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04-26-2008

Posted by Chris Edwards on April 26, 2008, 6:45 am

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'Morning Gents

        Slightly off topic....but at least I'm not selling shoes and it is
engineering of a sort.

        I have a good friend who has several modern vehicles and even more
older ones (pre-war Austins). Said friend is getting married soon and I
thought of giving them a vehicle-type satnav system as a wedding present. I
assume these things need 12volts, but I don't know the current draw?

         The older cars have six volt systems, without the convenience of
cigar lighter sockets. Would it be feasible to run a decent GPS system off
a (12v by 12Amp/hour?) sealed lead acid battery, the sort of things used in
a burglar alarm system? I'm imagining a small brick-sized battery on the
floor of the car, couple of spade connectors to a cable which terminates in
a cigar lighter-type socket and I've got a system which is portable between
vehicles.......or have I?
--

Chris Edwards (in deepest Dorset) "....there *must* be an easier way!"

Posted by Bob Minchin on April 26, 2008, 7:43 am

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Chris Edwards wrote:

> 'Morning Gents
>
>         Slightly off topic....but at least I'm not selling shoes and it is
> engineering of a sort.
>
>         I have a good friend who has several modern vehicles and even more
> older ones (pre-war Austins). Said friend is getting married soon and I
> thought of giving them a vehicle-type satnav system as a wedding present. I
> assume these things need 12volts, but I don't know the current draw?
>
>          The older cars have six volt systems, without the convenience of
> cigar lighter sockets. Would it be feasible to run a decent GPS system off
> a (12v by 12Amp/hour?) sealed lead acid battery, the sort of things used in
> a burglar alarm system? I'm imagining a small brick-sized battery on the
> floor of the car, couple of spade connectors to a cable which terminates in
> a cigar lighter-type socket and I've got a system which is portable between
> vehicles.......or have I?
> --
>
> Chris Edwards (in deepest Dorset) "....there *must* be an easier way!"

My relatively old tomtom Go says on it 5v 2amps. I strongly suspect the
2 amps is absolute worst case to run the unit and when the battery is
charging at max rate.
You will still need a regulated supply as a nomimal 6 volt car will vary
from below 5 to 7 or more complete with spikes etc and modern
electronics won't accept that wide range. Nice little switch mode supply
project for an electronics expert. you will need a two stage design as
most configurations do not like the input range being both sides of the
desired output range.(no I've got too much on before you even think
about it!!).

Bob

Posted by TT_Man on April 26, 2008, 8:32 am

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> 'Morning Gents
>
> Slightly off topic....but at least I'm not selling shoes and it is
> engineering of a sort.
>
> I have a good friend who has several modern vehicles and even more
> older ones (pre-war Austins). Said friend is getting married soon and I
> thought of giving them a vehicle-type satnav system as a wedding present.
> I
> assume these things need 12volts, but I don't know the current draw?
>
> The older cars have six volt systems, without the convenience of
> cigar lighter sockets. Would it be feasible to run a decent GPS system
> off
> a (12v by 12Amp/hour?) sealed lead acid battery, the sort of things used
> in
> a burglar alarm system? I'm imagining a small brick-sized battery on the
> floor of the car, couple of spade connectors to a cable which terminates
> in
> a cigar lighter-type socket and I've got a system which is portable
> between
> vehicles.......or have I?
> --
>
> Chris Edwards (in deepest Dorset) "....there *must* be an easier
> way!"

TomToms run of regulated 5V ( built into the cigar adapter.) If you build a
5V Low Dropout regulator then the 6V will be fine. This is only really
needed for charging the TomTom although it will drive the TT if connected.
My advice, start the car and then connect the TomTom supply.The regulator
may not like Load Dumping! The TomTom will happily run a few hours on its
internal Lithium cell. When almost flat, the Lithium will draw 1- 1.5 amps
from the external 5V supply.
Hope that helps.

Posted by ravensworth2674 on April 26, 2008, 1:48 pm

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>
>
>
>
>
>

> > 'Morning Gents

>

> > Slightly off topic....but at least I'm not selling shoes and it is
> > engineering of a sort.

