Ammeter, But How And Why?

[Bikerholic]

I have just install a Voltmeter and I've read; a Ammeter is needed to fully benefit from a Voltmeter.

Q: Why Ammeter should be install along with a Voltmeter? What's the benefit and why Voltmeter alone isn't enough?

I always thought, a low voltmeter reading (< 12.3v) indicate a "low" battery and a precursor to a battery replacement. :fing02:

Q: Installing an Ammeter:

Where to tap? Battery or the RR?

If RR: am i correct to tap off the output plug, yellow wire? (Maintenance Manual / Charging system / System diagram)

What output value should i look for on the Ammeter and why?

I am assuming i need to look for 38 to 40 AMPs, but if i see 20AMPs, then what? :rolleyes:

Does it meant my alternator isn't able to create the needed charges, should start looking into replacing the stator?

What is the total power output for a 02 VFR.

From the maintenance manual, it indicated the alternator capacity 0.47 KW/5k RPM.

Does this mean the total power outputs is 12v/470W or 39 to 40 AMP? How much power does the bike need to operate and how much is available for accessory?

So, is it safe to say, Voltmeter reads off the battery and gives me condition of the battery and give me clue or symptom to possible electrical problem when present. Ammeter read off the bike's electrical output, give me condition of the running electrical output (5kRPM)

Last Question: Fusebox's ground connection: :fing02:

Battery or Chassis?

I install the fusebox ground to the Chassis. I assume a ground is a ground. as long as i completed the circuit.

I have some minor understanding of how electrical system work, all self taught. Please excuse me for my ignorance. I know Amp, Volt and Watt is just like a triangle. With information on just 2 parts will get me the answer to the third and I also have a Fluke Multimeter and not afraid to use it.

(Just in case i was misunderstood: Installed on Bike is a Tightwad Voltmeter and Fluke is what I have in my crash kit)

Big Thanks in Advance. :goofy:

[Tightwad]

I can't imagine why an Ammeter is needed. Volt meter will give you all the info you should need generally. If you see less than nominal battery voltage then your system isn't producing enough Amps to cover the needs of the bike.

[IntAceptor]

A voltmeter is the first item in a line of defense. It alone will often do the job in troubleshooting a problem but it is also sometimes somewhat misunderstood.

A good voltmeter, like most Flukes, offer a very high input resistances (impedance) which in this case is good. It "disturbs" the circuit being measured very little, if at all. It placed in parallel with the device being measured and must share a little current to get it to work but because the input resistance is so high, it takes a negligible amount away from that device in order to operate.

I once had a battery fail while 700 miles from home. My voltmeter read that the battery was good because I got a full voltage reading on it. What actually happened was that the battery contacts open circuited internally but the voltmeter was getting a reading through the electrolyte in the battery even though there was no physical contact with the lead plates. The reason was because the meter needed such a small amount of current to give me a reading that the battery electrolyte provided it and if I was not experienced, I could have easily had a very difficult time with that one. The give away was that even though all fuses were good, nothing else worked because the battery could not provide the current needed to make things, that demanded way more current than the voltmeter, operate. A current meter would have displayed no reading in that case.

The main fuse on your bike is 30 amps. This means if all is proper, a current draw of 30 amps or more will blow that fuse. The total operating current has to be less than 30 amps because all the current that the bike and accessories draw goes through that fuse even though your diagram does not show this. Generally, but not always, a circuit is fused between the 50 and 70% of its total capacity.

The alternator capacity is higher than the actual current drawn by the bike. Remember, it feeds directly into the R/R and has to have the ability to charge the battery by providing more power than is being called for out of the battery. The R/R actually is the major player in the circuit and the battery, while being charged as you go, looks like a large capacitor across the entire circuit to dampen voltage spikes and smooth out any voltage spikes that the alternator produces. The regulator part tries to keep the voltage output within a specific range, not over or under the range but in theory, a bit more than the battery voltage. All the undeed power from the alternator is passed off to ground in the R/R and develops a lot of heat. That is why a good heat sink is needed and why the R/R fails as often as it does when not cooled via fan or larger heat sink.

