[brian_]

Why would you make a series hybrid out of a transmission which is already - in its stock form - an advanced power-split hybrid system? Why not just connect the motorcycle engine to the L110 (from GS 450h) input?

A series hybrid system will be less efficient, and more difficult to control, but of course you can do it. You're just duplicating the usual engine-driven generator set configuration, but with a ~300 V generator (the obvious source is any EV drive motor that is handy and for which you can get a controller). This is not normally sold as a ready-to-use package (because no one needs a 300 V DC generator set), but to use the motorcycle engine you're not looking for a complete set anyway. Typical "inverter" generator sets produce high-frequency high voltage DC from the generator, and rectify then invert that to produce 120 V or 240 V AC; the control system for both engine and inverter is one package specifically intended for these generator sets.

 

[brian_]

...the motor cartridge in there is good for 300A...do you really need 90kW (about 120hp) of power? You need to figure out how much HP you need to run 25MPH and do your calcs from there, not "whatever".

This is for a tracked vehicle.

Tracked vehicles need a lot more power than a wheeled vehicle at the same speed. Any vehicle on the types of surfaces where tracked vehicles are used needs a lot more power than the same vehicle on a road surface at the same speed.

 

[brian_]

I'm using the gs450H which you can get spinning at 40v but can go all the way up to 600v with a boost converter. My plan is around 300v and what ever amps it needs.

Boost is also a very bad idea...it's lossy and the current input on the low voltage side is ampere hell.

I don't think the intention is to use a boost converter; the reference to the boost converter is just to explain why the motors in the GS 450h's transmission are suited to 600 volts, even though the battery pack nominal voltage is only 288 volts.

 

[brian_]

My plan is around 300v and what ever amps it needs.

Amps isn't "whatever it takes"...the motor cartridge in there is good for 300A...do you really need 90kW (about 120hp) of power? You need to figure out how much HP you need to run 25MPH and do your calcs from there, not "whatever".
...
Get the battery rightsized for the job or you'll be cooking thanksgiving turkey in your tank tracked oven.

I'm sure that Rusted B&B meant that the plan is to operate the battery pack at about 300V, and whatever current is required to deliver the power needed for the vehicle... which has yet to be determined. The calculations are clearly not finished.