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I have been using an Orion for the past six years and it is very good. If I can answer and questions let me know?
Actually the two most important stages for charging lead acid and Lithium chemistries are Constant Current (often called Bulk) and Constant Voltage (called Absorb} The way it works is that the Power Supply or charger charges at the current the charger is set for until the voltage at the battery reaches the Constant Voltage point and then the current automatically tapers as the voltage stays the same. So there is no such thing as a "higher voltage bulk stage". Actually Lithium batteries can be charged faster and at higher current and they are much more efficient so they charge faster than Lead Acid batteries of the same capacity using the same charger or charge settings.
They both can use an absorb phase but to be healthy a Lead Acid battery must be kept at the Absorb phase longer. Yes Lead Acid is less efficient because you have to put in more than you took out. A Lithium battery does not require an Absorb phase and could be terminated at any voltage and be left there with no damage. A lead acid battery has to see a prolonged absorb phase to stay healthy. That extra time does not result in much increased capacity hence the less efficient charge characteristic
Just to pick up on your earlier comment about a 36 volt golf cart, I am confused by the 3.6 volt charger you mentioned. Most Golf carts used lead acid voltages and since a normal 12 volt battery is charged to 14.4 volts that would be 43.2 volts and if using typical LFP cells that would mean 12 of those. Conveniently 43.2 volts divided by 12 is 3.6 volts per cell. Perhaps that is what you are doing. I just did not want you or another reader to think that to convert a golf cart would only take 10 cells at 3.6 volts. That would actually be an underpowered golf cart and if the same charger was left in the ten cells would be way over charged.
Ampster is giving good advice here. I have done extensive testing, and the claim of 98% efficient might even be an underestimate. I consistently measured input versus output, and 98% is on the money. No need for anything fancy with adsorption, just make sure to use a good connection (no alligator clips). Don't try to get that last little bit in, 3.4v per cell is more than enough, maybe even less. As long as your connection is low resistance during charging, you can push plenty of amps in like that.
If your golf cart charges to 43.2 volts you should be fine unless you want to go to a lower voltage in which case a programmable charger might be better. There are some that interface with the Orion and that would give you some options. The Orion heritage is motive power like EVs, golf carts and mining vehicles so they do a great job of giving you an accurate SOC.
