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Discussion Starter #1
I have just had my Florida 01 E320 4M Wagon battery explode on me while on a winter visit to Guelph Canada (+10F). Unlike me, I suggest a frequent check on the electrolyte levels .... The quarter pounder tasted a little off not to mention the ringing in my ears ... this occurred after a 2 hr road trip in +10>+20F temperatures and a stop at Macdonalds. The key was just engaging the starter when the battery blew.

I had a Rear Brake light error display at least once a day for the previous week but when verified all lights were working. When the temp dipped below +10F the starter would not crank but easily started with a jump.

Cranking speed was normal and all electrical elements were functional aside from the spurious malfunction codes. I had a compete star diagnostic done with now anomalies done 4weeks before but not in a freezing environment.

Vent was clear and there was insufficient electrolyte in the battery compartment so I can only assume that low levels were the culprit. All fuses appear in good order.

I am trying to track down and eliminate a potential short but would appreciate any additional guidance before installing the replacement and possibly ruining another quarter pounder ... :)
 

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Umm. wow?!!! You were in the car when it happened? Damn. Did the rear seat contain the explosion underneith? That would prevent acid/shrapnel from flying about.
 

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Battery

froze.Low battery in those conditions will freeze an a jump will arc and cause explosive gas to trigger the explosion.Never jump or charge a frozen battery
a regular heating pad wrapped around it on low setting will prevent freezing.I hope the electrolyte did not ruin the fuse ox or the pse.
:bowdown:
not a pretty picture
 

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Discussion Starter #4
yes I was in the car at the time ... seat cushion was unmoved all fragments were contained within the compartment (nice to have had the foam cover over the air pump).

My first thoughts were of a backfire but when I saw the vapour coming out form the cushion I realized what had happened ... baking soda was my first order of business. everything is clean now but I am still nervous about the hookup I will try and trace the looms as far as I can.

An interesting item to note is that the instrument cluster and the interior lights were still functioning as the battery finally gave out.
 

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Discussion Starter #5
Funny thing was the car and I assume battery were still warm (2 hr drive no indication of problems) ... I had turned the car off only 10 min earlier ...

I am seriously hoping that the regulator is not involved in the issue and that a straight "field" replacement of the battery will get me the 60 miles to the nearest dealer ...
 

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Haven't heard about frozen battery exploding. Even if there is explosive gas in dry cells and even if there is a spark -it still needs oxygen mixture to blow.
Than I've seen batteries exploding because of overcharging on several occasions. When you overcharge the battery -it "boils" releasing lot of gas. With caps restricting the flow -the pressure builds up.
From the picture looks like all the cells blow up at the same time.
Did you had it taken to Fire Department? They might want to hear about it.
 

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Discussion Starter #7
Kajtek1: I did not consider the event critical enough for the Fire department as the gas dissipated quickly once I had opened the doors ... I was concerned about loom damage and struggled to get the neg post disconnected quickly.

My most urgent concern is if I can put the failure down to low electrolyte levels and if so why was there no overcharge warning? This is troubling as the vent tube to the outside of the compartment was clear of obstructions.

I would like to eliminate all non-battery issues as soon as possible to get back on the road, so any thoughts/guidance are welcome.
 

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You know you can display the car voltage on clima display? I would observe that pretty closely.
Fire Department might give you more scientific explanation. To my knowledge it is possible that with low acid level the starting current boiled the remaining acid in short time, but I am not expert in the field.
 

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http://autorepair.about.com/cs/doityourself/a/bljumpstart.htm

At 20f and below a battery with low level and poor charge can freeze and explode.
run the climate control diagnostics
How to Diagnose Air Conditioning Malfunctions | EclassBenz.com
and up around value 21-23 or so you will run by a value that is fluctuating between 12.8 volts or so.That way you know it is the charging value.
:bowdown:
 

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Remember a frozen battery could also be a "cracked" battery, allowing massive outgassing in that confined space. Add a spark from any poor connection or even static......
 

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Possibly....
1) Battery was frozen and cracked overnight.
2) Tried to start - frozen battery - not enough charge to start - required jump start.
3) Drove off with heater on - battery slowly thawed - started charging - started outgassing through the crack(s) in the battery case.
4) Short stop at McD - engine off.
5) Outgassing stops - but Hydrogen still contained in the battery compartment under seat.
6) Turn the key.... Load placed on battery - somewhere in there a small spark spark ignites the gas....... FLASH BANG
7) Cracked battery case exposes multiple cells to the flash......... KABLOOIE.
 

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I had a vokswagen , love bug, some years back and the battery was also located in the rear right passenger side, same as the benz and my overweight cousin sat there and coils touched the battery tips and caused a fire. We all got out, fast.
 

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Discussion Starter #16
Update:

A final inspection revealed what appears to be a design flaw in the OEM battery vent system. There is only 1 vent tube ... not 2! There are 2 banks of 3 cells ... the 3 RH cells were either not vented/plugged at the cover or vented to the battery compartment only. I do not have residual pieces to the right bank of cells but can find no external hole in the BII (floor) or tube for this bank of cells. The compartment could indeed fill with gas as suggested. Could any one else confirm this ???

robert
 

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The batteries we have on our cars have only single venting tube. Who made the inspection?
Your incident pictures show pretty clear to me, that it was internal battery pressure, that blow up. No signs of fire and all cells equally blown -meaning there was equal pressure in all of them.
 

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Discussion Starter #18
Kajtek1:
You are right the OEM VARTA has a combined vent cover thus all 6 cells are able to vent thru a single hose on the LH side. So things are not an issue with OEM vented batteries.

I just confirmed with a MB Mechanic that ~1k ohms is normal for a battery cable shunt value ... still looking for explosion damaged wires but all appear in a good state. Plan to fire her up in the morning ... need to get the VMI out for the codes.

Thanks to you all for the guidance and help ... robert
 

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I'm intrigued. Please keep us informed.....this is like diagnosing a MacGyver bomb.

I'm probably out of my league here but I'm still clinging to the electrical spark (inernal or external), hydrogen gas explosion theory.

Hydrogen burns so rapidly and completly in open air that there would be very little radiant heat generated. I'm theorizing that there was no time for other material come up to combustion temperature in the small fraction of a second of the actual explosion. So nothing but hydrogen actually burned and remember the byproduct of a hydrogen fire is water so there would be no residue. Plus the fact that it was timed precisely to you turning the key to start.

But frankly, I've never even seen an exploded battery.
 
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