Voltmeter & Ammeter

[DC]

oil pressure and voltage gauge

[Phil B]

Already got them in the Scimmy  

[Auto Addict]

Thanks for all the replies, I'm still going to abandon the idea.

[philhoward]

Already got them in the Scimmy  

I preferred the ammeter in my 5 rather than the volmeter in my 5a's...but prefer the 5 dash anyway!

[Taxi_Driver]

I am very interested in how anybody plans to connect an ammeter to a car which takes 200Amps cranking, upto 120 amps when running and still expects to see sub 1 amp draw when its turned off......plus what is proposed to be use as the measuring shunt without affecting the operation of everything!  

Now im guessing a bit here.......but there are 3 wires coming off the + batt terminal.......I assume one is feed to the starter.....one feed from the alternator and the other feed for the accessories.

If the case then you would only need to use the accessories wire.

Something like this would do i guess.....and i notice they do a solid shunt.....would this be better?  :-/

http://www.dpmeters.co.uk/DCDualmeterDPM62VA.htm

I am assuming the meter is auto scaling, if so you could see small a small drain when ign off  :-/

[Bandit127]

I am very interested in how anybody plans to connect an ammeter to a car which takes 200Amps cranking, upto 120 amps when running and still expects to see sub 1 amp draw when its turned off......plus what is proposed to be use as the measuring shunt without affecting the operation of everything!  

A decent shunt resistor between the battry and alternator would give the same info as mini coopers (and others) used to have. Charging current.
http://www.reuk.co.uk/What-is-a-Shunt.htm
No good for stationary current drain though.

I suspect there is a way to hijack the MID/ODBII system - but no idea how. There is probably spare I/O in the ECU though.

Also, armed with an RS catalogue, some Veroboard and a soldering iron you could probably make a small LCD/LED digital unit that would be easier to find space for. The ashtray space comes to mind.

[Taxi_Driver]

I am very interested in how anybody plans to connect an ammeter to a car which takes 200Amps cranking, upto 120 amps when running and still expects to see sub 1 amp draw when its turned off......plus what is proposed to be use as the measuring shunt without affecting the operation of everything!  

A decent shunt resistor between the battry and alternator would give the same info as mini coopers (and others) used to have. Charging current.
http://www.reuk.co.uk/What-is-a-Shunt.htm
No good for stationary current drain though.

I suspect there is a way to hijack the MID/ODBII system - but no idea how. There is probably spare I/O in the ECU though.

Also, armed with an RS catalogue, some Veroboard and a soldering iron you could probably make a small LCD/LED digital unit that would be easier to find space for. The ashtray space comes to mind.

Absolutely  

Thats the reason i mentioned the 3 wires......as said im guessing why the three wires........but if one of them is for accessories.......this wire would do nicely  

[Kevin Wood]

The problem is, you want the measure the battery current in / out not the current consumed by the accessories. You want to ignore the starter motor feed since the huge current this will take is going to be a pain. So, you'd need to separate the alternator and starter connections to the battery (currently a single wire right across the engine bay) and separate the accessories from the starter at the battery and insert a shunt so you're measuring the charge current into / accessory draw from the battery.

All a bit of a pain. You still probably won't measure with enough resolution to spot the 100mA of current that'll flatten your battery because you'll have to make the shunt big enough to measure up to the full alternator output (140 amps in my case).

I have an LED bar graph meter that plugs into the ciggy lighter and instantly shows the voltage, on the other hand. A couple of greens indicates a fully charged battery. Crank it, watching how much drop there is and then watch a few more green lights appear as the alternator wakes up. Turn on some loads and watch for voltage drop. Overcharging? Red light. Tells me all I need to know about the electrical system (which are pretty reliable these days, TBH) without messing about at all.

If I need to know currents, I have a clamp-on ammeter, or a multimeter for tracing small currents.

Kevin

[Auto Addict]

The problem is, you want the measure the battery current in / out not the current consumed by the accessories. You want to ignore the starter motor feed since the huge current this will take is going to be a pain. So, you'd need to separate the alternator and starter connections to the battery (currently a single wire right across the engine bay) and separate the accessories from the starter at the battery and insert a shunt so you're measuring the charge current into / accessory draw from the battery.

All a bit of a pain. You still probably won't measure with enough resolution to spot the 100mA of current that'll flatten your battery because you'll have to make the shunt big enough to measure up to the full alternator output (140 amps in my case).

I have an LED bar graph meter that plugs into the ciggy lighter and instantly shows the voltage, on the other hand. A couple of greens indicates a fully charged battery. Crank it, watching how much drop there is and then watch a few more green lights appear as the alternator wakes up. Turn on some loads and watch for voltage drop. Overcharging? Red light. Tells me all I need to know about the electrical system (which are pretty reliable these days, TBH) without messing about at all.

If I need to know currents, I have a clamp-on ammeter, or a multimeter for tracing small currents.

Kevin

Makes a lot of sense Kevin.