Even off of a Battery Tender registering fully charged, my battery was good for about three starting attempts after which I had to push start the bike in the morning.  I'm thinking a load test would probably declare it very weak, but I thought I'd ask what was the usual experience here, and a couple other questions.  So...

(1) Suppose each attempted start was, say, four seconds on the starter button.  How many such attempts should a good, fully charged batter be capable of?

(2) If the battery is weak or dead, once the bike is (jump or push) started, will there be a difference in how it runs?

(3)  Is running on a weak battery going to be noticably harder on the alternator, like in life expectancy?

I've always wondered about (2) and (3) in the abstract, and therefore would like to know what is the conventional wisdom.  I kind of figured that the battery not being up to proper useful capacitance would put more physical strain on the alternator, since the more the alternator has to put out, the more resistance it will encounter to its spinning, but maybe it's not enough to make any difference in actual life expectancy.  The battery should also, I'd think, smooth out any spikes of demand on the electrical power supply (meaning the alternator/battery system).

Thanks for your thoughts.

--Mike D.

PS:  FWIW the mechanic I took it to got a little deal on Yuasa batteries and will let me have them at his cost, so I said fine.  He tells me they're having some special this month, so this may be the time to buy them.  He tells me they are pretty good.  Cheaper still on EBay, but shipping is nonnegative cost.

Quote from: geekonabike..............................
(1) Suppose each attempted start was, say, four seconds on the starter button.  How many such attempts should a good, fully charged batter be capable of?

The starter draws about 80 amps. One attempt at 4 seconds (.0011 hr.) = .088 AH.  New fully charged battery capacity is 11 AH.  So one attempt will draw about .8% of the total battery capacity.

Quote from: geekonabike
(2) If the battery is weak or dead, once the bike is (jump or push) started, will there be a difference in how it runs?

(3)  Is running on a weak battery going to be noticably harder on the alternator, like in life expectancy?

I've always wondered about (2) and (3) in the abstract, and therefore would like to know what is the conventional wisdom.  I kind of figured that the battery not being up to proper useful capacitance would put more physical strain on the alternator, since the more the alternator has to put out, the more resistance it will encounter to its spinning, but maybe it's not enough to make any difference in actual life expectancy.  The battery should also, I'd think, smooth out any spikes of demand on the electrical power supply (meaning the alternator/battery system).

I think your paragraph following items 2 & 3  is a good explanation of what happens.

6 tries, 3 seconds each, 10 seconds apart ... bike has to be running by then ... else somehting is screwed up ... if I dont get 6 ... battery is screwed up ...
Cool.
Srinath.

Having thought a little bit more about Item 1, I think my answer is inaccurate    
because I used 11AH as the capacity.

11AH is the rating of the battery for complete discharge in 10 hours at 1.1 amp, not 80 amp that we are talking about. I don't know what the capacity of the battery is at an 80 amp discharge rate but I'm sure it is considerably less than 11AH.

The batteries capacity also depends on its temperature.  Progessively less as the temp. gets lower.

Bottom line: I don't know how to calculate it.  I do know that when my bike has been hard to start that my battery, which is fairly new, has given at least 10 attempts at more than 4 sec. per attempt.

Quote from: John BatesHaving thought a little bit more about Item 1, I think my answer is inaccurate    
because I used 11AH as the capacity.

11AH is the rating of the battery for complete discharge in 10 hours at 1.1 amp, not 80 amp that we are talking about. I don't know what the capacity of the battery is at an 80 amp discharge rate but I'm sure it is considerably less than 11AH.

The batteries capacity also depends on its temperature.  Progessively less as the temp. gets lower.

Bottom line: I don't know how to calculate it.  I do know that when my bike has been hard to start that my battery, which is fairly new, has given at least 10 attempts at more than 4 sec. per attempt.

The battery capacity depends very strongly on the discharge current. I had no experience on my bike (usually start from the first time) but back in Ukraine, sometimes I had discharged the battery (60 AH) completely by doing just a total of 3-4 minutes of cranking (with breaks, of course), so the discharge time is much-much smaller at higher currents. The starter of my car was drawing 30-40 A.

