Ammeter

[RoyC]

When converting to 12v from 6v does the ammeter have to be changed to a 12v ammeter ?

[a101960]

When converting to 12v from 6v does the ammeter have to be changed to a 12v ammeter ?

No your present ammeter will work perfectly well if you convert to 12v. Horn will be O.K. too, all you need to change are the lamps.

[RoyC]

When converting to 12v from 6v does the ammeter have to be changed to a 12v ammeter ?

No your present ammeter will work perfectly well if you convert to 12v. Horn will be O.K. too, all you need to change are the lamps.

Thanks for that. Only asked because mine never moves (all LED bulbs including headlight).

[a101960]

Only asked because mine never moves (all LED bulbs including headlight).

Worry not. That is exactly what happens with my set up  (12v and all lamps LED) in fact I rarely see the ammeter pointer move unless I blip the throttle. With main beam switched on plus tail light, speedo and rev counter lamps and even if I also operate the brake light I do not see any movement. The battery is being charged though. You need to bare in mind that the current drain is so low that for all practical purposes the battery is fully charged at all times which is why you see no ammeter pointer deflection. Just to reassure yourself that everything is working O.K. just blip the throttle and you will see the pointer move to the plus side.

[RogerSB]

Also your 6v horn will be noticeably louder with 12v

[RoyC]

Also your 6v horn will be noticeably louder with 12v

It sure is.

[stanwhite]

I don't know if there is an ammeter that has a lower full scale current that the one we have on our 6V bikes, but if there is, it could reasonably be called a "12V" ammeter, even though the voltage is irrelevant...

I have just got my first BSA (A10GF),  and this is my first post...  Been reading plenty though...! Great forum.

Right now, my ammeter does not move in a positive direction, but it does show a discharge. Then I did the "bulb test" with the dynamo, and that was fine. When the new reg shows up, it will be neg earth.... I changed the battery, ammeter, and polarised the dynamo already...

Look forward to contributing further,

 Regards,

 Stan.

[duTch]

 I like stans' logic; I had a 30A meter that I finally figured to be from a Massey Ferguson Tractor- nice brass body, but not much use because of our needs.

 I found a -8/+8 cheapie at a swappie, and much more readable; so much so that it tells me everything I don't need to know.....I just installed a new L.E.D headlight insert and the meter now tells me all kinds of stuff, but at the end of the journey, if the light still shows me the road and the battery isn't dead, I guess I'm happy no matter what the Ammeter had for dinner-or who with ....
 

[muskrat]

Yep my ammeter hasn't worked for years on the plunger. Running electronic ignition I soon get a message if the dynamo stops working. The engine dies when I use the rear brake (light) so I can get another 20-30 miles before she stops.
Cheers

[stanwhite]

I figure an ammeter can be quite useful. But understanding what it is telling you can be fun!

Consider:

A constant very high charge rate probably means a failed regulator. You are going to boil the battery/fry the dynamo.

A constant moderate charge rate. Good battery needing a charge. Poor battery getting overcharged. (One failed cell?)

A constant very low charge rate is a good sign... 

Constant slight discharge. You are not riding quick enough!

Heavy discharge with lights on. Generator or regulator has failed.

Ammeter never moves whatever you do. Ammeter is broken 

Lights gone dim, horn now silent. Maybe you should have checked the ammeter once in a while.

An excursion into the hedge: You paid too much attention to the ammeter!   

I am LOVIN' my '61 A10GF, had it six weeks. Haven't looked at the ammeter on the move, I can't screw my head that far over    And the battery went flat   New regulator on the way...

 Regards,

 Stan.

[stanwhite]

It is a pity that the ammeters work exactly as designed/calibrated.

What would be nice would be an ammeter that is very sensitive, say 0.1 amps or less for full scale deflection. But with a scale to suit the system (e.g. for 6V, 8-0-8).

Why? Well that would be pretty useless, even the smallest load would cause the meter to go "off scale" and probably get damaged. But...

You then place a "shunt" across the ammeter terminals. Most of the current goes through the shunt, leaving just a little to move the pointer.

You may wonder what the point of that is. If you were able to do that, you would find that the meter is now "damped" nicely, and you would not be wondering how to keep it full of oil to achieve the same result.

If you have an analogue test meter (one with a needle!), set it to a current range and swing the meter around. You will see the needle moving around quite a lot. Now connect the test leads together (you just "shunted" the meter), and wave it around again. There is a lot less needle movement. A decent meter will have an "off" position. Which shunts the movement, preventing damage in transit. Our ammeters are never in transit, are they? 

You can always increase the full scale reading of an ammeter, just by "shunting" it. Suppose you had a very large alternator on your bike (Really? !!!) and it "over-ran" the existing ammeter, but you wanted to retain that ammeter. All you have to do is run a length of wire from one ammeter terminal to the other, "shorting it out". But a long length of wire will not actually short it out, some of the current will go through the wire, and some through the ammeter. YMMV...  (Or your wire length may vary!).

 My 1978 Kawasaki Z1R has an ammeter, and it is very stable. The meter is quite sensitive. The "shunt" is a length of wire in the wiring loom, and most of the current flows through this.

So, increasing the amount of current an ammeter can handle before the needle gets bent is easy. Making it move further for less current is not. 

Incidentally, if your ammeter does not quite show zero (dead centre) with everything off, (and it worries you!), a small magnet strategically placed will probably get the needle where you would like it. I did that with my Z1R ammeter. Yes...  It worried me!

Now stop worrying about your ammeter, and get out riding 

Regards,

 Stan.

[groily]

And when the eyes start to pack up, you can't read the darn thing easily anyway!

The 2 inch Miller white-faced jobs are a lot easier for, er, older people, if you don't mind making a bigger 'ole in the h'lamp shell or whatever. AND they are rock steady, usually. They're what I have on the A and a couple of other bikes and I like them well.
Those LED gizmos discussed on here a few weeks back are pretty handy too.
 As a kid, I was brought up to think there are only 2 really worthwhile instruments on any vehicle - oil pressure gauge if fitted  . . . and the ammeter. Wouldn't be without one myself, especially with battery/coil ignition.

[stanwhite]

Oh..  The eyes have gone already. But my ammeter does now go positive. The new regulator showed up today. Just been out riding, "ricked my neck", and discovered that it is only balanced around 45-50mph.

I have got a few ideas I am going to try to help that, and no, not a 12V conversion, not an alternator, and not a drive chain upgrade for more dynamo rpm. And no, I am not going to elaborate until I have proved the point. Parts on order