Vampire phone car charger
- From: Kaos <no@xxxxxxx>
- Date: Mon, 24 Apr 2006 13:33:43 GMT
Hello,
Introduction
************
Please can someone help me with a problem I've got. I have recently bought
two GPS enabled GSM mobile phones with the view of installing them in each
of my cars as a cheap tracker.
The basics all worked out, a 50 pence pay as you go sim card from Orange,
hard wire a 12V phone charger into the cars electrics and hide the phones
behind the trim.
They work a treat, they appear to get decent GPS reception and when a query
is sent via SMS they respond with the location, speed and direction of
travel of the car - together with the battery charge level. However, there
is a problem!
The phones (Benefone Track One's) appear to be very thirsty when the GPS
function is switched on. Of the three GPS settings, the highest (FULL) only
gives the phones about a 8hr standby - which is useless. The next power
setting down (LOW) extends the standby to about 30 hrs, and the final option
is off - whereby I get about 5 days standby, but with the GPS functions
disabled.
The good news is that these settings can be sent remotely via SMS, and you
can get the phone to switch between Low and Full mode automatically when
external power is presented (for example on ignition of the car). If the
phones go completely flat, they automatically switch on when external power
is presented as well. (thanks for bearing with me so far!).
Problem
*******
The phone charger flattens the car battery if left on constant power. On my
BMW (80amp 12V battery) it only takes about three days if the car isn't
driven for the battery to get low enough not to start the car. If I put the
charger on the ignition wire, its obviously fine - but the tracking is only
possible if the engine is on since the car chargers don't seem to ever fully
charge the phones I get nothing like five days standby power.
In a nutshell can anyone think of a solution. I know a little bit, and have
tried the following:
1 - measure the current drain of the power going into the 12v charger... Not
entirely sure I got this properly, but it looks like about 200mA's
2 - buy a "battery saver" from Maplins, this plugs into the power and lets
accessories use the car power until the voltage drops to 11.8V and then it
cuts the power... Nice in theory, but it only delays the problem. If I
went on holiday for two weeks, the phone charger would probably stop getting
power after a day, and then there is a risk by the time I get back the
battery may have dropped due to other factors like the car alarm and then
I'm stuck again with a car that doesn't start.
3 - bypass the phone battery. If I remove the phone battery there are four
terminals. Measuring the power from the battery it appears that the phone
runs on 5V. If I connect just the +ve and -ve to the phone it powers up for
a little while and reports 'battery fault' and eventually switches off. The
good news is the consumption here seemed to be much lower (about 80mA I
think).
4 - even bigger problem. To make matters worse, if the phone has been flat
in the car for more than a couple of days, it does not switch on when power
is presented. The only solution appears to be to get the phone out of the
car (removing trim etc!) and use a mains phone charger for 4 hrs, at which
point the phone will power up next time power is presented.
To say I'm fed up is an understatement. In the ideal world it would be nice
to have a phone that¹s constantly on FULL power mode feeding from the car
battery in a way that does not flatten the car after a few days. In the
event of the car battery being removed, then it would be a bonus for the
phone to then fall back onto its own battery. The latter does not appear to
be possible however, so I'm hoping that someone knows of a way of fixing
this for me.
I'd be happy if I knew that the car could sit for three weeks without been
driven, and still have enough power to start up after keeping the GSM phone
active.
Anybody got some ideas?
Thank you.
.
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