Keeping a LiON mobile phone charged in GSM alarm

JimPerry

JimPerry

Senior Member
First the background:

I have a caravan in Scotland that just got broken into ... OK installing an alarm is no problem (was doing it 40+ years ago).

The caravan site stopped having security on Sunday evenings - when the break in happened. So as well as loud noises and flashing strobe I need a GSM TXT message option (as I live nearly 250 miles away). Commercial units are available - from £20 to £300.

Tried a £20 unit didn't work - got a full refund.

Bought a £15 unlocked Samsung E1200 phone with a free O2 SIM (Tesco version is only £9).

A lot of faffing about with Epoxy, two cheap servo motors, paperclips and configuring phone to not get ads etc later - ITS ALIVE!

The phone has an SOS feature that sends TXTs to upto 5 numbers if a certain button is pressed 4-times rapidly (hence servo).

Works a treat off an 08M2 at moment.

Now the question:

I've cut the charger cable so I can run 5V into the phone when needed - not a good idea to leave it on charge 24/7 - so I figured to charge for about 2 hours every few days.

Is this a good idea for LiON?

Plus I thought to use the TIME variable to count to 36000 then increment 10Hr by one - every 10Hr = 4 reset TIME then CHARGE until TIME=720 (2 hours) - then start again.

Photo's and code will follow as I build more.
 
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srnet

Senior Member
JimPerry said:
I've cut the charger cable so I can run 5V into the phone when needed - not a good idea to leave it on charge 24/7 - so I figured to charge for about 2 hours every few days.
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Why fiddle with the normal charger, plug it into one of those cheap mains timers (£3?) and set it to come on every so often ?
 
JimPerry

JimPerry

Senior Member
It all fits in a small box, next to the alarm control - adding a mains timer is even clunkier than my servo push-buttons!

See attached :rolleyes:
 

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nick12ab

Senior Member
JimPerry said:
Yes it does - the monitoring is either in the phone or battery pack. But is it wise to keep it fully charged 24/7 for months and months? :confused:
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Good point. Is there the luxorious feature of being able to set the phone to automatically stop charging once the battery has only been charged halfway?

EDIT: I don't think there's any safety issue but keeping it fully charged can shorten the life of the battery.
 
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JimPerry

JimPerry

Senior Member
For less than £10? No.

I figured to leave it on for a few days and check the charge bars to get a rough idea - hence the 3 days off charge then 2 hours idea. :rolleyes:
 
S

srnet

Senior Member
Keeping the battery fully charged, might shorten its life somewhat, but what do you think that means exactly ?

Do you expect that after say 2 years, permanently connected, there wont be enough charge left to make a call ?
 
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BeanieBots

Moderator
JimPerry said:
More like explosions - fires ? :confused:
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That would be my concern when unattended as well as shortening battery life.
My phone lasts for ~10 days on a single charge and is now about 5 years old. How long will you need to leave it?
You could consider replacing the battery with a regulator of correct voltage and drive that from a safer technology such as a large Pb battery which would be happy being float charged for long periods.
I'd also consider replacing the servo mechanism with either a relay contact or analogue switch direct to the button contacts.
 
JimPerry

JimPerry

Senior Member
The main security system has a 7AH 12VSLA that provides 12V for sounders and sensors. The autodial box will get this 12V and have twin 7805 regulators for the Picaxe and servos. No exposed wires to cut :cool:

I don't want to do any physical mods to the phone (apart from the charger lead) - had considered solenoids but can't find any small ones :rolleyes:
 
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