Another Battery Charging question - Honda RC51 Forum : RC51 Motorcycle Forums
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post #1 of 4 (permalink) Old 10-03-2016, 03:26 PM Thread Starter
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Another Battery Charging question

My 2002 SP2 is not charging the battery when running. I got stuck a few weeks ago and needed the AA to come and get me home, after the battery died while I was riding. I noticed something was wrong a couple of months ago as my Honda heated grips had a single red led flashing within 5 to 10 minutes of me leaving home, and I always have the bike on a C-tech charger. This red led indicates thee's not enough current for the heated grips to work; when I get home and plug the C-tech in, the charger led stays orange for a long time (usually it is instantly green after a ride). Only when it's green will the heated grips then work normally. The battery is only a couple of years old, and the AA guy checked it and said it was in good shape (pulling 20A when charging). I also noticed (on the day of this incident) my bike was stalling a lot and seemed to be idling lower than usual).

After trawling this site and YouTube, I tested the rectifier and found that to be at fault. Thanks to the amazing post here I went for the Mosfet FH020AA item (for those in Europe, MTP Racing, in Germany, sell an exact copy of the Japanese item, and made in Germany, with a 1 year warranty for £95.70; just search for "Mosfet FH020AA"). Having fitted it, and engineered a suitable bracket, I was all set to go this weekend. Once I got the green led fro the C-tech, the bike fired up first time and I went out for about 30 mins. The bike felt great and was running sweet, and idling as normal. But the heated grips red led cane on and my heart sank. Returning home I put the C-tech on and sure enough, got the orange LED for about 30 mins before it went green again.

My attention then turned to the Stator testing (again as described in several places on YouTube), and this is where I am now. The three stator pins on the white connector (from the stator) all have 0.4 ohms between them BUT they come up positive in the continuity test to ground, i.e. something is grounding them. Also, the bike will not start with this connection broken (unlike the YouTube demos where they test with the connector open, both with the bike off and then running), even if I fully charge the battery on the C-tech (lights are off, so nothing else drawing current). I have just taken the whole wire back to the crank case and checked for any damage, etc. It's perfect, and the symptoms still exist.

Other bits of info: I don't have an immobiliser (see my thread about by-passing the Datatool Duo I once had), and I have removed all other ancillary connections from the battery. The bike was running perfectly for 4 days solid at the end of April while I was away touring the Yorkshire Dales (no C-tech up there!), and I've not done anything to the bike since then, i.e. same battery, heated grips, etc.

Sorry for the lengthy prologue, but I wanted to set things out, and say that I have looked at all the battery-related threads here just in case. I wanted to ask for any further advice before I simply assume it is the Stator itself that has become grounded and I need to get that replaced. I'm not sure where the fault originated from, but it seems it has taken out the stator and rectifier, but left the battery in tact.

I appreciate any further help or things I might try, thanks.
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post #2 of 4 (permalink) Old 10-03-2016, 07:45 PM
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There is a lot of good info on the forum using search.

Here are a few for a start.

I'm no electrical expert so that's it for me.
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post #3 of 4 (permalink) Old 10-04-2016, 12:17 AM
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checking resistance of a stator isn't going to give you any valuable information as the meter you're using isn't likely to give you the type of precision required. winding resistances are going to be very very low.

the fact that it meters to ground is terrible news though, it should always meter (preferably megger) open to ground.

having the stator unplugged should have nothing to do with starting and running the bike. but considering the fact that it meters to ground, that may be irrelevant at this point. pull the stator and give it a visual inspection, it's likely you'll see burned windings and degraded insulation. at that point it's a matter of replacing it.

what test did you do to verify that it was a rectified issue?

i would also be testing your heated grips circuit prior to replacing the stator. if it's over-taxing the system due to a ground fault or similar then you may end up in the same situation you are in now.
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post #4 of 4 (permalink) Old 10-04-2016, 03:59 AM Thread Starter
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Thanks for the feedback and links.
Wibbly - I tend to agree that it's the Stator and not to worry yet about the non-starting (the starter motor works fine, and you can hear the engine trying to start, but needs that final "oomph"!). I have the full factory service manual so will get the crank cover off for inspection. I'm curious about your comment re. heated grips and cause of this problem. I've owned the bike for 14 years (it was only 6 months old when I purchased it), and it has never had any faults like this, so hopefully it is just "wear & tear" - it's weird having a new bike that you have to start treating as a "classic". It's done 44k miles, so not a great deal really.
I installed the grips about this time last year; they are genuine Honda items and the wiring is for the SP2. I previously had Daytona heated grips, which were very good, but the rubber on the grips had gone hard and uncomfortable, so I took the opportunity to purchase the Honda item when it came up on eBay. The new grips plug into the same connection points I had for the old ones, and have an in-line fuse, etc. and work fine normally. I wouldn't expect them to be faulty. but was wondering how they could cause the Stator problem, without a fuse blowing or some other warning sign first? Obviously it's important to identify the root cause, and now you have me wondering!
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