Intermittent Overcharging Issue

[Falco]

While out running errands over the weekend I noticed what may be a rather large issue looming - the battery appears to be overcharging. Most of the time it is fine (with the voltage holding around 14 V at anything over 2k rpm (or even dropping to 13.5 V) - which is making it difficult to test.

Every so often when I am out riding however it will jump up to 16/17 V range (It's possible it's occurring after being on the go for a while (I can't be sure though) and when I took the battery out to check it, the rubber...seal/ cap thing along the top (which I assume is over the top of the cells) was partially pushed out (suggesting the battery was being overcharged and gassing).

Are there any tests I can do verify what the issue is (considering the cost of reg/recs for the CB500S start at £40 (used)) ? I suspect the reg/rec, but I don't know if they can fail in this sort of intermittent fashion? Can Stators fail in such a way as to cause overcharging?
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I tell you what, mathematically, I'm having it

[jaffa90]

I would say your reg / rec.
Q, does this reg/rec have 3 white/grey wires input and a red and black wires output?
Also,
https://www.bikechatforums.com/viewtopic.php?t=328676

[ThunderGuts]

If it's that intermittent, could it be a dodgy ground somewhere that's shaking loose occasionally?
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TG.

[WD Forte]

CB500?
If the RR has a Black sense wire as well as a Red/White and Green
output wires, I d say it's probably got a poor sense connection.
If this black wire 'floats' the output voltage will rise and I've seen this issue quite a few times.
I alway strap my Black sense wire to the battery positive on these
older type RRs and never have any overcharging issues.

If it only has 2 output wires then it's internal sensing type
so ignore what I just wrote
and as Thunderguts says, I'd suspect an intermittent ground
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bikers smell of wee

[stinkwheel]

I'd go with a bad earth too. Or the reg/rec breaking down when hot.

If all the connections are good, then suspect the reg/rec.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[kawakid]

I noticed the reg/rec on mine after the bulbs started to blow.

Be careful, if your bike has an ECU it could blow it.
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I've a twin and a 4.

[Falco]

I ran through this flowchat this morning: PDF
Everything checked out fine (minor exception was theVac test on the stator. At 5K rpm the readings between stator wires were 41.6/41.5/41.1 Vac. The chat states less than 50 Vac indicates stator fault but that seems pretty close (and all the values are pretty close to each other).

[stinkwheel]

Any green wire from reg/rec goes to earth somewhere.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[ZebraDriver]

Not talking bikes but I have seen a similar thing on cars twice. Both intermittent and both caused the voltage to rise (lights suddenly get brighter, heater fan speeds up etc). In addition the cars would not start occasionally, but would start 20 minutes later.

After a lot of pissing about, trying to catch the fault when I could test things I discovered that the fault on both occasions was the battery. It was disconnecting itself internally and then, when left alone for 20 minutes or so would quietly re connect itself and the fault would go away for a couple of days.

Not saying that this is your fault, but worth bearing in mind

ZD

[Falco]

[Falco]

This is starting to get on my nerves.

Out on a ride yesterday and it spiked to 18V for ~5 minutes before returning to normal (Rising from idle at 12.4V, to 14.5V at 4K RPM, then dropping to 13.5V above that). Rode it slowly around backstreets to overheat the bike but it topped out at 14.8V.

Checked everything again this morning. Stator gives 0.6 Ohms between all 3 wires (haynes puts resistance specs between 0.18-0.20 Ohms but I've seen almost everywhere else say anything less than 1 Ohm is fine. Is Haynes being conservative or is the stator a bit wonky?), 11Vac @ idle, 41Vac @ 5K, 45Vac @ 6K. Not sure what to make of those since it's supposed to be >50Vac @ 5K RPM, but they are all pretty close to each other.

RR checks out fine (of course). Earth terminal (and surrounding area behind RR was cleared of rust and crap). Idled the bike and tried pulling all the bits of the harness I could get to (to simulate bad earth/bad connection) with no change of voltage at the battery.

Kind of pulling my hair out with this one. Supposed to be going on a trip back home next week, but the idea of being stuck on the motorway at 8K with the battery seeing 18V+ makes me nervous. What are the odds it is the RR as I can get a SH693-12 replacement (with fins!) by tuesday or wednesday if pull my finger out, but replacing random parts and hoping is not my prefered method of repair.
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I tell you what, mathematically, I'm having it

[Kawasaki Jimbo]

Overcharging can't be anything else but the reg/rec, can it?

[Nobby the Bastard]

Start bike, disconnect battery. Ride bike. See if voltage says 18.if yes, battery fucked. If no, battery not fucked.
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[Triton Thrasher]

There are £7 regulators on EBay. Trying one wouldn’t be an expensive test.
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Rrrrrrrrrrrrrrrrrr

[stinkwheel]