Why I'm posting this on Christmas instead of Halloween, I've no idea.
These things just come to me.
On the subject, Happy Christmas, everyone! :D :D :D

While mostly creatures of myth, batponies and the vampirism of equines is a complex science.
Just like the diet of bats, batponies need a very high intake of sugar, iron and protein to properly function.
[Note: My sources tell me that this is why Lord Commander Midnight Blade has the strange habit of pouring honey, jam, mincemeat and/or scrambled egg over most things he eats. He always has these things around him but nopony knows where he keeps them.]

Batponies only resort to drinking blood when they're starving. This can often happen soon after a pony's bitten as the normal diet of a pony doesn't produce enough nutrients for batponies. Their metabolism is too fast and their powers over sonar, flight and shadow-magic can become impossible to control without proper focus. In moments after infection, a batpony can resort to hematophagy in a fit of maddening hunger, a frenzy known colloquially as ‘Blood-Moon Fever’ but among Vampony covens is known simply as ‘The Thirst’ or occasionally, among the leaders ‘The Calling’.

The difference between a batpony and a Vampony is a question not so much of biology as it is of conscience. New carriers of the batpony gene will experience trauma and debilitation in the main detriments of the transformation such as the aversion to sunlight, the extreme dryness of skin, loss of equilibrium, the hyperacusis of hearing, sight, smell and touch and, of course, the reactions of others, all so sudden and simultaneous, can drive a pony quite irrational. But he/she will still retain memory and outlook. It is only when The Thirst become too great that one will steadily lose one’s mind and regress into ravenous cannibalism.

The Thirst can be overcome with great self-restraint as one is eased onto the necessary diet until a cure can be produced.
Numerous cures exist in Earth Pony alchemy, Pegasus aerotherapy or Unicorn magic but if one remains as a batpony for more than a full season or if one is bitten by a fully fledged Vampony with affinity in blood and shadow magic, the transformation is, as far as research can tell, permanent.

There are, depending on one’s outlook, benefits to the transformation. Once focus and equilibrium are regained, batponies possess heightened senses and reflexes, powers of flight, sonar, thermoception, rapid healing and an affinity with shadow magic, granting them powers shared by all three pony tribes at once, though not on the same natural level.
Batponies also possess incredible longevity, though not on the same level as Alicorns and Draconequui. Batponies have been known to die of old age, usually subjects who were already old by time of transformation, after several centuries.

Shadow Magic

Skiamancy is an affinity with the manipulation and weaponisation of natural or beast-made shadow. The batpony gene carries a natural affinity with skiamancy and a subject may notice signs of this element soon after their transformation.

Standing in the shadow, one’s coat steadily darkens and dulls in camouflage. Honed over time, they can become virtually invisible in the darkness. Adept skiamancy produces even greater capabilities. They can channel their own shadow and manipulate to any size and shape. They may cast moving shadows on surfaces without a solid body. They may even use their own shadow as a sanctuary as they sink into it and rise from another area of darkness in swift, medium-range teleportation upon themselves or others.

Inside one’s shadow, one is not separate from this world but certainly not touched. It is believed this is some form of low-level inter-dimensional magic, quite similar to Princess Luna’s Onaromancy, Dream Magic.

In battle, a batpony can morph their shadow into a deadly weapon or ally. The earliest stage is what is known as ‘Shadow Claws’, a magic taking the form of four misty, oily-black claws that form on the forehooves of batponies, activated seemingly at will though can come out instinctively in moments of tension or aggression.
As this ability develops, the shadow can be used at will to form claws, scythes and whips of dark magic, channelled by rage, vigour or hunger.

One certain sign to separate a batpony from a Vampony; the shadow magic of batponies can cast a colour that can be black, grey, navy blue, khaki, sepia or indigo, depending on one’s natural colours, while the magic of Vamponies will always be a deep blood-red.

Batpony Communities

Controlling The Thirst can be accomplished and, over steady periods of time and care adapting to their new lifestyle, it is entirely possible for a batpony to reintroduce themselves to society.
There are cases of batponies in pony family lines but the gene is prevalently subservient. A pony born to a batpony and a non-batpony parent will not become a batpony. Only a foal of two batponies will produce a batpony and the pregnancy will take around a full decade.

