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Old Nov 20th, 2010, 06:24 PM     #18
Play The Throttle
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Join Date: Oct 13th, 2010
Location: Norway, Europe, Planet Earth
Posts: 264
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Re: Let's see some data on batteries


Firstly, thanks for taking the time to explain this stuff to me.

A couple of things I am still wondering about, though:
"Since your bike is a '91 and has a single phase stator, the charging current most likely is low around & during idle speeds."Therefore, when at idle speeds, the FLTC will receive the bulk of its required electrical current from the battery and not the alternator."
Yes, although my bike probably has less current draw than any new-ish scoot.

"Then once the "light turns green", and RPM increases, the alternator now supplies the current demand to the bike in addition to recharging back into the battery what was removed while waiting at the stop light. "
Yes, but I'd say the alternator supplies the demand together with the battery at idle, gradually taking over from the battery until it also supplies charging current to it...

"But as the battery capacity falls with age (as in your case),"
Well, the funny thing is - which is the reason it has been left alone all this time - it does not show any signs whatsoever of having lost capacity

"... the surface charge falls off much more rapidly when we are at a red light."

"The light now turns green and bang, the alternator has to immediately come into play at near 90% (?) in order to try and keep up with the demands of the electrical system and at the same time charge up the weak battery. "
Well, here I am not following you: My understanding is that the HD permanent magnet type alternators are supplying the same current regardless of demand.

"***It can be debated that based on the fact that energy can not be created or destroyed, what we take out of a battery must be put back in and the only source we have is the alternator."
I do not see the connection, although I do agree with the first part. Energy can and does transform, mostly into heat.

"Therefore it can be argued that "in the end" the regulator will still see or pass the required amount of electrons needed to recharge that battery regardless of the amp hour of the battery. That is a TRUE statement, but having a Good Large Capacity battery will BLEND that demand over a longer period of time rather than having PEEK demands placed on the regulator & stator immediately after the light turns green. That is the KEY point.***"Again, this is the sticky point that I do not understand - although the deamd may peak, the good ole alternator still deliver the same (rpm dependent, of course).

"Of course we also have to take into account what the bike demands are during cruising. If we had a carburetor, magneto ignition and was kick start, the only electrical demand would be a headlight and we would not have to care less what condition our battery was in. The guys at highest risk are the Baggers with lights, stereo amps and accessories along with being a single phase charging system. Those guys should make it a point to have good battery on board. I on the other hand, have low electrical demands (just a base Dyna) and a 3 phase charging system so I can push my luck a little more."

"98% of the regulator could not care less what the batteries "state of charge" is in. But the other 2% is what really takes the beating when your charging a weak battery and also supporting the Bikes running electrical load at the same time. To date, the only regulator I have taken apart is the current 3 phase model. The 2% that gets a beaten are the 6 final rectifiers made up of (3) 2N6507 SCR's and (3) FES16GT TO220 rectifiers."
Yup, it does take a (heat) beating.

"A peek inside a Black Box - Harley Davidson Community."

Excellent stuff - you are an asset to this list.

"All it takes is 1 of the 6 load rectifiers to overheat and open or short to destroy a regulator. If the rectifier shorts, the stator output is shunted to ground. Once that happens the end is near for the stator."
Now we are onto the regulator. So the bottom line as I read it is:
A weak battery does not affect the alternator in itself, however it may cause overheating of rectifiers. If these go, a short circuit may result, causing damage to the alternator. I'm with you.

" Another thing to remember is if the rectifier shorts, a huge amount of AC ripple will hit your sensitive electronics (ECM, TSSM, Stereo etc) and that is something you don't want. "
I fully agree with you, but the good thing (for me) is that my scoot does not have much in way of electronic stuff: No EFI, ECM, bank angle, O2, temp, speed, NOx, VOC, etc. sensors (I added the two last ones for good measures;). Only a very simpe version of TSSM (speed & timer), and the ignition AFAIK.

"My guess is 1 set of rectifiers are used in the single phase units but with a much more beefy rating since the 38 amp load is not a vector output among 3 pairs of solid state rectifiers. What COULD exist inside a single phase regulator (and really hope not) is they just took several low current rectifiers (such as the ones used in the 3 phase unit) and stacked them together in order to meet the required pass through current. That would be cheaper to manufacture but would not have as near the reliability as a single high capacity rectifier. (that is stacking (3) T220 rectifiers instead of 1 large 1/4" stud rectifier)"
I did not fully understand all you said here, but if a single, large recitifier is used, then you are saying that my regulator (I have 32A alternator, BTW) has a much better MTBF rate than a three-phase system?

A pledge from those of us that are a bit ignorant but still interested in the workings of electrons: Please do surgery on a single phase regulator.

"So the bottom line as I see it. Why make it a contest to see how much time you can get out of a battery. If a battery costs $120, that means it costs $30 per year to own that battery for 4 years or $20 a year to own the battery for 5 years. Is it worth 20 bucks based over 4 years to push your luck."
I am not making it into a contest - I was merely responding to the authors' request to hear about other riders batteries. I am also interested in learning more on this topic, but I will replace the battery this winter (your $120 transforms into $240 on the voyage across the deep blue sea, prior to arriving on European shores)
All the best,
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