As others have said, the solution to this is to get a AGM battery like an Odyssey. This is the way we addressed it over in the motorcycle world where like the Porsche world some vehicles get sporadic use.

 

This is mostly a low electrolyte issue which can be caused by either a cheap/bad charger or a voltage regulator that is overcharging. When a battery is overcharged it tends to "boil off" (not actually boiling though) the electrolyte and in the process creates hydrogen. This can happen even on "maintenance free" batteries so do not assume you're safe with a maintenance free battery. Normally the Hydrogen vents through the vent tube but if the liquid level gets low enough it builds up inside the battery. As the cell plates get exposed they can fall apart and create sparks when you try to draw current.....then Boom! Check your battery electrolyte levels often and add distilled water up the the recommended level anytime it gets low. If you notice the battery needs frequent refilling check your charger and charging circuit. This is especially important in hot climates. A properly maintained battery will not expolde and should last years in normal service. Just like our with other areas of our cars, ignoring proper (battery) maintenance can lead to major problems.

 

Thanks for the detailed response......I'm off to go check my fluid level.

 

35 years of flooded lead acid batteries and I've never had one explode, but they do get periodic maintenance.

I have my ideas as to why that happened.

 

How do these trickle chargers work. ie are they plugged into the cigarette lighter? I guess more likely the leads of the charger go directly to battery terminals.

I would either leave the bonnet open for ventilation (remove compartment light), or take the terminal of the battery if left for long periods.

Build up of gases under closed bonnet, will likely cause explosion on turning the ignition on. The fuse box is under there as well increasing likely hood.

I've had one explode in my face whilst removing terminals from battery. I hadn't turned the charger off causing spark. You don't make the same mistake twice.

 

It's not so much the Hydrogen around the battery that's the problem but rather the hydrogen IN the battery that makes it explode. Hydrogen is lighter than air so it will disapate pretty rapidly if you give it a chance. The gas in the battery is a different story and it only takes a wiff of it outside to ignite the load inside. It's sparks around the battery terminals that you need to most avoid.

 

A quick web check indicated a Group 48 Odyssey battery cost $298.00; stopped right there with the web-site's purchase cart, etc.,,, And shipping? Go figure an AGM type battery...

My 911 will be fitted with a Johnson Controls manufactured Group 48 at a retailer near you for under $80.00. Add a battery tender for the off use months and its Good-To-Go for another 6-8 years. My last 999.611.070.20 lasted 6 years .... I'm just saying.

Never had a battey explode..... Got'sa be freaking scary!

 

I found some AGM's for the bikes for less but yeah, those Odyssey's are expensive.

I had a battery explode and splash acid all over me. I was ok because I got to a safety station right off but my clothes sure didn't make it through. That stuff is nasty.

 

Ya all don't want to know what the batteries cost for a boat... and there are 6 of em in the raggy....

 

Desmysthifing batteries.

Porsche brand or not, most of trickle chargers are basically the same.
I have one for years and no problem (no porsche brand)
Of course a good brand makes us feel safer.

if you live in cold weather, yes ... a high amp battery makes sense.
if not, like here in miami, ANY reasonable quality battery that fits the box and has the right connectors for the cables will do the trick perfecty. Optima is great but actually you dont need it. You dont have a RV or a Yacht, just a small sport car. I bought a generic low cost battery and works like a champ.

AMPS: you dont need a 700AMP battery for God's sake .
993 is very modest on compsuntion. I repeat, a regular model that fits nice the batt box is fine.


(A Porsche-tech recommended 74amp or 75amp instead of the original 70amp)
The porsche tech that said this is a Moron. Go back to school.
66 73 69 71 ... B.S. This is a lead battery. Not a pace maker.

Porsche original battery. If you feel safer, is ok. But you are just making richer another german guy. I repeat, ANY brand, ANY model that fits the hole and has a decent capacity will do the trick perfectly and safe.

Why the explosion ... well , as other members mentioned, probably hydrogen gas accumulation due a clogged vent. Also, much less frecuent, a strong vicious overcharging current may do that, but that means your electrical system has a problem.

A hot battery is an indication of a problem.
When a battery is very discharged, probably will get a little hot when charged, but then should be more or less cool to the touch. A hot battery is a bad indication.

When to change a battery ...?? when the car doesnt crank up... hehehe


and yes, I am a smart *** electrical engineer that works and play a lot with batteries since a boy ..






Amazingly I had a similar incident in 2004 - see THIS TREAD - when the battery (original, still under parts warranty) unknowingly cracked. Since then, I've been using a Porsche battery trickle-charger.

I bought a new 70amp original Porsche battery which I installed today, and I can eliminate any alternator issues: After 10 mins idle (as per owner's manual) it charged 13.98 V, and after an hour's drive (to reset the computer) it charged 14.13 V. I then went on to check the vent hose, I blew in it but the first time it appeared blocked. However next time I tried it appeared completely open. I conclude the reason for the explosion was either a blocked vent-hose or a short-curcuit in one/some of the battery cells. I will take the car on a lift to investigate the venting since this could explain both incidents.

I've learnt this:
- If using wetcell batteries, replace it for preventive measures every 2 years.
- Preferably use a yellow-top Optima drycell battery (not available where I live).
- A Porsche-tech recommended 74amp or 75amp instead of the original 70amp.