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I'm at a loss trying to figure out a charging issue on my 2007 SV650S (35k miles) and am hoping someone here might have a suggestion I haven't tried.

Problem: My bike wouldn't start one morning before work. Come to find out the battery is dead (11.8 V at the terminals). I had just ridden the bike for over an hour the day before with no issues starting or running. The battery is 4 years old so I figure maybe its time is up. I charge it overnight and bring it to Advance for a load test, which it passes with flying colors. It also does not dip below 10.5V when starting the bike so I believe it is still good. I put the battery back in the bike and fire it up. The multimeter is only reading 12.7 V at idle and barely moves @5k rpm, so clearly the charging system is not working.

The following is what I have tested so far and the results of each test:

  • Stator resistance between each connector pin. Results within spec.
  • Stator AC voltage between each connector pin. Reading 60 V+ @5k rpm, within spec.
  • Stator continuity to ground on battery. No continuity to ground for each connector pin, so it does not appear to be shorting out.
  • Removed Regulator/Rectifier and performed diode test between 3 and 4 pin connectors coming out of the R/R. Results all consistent and within spec per the table given in the shop manual.
  • Visually inspected all wiring and connectors which I could see and did not find anything melted or obviously shorting. There was a small knick in the insulation of one of the wires coming out of the R/R, exposing a little bit of copper, but it did not look like it would be shorting anywhere. I wrapped this in electrical tape to be sure.
  • Cleaned battery terminals even though they were tight and not corroded.
At this point I put the bike back together and it appeared to be charging above 13 V at idle and 14.4 V @ 5k rpms. Perfect! Take the bike for a 10 min ride and then pull the seat off again to check voltage, only to find it charging at 12.8 V @ idle and a little over 13 V @ 5k rpms, slowly dropping.

I've ridden the bike a few times now and it always charges normally when I first start it but seems to stop charging correctly when I check after each ride, so at this point I'm thinking it might be heat related. I've tested the Stator when hot and it still seems to be outputting the correct AC voltage with no continuity to ground, so I'm pretty sure that's functioning properly. I'm leaning toward R/R (I know this is common on 1st gens, didn't think it was as common on 2nd gens), but it passes the bench test fine. I would like to cover all bases before replacing parts that are otherwise testing fine. I am admittedly not very skilled when it comes to electrical system troubleshooting, so any help is greatly appreciated.
 

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Discussion Starter #2
Bumping because I still haven't been able to solve this.

I've been taking the bike on occasional 10-15 minute trips (sometimes 30) and while it's been running fine, my charging voltage at idle once the bike is warmed up hovers around 12.6-12.8V.

When I cold start the bike the voltage at idle is usually around 14.3V and goes up slightly @5krpm to 14.4V. The issue is after I ride it for a little bit, pull the seat and measure the voltage I only get 12.6-12.8V at idle. It goes up to 13.5V @5krpm. If anything I would think the voltage would be lower on cold start as the battery becomes fully charged.

I haven't been able to find any burnt wires or connectors. I even replaced the R/R and am getting identical readings, so I think I can rule that out. I'm pretty stumped and frustrated, as I'm worried about riding the bike any longer than 30 minutes since I don't want to be stranded somewhere.

Anyone have any other suggestions? I know 13.5V+ @5krpms is correct, but I really don't trust the charging system since it's been below 13V @5krpms when I first encountered this problem last month.
 

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You have done all the right tests, BigAl.

At this point I would replace the battery. Typical battery life is 5 years so at 4 years it is getting long in the tooth.

Worst case, even if the battery is not the problem, you only give up 20% the cost of a new $65 battery, so maybe $15. Nice to have a fresh battery in the bike regardless.

Do not trust auto parts stores to give accurate motorcycle battery test results. We've seen many posts here where the parts counter guy says the battery is ok but turns out it is toast.

It is not typical for a battery to fail this way, droping charging voltage when warm is more likely due to a failing R/R but that has been replaces so can not be the problem. Good AC stator voltage when warm says that is not the problem either. Maybe check the Stator and R/R connectors again, inspect, clean, apply dielectric grease, reassemble. If Stator, R/R, and wire/connectors are okay, the only thing left is the battery.

I would stay away from cheap off-brand batteries. You can not go wrong with OEM Yuasa YTX12-BS, $65 on Amazon.

Good luck, please let us know how this works out.
 

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Thank you for your response!

Quick update: I just started the bike cold and watched the voltage for about 10 min until it was up to temp. Voltage started to decrease a little once the bike got close to operating temp, and bumped down to ~12.8V once the fan kicked on which I suppose is to be expected. It then fluctuated around there (regardless of the fan being on or off) but would charge around 14V @5k rpm, so I decided to ride around for about an hour.

When I returned and measured it again at idle it fluctuated around 12.9V and still over 14V @ 5k rpm. Charging system appears to be working at the moment if a little weak at times.

Good comment on the battery, that was going to be the next thing I replace. I bought that exact battery you linked 4 years ago, however I do quite a few short trips in the winter (20-40F where I live) so I'm sure it's short lived at this point. I'll update again once I get a new battery.
 

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Had a Gen 1 that wouldn't charge, drained the batt etc. Replaced R/R and stator, and when we opened it up to fit the stator, found that one of the magnets in the alternator had come off and smashed to bits - pieces were everywhere and a second magnet was also off and stuck out of position. I'm quite certain this is not your case but the point is that in the course of fixing this, a bit of research found out that it's extremely rare but sometimes the magnets can lose their magnetism and produce low readings, and that this can be affected by heat. If you haven't opened up the cover yet might be worth a look. If nothing else it's a last resort. My mechanic said he's been working on SV's since they were new and it's only the 2nd time he's come across or heard of magnet failure... Guess I got lucky but it does happen. Good luck with yours!
 

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Thank you for your response!



Quick update: I just started the bike cold and watched the voltage for about 10 min until it was up to temp. Voltage started to decrease a little once the bike got close to operating temp, and bumped down to ~12.8V once the fan kicked on which I suppose is to be expected. It then fluctuated around there (regardless of the fan being on or off) but would charge around 14V @5k rpm, so I decided to ride around for about an hour.



When I returned and measured it again at idle it fluctuated around 12.9V and still over 14V @ 5k rpm. Charging system appears to be working at the moment if a little weak at times.



Good comment on the battery, that was going to be the next thing I replace. I bought that exact battery you linked 4 years ago, however I do quite a few short trips in the winter (20-40F where I live) so I'm sure it's short lived at this point. I'll update again once I get a new battery.


Was it the battery BigAl?


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