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Discussion Starter · #1 ·
My 82 gs750 won't charge while running. I've been told it's the reg/rec, the battery, or the stator itself. I have a brand new li-Ion battery just installed, so it's not that. Reg/rec is also brand new, but it's possible. Best guess is the stator. Any thoughts?
 

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Modern solid state batteries are not suited to old motorcycle charging systems, so your choice of battery is a big problem, Li-ion battery can not tolerate over-voltage or permanent damage results. Your original charging system was designed for a lead acid battery that is very tolerant of over-voltage, basically because it is liquid cooled. Manufacturers designed the charging system around that wet cell battery, not a Li-ion battery type that didn't even exist when your motorcycle was built.

Power generation starts at the alternator coils and magnets so that's the first place to start testing and then work down stream to the rectifier and regulator. The output from the rectifier and regulator needs to be compatible with your fancy expensive battery or else you need to go back to stock everything.

You don't need to guess with electrics because you can test every part if you have the proper equipment. ... except that Li-ion battery, if the battery has been damaged internally there is no test for that, it will just have a shorter life expectancy until it finally melts down, catches fire or just quits working.
 

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Discussion Starter · #4 ·

This is what I could find for my bike. I don't know much about regulators.
 

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This is what I could find for my bike. I don't know much about regulators.
Stop running it with the Li battery, you'll end up on fire. Trials explained the why not.

Desmodog did a post on how to avoid the hazards of old bikes, new batteries and the discomfort of a fire developing under your manhood.
 

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Discussion Starter · #6 ·
To clarify: it wasn't charging while I had a Cycle Gear Megaboost in it. That one shorted out, so I upgraded to Li-ion, but have not run it yet. I'm still working on the bike, so I haven't ridden it again. I just went to @DesmoDog s post on the regulator, but it's an old thread. Do you know where I can get a modern regulator?
 

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I buy the cheapest battery I can source and replace them when they let me down which is not for a couple 3 years, then they give me some money back for the old one, that's hard to beat.
You can regulate the power output you have, unless it's total garbage and you can determine that with an oscilloscope in minutes. You still need to know the charging voltage appropriate to your battery and only the battery manufacturer can tell you that.
Anything short of looking at the output from your existing alternator is just a guess, they output voltage all over the place and that's destructive to solid state devices, you need to clean up the power output.
 

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What does your shop manual say for checking the charging system? It's relatively easy to check the output to see if there is any, but a manual will cover it in specific terms. Do you have questions with what it's saying? If you don't have a shop manual for your specific bike, buy one before you spend any more money on charging systems.

When I googled info on regulators I came up with this link:

Does your battery have a built in BMS? If it doesn't, I wouldn't use it no matter what regulator you have. Fun fact - you can kill your lithium battery by putting too many volts into it, and you can kill it by discharging it too far. Yep, discharge it too far and it's game over, no recharging. Toss it and buy a new one. A built in BMS will typically protect against that and shut things down before the battery is damaged.

Did you get a lithium specific charger with your battery, or is the charger you're using safe to use with lithium batteries? A built in BMS also allows you to use some chargers that aren't lithium specific. Even with BMS though, a charger with an anti-sulfation cycle can harm the battery.

I'm a big fan of lithium iron batteries. I COMPLETELY understand why some people are not and would agree the best bet with vintage bikes is to check/optimize everything and then install an AGM battery. (I DETEST lead acid batteries, I don't care how cheap they are). That said I won't be running a lithium in either of my single cylinder projects. There comes a point they aren't worth the cost/hassle/risk of using.

Here is the aftermath of what can happen when you put a BMS protected battery into a 30 year old Ducati with no other safeguards and then roll the dice thinking it will all work. Spoiler alert - the bike said "Built in BMS? Bitch, please. Hold my grappa and watch THIS!"