The best ground is at the battery and over the years, we have found the importance of a good ground connection on our VFR's. A solid and clean ground on the chassis should be good. The battery itself is grounded to the rear of the engine if I remember correctly. If not, someone will correct that statement real quick. :biggrin: But there is just not enough room to ground everything at the battery so chassis grounds take over.

A true amp meter should be connected in series with the output of the R/R and show the full current being drawn by the entire bike. If not done using the proper gage wire, it could actually drag down the overall current and voltage output with losses. I would not put one in unless absolutely needed for troubleshooting purposes.

[Bikerholic]

"A voltmeter is the first item in a line of defense. It alone will often do the job in troubleshooting a problem but it is also sometimes somewhat misunderstood.

A good voltmeter, like most Flukes, offer a very high input resistances (impedance) which in this case is good. It "disturbs" the circuit being measured very little, if at all. It placed in parallel with the device being measured and must share a little current to get it to work but because the input resistance is so high, it takes a negligible amount away from that device in order to operate......."

To IntAceptor

Thank you very much for the detail explanation and crash course on electrical in general. :biggrin:

From your writing; I now understand a Ammeter is a "nice to have", but not necessary worth the trouble of putting it in. A Voltmeter should give me all the necessary warning if used properly in conjunction with a more accurate handheld unit.

30A is my main fuse, bike put out 39-40A. I have more or less 10A to play with.

Ground to Negative Terminal is always best, but chassis will work as second best.

Presently, I have tapped the power straight from the battery to the fuse box then output through a relay than to my accessory (2 relays in total, Stebel and Voltmeter). Since i only have 10A to use. I will moved the 30A relay back near the battery and a inline fuse will be placed before that, outputting to the fusebox.

Thank you.

[bear22099]

"A voltmeter is the first item in a line of defense. It alone will often do the job in troubleshooting a problem but it is also sometimes somewhat misunderstood.

A good voltmeter, like most Flukes, offer a very high input resistances (impedance) which in this case is good. It "disturbs" the circuit being measured very little, if at all. It placed in parallel with the device being measured and must share a little current to get it to work but because the input resistance is so high, it takes a negligible amount away from that device in order to operate......."

To IntAceptor

Thank you very much for the detail explanation and crash course on electrical in general. :biggrin:

From your writing; I now understand a Ammeter is a "nice to have", but not necessary worth the trouble of putting it in. A Voltmeter should give me all the necessary warning if used properly in conjunction with a more accurate handheld unit.

30A is my main fuse, bike put out 39-40A. I have more or less 10A to play with.

Ground to Negative Terminal is always best, but chassis will work as second best.

Presently, I have tapped the power straight from the battery to the fuse box then output through a relay than to my accessory (2 relays in total, Stebel and Voltmeter). Since i only have 10A to use. I will moved the 30A relay back near the battery and a inline fuse will be placed before that, outputting to the fusebox.

Thank you.

You have 30 amps to "play" with, if using the original spec main fuse. If the charging system can put out 40 amps, it will blow that fuse. You are also forgetting that the 470 watts is not at 12 volts, it is at about 14 volts. That reduces the amperage to 33 amps at peak output.

[Bikerholic]

You have 30 amps to "play" with, if using the original spec main fuse. If the charging system can put out 40 amps, it will blow that fuse. You are also forgetting that the 470 watts is not at 12 volts, it is at about 14 volts. That reduces the amperage to 33 amps at peak output.

To bear22099

Please clarify?

I though I have 10 amps only, what do you mean by "30 amps to play with" and "original spec main fuse"? I though if I wired my (BlueSea) auxiliary fusebox right off the battery, I can used no more than "extra" unused current without negative effect on the overall integrity of the system. For just this discussion sakes (not actual spec number), Charging system put out 40 A, bike uses 30 A, than only 10 A is left. This 10 A represent the additional load i can place on the electrical system.

Am i correct? :biggrin:

[bear22099]

You have 30 amps to "play" with, if using the original spec main fuse. If the charging system can put out 40 amps, it will blow that fuse. You are also forgetting that the 470 watts is not at 12 volts, it is at about 14 volts. That reduces the amperage to 33 amps at peak output.