Thanks.  Especially the last couple posts helped verify that my battery was weak since it could barely do a third attempt, and in fact my first one was usually less than four seconds--my thinking that it should start right up--and my second would be more of the four-second variety (let's get some gas in there!), and the third would slow after just a second or two, at which point I'd know it's time to push.

So otherwise you think the bike actually would run better, once started, and be easier on the alternator if the battery is good?

It will be interesting to see if a new Yuasa make the bike not just start better, but run better.  But I'm going to be wrecking that experiment since the fellow putting in the battery is also going to mess with the jets, since I seem to be running lean too.

Hmmm....in fact I was getting what seemed like lean misfires.  A weak battery wouldn't cause something like that, would it?

Thanks,
Mike D.

Quote from: geekonabike
(3)  Is running on a weak battery going to be noticably harder on the alternator, like in life expectancy?

Motorcycles don't have the same set-up as cars.  In a car, there is an outer winding, that current is passed through, which sets up the magnetic field around the stator.  The amount of current passed through the winding determines how "hard" it is to turn the alternator; and how much power the alternator produces; and how much heat is generated to cause wear and tear on the windings.

But on a bike, the magnetic field is fixed, because a ring of stupid magnets is used to set-up the magnetic field around the stator.  This means that at 5k RPM, the stator is producing the same current to the regulator regardless of whether the battery is dead or healthy.  And it is just as much work to turn the stator, regardless of load.  To compensate to receiving too much voltage, the regulator will shunt one (or two!) of the three phases to ground, dissipating extra energy as heat.  That allows the R/R to keep the voltage in the target window (12.5v-13.8v).

It's a pretty crude system.  I don't actually understand it all that well, and I know I've read conflicting comments, implying that the engine needs to "work harder" to charge a flat battery.  Perhaps when the regulator shunts a phase to ground, that reduces the heat at at the stator?  I'm just saying that, to the best of by limited knowledge, the need to charge-up a flat battery will not affect performance.  If you push-started the bike every day, you'd probably be able to get-by with a small 12v gel-cell battery.

Thanks for the explanation.  In theory I think you're missing one little point, which might not matter, but in fact I myself am reaching back to some old knowledge/experience so I may be proven wrong about this.  See if it makes sense to you.

That is, if a winding on the alternator/stator/whatever is sent to ground, and if this is essentially shorting that winding (I'm not sure that's what's going on, but if it is) then you are giving the generator a load essentially, and it will mechanically resist.  If you ever take a generator, and get it spinning, and short the terminals, it slows faster because of the reactance from the current actually moving through the coils.  (The induced voltage is actually put to work moving current.)  I don't really know much about what I'm "talking" about, but something like the current induced causes the same kind of magnetic field that induced it, and likes repel, or something like that.  Anyhow if the energy from the moving magnet is actually put to work (work=voltageXcurrentXtime) that energy will be robbed from the movement of the magnet.  Anyhow that's my Dr. Who explanation, though I did once take an electricity/magnetism class so I'm embarassed I can't understand it better.

Still, I have also read (as you say) that a lot of the electrical energy is actually directed/absorbed by the regulator, hence the conspicuous heat sink on it.

Thanks again for the explanation.  A lot of good information there.

Regards,
Mike D.

This may seem a little off topic, but if in fact he just needed a new battery, how much would one cost? This question is more for me though-the last two bikes I owned took an $80 battery and a $22 battery respectively. Are GS batteries pretty reasonable? Peace

they run 25-30 bucks at most auto parts stores,  the hard part is finding one with the vent tube on the right side.  

ok, so here is my 2 cents on the topic,  first check the battery fluid level about 80% of battery problems are related in some way to the fluid level.  then if it is ok, and the battery is less than 2 years old take it out of the bike and set it on a piece of dry wood, make sure it's level take the vent plugs out of the top and charge it for a while.

normal battery chargers come with a book to tell you how long to do it but a rough way to do it.  you take the rating of the battery (gs is 11Amp Hours) and devide by the capicity of the charger, most will be 1-2 amp chargers so you whould have to charge it for 11 hours for a 1 amp charger.
sidenote: if you are getting a good charge you should see little bubbles like it is boiling.  these are hydrogen gas  which is extremely explosive.  make sure you do this outside so the gas disperses into the atsomephere.

ok so after you do that and it won't hold a charge or if the battery is more than 2 years old. go buy a new one.  end of post.