LiPo offer no protection against damage, and don't
> incorporate any battery management on board the battery.
> This includes any thermal device to open the connection when the
> discharge is too great.

Do you have a good source for them? Or how exactly is it described if
that protection is included? (Hard case not needed for me.)

Does that include *dis*charge protection as well? As in does it cut the
load below a certain cell voltage?

> The RC car club requires them to be charged in the special bags you can get.

Those bags don't look to me like they could contain a fire much. Control
a little bit, yes, but they'd still do nothing about the impressive
mess. Yes I'd use them (pityful price anyway), but better assume they're
not there.

> And then of course there are those itoys that decided to commit
> suicide and catch fire ...

yep...

> If you look in the June Silicon Chip, Stan Swan has a write-up about

If you mean http://www.siliconchip.com.au/ the June issue isn't there
yet.

> In circuit charging is unlikely to be of a rate high enough to
> generate the amount of heat required.

Uhhhm, I have been warned that there is no safe limit of continuous
charge, and all the energy is stored up and at some point, things *will*
get interesting! In contrast, NiMH go over to an oxygen-recombination
cycle that converts the surplus energy into heat and doesn't damage the
battery provided you stay below some limit (in the order of 0.5-5% C).
I'd probably use an integrated LiPo charge controller because it's less
risky.

Volker

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Volker Kuhlmann
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