Whole communities of batponies have developed across the Known World over time.

The House of Noctulesti, who have ruled the County of Trotsylvania since the Alasarian-Cailorian War, is a family of batponies of great fame and influence.
According to their histories, during the Invasion of Tirek and the Barbarian Horde, the valiant Prince Triscan Noctul ventured forth with his finest knights to fight at Testudeon, the greatest and most costly battle of the Invasion. He claimed victory but was fatally wounded. As he lay dying, his knights pleaded every nearby village for aid and were pointed to a mysterious healer named Leylacora, who lived in a cave, isolated from society, but were warned they would only find her come nightfall. Finding the cave and fearfully waiting as the prince drew closer and closer to his passing then Leylacora, a crimson-coated, white-maned, emerald-eyed beauty with bat-like wings and gleaming fangs, showed herself. She looked over the prince and promised them that she could cure him but they would find the measures she took unorthodox. With his consent, they agreed.
It was then that Leylacora whispered in the dying prince’s ear in a language he knew not of. Then she raised her head, her fangs gleaming brilliantly under the moonlight, and bit into the prince’s neck, drinking his blood.
The prince began breathing again, his wounds mysteriously healing. The knights were unnerved, many of them believed the mare was committing some unholy witchcraft but she had nonetheless delivered what she had promised and assured them that if she was allowed to journey to Trotsylvania with them and aid Prince Triscan in recovery, he would be greater and stronger than ever before in a full season’s time.
Throughout the season, Leylacora worked in seclusion, claiming to heal his wounds. In truth, she was helping him adapt to becoming a batpony, ensuring his transformation would not be a danger to others and would hopefully bring batponies like her into Trotsylvanian society. Her efforts paid off. Triscan Noctul recovered, more full of vigour than ever before. He married Leylacora and the Noctulesti family willingly allowed themselves to become Batponies so as to watch over Trotsylvania for eternity and see it prosper under their rule.
It has largely been successful. Despite its grim atmosphere and the unnaturally long night cycle of the country caused by a long-ago ritual, Trotsylvania has indeed prospered, judged seventh of the ten most-powerful Stirropean States. Its batpony community is extensive and Leylacora is held worldwide as one of the first and greatest pioneers of batpony rights.

Strizia, near Hippomorphia, also has a high batpony population, recognised and respected as a community. Their food is based around the batpony diet, predominantly cooking in honey, milk, fruit, flowers, eggs and even insects.

The Tikbalang of the Fillypines can also be classified on the same level as batponies.

Vamponies

Once a batpony is gripped by The Thirst, he/she will, quite literally, go for the throat, attacking nearby beasts, sentient or non-sentient, and draining them of their blood.
Then, the batpony may look at what they have done and choose to fight The Thirst or embrace it.
Those who embrace are, by official designation, Vamponies, their shadow magic taking on a blood-red hue as they gain power and focus from their victims, either killing them or putting them through the same torture they endured.
A selfish and fundamentally evil path.

Numerous times across Equestria, vampony epidemics have threatened society, either as a frenzied mob of blood-crazed beasts or collective organisations of wilful predators.
Vamponies are powerful creatures, particularly in their packs. By organising themselves into groups, spreading the curse of vampirism across village-worth’s of ponies, they formed something of a cult-slash-kingdom in early Equestria during the mid-reign of Princess Laurelore, dubbing themselves the Blood-Moon Empire.

Thus was formed the Guild of Slayers known as The Blades, a great congregation of master-level spies, trackers, assassins, warriors, alchemists and knights, bound in service to the crown and the ponies of Equestria to ward away the vampony threat, ward batponies away from the dark path, quarantine cursed zones, cure the vampirism in ponies and bring down the Blood-Moon Empire.

6258670
Sounds very good. I also can imagine that Midnight would sleep in a bed from time to time instead of hanging upside down, due missing the comfort of a bed.

6258670
Why don't they all become bat-ponies ?

p.s. Do they get bat wings ?

What if a unicorn gets biting ?

What if a mare with child gets biting ?

What if a bat pony drinks the blood of a other batpony ?

Has there ever ben a batpony who bit the child of a bat-hanter ?

What do the princess thinks of them ?

Can they go out when the sun is behind clods ?

