Antigravity Batteries. 4 or 8 cell?

[BBS360]

The point of the mosfets is to handle excess current for much larger bikes without wearing out.

The point of the mosfets is that they can be electronically controlled to regulate voltage. The circuitry in the regulator fires the mosfets at different phase angles depending on the voltage output from the stator in order to convert the three phase AC output from the stator into a regulated DC voltage.
These regulators are meant for bikes with permanent magnet alternators where control of the field coil is impossible so voltage regulation must happen electronically.

The lithium graphene battery can handle more volts than a functional regulator will put out.
Once it's charged to the charging voltage the current should just pass through the battery and since the graphene batteries have nearly zero internal resistance this shouldn't produce any heat.

The Turnigy batteries look to be pretty robust little guys. Looks like hobby king has 4 cell versions all the way up to 10Ah.
Could be a good alternative to AntiGravity batteries.

I suppose my main concern would be the feild coil and stator. I'm worried since the stock regulator rectifier isn't charging at rpms less than five thousand that keeping the stock regulator will continue the same problem.

The problem below 5000rpms isn't that the voltage regulator isn't trying to charge the battery, the problem is that the entire alternator physically does not produce voltages high enough below that speed.
Below 5000 rpm, with the battery presumably discharging, the stock voltage regulator would be outputting its maximum rate but the rotor just isn't spinning fast enough. It's only when the rotating field cuts the stator windings above 5000 rpm that the generated voltage exceeds the voltage required to charge the battery.
Changing to a modern voltage regulator or removing the stock one will have NO effect on the voltage output below 5000rpm other than possibly being more efficient by virtue of being newer and made to modern standards. Might mean that you'll see the required voltage generated at a slightly lower rpm. Maybe 4800 instead of 5000.

50 watts of power in the feild coil doesn't mean 50 watts of heat. I'm assuming most of that is turned into a magnetic field and only the current lost in resistance turns into heat. A fraction of 50 watts isn't much heat.

The 50W is a rough approximation based on (14.5^2)/4.04 (stock field coil is 4.04ohms) and is almost all heat. There's no simple formula that could accurately calculate the power consumed to generate the magnetic field, especially in our type of alternator with its mutual-mutual-induction design, but I'm sure it could be deduced by observation with the right equipment.
In any case though, it's heat in the field coil which is dissipated pretty well into the engine casing. It's no more heat than it sees when the bike is running and charging a depleted battery, but it's not meant to be doing that all the time. Especially with our aging components I'd want to reduce any stress on them, not increase it.

 

[maydaverave]

So is there a relay in The stock regulator that completes the circuit when voltage drops? I wonder if the mosfet regulator would take the brunt of the work or will it be split between the two regulators? having two regulators should definitely extend the life and reliability of the stock unit. I wonder if there is a charging relay for a twelve volt system i could put in place of the stock regulator to turn the field coil on and off?

 

[maydaverave]

The turnigy graphene batteries are amazing. I'll keep you updated on it's durability. I'm running a 4s 5ah one right now. I'm hoping for more durability than lead acid.

 

[BBS360]

So is there a relay in The stock regulator that completes the circuit when voltage drops?

The OEM mechanical regulators have a kind of relay in them. The circuit diagram for the early models shows how the mechanical regulators work. There's a resistor in series with the field coil for the maintenance charge and a contact that shorts around the resistor for full power to the field coil.
The later models are electronic equivalents. A reduced voltage/current for the maintenance charge and full voltage to the coil for full battery charging.

I wonder if the mosfet regulator would take the brunt of the work or will it be split between the two regulators?

Probably a bit of both. The stock regulator should reduce the load on the MOSFET reg once the battery is charged.
The MOSFET regulator wouldn't really do anything to help the stock regulator but it provides overcharge protection that the stock one does not do well.

I wonder if there is a charging relay for a twelve volt system i could put in place of the stock regulator to turn the field coil on and off?

