Red Harvest, do you mind telling me what kind of RTW are you running with? 1.2 or not? Vanilla? SPQR? RTR? EB? Or self modded? If your version do work correct, then I would like to see what may cause the nullify of the charge bonus as some if not many people see. I don't know if you will bother with this but I suggest you just try to do the following test:

Grassy Flatland
Round Shield Cavalry with 0 charge bonus VS Iberian Infantry, head on charge, double click on the infantry right after employing. Look carefully at the result of the first clash. Exit the battle. Do this 3 times.

Next, Round Shield Cavalry with 10 charge bonus VS Iberian Infantry, head on charge, double click on the infantry right after employing. Look carefully at the result of the first clash. Exit the battle. Do this 3 times.

Last, Round Shield Cavalry with 20 charge bonus VS Iberian Infantry, head on charge, double click on the infantry right after employing. Look carefully at the result of the first clash. Exit the battle. Do this 3 times.

Tedious, isn't it? Heck, I spent 3 whole days doing similar tests.

If anyone is interested, I sincerely hope you can join in this research and see if the charge bonus actually exist or not. If it do exist, then what it actually do, and how much the effect is.

And an additional note: CA said that units with the Spear attritube fighting cavalry would use the cavalry's charge bonus against that cavalry. Yet a Round Shield Cavalry with 2 charge bonus and with 52 charge bonus head on charge into a hoplite phalanx suffered similar casualities, without any critical difference. So apparently either the phalanx ignore the cav's charge bonus, or the charge bonus doesn't even exist.

If anyone insist that charge bonus do give difference, and for difference I mean big, noticable increase in casualties, not some small error due to the randomness in each test, then I would gladly to reinstall the whole game just so I can see if the original world is clean and clear.