And finally - if you must jump on the lithium bandwagon make sure you are buying a lithium IRON battery, and not a lithium ION battery. It's confusing, but there is a difference. Lithium iron batteries do not tend to burst into flames like lithium ion batteries have been known to do. I'm not sure but I think most motorcycle starting batteries are lithium iron. It gets confusing though, I once bought a less expensive brand and it was labeled iron on the box but ion in the documentation!
 

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lol I just checked the price for the 4 tiny little lithium batteries in my TRS headlight,
£ 286.82 plus tax and shipping,
that's 443 Canadian$ FOB England :ROFLMAO: like that is going to happen. I guess I'm trading in my TRS when the battery gets old.
 

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Discussion Starter · #10 ·
What does your shop manual say for checking the charging system? It's relatively easy to check the output to see if there is any, but a manual will cover it in specific terms. Do you have questions with what it's saying? If you don't have a shop manual for your specific bike, buy one before you spend any more money on charging systems.

When I googled info on regulators I came up with this link:

Does your battery have a built in BMS? If it doesn't, I wouldn't use it no matter what regulator you have. Fun fact - you can kill your lithium battery by putting too many volts into it, and you can kill it by discharging it too far. Yep, discharge it too far and it's game over, no recharging. Toss it and buy a new one. A built in BMS will typically protect against that and shut things down before the battery is damaged.

Did you get a lithium specific charger with your battery, or is the charger you're using safe to use with lithium batteries? A built in BMS also allows you to use some chargers that aren't lithium specific. Even with BMS though, a charger with an anti-sulfation cycle can harm the battery.

I'm a big fan of lithium iron batteries. I COMPLETELY understand why some people are not and would agree the best bet with vintage bikes is to check/optimize everything and then install an AGM battery. (I DETEST lead acid batteries, I don't care how cheap they are). That said I won't be running a lithium in either of my single cylinder projects. There comes a point they aren't worth the cost/hassle/risk of using.

Here is the aftermath of what can happen when you put a BMS protected battery into a 30 year old Ducati with no other safeguards and then roll the dice thinking it will all work. Spoiler alert - the bike said "Built in BMS? Bitch, please. Hold my grappa and watch THIS!"


And finally - if you must jump on the lithium bandwagon make sure you are buying a lithium IRON battery, and not a lithium ION battery. It's confusing, but there is a difference. Lithium iron batteries do not tend to burst into flames like lithium ion batteries have been known to do. I'm not sure but I think most motorcycle starting batteries are lithium iron. It gets confusing though, I once bought a less expensive brand and it was labeled iron on the box but ion in the documentation!
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How come when you click on any of Rick's Rectifiers it says currently unavailable :unsure:

This is probably closer to what you really need anyway:
 

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im probably repeating what the above people have already said, check the battery with bike running. should be 13 plus volts or there abouts. if theres no difference with the bike running or not- stator. early suzukis or infamous for crap stators. should take no more then 15 min. pull off engine cover. look at stator . one or more of the windings might be toasty. replace.
 

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Nice. The label on the battery lists it as both a lithium ion and lithium iron battery.

So I did more googling and it seems that some places are saying that a lithium iron is a type of lithium ion, which I don't believe but chemistry isn't my thing so whatever. I'd be surprised if anyone was selling something other than lithium iron for bikes.

Anyway... there's nothing in the description that says it has any protection against over charge or discharge. Maybe it's got it, maybe it doesn't. If you already have it you may as well run it until there's a real issue. Just remember not to let it drain too far.
 

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So I did more googling and it seems that some places are saying that a lithium iron is a type of lithium ion
I found this on a company website - it's a good explanation.

 

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I was working at Suzuki dealer in early/mid 80's.
GS750 was a bit overweight but still a good motor let down by crap charging system.
No where near as unreliable as the GSX550 though.
Get a re-wound stator, modern Mosfet R/R and you'll be golden.
It's a permanent magnet system, you can check outputs for contiuity and probably find a winding burned out or broken (where did you take it that doesn't even know basic electrical troubleshooting?)
 
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