I have my own load tester, otherwise you can just bring your battery in to an Auto parts store, they'll do it for free. It's all about the amps.

Sounds like cleaning the connections did the trick though.

 

If you replace the battery cables go with heavier gague ones, helps deliver more amps to starter

Went down the inexpensive litium battery road once, that's how I learned about the ACR closing under low voltage, I would stay with a tried and true like "Antigravity"

 

Interesting. I was under the impression that the voltage drop in a lithium battery is about .1% in a resting state. I wouldn’t call it a cheap version… about $165 where as the agm is about 150. I hear you on the “tried and true” theory though.

 

I went with the same 4 gauge wires. I believe 2 gauge would be too tight of a fit in the battery box. Pretty tight as it is. I believe that is how the other 4 gauge cable got punched to begin with.

 

Not so much of a thing with softails since they are not rubber mounted but I add a ground cable from the battery to a starter bolt.
The ground is usually more the issue.

 

When you are it, check for a voltage drop over the positive cable from battery to solenoid and solenoid to starter. If you have any voltage drop, even like 1/10 of a volt, from one end of the cable to the other, suspect that the cable has corrosion inside and you can't see it. When that cable comes under load for the starter it can cause the large voltage drop you are seeing.

Ideally the battery should stay above 11 Volts when cranking, and anything lower on a FI bike and the fuel pump won't run. Anything in the 9 range is not good news.