Topic: Wiring in an Amp Gauge

[Steelo]

Can someone tell me the best locations to wire a permanent Ammeter onto my bike. What wires do I splice or connect the two wires too. Thanks in anticipation!!!

[Bob Wessner]

Take a look at this http://www.motorcycleproject.com/motorcycle/text/ammeter.html. I considered one myself, but I've never found one dimensionally small enough with the correct range of values. Have you found one?

I wouldn't ever cut into the bike anywhere to mount one, but thought perhaps a thin plate bolted under the bar clamp or something. Since I have yet to find a suitable gauge, the thought process hasn't gone very far.

[SD750F]

Steelo,

You will have two options depending on your intended purpose. Are you looking at your entire power budget or are you wanting to monitor your battery charge only?

To monitor your battery charge place the meter in line with the regulator output that attaches to the battery positive terminal. And if you want to monitor your bikes load/budget, then attach the meter on your switched power out of your key switch.

Scott

[Raul CB750K1]

I don't support putting an ammeter in line with anything. We are talking about high amperages, and inserting a metering device means new connections -resistance- and decreased wire section -more resistance-

To my understanding, the only real need for an ammeter in a vehicle is to check wether the battery is charging or discharging, because it really doesn't make much difference for the driver to know if the charging rate is 5 amps or 6 amps.

For those who doesn't know, an ammeter is just a voltmeter that reads the voltage drop on a resistor of a known value, that is integrated inside the instrument. That resistor is known as shunt.

Take you have a needle instrument with a 20 v maximum reading. Now you get a 1 ohm resistor, and connect the voltmeter in parallel with it. Now you have one ammeter. If there is a current of 3 amp across the resistor, the voltage drop will be 3 volt, and the instrument will read "3". You need to know that the reading is amps not volts.

Obviously, if the shunt resistor value is not a factor of 1, the reading will not be accurate -you cant just replace "volts" by "amps". You can overcome that by changing the instrument face with the new scale. You have to take into account that there will be a high current across the resistor, so it will have to withstand high power -in our case, a maximum of 20 wats-

There is a simple way to do what you want. Get a voltmeter, and put one lead on the battery negative connection, and another lead in the other end of the battery ground cable, where it bolts to the frame. Start the bike and read the voltage. The starter motor is by far the device that sucks the more current. As the ground cable has some resistance, you are reading how much voltage drops in the cable. Now you only need an instrument whose full scale value is around what you have read. You will need a centered-needle instrument, because the current in the ground cable goes both ways, either charging or discharging, and therefore the voltage in the cable will read positive or negative.


I wouldn't use a needle instrument in a bike, they are way too delicate and the vibration will harm them. But you probably can find one of those cool led bar voltmeters.


Raul

[vames]

Problem with an ammeter is that it has to be "in line," or getting the full flow of what you are measuring going through it - ie between the battery and the regulator output, unlike a volt meter which just "touches" the wiring at two points and measures the difference in potential. That means for the ammeter, you will have to take the whole load electrical output, divert it from the harness, run it up to your instrument, then back into the harness. Adding all that wire will tax the output, create more opportunities for shorts, etc.

Ask the owner of any old dodge or other mopar - they used to put ammeters in for some reason, and the full output of the alternator would then have to be wired to the dash, then back to the fuse block, then distributed. It created lots of high-power junctions and plugs which melted over time and caused untold numbers of charing problems. It's a big frustration of the mopar set. Like  my 72 Dart, most have since spliced the ammeter out of the system and put in a volt meter, which is far less obtrusive and gives just as much of a indication of whether you are charging or discharging the battery.

So I say go for a volt meter.

[Bob Wessner]

OK, maybe it's not such good idea.

[crazypj]

Its a good idea to check charging amps though.
 Easiest way to do it is get a blown fuse (if you have the 1" glass fuses) solder wire to each end, (or use alligator clips on wire ends) connect to 30-0-30 ammeter and fit in place of main fuse (if you fit it backwards it shows positive when engine stopped) You could use same method for permanent fitting but with inline fuse on supply end, it will show what your really getting, including all the voltage drops, etc
BTW, Honda now recommends using ammeters as well as voltmeters as they are measuring differently (Suzuki has always recommended using amps/volts test)
 You can use 19.1" of 8 gauge wire as a shunt and measure in millivolts DC from one end to other for direct reading of amps (actual length doesn't matter as long as measuring points are 19.1" apart)
You will only need 15 Amp ammeter as thats all the main fuse is rated for but smallest reading I've seen 30-0-30 in auto supply shops (Pep-Boys,Autozone, etc)
PJ

[SD750F]

The ammeter that was listed in the first reply is a typical aircraft style meter. And they have been wired depending on the aircraft, in line or series in lower current systems or in parallel by using a shunt resistor producing a calculated voltage drop per amp.

And to add to the other replies, a voltage meter which is a extremely low current tap can provide a fairly good sense of your battery condition. Something to consider? Look here: http://www.kuryakyn.com/products.asp?bn=metric&ci=2695

Scott

[TwoTired]

Assumptions:  (Being made because the initial problem statement did not include thorough data.)

1. The bike you are referring to is the one in your avatar.
2.  It still resembles the wire diagram on page 264 of the Honda shop manual.
3. You wish to monitor whether the battery is receiving or depleting it's charge.
4.  You have an ammeter with about a 15-20 amp range and can measure positive and negative current flow. (you didn't say if you already had an ammeter.)

