Triumphrat

06-16-2005

1969 T100 Daytona

How does one use a v/ohm meter to check if the system is charging?

ArmyBonnie · 06-16-2005

John Healy, a renowned Boston area Triumph Dealer for over 30 years gave an impressive tech session on battery charging...basically you need to find out how the system charges UNDER LOAD...ie. with the lights, turn signals, high beams etc...

If you just plug a voltmeter to the battery, almost all of them will say 12v or so...it's under a load when the battery will give you trouble b/c the load might take it under the 9 or so volts required to run through the rectifier...

So, unless the battery is brand new, he said that most of the problems are from batteries that have enough life left in them to start out, but die out and/or won't recharge under load.

If the battery is not new, take it to a Harley dealer or a local dealer with a battery tester capable of testing it under a high motorcycle amp load...

If that checks out, then its a hunt and peck with a test light to see if you have any connections that might be leaking...(ie. additional resistance)...

Hope this helps...

Frank

Paul · 06-16-2005

Frank is about got it. But, you can get an inductive pick up ammeter and lay it across the battery cable (doesn't matter which one). You should read an output about equal to specification with the engine at about 2 grand.
What Frank talks about is a load tester, in which you load the system through a carbon pile, holding the revs to about 2,000. The load should be increased until the voltage is 12, and at that point the amperage should match specifications. Many shops have these load testers, but I have to say that in many years of teaching auto electrics for a major manufacturer, I never once met a tech who used the machine the way it was designed to be used. In the case of our bikes, the lights would have to be turned off while this test is being run.
But Frank is correct that voltage is meaningless information; it's amperage that counts.

Diego · 06-16-2005

A really basic test is this: if a good lead-acid battery (not excessively discharged and no shorted cells) has not been under charge or under load for a day or so, it will have a resting voltage of about 12.6V right on its terminals. That by itself is no indication of the condition of the battery or charging system. However, after you start the engine and bring it up to high enough rpm to give a bit of charge, that voltage will be higher than the resting voltage by a good volt or two. (Again, right at the battery terminals themselves, not the electrical lugs that connect to the terminals.) It should not vary much as you switch the headlights, apply the brakes, etc.

That's not a thorough test of the electrical system, but it provides basic confirmation that at least some charging is taking place.

rickykarate99 · 06-17-2005

I've heard rumors / urban legend that motorcycle generators really only charge the battery if you're over 5,000 rpm or so. Any lower rpm and you're draining more juice than you're charging, says the rumor. I don't buy it -- otherwise, how would any Harley ever charge? Is there any truth to this?

Shorty · 06-17-2005

With a digital VOM I read approx. 14.2 volts with the bike running. To check, simply put your test leads across the battery terminals and verify that the battery reads approx 12.6 volts (bike not running). Start the bike and then check the voltage across the terminals again (you should read high 13 plus volts to low 14 plus) As stated in the above comments, to check the condition of your battery it really needs to be under a load. VOM's have such high impedance that they will not load the battery / charging system by themselves.
They do make inexpensive battery checkers which actually provide a load with internal resistors and these can be bought at various auto part supply houses, but they are limited on current also.
I use an inductive type clamp-on attachment in conjunction with my digital voltmeter (clamped around one of the battery leads) to see how much current my bike is actually drawing under operating conditions.

Shorty

[ This message was edited by: Shorty on 2005-06-17 08:07 ]

Gohm · 06-17-2005

Quote:

On 2005-06-17 00:23, rickykarate99 wrote:
I've heard rumors / urban legend that motorcycle generators really only charge the battery if you're over 5,000 rpm or so. Any lower rpm and you're draining more juice than you're charging, says the rumor. I don't buy it -- otherwise, how would any Harley ever charge? Is there any truth to this?

I know that is partially true for some bikes (that I've had) not sure all though (I think it depends more on the rev range, not 5,000 the number). All motorcycles have minimal capacity systems. Several of my bikes needed to be in the 5,000 rpm range to charge, though they were fairly high revving. However, running lower than that doesn't drain the battery, you use what you generate( unless you have a cup warmer,electric toothbrush,etc. installed ). Starting/lights only will drain the battery though.

bmwhd · 06-21-2005

An easy fix for peace of mind is to pick up an LED battery condition indicator from electricalconnection.com and mount it on the dash. I did this on my TBA. Green means good, red means bad. Very simple.