Can a batpony hold a cross, and go indoors ?

Can they change into bats ?

6258793
Very good questions.
While batponies have many advantages, it's still a very painful and distressing experience that has no guarantee of coming out rosy. As the equine body tries to get used to the changes, the early periods of post-transformation can offer numerous challenges, some of which can be fatal.
For a long time, the transformation had been seen as a life not worth living as the swiftness of The Thirst drove those subjected to it into madness.

As to the other questions.

1. Yes but the hypersensitivity of the bare wings can make adaption slow. One grows wings but must still develop the skill to use them like any new flier.

2. Unicorns will have enhanced capabilities over shadow and blood magic as well as telekinesis but they won't be able to cast spells in the same way. Eventually their horn will degrade and break off as the nerves deaden inside it. Similarly, earth ponies will have enhanced strength and botanical manipulation (Using their life-force to ripen crops or fruit trees) and pegasi will have enhanced flight, swiftness and the ability to communicate with bats via sonar.

3. A dangerous circumstance. The Thirst will kick in twice as fast and take twice as long, normally enough to cause a miscarriage. It is possible to save the foal, born as the same pony it was meant to be, but its risky and can cause the mother to die of shock and malnourishment.

4. Drinking the blood of another batpony will cause the drinker to undergo a form of intoxication due to excess sugar and protein known as 'Red Rush', a short frenzy and a long stupor that can cause cardiac arrest.

5. Yes. Several times, this was meant as a form of retaliation from the Blood-Moon Vamponies upon prominent slayers, forcing them to put their loved ones through painful cures or, in some cases, put them down.

6. Princess Laurelore regarded Batponies as equines gripped by a terrible misfortunate and put her officials to work producing cures. But she regarded The Thirst as a dangerous epidemic and had transformed subjects detained and infected zones quarantined. It wasn't until much later in her reign that ponies discovered that batponies could become self-controlled, whereupon she was happy to offer her service to helping permanent-case subjects cope with their new lifestyle. But nonetheless, when batponies or vamponies became a threat to Equestria, she did not hesitate to ward them off and eradicate those who willfully harmed her subjects. This ideal has been taken on by Princess Celestia.
Princess Luna, meanwhile, finds them fascinating and works to help the batpony community develop and investigate vampony conspiracies wherever they surface, ensuring Equestria can tell the difference between an innocent batpony and a malignant vampony.

6. In thick fog or storm-clouds, batponies and vamponies will be fine but only in such cases. It's not simply the sunlight that disorientates them but the presence of the sun in the sky itself overstimulates their hyperacute vision.

7. They can venture indoors but are prone to claustrophobia except when sleeping where they must lie flat in a body-size container or upside down in a dark, quiet, enclosed environment. Crosses won't affect them. Gilded horseshoes however can dazzle them. Vamponies however develop a weakness to silver, countering their blood-magic and burning their flesh.

8. There are no recorded cases of polymorphism in batponies. Vamponies can take the form of a flock of bats but it's simply illusion, not transformation.

Anything else?

6259271
Ummm... make love ?

Cloths ?

restaurant ?

doctors ?

Are they bigger or smaller the Pegasus, earth ... ?

weight ?

None bat drinks blood ?

6259371
1. Usually upside-down from an overhanging, wrapped in each other's wings. Everything else is standard procedure.
2. Generally, any clothes that can fit a pegasus will fit a batpony.
3. As previously mentioned, batpony cooking uses high-sugar, iron and protein ingredients such as honey, fruit, eggs and beans.
4. There are treatment facilities for those recently striken with the batpony transformation and therapy clinics for those trapped in it. There were recent foundations when first the epidemic gripped Equestria.
5. Usually, a slight shrinking occurs during transformation as the body warps. In general, batponies tend to be slightly smaller than the average pony.
6. They are, however, surprisingly dense. Usually a batpony's mass will be at least 150% greater than a pony of the same size, hence why their large diet is crucial to maintaining their bodies. Energy depletion will leave them a prisoner in their new bodies, trapped in a stupor, unable to move.
7. Technically speaking, they don't drink blood naturally. Batponies only thirst for blood as a last resort when seriously depleted of nutrients, living blood containing all the vital chemicals they need for nearly instant invigoration. When a batpony develops a taste for the stuff, the shift towards vampirism occurs and it becomes its only diet.