At the starter solenoid there connects a big ole fat cable that goes to the POS battery terminal.
At the same junction is a smaller ring terminal with a nearby two prong connector having Red and Red/White wires.
Apart from the starter motor draw (150 Amps), the small wire ring lug terminal carries all the load from the battery as well as the charging current into it.
If you remove that ring lug and insert your ammeter shunt (internal to meter or external), you will monitor all the current leaving or entering the battery (except the starter draw that would peg/smoke a 20 amp needle movement).  It's the only place on the diagram where two-way current can be monitored.  The main fuse is only the bike load, not charging current.
Do insulate the inserted meter connections well from touching any other bike components, as this portion is not fused and will draw current until conductors are melted or the battery depletes.

I agree with others that an expanded scale voltmeter offers all the info you need without breaking into the current delivery paths of the bike.  But, it is indirect as you have to infer charging or discharging by watching the volt level and interpreting voltage change trends.  This makes it a bit more attention diverting than an ammeter which is an AT-A-GLANCE indicator.
To elaborate, the Voltmeter is a battery state indicator.  And the Ammeter is a status change indicator.

Cheers,

[RRRToolSolutions]

Voltmeters are the ultimate charging system indicator. I do a lot of boating and have for almost 40 years. My dual Group 30 deep-cycle fishing batteries run close to $200 each.  I monitor battery charge constantly and I've always had a voltmeter installed - heres why -

1) Turn the switch on and it should read 12.5~12.8 volts with all accessories "off".
   A) if not, the battery needs charging due to non-use, low water, or faulty charging.
   B) if so - the entire system is probably good (note 12.8 volts is 100% of full charge)

2) Start engine and it should read 12~13 volts at idle and then to 14.5~15.5 at anything above 3,000 rpm.
   A) if not, then there is a charging problem (system or battery)
   B) if accesories use drops the votage below 12.8 volts, you are discharging (pulling from the battery) and can indicate a weak charging system or damaged components elsewhere in the system.
   C) if the full 15.5 volts is achieved while running after a long ride and the bike shows 12.8 ~13.2 volts with engine off - this is absolutely normal. If the voltage drops to below 12.4 volts in 2 hours or less - then it indicates a battery low on water or one with sulfated plates.

Batteries will normally lose .5 volts per month sitting. Sitting and discharged state is the #1 killer of batteries. The lead plates that are responsible for the exchange of current with the surrounding sulfuric acid get "sulfated" or coated with deposits and will never re-gain their ability to exchange current once sulfating occurs. The one and only way to prevent sulfating is to keep those batteries fully charged.

For my bikes, I have a small, automatic trickle charger that has a plug-in terminal. I then have pigtales on every bike in my garage that allows me to keep them charged. It's essential and it's a simple plug in affair. Let's see - once monthly, .5 volts lost per month overnight and I'm good at 12.4 volts average.

No, not a single bike I own has a voltmeter mounted, but it's an excellent idea. My boats won't kick-start or puch-off and the fear of getting in open water without starting power keeps me in tune with battery and charging conditions. I do that on the bikes using my Fluke meter, but a simple gauge would be a smart and cost effective addition to any bike.

Regards,
Gordon     

[oldfart]

Not only the best, but the only way to install an ammeter is to separate the red and red/white wires from the red where they meet at the battery and put the ammeter between these two points.   Refer to the image above.  With this connection, you get needle movement both ways, which is the point.  Contrary to what is said, this requires only the separation of the red/white & red from the red, an easy and clean (and reversible) task.

A lot of bad advice being given re ammeters, I'm afraid, nothing personal intended.  I'll address a couple things said.  First, unlike many other things on these old bikes, such as the inherent 1 volt drop at the ignition coils due to resistance, there is absolutely no resistance issue with installing an ammeter.  The internal shunt is thick metal, no connectors to worry about. 

Second, aammeter is worlds better than a voltmeter for monitoring charge to the battery.  That's because charge is amps, it is not volts.  Volts is only the end result of charge, not he charge itself.

Third, the advice to wire the ammeter at the main fuse is helpful, but unfortunately this will not work for some motorcycles, notably the CB750 having the mechanical regulator.  The wiring is some different between the mechanical regulator and electronic regulator CB750.   

Lastly, ammeters were once the accepted standard.  They fell into disfavor because the average motorist didn't like the wiggling needle, and because like people all over today, folks tend to prefer to be told what they did wrong after the fact, not how to prevent it from happening in the first place.  Human nature gravitating to its baser level. 

[dusterdude]

Problem with an ammeter is that it has to be "in line," or getting the full flow of what you are measuring going through it - ie between the battery and the regulator output, unlike a volt meter which just "touches" the wiring at two points and measures the difference in potential. That means for the ammeter, you will have to take the whole load electrical output, divert it from the harness, run it up to your instrument, then back into the harness. Adding all that wire will tax the output, create more opportunities for shorts, etc.

Ask the owner of any old dodge or other mopar - they used to put ammeters in for some reason, and the full output of the alternator would then have to be wired to the dash, then back to the fuse block, then distributed. It created lots of high-power junctions and plugs which melted over time and caused untold numbers of charing problems. It's a big frustration of the mopar set. Like  my 72 Dart, most have since spliced the ammeter out of the system and put in a volt meter, which is far less obtrusive and gives just as much of a indication of whether you are charging or discharging the battery.

So I say go for a volt meter.

durn tootin,melted my truck cause of that bs

[Steelo]

Mike Nixon you might be an "OldFart" but you are a legend as well! I fitted my ammeter today using your wiring diagram and everything is good with the world!
Thanks for the help  

http://www.motorcycleproject.com/motorcycle/text/ammeter.html

[Bob Wessner]

What did you use for the ammeter housing?

[Steelo]

I used a 2" plastic gauge housing I bought off ebay. Then I made a bush using pvc reticulation bushes to reduce the opening to the size of the guage. Smoothed off the union and painted with flat black. Press fits into the housing sweet!

I also made a bracket to go between the two dome nuts on the Tacho and Speedo with a lug to attach the gauge housing.