SH775 swap - engine won't rev over 6k

[posplayr]

And while you're at it, ditch the Lithium battery. As previously mentioned, they can not be properly charged by an old GS. In fact, that might be the entire problem, not any of the other stuff.

And with all the well-publicized problems with Lithium batteries, are you sure you want one under your butt, right near the fuel tank while riding?

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This document summarizing LiIon battery charging. I suspect any LiIon battery pack designed to be a drop-in replacement for a Lead Acid, must have some type of charging conditioning electronics built in.
Here is an example of voltage and current profiles for charging. A standard R/R is going to put out a fixed 14.5V nominal and the current will be whatever the battery itself controls or (doesn't control to).
Maybe the charging system can't support the current demand and it can't actually get to 14.5 till charged. That is also what happens to Lead Acid which is why you have to charge the battery to get the proper charging test results.

They sell them so they must be OK, that doesn't mean that they will have optima longevity without some internal electronics.

https://www.digikey.com/en/articles/techzone/2016/sep/a-designer-guide-fast-lithium-ion-battery-charging

Figure 2: Li-ion charging profile using constant-current method until battery voltage reaches 4.1 V, followed by ?top-up? using constant-voltage technique. (Image source: Texas Instruments)

[Steve]

Thanks, Jim, I have never seen the curve or the actual numbers.

Looking at the 4.1 volt "full charge" number, I would guess that the battery will never get to full charge. If you put three cells in series, the nominal voltage will be about 9 volts, the "full charge" voltage will be 12.3. If you put four cells in series, you would have a nominal 12.4, which is pretty close to what the bike is designed to use, but your "full charge" voltage would be 16.4, which simply ain't gonna happen.

Maybe there is some circuitry to control the charge, maybe there isn't, I don't know. It is also possible that the manufacturers are going on the assumption that we are willing to accept some trade-offs for the 'benefit' of weight reduction. Even a modestly-charged Lithium battery should be better than a poorly-charged lead-acid battery, and I'm guessing that most purchasers are getting a Lithium battery when their lead-acid battery fails, so ANY state of charge on a battery will be better than what they had.

Just guessing.

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[posplayr]

Thanks, Jim, I have never seen the curve or the actual numbers.

Looking at the 4.1 volt "full charge" number, I would guess that the battery will never get to full charge. If you put three cells in series, the nominal voltage will be about 9 volts, the "full charge" voltage will be 12.3. If you put four cells in series, you would have a nominal 12.4, which is pretty close to what the bike is designed to use, but your "full charge" voltage would be 16.4, which simply ain't gonna happen.

Maybe there is some circuitry to control the charge, maybe there isn't, I don't know. It is also possible that the manufacturers are going on the assumption that we are willing to accept some trade-offs for the 'benefit' of weight reduction. Even a modestly-charged Lithium battery should be better than a poorly-charged lead-acid battery, and I'm guessing that most purchasers are getting a Lithium battery when their lead-acid battery fails, so ANY state of charge on a battery will be better than what they had.

Just guessing.

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Electronics is asymptotically going to zero so don't underestimate the ability to stick some DC to DC converter in to optimize charging. I don't expect every joe blow to do it, but it is certainly economically feasible/possible.

I bought a Lithium Ion batt from one of the top manufacturers (about 7 years ago), and went to all the trouble of cutting my battery box down and the battery went dead in one week from a small current drain and killed a $150-$175 battery. It obvioulsy had no electronics in it to prevent that.

[Steve]

Which is pretty much why I watch with amusement all the posters that install them for weight savings. Saving what, 8-10 pounds on a 500+ pound bike? On a race bike, yeah, no problem. ANY weight saving is better performance, but I just don't see any advantage on a street bike.

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[posplayr]

Which is pretty much why I watch with amusement all the posters that install them for weight savings. Saving what, 8-10 pounds on a 500+ pound bike? On a race bike, yeah, no problem. ANY weight saving is better performance, but I just don't see any advantage on a street bike.

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Hand grip tassles might be more functional? With a dead battery the first week , it would certainly have been the case.

[hotrodalex]

Turning the key on only drops voltage .01v

I did a resistance test on the stator wires and the white/red wire says it's an open circuit. AC voltage test says the same thing. So I'll dig into that and see if it's the wiring or a partially fried stator.

