GT550 battery elimination who has done it? kick only

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rubbersdown550
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Suzuki 2-Strokes: gt550

Re: GT550 battery elimination who has done it? kick only

Post by rubbersdown550 »

Ya but alternator has to be change to eliminate the battery and thats my main goal. I want the entire area where the battery is to be clear and nothing but a custom aluminum oil tank. All electronics there will be relocated as well
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jabcb
Moto GP
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Suzuki 2-Strokes: 69 T350 thru 75 GT750
Location: southwestern Pennsylvania

Re: GT550 battery elimination who has done it? kick only

Post by jabcb »

That is what we are doing on the GT250 cafe project.
We are using a small Antigravity battery located under the seat bump & a custom made oil tank.

The oil tank was made by: http://www.anythinggoescustomcycles.com ... tanks.html
We used a simple cylindrical shaped tank.
They can also make a tank with a compartment for a hidden battery.
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
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Alan H
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Suzuki 2-Strokes: 4 x GT550s - J, M, A, B.
Location: The Republic of South Yorkshire

Re: GT550 battery elimination who has done it? kick only

Post by Alan H »

jabcb wrote:
Alan H wrote:That graph looks wrong. A '12v' battery needs at least 12.8vdc to charge and that only gives 12.6 at 8000rpm. The bottom line '14v' never actually gets to 12v, so best of luck with that system.
Suzuki make an alternator that does the trick - 2 types 15amp and 25amp. They're fitted as standard but do need a battery to run the regulator , which in turn runs the exitation coils in the rotor.
You do as you feel, but I can't see the point of spending lots of time and good beer money to do a job that Suzuki sorted out 40 odd years ago. Of course, I prefer riding the darn things than building them. (Says him that's just started yet another GT550 resto!)
The alternator voltage is a function of the load.
So for a given rpm, the no-load voltage (voltage at 0A) might be 40V, with 8A current it might be 14V, and with 10A current it might be 12.6V.
40v will fry everything. Voltage and current increase with rpm. Voltage shouldn't exceed 14 volts or so or bulbs go first. Track use onlt really.
Think of how stupid the average person is, then realise that half of them are more stupid than that.
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jabcb
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Joined: Mon Dec 13, 2010 4:32 pm
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Suzuki 2-Strokes: 69 T350 thru 75 GT750
Location: southwestern Pennsylvania

Re: GT550 battery elimination who has done it? kick only

Post by jabcb »

Look at the vertical line for 2,000 rpm in the Powerdynamo chart.
At 2,000 rpm with a ~7.5A load, you get 12.6V
At 2,000 rpm with a ~6A load, you get 14V
They don’t specify the open circuit voltage at 2,000 rpm (voltage with zero A load), but its likely over 20V.
Image


Per the GT750 shop manual…
To test the alternator open circuit voltage, you bypass the voltage regulator & provide full battery output to the file coil (the rotor).
Then with the alternator output not connected to a load you get:
for 1,500 rpm the alternator output open circuit voltage is more than 16V
for 2,500 rpm the alternator output open circuit voltage is more than 27V

The GT-triples have a voltage regulator that controls the current going to file coil so that the alternator output voltage is correct.

The Powerdynamo uses a permanent magnet alternator.
Permanent magnet alternators don’t have a field coil.
Traditionally they use a shunt-type voltage regulator that controls the voltage by adding additional load to the alternator.


The T250/T350/T500 also have permanent magnet alternators.
They have switched alternators with charging & lighting coils. The lighting coil is switched on only when the lights are on.
The switch provides most of the alternator output control.
Beyond that they mostly rely on the battery to make sure the voltage doesn’t get too high.

A costly example...
Some time ago I was working on my 71 T350.
Disconnected the battery & adjusted the points.
Then was interrupted & forgot to reconnect the battery.
Then kick started the bike. After a few moments the neutral light went out.
No battery ==> no voltage regulator. And I burned out the headlight, neutral light & taillight.
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
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Alan H
Moto GP
Posts: 3160
Joined: Thu Feb 16, 2012 11:50 am
Country: England
Suzuki 2-Strokes: 4 x GT550s - J, M, A, B.
Location: The Republic of South Yorkshire

Re: GT550 battery elimination who has done it? kick only

Post by Alan H »

I'll stick to standard and not boil the battery or over voltage/charge the system.
Just in the middle of a 1500 mile tour of Southern Ireland on a GT750 and I do appreciate the electric start and lights etc!
Think of how stupid the average person is, then realise that half of them are more stupid than that.
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