Slowly fading voltage while riding

[Skinner]

My setup: 1982 Katana 750, brand new Electrosport stator connected directly to SH775, which is grounded to the SPG and connected to the positive at the stock wiring harness location, new Yuasa AGM battery, coil relay mod. The battery shows 12.7 to 12.8 volts when the bike is off, drops to about 12.2 with the key on.

For the first 5 or 10 minutes of a ride my voltmeter shows 14.2-14.3 volts, which is just fine. However, after the bike gets really warmed up the voltage will gradually drop to 13.4-13.6. This is all when cruising at about 5000rpm. It doesn't go below that, but I'm wondering where I'm losing that voltage after the bike is fully warmed. The bike is charging - voltage is good when I return home and shut the bike down.

I also disassembled the fuse box last year, cleaned it up, De-oxited it and reassembled. All connections on the R/R wiring harness and associated wiring are crimped/soldered. My suspicion is that the stock connection in the wiring harness may be the culprit. Perhaps as the bike heats up there is more resistance in this connection or where the wire joins the harness? I installed a new terminal on the end of this wire, but didn't go back into the harness any further.

Any ideas?

[LAB3]

My guess is that it's doing fine, this is based on years of living with an alternative energy system that powered my home. Depending on the charge controller, the battery bank would ramp up to 14.2v early in the day and stay there for a bit then drop to 13.5 to maintain the charge on the batteries. A starter battery is meant to be recharged quickly in case of a short time between start cycles and keeping it at 14.2 is actually running a bit "hot" At 13.5 is where the best charging performance happens, I'm sure someone else will pipe in with an opinion but my feeling is your system is acting normally.

[twowings]

After starting the bike, the charge rate ramps up to a 14+ volt bulk charge which uses almost all that the charging system can put out and as the battery charge reaches normal levels, the charge should back down to a maintenance charge. That's normally about 13.2 to 13.6 or somewhere in this area. This takes into account the ongoing electrical loads of the bike while running with enough to maintain the battery's state of charge. Your readings sound perfectly normal.

[Skinner]

Thanks for the quick replies. I was under the impression that I should be seeing 14+ volts at all times. But this makes sense.

Cheers!
K

[Gorminrider]

It makes sense in large stationary systems with particular batteries, and will do your battery very little harm, if any, especially as it's a sealed battery..

HOWEVER. I didn't know and have never heard here that the SH775 was so "sophisticated". There's certainly been lots of blather about it....

Maybe it is (sophisticated)- I don't have one. Still, any regulator I have in a car or motorcycle does no more or less than maintain a steady voltage above 14v. Or at least they try to.

If I'm correct, I can think of various reasons yours is dropping when warm but you'd better wait for more people that have these regulators to chime in as a poll as to the first question. I'm curious too. The "stator papers" will need some kind of update.

[Skinner]

but you'd better wait for more people that have these regulators to chime in as a poll as to the first question.

Agreed. I'm hoping some of the electrical experts will chime in.

My SH775 is mounted in the tail piece - no room anywhere else on the Katana - so doesn't get much air flow. Could be that the R/R is getting hot causing output to drop.

[tom203]

My 650 behaves similarly....after startup 14+ ,but eventually tapers off to ~13.8. I figure maybe just my 36 yearold stator warming up..but might be my voltmeter also. It's been consistently like this for 5 years

[Steve]

Skinner, you may have a point on the R/R warming up. I have never noticed that mine ever got warm enough to be concerned, but it lives under the battery box, in the stock location.

Just out of curiosity, where is your sensor for your voltmeter?

.

[Skinner]

Just out of curiosity, where is your sensor for your voltmeter?

Hi Steve,

Positive is connected to starter solenoid post. Negative grounded to a convenient spot on the frame near the steering head.

[Steve]

OK, so you are essentially conected directly to the battery.

I have seen erratic voltage readings when the meter was connected several connection points downstream, so it was a lot of "fun" trying to find which connector was giving the funny results.

.

[Nessism]

I tend to think this is a non issue. I think the system will recognize when more juice is needed and respond accordingly.

[Gorminrider]

My SH775 is mounted in the tail piece - no room anywhere else on the Katana - so doesn't get much air flow. Could be that the R/R is getting hot causing output to drop.

this is an interesting question seeing as many here have these R/Rs.

It is not so unlikely this device has a safety feature per overheating. It would be noted in the spec sheet as "overload" protection.
As to heat and simple conductors like copper wire and so on, resistance increases as they get hot.This explains fuses that can't handle the heat and toasters and lightbulbs that can.

[Gorminrider]

...another thing, seeing as the R/R is so far away in the tail, would be voltage drop in the connecting wires themselves. I trust that these are a nice healthy gauge with their own perfect connections to the battery? + and -/ground? a Voltage drop across either path when the trouble appears would indicate trouble here...perhaps the R/R thinks it's putting out 14v+ if it is sensing regulation voltage point internally...(These don't have external sense wires like Honda shunt r/rs, do they?)

Or just in case you might be connecting R/R output to nearby wires of the tail-light or whatever -it would not be what I would do ...it theoretically would work but this is a seperately-fused circuit and some of Suzuki's wire gauges seem a little thin to me anyways ...

[LAB3]

Hmmmm, could this be that the SH775 somehow KNOWS it's connected to an AGM battery? Mine had a plain jane wet cell the last time I checked my voltage and haven't checked with my new AGM in place. Just a thought.

[Gorminrider]

Certainly lithium type batteries communicate to laptops, cell phones- but I don't think agms from Walmart do. Still they may be responding differently to the SH775s charge rate and mybe the sh775 "knows" from that...whether or not that might be a good thing. As said in the earlier posts, a lower battery voltage is not a bad thing and especially for sealed batteries like these agms...It's a reason I hesitated to buy an agm- the wet cells are a bit more forgiving per charge voltage- they just lose water when voltage is a little high...

AGM batteries are sensitive to overcharging. A charge to 2.40V/cell (and higher) is fine; however, the float charge should be reduced to between 2.25 and 2.30V/cell (summer temperatures may require lower voltages). Automotive charging systems for flooded lead acid often have a fixed float voltage setting of 14.40V (2.40V/cell); a direct replacement with a sealed unit could overcharge

https://batteryuniversity.com/learn/article/absorbent_glass_mat_agm