Please clarify?

I though I have 10 amps only, what do you mean by original spec main fuse? I though if I wired my (BlueSea) auxiliary fusebox right off the battery, I can used no more than "extra" unused current without negative effect on the overall integrity of the system. For just this discussion sakes (not actual spec number), Charging system put out 40 A, bike uses 30 A, than only 10 A is left. This 10 A represent the additional load i can place on the electrical system.

Am i correct?

No. What you actually use is what the battery can supply (and stock that is through the main fuse, the 30amp one, Honda has figured that the most all the stock accessories will ever draw is about 75% of that number). The charging system will replenish the battery best it can.

Your bike does not draw a constant 30 amps. That is the max it is allowed to draw at any one time through that fuse. The fuse does not maintain the current or set the current, it limits it. At anyone time your bike may only be "using" 10 amps of current. That does not mean you have 30 amps left to play with. That simply means that your bike is only requiring 10 amps at that specific time. You are thinking that the max output of the alt is all you have, when you actually have the max output of the battery. If you use more power than the alt can provide for long enough a period of time, the battery will not be charged back up, it will be drained.

It is easier to think of it as you run off the battery, and the alt recharges or maintains the charge in the battery. I think you are simply thinking of it backwards.

If you are placing a new fuseblock in, you need to figure out what the max draw is you require for all the new accessories you are adding. Then add an additional 25% to safely get the right size fuse. This margin allows for the initial surge some electrical devices create to start up (like motors). You need to pay attention to the total amount you will be using at any one time, and pay attention to how often you wll be using it. You can use a device that draws 50 amps for very short periods of time without causing the bike to quit, the battery will supply it. As a matter of fact, every time you start your bike you are putting that kind of load on it with the starter motor.

[Bikerholic]

"....No. What you actually use is what the battery can supply (and stock that is through the main fuse, the 30amp one, Honda has figured that the most all the stock accessories will ever draw is about 75% of that number). The charging system will replenish the battery best it can. Your bike does not draw a constant 30 amps. .....and pay attention to how often you wll be using it. You can use a device that draws 50 amps for very short

periods of time without causing the bike to quit, the battery will supply it. As a matter of fact, every time you start your bike you are putting that kind of load on it with the starter motor...."

Now I think I got it: My electrical load limits isn't dictated by the alternator/charging output, but by the battery itself and what it is capable of outputting.

So my available "play" current isn't really 10Amp or even anything close if it is a constant draw on the system. The accessory will get it's power from the battery and the battery will be recharged by the alternator/stator. And the recharging capacity is 0.47KM/470Watts @ 5000RPM. I will still able to run accessory at above 30A (including bike itself), just not constant, otherwise the charging system wouldn't be able to "catch up" and recharge the battery. And at anyone time, the bike during normal operation will not draw a constant 30 Amps, but more like 10 ish amps. that is why ones can add so many accessories (with limits).

My fusebox has 10AWG wire from the battery. Should be sufficient for a 30A max draw, but i will not draw that much/high. Also in order to play it safe, i have to be very conservative when i do my current calculation otherwise i might run the risk of draining my battery.

I should also look into minimizing my existing draw on the bike in order to maximize available current, one of the way I know is by switching to LED light (license plate, brake & signal...etc)

Is like have a very frugal parent dishing out allowance. I have to be very selective and careful about how to spend my current off my bike..

So, even with a upgrade RR + High capacity output Alternator/Stator, this would just charged up the battery quicker and wouldn't increase the overall current capacity. For greater capacity, I have to neither increase the battery size or increase the numbers of battery.

Is it dangerous to mix battery types? Lead Acid with lithium or nickel-cadmium batteries. Series them into 12V then parallel into the bike's battery?

Or is it a bad idea, I might get my face covered with ACID...

Now, i am now one step closer to getting my PHD in double EE... hehe

Note to self: Put a on/off switch on all bolt-on electrical accessory: Help reducing initial draw/surge during startup.

Big Thank You to Bear; for willing to explain in detail how this all work, please remind me that I owe you two a cold one :huh: when i see you.. you too InAceptor :biggrin: