charging system nfg ; battery takes charge but dies after
stevemunyon at comcast.net
Mon Feb 13 17:41:03 PST 2012
This sounds like the problem I had last summer where my SV would start
missing after 1/2 hour of riding. Here's a write up of what I did to find
I got out the voltage meter and recorded the initial states of battery
condition. I also checked primary and secondary resistance in the coils,
etc., which were in-spec. The battery with the ignition switched off was
12.47v. Anyway with the headlight (low beam) as a load, the battery voltage
dropped to 11.8v after 5-10 seconds. So I know the battery is marginal. I
started the bike and the voltage went to 13.1v.
I checked the primary side of both coils with my scope and I was seeing
400v. The shop manuals states 150v & up, but a scope is a lot more
responsive the just a peak and hold meter that the factory manual suggests.
To me, that explains the higher voltage.
I took the bike for a 20 minute ride and the idle voltage was still 13.1v,
so I revved it to about 5K and the voltage was 13.3v, when I revved the
engine higher the voltage dropped back to 13.1v. Ive been searching around
the net for similar problems. One interesting find, was a bad solder joint
on the signal generator pickup, but my solder joints looked good. Another
find, was that most Suzukis have weak regulator/rectifier based on SCRs
while other bike have an R/R based on MOSFETs. Google them if youre
interested. As a band-aid for the weaker R/R the author used 12 gauge wire
with a 30 amp fuse to provide a more substantial current path then the
standard Suzuki wiring which looks like a 14-16 gauge with lots of
connectors. Whenever I see an electrical connector I always figure on a .1
v drop at each connector. So I ran a 12 gauge wire from the R/R output
connector directly to the positive battery terminal and took some
measurements. Key off battery voltage is 12.44; key on and headlight on
battery voltage is 11.9, started bike and voltage jumped to 13.6v, after a
minute the idle voltage was up to 14.2v and when revd the voltage was 13.8.
So I removed the wire, went back and cleaned all the connections, check the
voltage and the voltages were back to where they were before. At this
point, I soldered in the additional 12 gauge wire and the 30 amp fuse ending
with a terminal lug so I can screw the lug to the positive battery terminal.
Checked the battery voltages again and they were back up to the jumper wire
voltage levels and sometimes a little above. I also clipped a ½ inch off
the spark plug wire just to make sure the connection to the coil is good.
So that wiring fix combined with a new Yuasa battery I ordered and the
problem hasn't been back. Right now I dont think it was the batteries
fault at all, just the small wiring for the charge circuit.
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