Huge voltage drop! Need diagnosis help

[Jan_P]

Generally speaking on these bikes there is one or two faults at the same time
One is identified the battery.
We dont know if this is cause or effect
If it was a running bike ..I would wait for the battery before doing other things
Paying attention when connecting.
All fuses in

Empty battery ---I would have a sneaking suspicion that the charging fex Regulator can have problems
( one of the situations where one falut can generate more faults )

 

[nj1639]

I know you bought the bike like that with an aftermarket ignition system.......I'll say it galls the hell out of me to see a TCI bike converted.
Convert points to pamco? Yeah, OK.
Convert TCI to anything else? No. No. No.
Rant over, carry on.

 

[jpdevol]

So i just did a little short circuit test using the old battery (didnt want to immediately ruin another one) removing fuses i found that i have one wire running up my tube to my headlight turn signal controls cluster thats got a short on it. fine removed it from the fuse.

still another short somewhere....

found that removing any one of the pamco primaries eliminated the short.

"Short" is short for a power carrying wire that is "short circuiting" to ground before it gets to its load destination - that will blow fuses on that circuit when power is provided. So if it is blowing fuses, then the next step is to disconnect power and isolate sections of the circuit and check continuity to ground with an ohmmeter. Is that what we're talking about?

 

[Paul Sutton]

If you have the voltmeter fitted and have access to another bike battery then just check the voltages when idling and maybe a few other rpms up to 3000rpm. At 2000-3000rpm you should see a voltage of 14.2V or maybe a bit higher like 14.6V. This will confirm the charge system is healthy

I hope you are making progress...


Note 1: Thinking ahead a little when your bike is running happy. I found that H4 bulbs at 55-60W are just too big a load for gentle riding like around town or crusing at 40-50mph on slow roads. I switched to using 35W H4 bulbs which produce approximately the same amount of light as the original sealed beam headlight did. I also set the idle for 1200rpm to minimise battery drain when stopped at lights, or running below 2500rpm.

Note 2: Something I did not know was that a 12V automotive battery is not 12Volts. As pointed out earlier 12Volts can be a close to flat automotive battery. When a motorcycle or car is running the system voltage is about 14.2Volts. Your indicator bulbs may say 12V but they are really designed to run in the 14V range. The following table gives an idea of battery voltage compared to battery charge capacity:

 

[Paul Sutton]

Also, before considering starting your bike with a car battery. I read several years ago that because a car battery is capable of drawing a much higher charging current there is a risk of damaging your charging system e.g. PMA/Alternator/Regulator.

Has anyone else heard of this precaution? Perhaps it is not True? Might be a myth?

 

[Jan_P]

Also, before considering starting your bike with a car battery. I read several years ago that because a car battery is capable of drawing a much higher charging current there is a risk of damaging your charging system e.g. PMA/Alternator/Regulator.

Has anyone else heard of this precaution? Perhaps it is not True? Might be a myth?

I have heard of early 80 ies Suzuki's it was in the press --here having regulators that was weak .Not strictly answer to your question
Parked in the fall no Trickle charger even existed back then.
Come spring Turn the key ..bike started but the battery was low..
Regulator opening for charging but .Since the battery was low The regulator was open for longer time with higher
Electric power going through .So it fried and it fried in such a manner that it kept on charging and then Fried the Alternator also.
So charging a low battery in the Motorcycle is not a good idea.
The repair ( In some cases ) in a new alternator and it fried again if not noticed that the regulator was Closed circuit.
Needless to say it was a hit for the owner. Not much aftermarket back then either and No internet.

So back then the regulators was sensitive .
I have in recent years read about pirated regulators that can have substandard quality

If interested google - fake shindengen

 

[Kevin Werner]

Lead acid cells produce 2.2v before internal resistance voltage drop. A fully charged battery wit 6 cells should produce 13.2v. I often test car batteries at 12.8 or 12.9. As an aside, take the caps of each cell. dip your multimeter propes cell to cell, you will measure 2.2v per cell. Don't let the probes drip on your custom paint. So the smaller size of the motorcycle battery probably has something to do with our batteries registering 12.6v.

 

[650Skull]

Personally I prefer to continuity test for shorts.
Don't need a volt meter when using power to check..............just look for smoke


I know @fredintoon uses a car battery on his sidecar rig. Maybe he can chime in.

My understanding is never use a running car to jumper start a motorcycle. That will cause damage.

 

[Tlted_Jelli]

One thing I can think why I don't have blown fuses is my block has all 15a fuses. Maybe fuses too high. I think I saw a diagram for hughs PMA and pamco with all 10A fuses except the one from battery to regulator was a 20a

Also just ran around all my wiring....it's messy. See my crude diagram

 

[Paul Sutton]

When my battery is fully charged it shows 13.2V. This is quite common to see, but at the very hint of a current drain it will rapidly drop to the value of about 12.7V. A couple of entries back there is a mention of leaving the battery to sit 24 hours after charging before checking voltage and its for this very reason so you measure the practical working voltage of the battery.

