Hot Battery, Smoking and Smells

Sounds like it is overcharging indeed. The voltage regulator on the back of it is most likely the culprit. Be sure to properly wash off all that acid with acid and perhaps some soda.

 

Maybe the original Nippon Denso alternator is a better item;i prefered to buy this oem part than adaptable tension regulator maybe not safe (tension regulator bad)

 

Obviously I meant washing any acid on the car, chassis components etc, off with water and maybe some soda to neutralise it. Battery acid is nasty stuff.
Yes 19volts is way way too high. You're taking large risks, too high voltage can damage electronics like nothing else, so I would take no chances, and not restart the car anymore without actions taken. As alternators are generally not expensive, especially when compared with the risk of damaging expensive electronics, I would seriously consider changing out the alternator, or at the very least its regulator, and if you opt to keep this alternator would favor to have it completely tested before putting it back into service.
And replace the battery no matter what, I would never demand starting current from or put any charge back on a bulging battery, as it can still do damage.
Is the cooling hose from the undertray properly attached?

EDIT: When starting the car with its new battery and new/overhauled alternator, do so with lots of power consumers on (lights, rear window heater, blower motor), as it will keep down voltage should the overcharge condition for whatever reason still be present.

 

You probably just need to replace the voltage regulator, and it will be fine. Replace voltage regulator, start car, and measure charging voltage to verify. Not familiar with the 550 and whether it is possible to replace without disassembly...
Jes

 

At last the oem alternator is a good way ;and you ll get a waranty because it s the Nippon Denso genuine part used and it will last ten years more....

 

Battery explosions caused by faulting charging are surprisingly common on boats, perhaps because the engine compartments tend to be poorly ventilated. They always cause a mess, frequently cause significant damage, and sometimes serious personal injury.

Even though battery explosions are seemingly rare in cars, the symptoms mentioned by the OP are pretty frightening. Please don't treat this as some kind of inconvenience. It's potentially dangerous to your car and perhaps to your person. Make SURE you solve the problem sooner rather than later. A bulging battery spitting acid (and hydrogen) is no laughing matter.

 

For few bucks more ,be safe ,take the Oem part Nippon Denso and everything will become okay for the next ten year.
I had quiet same problems some month ago .I did it so and i enjoy driving without thinking :
'This adaptable part will maybe fail...or not????
I paid 750euros and i m happy!!
Enjoy

 

Do a little searching, I have read somewhere before that a particular Nippon Denso alternator for some John Deere was identical to the 550 - and a lot more favourably priced.

 

Well your base mechanical and even electrical parts of the alternator (rotor, coils and probably the rectifier) are probably OK as it is, since it managed to overcharge by such a degree. The charge is regulated by the voltage regulator which modifies the current through the rotor, to influence its magnetism and as such the output current. If the output voltage drops because of increased current demand, the alternator output current is increased by increasing the current through the regulator and rotor, to match the voltage again. Now if the voltage regulator gets damaged and short circuits - because of voltage peaks, excessive heat or otherwise - the rotor will me magnetised to the max because of the high current through it, and the system will overcharge. So 99% sure only the regulator is at fault right now, the biggest question however is what caused it to fail.

EDIT: Failed isolation diodes in the rectifier for the regulator circuit can cause a similar situation as well if only one of the three isolation diodes has failed, as the regulator uses a voltage created by these as a reference voltage - but then the alternator light would have been slightly on with the engine running (though this might have been difficult to see in the daytime).

 

It is not the real Nippon denso alternator but an adaptable one.
Be carefull with this quality .....you can see the result....

 

An alternator problem can become a very important problem as explain on last posts.
I prefer in this case not´to play with the fire ´ even if Morfan is lucky from now with his adaptable alternator.