[SHR-Unstable] Battery Hotswapping

Joerg Reisenweber joerg at openmoko.org
Mon May 25 12:16:26 CEST 2009

Am Mo  25. Mai 2009 schrieb Petr Vanek:
> On Sun, 24 May 2009 16:28:29 +0200
> Johny Tenfinger <seba.dos1 at gmail.com> (JT) wrote:
> >On Sun, May 24, 2009 at 00:21, The Digital Pioneer
> ><digitalpioneer at gmail.com> wrote:
> >> Hi. I'm trying to hotswap the battery in SHR-unstable, and it's not
> >> going well. The GSM chip never comes back online, and the phone
> >> section of the settings menu locks up when it tries to load the
> >> modules. I have to reboot the phone to get it to work again, and
> >> this makes the entire process of hotswapping a pointless waste of
> >> time.
> >
> >GSM can't work without battery. You have to turn off GSM before
> >changing bat.
> i normally hotswapp my battery in shr with no problems and with gsm
> registration performing ok. it has also been discussed here in
> community list that this should not cause any issue. has anything
> changed?

I think this largely depends on state of main battery charger unit in PMU. If 
it's charging bat with Constant Voltage (~4.16V) from a 500mA or 1A source 
(host or OM-wallcharger) then the modem should happily survive a short period 
without bat - at least if it's not trying to send during this period (active 
cell handover, SMS, inbound call). 
OTOH if modem draws *too less current* (maybe related to sleep4 vs sleep2), 
MBC might decide to stop charging and cut the CV, leading to a glitch in 
modem's VDD and thus resetting it. It's very difficult to predict what's 
actually going to happen (just only guarantee is nothing will break), so I 
would recommend shutting down GSM prior to bat swap - alas this doesn't seem 
to work on SHR ATM.

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