>

> > I have a good friend who has several modern vehicles and even more
> > older ones (pre-war Austins). Said friend is getting married soon and I
> > thought of giving them a vehicle-type satnav system as a wedding present=

.

> > I
> > assume these things need 12volts, but I don't know the current draw?

>

> > =A0 The older cars have six volt systems, without the convenience of
> > cigar lighter sockets. =A0Would it be feasible to run a decent GPS syste=

m

> > off
> > a (12v by 12Amp/hour?) sealed lead acid battery, the sort of things used=

> > in
> > a burglar alarm system? =A0I'm imagining a small brick-sized battery on =

the

> > floor of the car, couple of spade connectors to a cable which terminates=

> > in
> > a cigar lighter-type socket and I've got a system which is portable
> > between
> > vehicles.......or have I?
> > --

>

> > Chris Edwards (in deepest Dorset) =A0 =A0 =A0"....there *must* be an eas=

ier

> > way!"

>
> TomToms run of regulated 5V ( built into the cigar adapter.) If you build =

a

> 5V Low =A0Dropout regulator then the 6V will be fine. This is only really
> needed for charging the TomTom although it will drive the TT if connected.=

> My advice, start the car and then connect the TomTom supply.The regulator
> may not like Load Dumping! The TomTom will happily run a few hours on its
> internal Lithium cell. When almost flat, the Lithium will draw 1- 1.5 amps=

> from the external 5V supply.
> Hope that helps.- Hide quoted text -
>
> - Show quoted text -

Greetings Chris,
Having reached the age to claim both 6v and
ancient cars, wasn't the other question -polarity?

Regards

Norm

Posted by Chris Edwards on April 26, 2008, 3:35 pm

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On Sat, 26 Apr 2008 10:48:37 -0700 (PDT), ravensworth2674

>>
>>
>>
>>
>>
>>

>> > 'Morning Gents

>>

>> > Slightly off topic....but at least I'm not selling shoes and it is
>> > engineering of a sort.

>>

>> > I have a good friend who has several modern vehicles and even more
>> > older ones (pre-war Austins). Said friend is getting married soon and I
>> > thought of giving them a vehicle-type satnav system as a wedding present.
>> > I
>> > assume these things need 12volts, but I don't know the current draw?

>>

>> > The older cars have six volt systems, without the convenience of
>> > cigar lighter sockets. Would it be feasible to run a decent GPS system
>> > off
>> > a (12v by 12Amp/hour?) sealed lead acid battery, the sort of things used
>> > in
>> > a burglar alarm system? I'm imagining a small brick-sized battery on the
>> > floor of the car, couple of spade connectors to a cable which terminates
>> > in
>> > a cigar lighter-type socket and I've got a system which is portable
>> > between
>> > vehicles.......or have I?
>> > --

>>

>> > Chris Edwards (in deepest Dorset) "....there *must* be an easier
>> > way!"

>>
>> TomToms run of regulated 5V ( built into the cigar adapter.) If you build a
>> 5V Low Dropout regulator then the 6V will be fine. This is only really
>> needed for charging the TomTom although it will drive the TT if connected.
>> My advice, start the car and then connect the TomTom supply.The regulator
>> may not like Load Dumping! The TomTom will happily run a few hours on its
>> internal Lithium cell. When almost flat, the Lithium will draw 1- 1.5 amps
>> from the external 5V supply.
>> Hope that helps.- Hide quoted text -
>>
>> - Show quoted text -

>
>Greetings Chris,
> Having reached the age to claim both 6v and
>ancient cars, wasn't the other question -polarity?
>
>Regards
>
>Norm

Sorry Norman....I don't understand your point about polarity? I'm
getting some good stuff by way of response, but since I barely know a watt
from a widget I'm still absorbing all the advice being offered. I assume
any incoming advice re 6v car battery use would apply equally to my idea of
a self-contained, stand alone system using a small sealed lead-acid battery
for use when installed in the Austins? I must ask Bob Minchin about that
later.

Keep taking the tablets
--

Chris Edwards (in deepest Dorset) "....there *must* be an easier way!"

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