Also, my bike is only a smidge over 400 pounds.

As for lithium batteries, I've got a Shorai and it's a lithium-iron battery, not lithium-ion. These won't burst into flames - they'll just smoke and melt down. I got it because it'll hold its voltage for like a year without charging, plus it's a bit more lightweight. I had troubles with the previous lead-acid battery so I decided to try something new. I'm a restomod guy so I just enjoy putting more modern tech on old things (I've got a '69 El Camino pro-touring car as well)

Here's a link to Shorai's charging guide: https://shoraipower.com/charging

[posplayr]

Mine was a Shorai as well (discharged itself into oblivion the first week). I hope they had added some basic control electronics by now.

[hotrodalex]

https://i.imgur.com/VQoTnWD.jpg

I pulled the stator cover off today. No signs of burn out. Could it still be bad, or should I turn my attention elsewhere?

VQoTnWD.jpg

[hotrodalex]

Ok so I have a couple of lights that aren't working right now either. The tail light doesn't come on with the headlights, even though the brake light works fine (same bulb). Neither do the dash lights for the tach or speedo (but all of the other dash lights work fine). In Park, neither the tail light or the front yellow bulb in the headlight comes on. The two affected wires are the gray or brown wire on the wiring diagram. They go through the ignition switch and lighting switch. The lighting switch is where the gray wire originates, and it also happens to be where one of the stator wires goes through (so the stator is only running 2/3 power unless the headlight is on?)

If I replace the lighting switch, it might solve all of these issues. I'll do some testing tomorrow.

Tb6eh0I.jpg

[tom203]

Way back you said your stator tested bad....

"I did a resistance test on the stator wires and the white/red wire says it's an open circuit. AC voltage test says the same thing. So I'll dig into that and see if it's the wiring or a partially fried stator."

Unless it's Cajun fried, a visual test is sorta useless ..
you likely have switch issues, but hopefully you have connected the stator wires directly to the SH-775 to eliminate a switch interfering with charging.

[cowboyup3371]

Did you also check your fuses as the headlight/taillight are on the same circuit? Is it the older tube style or a new blade style? If the tube, keep in mind that it can be broke under the caps where you can't see it. Please test it using a test light to be sure you are getting power to both sides of it before trying to replace switches

[hotrodalex]

Way back you said your stator tested bad....

"I did a resistance test on the stator wires and the white/red wire says it's an open circuit. AC voltage test says the same thing. So I'll dig into that and see if it's the wiring or a partially fried stator."

Unless it's Cajun fried, a visual test is sorta useless ..
you likely have switch issues, but hopefully you have connected the stator wires directly to the SH-775 to eliminate a switch interfering with charging.

I figure since it looks pristine still, it's worth investigating the rest of the wiring harness & switches first.

[hotrodalex]

Did you also check your fuses as the headlight/taillight are on the same circuit? Is it the older tube style or a new blade style? If the tube, keep in mind that it can be broke under the caps where you can't see it. Please test it using a test light to be sure you are getting power to both sides of it before trying to replace switches

As far as I know, these '77s only have the 1 main fuse back by the R/R.

[Nessism]

First off, the charging system should be rewired to bypass the stator leg through the headlamp switch. This has been discussed countless times here and should be the first thing done when investigating charging system problems. https://www.thegsresources.com/_foru...nstall-Diagram

Secondly, as already mentioned by more than one of us, a charging system issue won't cause the bike to not rev, assuming the battery has a decent charge. If the battery has enough charge to spin the starter motor the bike will rev to redline. Running problems will only come in after the battery gets run down.

[hotrodalex]

First off, the charging system should be rewired to bypass the stator leg through the headlamp switch. This has been discussed countless times here and should be the first thing done when investigating charging system problems. https://www.thegsresources.com/_foru...nstall-Diagram

Secondly, as already mentioned by more than one of us, a charging system issue won't cause the bike to not rev, assuming the battery has a decent charge. If the battery has enough charge to spin the starter motor the bike will rev to redline. Running problems will only come in after the battery gets run down.

Thanks. My next step will be to re-route that stator wire direct to the R/R. Is that recommended even with a stock R/R or only with the SH775? And then I'll see if the dash lights/etc work if I temporarily bypass the lighting switch.