The voltage for a battery is related to the ratio of certain chemicals in the acid solution. When you give a battery a good charge one of these chemicals almost drops to zero and this puts the ratio high so you see 13.8V. But a very small current drain such as self discharge causes voltage to drop rapidly from 13.2V to approximately 12.6-12.8V as the concentration of the chemicals in solution change. At this point the voltage drop becomes less sensitive towards the changing ratio due to battery discharge. It's been years since I saw the equation for battery voltage but if I remember correctly it involves the Log of the ratio and this gives rise to the unusual behaviour. When a battery is nearly discharged we see similar behaviour again with rapidly dropping voltage as the ratio of chemicals in solution flips the other way.

In practical terms a fully charged battery is taken as approximately 12.6 -12.8 Volts because the drop from 13.2V to say 12.8V represents a very insignificant discharge of stored energy. Try it some time to see the voltage drop by flicking your lights on for a split second immediately following a good charging.

Edit: Whether we use 12.6V, 12.7V, 12.8V or 12.9V as the voltage of a fully charged battery depends on the battery technology e.g. the composition of the lead plates such as additives like Calcium or Bismuth, the physical structure such as AGM type, or where we want to say where 90% or 99% of the battery charge lies.

 

[Kevin Werner]

t
In practical terms a fully charged battery is taken as approximately 12.6 -12.8 Volts because the drop from 13.2V to say 12.8V represents a very insignificant discharge of stored energy. Try it some time to see the voltage drop by flicking your lights on for a split second immediately following a good charging.

Edit: Whether we use 12.6V, 12.7V, 12.8V or 12.9V as the voltage of a fully charged battery depends on the battery technology e.g. the composition of the lead plates such as additives like Calcium or Bismuth, the physical structure such as AGM type, or where we want to say where 90% or 99% of the battery charge lies.
[/QUOTE]
You are practical and I think correct. To pursue this further is to search for hens teeth. If you don't have 12.5 - 12.6 v after 24 hrs trickle charge, you may have a battery problem

 

[Tlted_Jelli]

I'd still like to know what killed my battery in the first place.
And I'd hate to just keep killing batteries

I put a good battery on.

Im going to disconnect everything but the battery, reg/rec and pamco circuits. See what voltage I'm getting on the battery if I can get it started.

I'll probably end up remaking the entire harness for the accessories after testing each thing on its own.

 

[jpdevol]

I'd still like to know what killed my battery in the first place.
And I'd hate to just keep killing batteries

I put a good battery on.

I agree.... You said you had a "short" earlier. You need to test for a short with an ohmmeter and power off or disconnected: each circuit on the load side of the fuse first. If no shorts are found - they're actually kinda rare on decent wiring - then no fuses should blow when power applied. If you have a short to ground, it will blow a 10amp fuse or a 20amp fuse

Then the charging system needs checked - first by testing running voltage at the battery terminals with a voltmeter.

 

[Paul Sutton]

I think Skull's comment right at the start of the thread is key to solving this issue:

Get the battery tested first

Is the battery confirmed as dead?

 

[Max Midnight]

A couple of points, the battery is there to provide power when the output of the generator can't satisfy the demand and to start the bike if it has an electric leg.
For the majority of time the battery can be considered dead weight as it isn't required.
The r/r would normally put out a no load voltage of c. 14.4 V.

If you measure battery voltage just after you have stopped the motor you will get a higher reading due to surface charge.
The charge activity occurs on the plate surfaces and the conversion of lead sulphate to lead and lead dioxide is sluggish when charging. It takes time for the inner part of the plates to be converted. This action results in an elevated state of charge higher than the normal resting voltage.
The elevated reading you will get depends on how soon after you stop the motor - the longer you leave it the lower the reading until it reaches the nominal state of charge of around 12.7 V.

To get a correct battery reading after a run or after charging you need to let the surface charge dissipate either by letting it rest for an hour or so or apply a load for several minutes to remove surface charge and allows the true stored voltage that is deeper within the plates to be measured.

 

[Jan_P]

Perhaps Helpful
A Short can be viewed as digital -- a one or zero as if a cable is cut.
But as the proverbial " Different levels of punishment in hell "

It can happen that there is a partial short to Ground not blowing the fuse and still use up power
Furthermore and more evil ..it can be Temperature and Vibration dependent.

Worst case .Not Manifesting itself at a non running cold still standing bike .Then it is impossible localize that fault.
Cannot work on a hot bike and when it cools off it runs fine cannot find it.

A Co worker bought a Brand Spanking New Toyota Corolla that turned on the headlights by itself on the Parking Lot and drained the battery.
It took 3 trips to the Dealer factory Shop They could not find it first 2

That is why the CSF rule,is the best way forward Cheapest Simplest First.
Especially when there is a Measurement to work on The Battery low Voltage

Try to clamp the wires the red one in the middle is To battery If Main switch is on ( look at the wiring post # 29 ) .If that touches ground /frame ..There will be smoke

 

[MacMcMacmac]

As an aside, did your H4 headlight come with 55W/60W bulb? Unless you are running highway revs it will kill your battery. Put a 35W or LED in it and check again, or maybe just run without a bulb for an hour or so as an experiment.

 

[Tlted_Jelli]

Yeah it's a 55watt h4

 

[MacMcMacmac]

Ruh roh...

Easy thing to miss. It caught me a few times when I should have already known better.

 

[arcticXS]

As an aside, did your H4 headlight come with 55W/60W bulb? Unless you are running highway revs it will kill your battery. Put a 35W or LED in it and check again, or maybe just run without a bulb for an hour or so as an experiment.

Doesn't that depend on the type of PMA he has?