I'd suspect the triggering voltage of a simple relay wouldn't be accurate enough to just drop-in. Something could be made with a carefully selected zener diode that'd do it.
A quick google search found this: https://books.google.ca/books?id=6SiOAQAAQBAJ&lpg=PA178&ots=W4AC15-VOc&dq=14.2V zener diode&pg=PA178#v=onepage&q=14.2V zener diode&f=false
The diagrams don't seem to be visible but it matches our application.

Rather than making a voltage regulator from scratch it'd be a lot easier to just buy an aftermarket regulator for field coil alternators.
I linked to two adjustable aftermarket regulators in post #6 of this thread. There are also plenty of non-adjustable regulators on the market with various different voltage setpoints.

Some aftermarket regulators might need slight wiring modifications to work. To quote the Oregon Motorcycle Parts page:

Voltage regulator for all 12 volt bikes with an electro magnet field alternator that
has one pole grounded.

XS400s with mechanical regulators have one pole of the field coil grounded but later models with electronic regulators changed it to the opposite setup, one terminal to + battery voltage and one grounding through the regulator.
It's a pretty straightforward wiring change though.

 

[Jeff0133]

The turnigy graphene batteries are amazing. I'll keep you updated on it's durability. I'm running a 4s 5ah one right now. I'm hoping for more durability than lead acid.

Are you using kick Only? Does the e-start work with Those? I know nothing about the electrical part of these bikes yet but would imagine that with the e-start you would need an 10000mah Minimum?
I may be wayyyyy off,like I said I know nothing , but am looking for a lightweight/small battery for my build.

 

[16VGTIDave]

"Ah" or "mAh" are basically a capacity rating. The amount of current (A) that a storage device can deliver in an hour (h). A valuable number, but not relavent to starting an engine. Starting requires current flow. Amps, typically stated as Cranking Amps. Cranking Amps is the current a 12V battery can deliver at 0C/32F while maintaining a minimum voltage of 7.2V. About 30A is required by the starter on our bikes, if I remember correctly.

 

[maydaverave]

I have given up on lithium. I'm installing a 16volt 83 farad ultracapicitor. Pros, never wears out, charges and discharges as fast as you can put in or take out power. Cons looses stored power in a day or two.

 

[16VGTIDave]

So, I guess leaving the bike at a marina on the main land and spending a weekend at an island cottage would be out of the question?

Thanks, but I'll stick with my AGM battery. It can easily start my bike at -10ºC / 14ºF after sitting for a week.

 

[BBS360]

Good point. What's the minimum temperature the ultracap can withstand?
Some capacitors don't like freezing.

 

[maydaverave]

I think its rated for -50f. Its designed to start large engines in cold weather in tandem with a battery. I should literally be able to jumpstart a dump truck.

 

[maydaverave]

It's not an ideal solution. It works but i was hoping it would help my bike at lower rpms. I think a lithium battery with a battery management system would be best. For as much as they charge for a lithium starter battery it should have low voltage cuttoff, and a regulated charging voltage that charges and balances at the cell level. The two hundred dollar 8 cell antigravity battery is a fifty dollar lipo battery with no bms.

 

[NewHavenMike]

So there's no other options out there for a small battery that won't burn out the bikes electrical?

When you run a lithium battery, you will damage various components?

 

[maydaverave]

Lithium batteries shouldn't burn out your electrical system i think its more an old weak charging system destroying your lithium battery. If your charging system constantly runs at 14.1-14.5 volts even at idle then you should be fine with a lithium batterry. My charging system is erratic with voltage anywhere from 8-14.4 volts. This is extremely hard on any battery. Luckily my ultracap last forever on voltage from 0-16 volts and it does have balancing and high voltage protection.

 

[16VGTIDave]

If your charging system is only making 8V, there is something wrong with it. No battery is going to resolve that.

 

[maydaverave]

It can not be destroyed everytime i take a test ride. Allowing me replace components and wiring then take a test ride without being stranded and having to buy a new battery.