1) I making.. doing it. Is there someting they need to look out will they are doing it ?

1.5) Say that one of my parent is a bat-pony, and my Mare is a bat-pony, would my kid be one ?

2) Picking of which, does a pegasus going to bat-pony looks feathers ?

3) So... there are restaurant that cater to bat-ponies

4) But are there Bat-pony doctors ?

5) Does ever thing get smaller ?

6) How do they fly if they are not as lite as a pegasus ?

7) But what if a NONE bat one does that ?

1) Not as far as research shows.
1.5) No. Unless both parents are bat-ponies, the gene is recessive. It's treated as if the partner never transformed.
2) You mean does a pegasus wing look like a batponies underneath the feathers? No, they're two very different builds.
3) In some cases but most of the time, all it takes is adding extra condiments. There's no food that's dangerous to them. Garlic only harms vamponies as it interferes with their blood-magic.
4) Yes. After batpony were given rights and citizenships when the campaign to help them control the Thirst proved successful, they were free to choose careers in normal pony society.
5) No. The heart, liver, kidneys and pancreas actually increase in size. It's just the exterior body that shrinks.
6) Their diet is crucial to the focus and strength necessary to take flight. The wings are built to support the body's mass, its simply a matter of keeping them active.
7) Mostly the same outcome. The vast intake of sugar, iron and protein causes shock and usually death.

6259671
1) so.. no, don't go to into it or the bat-pony may make you into a batpony

1.5) Even if my mom was born bat-pony, my dad's mom also was born bat-pony, and my mare-friend is in the same bote, my kid wouldn't not be a bat-pony.

2) no, I mean,.. the unicorn that becomes a bat-pony loses it horn. A pegasus that becomes a bat-pony .. ?

3) What about Wolf-bane ?

4) But is there a doctor that sames lives, by making the die-in pony into a bat-pony ?

5) You know what I was asking ?

6) Are there wings bigger ?

7) Oh.. ok. what about a little bit ?

6260269
1) Oh, I see. No, there's no chance of catching the epidemic via coitus. It's only through direct administration of blood.
1.5) No. The gene's recessive so only in a 'double dose' will it produce a batpony foal.
2) Ah right, sorry. A Pegasus's wings grow but the feathers fall out rapidly.
3) Again, it hurts vamponies but not batponies. Their dependence on blood magic makes them very vulnerable to alchemy.
4) That is a practice in some circles but its considered highly unorthodox and very risky. Only as a last-resort for life-saving treatment.
5) Sigh...No, that particular part doesn't shrink. It doesn't grow either. It stays the same.
6) Yeah. Pegasi have feathers but the actual wings themselves are very small, like those of birds. Bat wings are huge for their bodies and can support the mass and size of batponies but require a lot of energy.
7) Look, even a drop of batpony blood would be like drinking a dozen jumbo squishees made of pure syrup. Biggest sugar o.d known to equine-folk. You'd be lucky not to wind up in hospital. Its classified as drug intoxication under pony law.

6260285
1) what about if a Bat-pony give blood ?

1.5) What if the mother becomes a bat-pony will with child ?

2) and nothing else changes ?

3) what about https://www.youtube.com/watch?v=eHEItvqF-tg

4) What about they ones that don't want to live ?

5) What about mare's ... ?

6) So the wings get bigger !?

7) Are there some that uses it to cook ?

1) That would work but it carries the same risk of unbalance to the Thirst.
1.5) That would probably kill the child.
2) Well, the wings tend to be wider and more mobile but still work differently so they need to adapt.
3) Well, as it shows, those treatments would probably kill anypony regardless of whether they were vampires. As to the methods by which they live, it sort of depends on the vampony, really.
The rice and seeds thing? Yes, that's a habit of theirs but their heightened senses would have them count the whole lot in minutes and only if they weren't set on satisfying their thirst.
4) Well a batpony's longevity is partly dependent on their shadow-magic. So if a batpony wishes to kill itself, it works just as fine as if it were a pony.
5) Same rule. That's all I'm going to say on the subject.
6) Yes but thinner and tighter. They don't so much 'grow' as 'stretch'.
7) No. Though the fumes can create a hallucinogenic.