Charge in DO

units in DO has two types of charge:

• Auto-charge
• Manual charge

Auto-charge (Acharge): executed automatically when targeted enemy gets in unit Acharge range. Acharge range has fixed distance which depends on unit's movement and initiative characteristics. It is uncertain if DO uses either time or speed to calculate Acharge range since there is also a chance element in the formula and both parameters' values vary each time (see SOTHR manual on this chance). Targeted unit that receives charge can't move during Acharge execution and this guarantees successful collision between units and start of melee combat.  If two units attack each other simultaneously then the unit with higher real speed will get Acharge.

Manual charge (Mcharge): executed manually by player pushing button and doesn't require pre-targeted enemy unit. Mcharge has fixed distance based on unit charge speed and time and has greater range than Acharge. Mcharge is targetless, thus charge potential target can move and has a chance avoiding collision with charging unit. 

When charging unit successfully connects with enemy unit it initiates melee combat between them. Charging unit receives 1 bonus to its Strength and strikes first despite its and enemy Initiative. These bonuses applied to the 1st round of combat only.

If both units simultaneously Mcharged into each other than they both receives 1 Str bonus and strike according to their initiative order.

Charge bonuses

Charging unit receives following advantages in melee:

• +1 bonus to Str characteristic for one round despite of arc being charged 
• first strike for one round despite of arc being charged
• +1 point for flank arc ( +2 for rear arc) charge to combat round score

in 8thE instead of first strike and bonus to Str charging unit only gets additional +1 bonus ( +2 from hill) to combat round score  for one round.

Test notes

• Unit charge is affected by charge speed and time.
• MCharge speed depends on unit Movement and Initiative characteristics (just like movement speed or so called RS). MCharge time depends on unit Movement and Initiative characteristics as well and the lower unit's m and i values the longer the charge. As an assumption, DO devs use this approach to balance distance gap between units with high m,i and units with low m,i 
• Unit type (i.e. cavalry or infantry) doesn't affect charge parameters
• Acharge has 100% collision chance and start of combat unless enemy or charging unit flee and/or charging unit intercepted by holding magic spell (pls, see video). Chargin unit may be also gets destroyed during charge.
• Charge increases unit Strength  characteristic for 1 during first combat round
• Acharge has constant distance and not speed/time like Mcharge

Charge speed 

DO precise formula is unknow for both types of charges. Numerous tests only show that Acharge and Mcharge are calculated differently.
Mcharge is most likely based on unit RS and charging time values due to the fact that unit with m0,i0-5 can't move but still can charge on the spot during specified time duration.
Acharge on the contrary has constant charge distance but different charge speed and time. This means that calculation of Acharge is based either on distance and speed or distance and time, plus some probability element (according to SOTHR manual). 

Due to mentioned above reasons, DOR uses own Mcharge and Acharge formulas which still try to preserve true to DO charge values.

Mcharge real speed (McRS) formula is the following:

McRS=RS*a

where:
McRS - manual charge real speed
RS - unit movement real speed
a - modifier (default value is 1.375)

final formula is McRS = (m*0.45 + i*0.1 - 0.2) * 1.375

Acharge real speed (AcRS) formula is the following:

AcRS = McRS - 0.1 * randbetween(min,max)

where:
AcRS - auto charge real speed
McRS - manual charge real speed
min,max - minimum and maximum values of chance element (default values min 1, max 6)

final formula is AcRS = (m*0.45 + i*0.1 - 0.2) * 1.375 - 0.1 * randbetween(1, 6)