Battery Tray Corrosion

[KUMARB]

The battery tray on my 280SL is badly corroded. One half of the tray is completely gone. Additionally, the wheel-well metal underneath the battery tray has corroded through. I have bought a new replacement battery tray from the local MB dealer, and am going to get the metal corroded part fixed. I was wondering what caused such corrosion around the battery area and what can be done to prevent it in future. I am in the process of restoring the car.

Your thoughts will be very much appreciated.

[mdsalemi]

Kumarb,

The tray corrosion is almost certainly caused by spilled battery acid.  This comes about in any of several ways.  First, if you are refilling a battery, when you add the water to the cells and the cells overflow, what overflows is acid.  Second, those caps on the cells are vented, so hard stops or fast starts can actually spill small amounts of the acid out.  Older batteries, or those that have had the hold-down too tight can also crack--thus leaking the acid.  Lastly, certain charging conditions can cause the acid to boil or bubble in the battery, thus also spilling out.  Any time you get what appears to be water coming from your battery, it is actually acid and it goes in and around the battery tray, causing the corrosion you note.

What to do?  Well, first--if you are not going to show your car in an MBCA Concours where originality counts, get a sealed Optima Gel battery and your problems will be over--expensive but worth it.  If you continue with a lead-acid battery, you can purchase a "mat" that fits under the battery.  You can buy these at any auto parts store for a few dollars.  The mat is like a thin sponge and is impregnated with "basic" chemicals which neutralize the acid and minimize corrosion to some extent; you should change them annually.  You can be careful NOT to overfill the battery cells.  You can, annually, remove the battery, and neutralize/clean the battery tray.  Baking soda and water or dilute ammonia will do a fine job of neutralizing followed by a thorough rinse with clean water.  If you are concerned about water, be sure to dry the area thoroughly using towels and either compressed air or even just one of those small electric leaf blowers before you reinstall the battery.  Be sure not to spill any acid in the reinstall process!

Your new battery tray is probably painted.  This isn't as durable a surface as powder coat; you might consider powder coating the tray and the hold down as well.  This offers a greater measure of protection against the accidental spills.  I've done my hold down and my battery tray is next.

Hope this helps and good luck!

[KUMARB]

Thank you, mdsalemi, for a detailed explanation of battery corrosion. Your help is greatly appreciated.

In my 280SL, the battery is located under the crack opening between fender and hood. Rain water can get into engine compartment through this crack. Rain water falling on battery top dissolves the acidic residue on battery top and runs down to battery tray and wheelwell metal underneath the battery, thus, corroding everything in its way. My MB 107 car has rain gutter which keeps rain water from entering the engine compartment. I have very little battery corrosion on this car. If I provided a rain gutter over the battery or protected the battery from rain water somehow, corrosion could be minimized?

[dseretakis]

The location of the battery on the pagoda doesn't help much since its installation is very awkward.  Tilting the battery at an almost 90 degree angle to slide it into its tight quarters can also help facilitate battery acid leakage.
Dimitri

[perry113]

All batteries will eventually leak for many reasons.
Here is another solution. You can replace yours with a dry cell battery that will look like stock. It's more money, but it completely eliminates the possibility of this happening again.
http://www.sonnenschein.org/

Peter Perry
1965 230SL

[john.mancini]

Which battery from this company will fit the 113's?
John