Battery light reliability - PeachParts Mercedes-Benz Forum

Mxfrank · #1 03-31-2020, 09:15 AM

Quote:

Originally Posted by 5cylinder

This looks like something that might be useful to me.
If you're willing, could you please elaborate on the part(s) that you installed and how you did the wiring? Thanks-

This really isn't a big deal. Any generic voltmeter with a suitable range will do the job. Drill a suitable hole and mount it in the dash. The one in the photo came from a direct-from-China seller on Ebay. This is a similar example:

https://www.ebay.com/itm/LED-Digital-Display-Voltmeter-Car-Motorcycle-Voltage-Volt-Gauge-Panel-Meter-12V/382624102408?hash=item59162c7808:m:mjOteNyJ32wi3AcLHzv4Mzw

A voltmeter has two wires: one goes to any ground, the other goes to any switched 12V source, I think I used the lighter wire for this installation. If you want to be anal, you could run wires all the way to the battery, but it's not really necessary.

As far as reading it. A fully charged battery reads 12.5V. Above 13V means the alternator is charging. Bosch alternators are usually regulated to 14.25V @70F. They will vary from 13.5V to 15V depending on operating temperature. If the reading drops below 12.5V, it means the battery is discharging. There are extreme conditions when this may be ok: idling for a time with the headlights, wiper and heater on, for example. So much more information that you get from an idiot light.

5cylinder · #2 03-31-2020, 11:53 AM

Quote:

Originally Posted by Mxfrank

This really isn't a big deal. Any generic voltmeter with a suitable range will do the job. Drill a suitable hole and mount it in the dash. The one in the photo came from a direct-from-China seller on Ebay. This is a similar example:

https://www.ebay.com/itm/LED-Digital-Display-Voltmeter-Car-Motorcycle-Voltage-Volt-Gauge-Panel-Meter-12V/382624102408?hash=item59162c7808:m:mjOteNyJ32wi3AcLHzv4Mzw

A voltmeter has two wires: one goes to any ground, the other goes to any switched 12V source, I think I used the lighter wire for this installation. If you want to be anal, you could run wires all the way to the battery, but it's not really necessary.

As far as reading it. A fully charged battery reads 12.5V. Above 13V means the alternator is charging. Bosch alternators are usually regulated to 14.25V @70F. They will vary from 13.5V to 15V depending on operating temperature. If the reading drops below 12.5V, it means the battery is discharging. There are extreme conditions when this may be ok: idling for a time with the headlights, wiper and heater on, for example. So much more information that you get from an idiot light.

Truly, I sincerely appreciate your willingness to share not only the details of the kind of part and wiring, but also the proper way to read the information.

This will be a nice project for me. Thank you!

Usaguy · #3 03-31-2020, 07:58 PM

Thanks everyone for your responses.

I wonder how hard it would be to either buy or make an electronic circuit that would trigger a buzzer or a warning light when voltage drops below 13V ?

would work better than a voltmeter because you wouldn't have to look down and you would know instantly.

vwnate1 · #4 04-01-2020, 01:35 PM

Thanx Frank ;

I don't see what size hole it requires....

The colors thing is nice but, blue isn't so easy to read at night when there's ambient light around...

BT, DT and wasn't pleased .

Too bad they don't make this round one in 6 ~ 24 volts, it'd be very handy for vintage vehicles and ex military with 24 VDC systems .

-Nate

Quote:

Originally Posted by Mxfrank

This really isn't a big deal. Any generic voltmeter with a suitable range will do the job. Drill a suitable hole and mount it in the dash. The one in the photo came from a direct-from-China seller on Ebay. This is a similar example:

https://www.ebay.com/itm/LED-Digital-Display-Voltmeter-Car-Motorcycle-Voltage-Volt-Gauge-Panel-Meter-12V/382624102408?hash=item59162c7808:m:mjOteNyJ32wi3AcLHzv4Mzw

A voltmeter has two wires: one goes to any ground, the other goes to any switched 12V source, I think I used the lighter wire for this installation. If you want to be anal, you could run wires all the way to the battery, but it's not really necessary.

As far as reading it. A fully charged battery reads 12.5V. Above 13V means the alternator is charging. Bosch alternators are usually regulated to 14.25V @70F. They will vary from 13.5V to 15V depending on operating temperature. If the reading drops below 12.5V, it means the battery is discharging. There are extreme conditions when this may be ok: idling for a time with the headlights, wiper and heater on, for example. So much more information that you get from an idiot light.

5cylinder · #5 04-01-2020, 02:55 PM

Quote:

Originally Posted by Mxfrank

A voltmeter has two wires: one goes to any ground, the other goes to any switched 12V source, I think I used the lighter wire for this installation. If you want to be anal, you could run wires all the way to the battery, but it's not really necessary.

As far as reading it. A fully charged battery reads 12.5V. Above 13V means the alternator is charging. Bosch alternators are usually regulated to 14.25V @70F. They will vary from 13.5V to 15V depending on operating temperature. If the reading drops below 12.5V, it means the battery is discharging. There are extreme conditions when this may be ok: idling for a time with the headlights, wiper and heater on, for example. So much more information that you get from an idiot light.

Any opinions about the usefulness of a display that in addition to current (voltage), also displays amperage?

Thanks-