Rotten Egg Odor In Barn/Suspected Battery Issue

[raywaller]

I own a 2007 Travel Supreme MS (Mid-Engine) RV that came equipped with two Harris Commercial Plus batteries (CTX31S-9 CCA 954 CA 1185 RC 210).

In the past couple of days, my storage barn has been reeking of a“rotten egg/dead animal” odor that seems to be coming from the batteries. I have disconnected the 50 AMP shore power, so the charging system will not continue to charge/maintain the batteries, while I troubleshoot the issue. As a result, I have a few questions:

1) Since the batteries are 4 to 5 years old, do you suspect they are the source of my problem.

2) If you don’t think the batteries are old enough to have caused the problem, do you think the charging system might have damaged the batteries, and would have to be repaired before replacing the batteries (if they are damaged).

3) How do I determine if the batteries are bad/damaged.

4) How do I determine if the charging system is performing properly.

Any help with these questions would be appreciated.

Thank you,

Ray Waller

[wolfe10]

Ray,

A couple of check you want to make:

With a digital voltmeter (prices start under $20 at Radio Shack, Sears, etc) check battery voltage at the batteries before plugging in shore power/turning on generator. A fully charged 12 VDC battery will read around 12.7 VDC, anything higher is surface charge and will dissipate quickly with even a small load on the battery. A 50% discharged battery will read around 12.2 VDC.

Plug into shore power and check the reading. If you have a smart charger (aka 3 stage charger) it will begin charging (bulk mode) in the 14.0-14.3 VDC range. That is of interest, but of more importance is after a few hours with the batteries 90+% charged and the charger in float mode what is the voltage reading. Should be 13.2-13.5 VDC.

Note, most smart chargers and smart inverter/chargers have some programmable features. Be sure they are properly set. One that is often neglected is temperature. If set to cold temperature and it is 90 degrees out, it WILL overcharge the batteries.

OK, so we have covered the charging part-- and clearly if the voltage is too high, you will get outgassing from a perfectly good battery. Now for the battery. The inverse is also true-- a perfectly functioning charger will outgas a bad battery!

If one cell in a battery is bad, that would take it from a nominal 12 VDC to 10 VDC battery. But, the charger knows it is supposed to charge at 13+ VDC. Charging a 10 VDC battery at 13+ will cause severe overcharging of those remaining good cells.

The best test for a wet cell battery is to fully charge the battery and test with a HYDROMETER. They are around $5 from any automotive store and very easy to use/read. Again, the battery must be fully charged for the results to be accurate. Look for one cell with a materially lower SG (Specific Gravity) than the others.

Let us know what you find.

Brett

[raywaller]

I'm sorry. I should have mentioned that the 2 Harris batteries I'm referring to are "maintenance-free" and are used for starting the main diesel engine. I don't seem to be having any problems with the bank of 8 wet-cell batteries I routinely maintain, and that are used for coach requirements.

As far as the make and model of the charging system(s), and what the optional settings are, I'll have to check on it. Again, I should have done this ahead of time, and included with my original post.

Thank you for your in-depth response. I really appreciate it.

Ray

[hermanmullins]

Ray, I had two Interstate 12v batteries that were maintenance free. When they went bad and I took them to Interstate, I was told they were low on water. I said that they were maintenance free and sealed. The tech proceeded to pop off the cell covers to show me that they were low on water. I remarked that I had always understood that maintenance free meant no maintenance needed or could be done. Now I know. They did replace the two under warranty at no cost.

A visual way to check your batteries is to look at the sides of them. An older Bat. near the end of its life will sometimes swell out on their sides. The only time I got the rotten egg smell was when a battery exploded.

Good Luck.

[mclavey]

Are you sure it is not a dead mouse ... or other rodent .... I have had many of them in my coach.

[mikendar]

I have a related and interesting twist on this issue. We have a 2002 Winnebago Adventurer, Gas, Workhorse chassis. After numerous issues with house batteries going down rapidly, I replaced the sealed (2) 12v batteries with 2 deep cycle 6 volts.

Since then, sometimes after about 2 hours of driving I get the rotten egg smell. voltages, temp, etc all seem to be normal and everything seems to be working fine. Any thoughts or ideas, anyone? Thanks, Mike.

[wolfe10]

Mike,

When you say everything is normal, what voltage are you talking about? After they reach full charge, anything over about 13.5 VDC can overcharge a battery. Most alternators/regulators are temperature compensated so they start out at around 14 VDC, but taper off slightly as you drive.

If the alternator stays at 14+, yes it can cause overchanging. It can show up as the sulfur (rotten egg) smell and/or excessive loss of water in the batteries. Are you having to add a lot of water?

Another source of the rotten egg smell in a gas coach is the catalytic converter. Have you ruled that out?

Brett

[mikendar]

Brett,

Thanks for the quick response. I have not had to add water yet as the level has not gone down at all. The dash voltage meter shows about 14v. When shut down the voltage on the house meter as well as a multi meter is 12.7. I did not think of the catalytic converter but will have it checked as well. My gut feeling is that it is overcharging somewhat. Possible alternator problem? It only seems to happen when driving so I don't think it is a converter issue.

Thanks again,

Mike

[wolfe10]

Mike,

Another common cause of the smell is from a battery with a bad cell.

While it is fine to charge a 12 VDC battery at 13.5-14 VDC, if one cell is bad, the regulator/alternator will then try to charge a 10 VDC battery at 13.5-14 VDC. That will severely overcharge the remaining good cells.

If these are wet cell batteries, use a battery hydrometer (under $10 at any auto parts house) to check SG (Specific Gravity). If a cell is bad, SG in that cell will be low and easy to identify.

Your mention that the voltage drops from 14 to 12.7 when the engine is shut off brings this to mind. While 12.7 is the reading for a fully charged 12 volt battery, generally there is enough surface charge to hold the battery voltage at 13 or higher for awhile (until a few amp-hrs have been consumed). So, if this drop is the instant the engine is turned off, it is a red flag to check the batteries.

Brett

[mikendar]

Thanks again. The volt drop off is not instantaneous but occurs after several minutes and then stays steady. The batteries are brand new but I will get a hydrometer today and check them just to be sure.

[wolfe10]

Mike,

That sounds normal. It doesn't take many amp-hrs of drain to remove the surface charge and return a battery to its true fully charged level (about 12.7 VDC).

Brett

[vtbigdog]

Dumb thought but that rotten egg smell could also be coming from the hot water tank. Turn on the hot water faucet and see if you smell it.