Checking Resistances / Battery issues

[gsxbarmy]

A bit of a tale.......

I recently had a forum member call me regarding a C28 (STPV) issue. Bike started and ran, and he had done the normal checks that one does, but was still getting a C28 (which actually turned out to be a red herring, as when we checked the STPV, it was within tolerance, plus he had a second set of throttle bodies and got the same reading)). Just in case the battery was a bit low on charge, he had done a couple of 40-50 mile runs (more to check out the tests he had done), so initially we discounted it, as to all intents and purposes the battery appeared to be within limits (according to the workshop manual), albeit the lower end.

In reading through all the various checks in the workshop manual though, there was one common factor that consistently appeared. "Readings assume a fully charged battery". After some discussion we came to the conclusion that the common factor here for all these tests was the battery. And were we sure it was really fully charged (it seemed so, but...)

And so (in this case) it was the battery that was a fault. Whilst to all intents and purposes, the battery was showing as good - it was after all starting the bike - essentially it was on its way out (remember I mentioned earlier that readings, whilst within tolerances, were at the lower end of the allowed scale?). Battery replaced, tests done, and a complete new set of readings obtained. Also the C28 disappeared.

So the morale of this is - if you are doing any electrical checks for resistances (or whatever) on your 14, then YOU MUST HAVE A FULLY CHARGED BATTERY, as if you don't, the readings you get could well be false. Or, if you get error codes (for instance, as above), and nothing seems to make sense, then get your battery checked by a specialist to check actually how good it really is as that could be the root issue of your "problem"

[Andre]

Three different Dealers wanted to replace the starter motor on my neighbors Yamaha. Maybe the starter clutch if the new starter change wouldn't solve the issue. Just for the starter change the Yamaha dealer wanted 1000 €!

He demonstrated me his start up problem. It was obvious that it was a weak battery (charge was just below threshold for this battery) . Now he is happy.

[grog]

So guys, i agree battery is heart of system. Lots overlook it. What do you consider a charged batt voltage. What do you consider acceptable voltage under load, that is cranking. The best test. Ill wait for answers, i think i can answer most, just what i get paid to do. Im very good at it. One to think about, your bike/ car, modern efi type has old batt. Resistance is much higher. Voltage has changed. What is outcome?

[gsxbarmy]

So guys, i agree battery is heart of system. Lots overlook it. What do you consider a charged batt voltage. What do you consider acceptable voltage under load, that is cranking. The best test. Ill wait for answers, i think i can answer most, just what i get paid to do. Im very good at it. One to think about, your bike/ car, modern efi type has old batt. Resistance is much higher. Voltage has changed. What is outcome?

mate I have no idea, not an auto sparks by any means, I just read the manuals LOL!

What I do know though is that the slightest change in voltage (etc) can cause hassle. Years ago I had a BMW X5, For 2 years from new, no worries, everything worked brilliantly. Then towards the end of one summer, if you left the car for more than 8 hours without starting it, it would hardly crank. Dealers pinpointed the issue that the battery was .1 of a volt down (which apparently threw out the clever electrics as it started to shut some off). New battery fitted by dealer and all was good again.

So the only answer I can give to you as an outcome is that it doesn't take much with modern electrical systems!!!

[Andre]

Dealers pinpointed the issue that the battery was .1 of a volt down (which apparently threw out the clever electrics as it started to shut some off). New battery fitted by dealer and all was good again.

Same as with the Yamaha: .1 volt down!
Yamaha says the issue with starter/starter clutch is due to a variety of causes that lead to lean conditions which can kill the starter/starter clutch (actually it is a design issue for which they have a kit put together at over 600 €; + starter + starter clutch if you are unlucky). One of the causes is weak battery. Neighbor was lucky that it hadn't destroyed anything.

[Irish in Oz]

So guys, i agree battery is heart of system. Lots overlook it. What do you consider a charged batt voltage. What do you consider acceptable voltage under load, that is cranking. The best test. Ill wait for answers, i think i can answer most, just what i get paid to do. Im very good at it. One to think about, your bike/ car, modern efi type has old batt. Resistance is much higher. Voltage has changed. What is outcome?

They say about 3 percent for a battery lets round it off to half a volt drop.
Resistance up means current down, current down means power down.
All theory of coarse what I was taught in TAFE a few years ago.
But if your battery is really good it could be any feckin thing.

[KiwiCol]

This is what I go by Grog,

Fully charged battery in good condition: 12.65v
Underload voltage, (while cranking) not below 10.5v
Battery should show charging after start, (at idle) would show 12.85v+ rising quickly to high 13's - low 14's, top out around 14.85v with revs
Best Test, my 500amp carbon pile battery tester

[Irish in Oz]

 Col, so that means a 2 volt drop. So theory is rubbish.

[Irish in Oz]

What are the current readings from the tester!

[KiwiCol]

Col, so that means a 2 volt drop. So theory is rubbish.

The voltage drop mentioned above, is only whilst cranking. I can accept the battery is ok if it doesn't drop below 10.5v at this stage, ideally, it wouldn't drop below 11v whilst cranking, but 10.5 is still ok. IMO.


I'm not a sparky though - you are (as far as I know)

[Irish in Oz]

Col, I don't have a problem with your opinion just theory.

[KiwiCol]

Thx Irish,  Just my 2c worth.     

You can also have a battery that's showing good voltage at rest (12.65 or more even) and it still won't start your vehicle. This is usually because the battery is old, & is no longer able to deliver the load required for starting. 
Think of it along the lines of static electricity, to get a spark to jump off you to an earth, you need quite a charge, sometimes hundreds (or thousands) of volts, but there's no current / flow with it, so it doesn't do any harm. Now think of your home electricity, only a couple of hundred volts, but plenty of current / flow, this is what kills ya & also what's needed to turn your engine over.  So, just because you have good voltage, your battery can still be naf.  (BTW, Naf is a technical term used to describe dud batterys in the sparky world - ask Irish!)

[KiwiCol]

For the last part of your question Grog, I think the post I put above would be the outcome. 
Hard to start or won't start, as it's not only the starter the battery has to cope with on start up, it's also the ECU, the fuel pump, the injectors etc, all taking power at once from a tired battery.

As I said prior, I'm not a sparky, just my understanding of how these things work. Happy to be corrected as it means I've learned something new.  Never too old to learn stuff I reckon.

[grog]

Col, youre onto it. engine management is tested in a lab somewhere, using perfect voltage. our batts change as they age, resistance, they clog up. voltage changes. amps change. all our sensors are set to deliver a message to ecu while having perfect power supply. your replies welcome gentlemen, delivering wrong message, that is supplied in volts, is our bike confused. power, economy, general running. has to be. IMO

[gsxbarmy]

Col, youre onto it. engine management is tested in a lab somewhere, using perfect voltage. our batts change as they age, resistance, they clog up. voltage changes. amps change. all our sensors are set to deliver a message to ecu while having perfect power supply. your replies welcome gentlemen, delivering wrong message, that is supplied in volts, is our bike confused. power, economy, general running. has to be. IMO

So - if I understand you correctly @grog - even though batteries may last more than the (manufacturers) forecast 3-4 years, after that they could still show as being "good" but in fact have deteriorated such that incorrect readings of components could be obtained.

Hence - is it worth replacing batteries every 3-4 years even though your existing one may appear "good"?