Battery Charger / Rotten Egg Smell

[R1Guy]

Hello,

Need a little advice. I noticed a couple days ago that there was rotten egg smell, H2S. At this point, it is definitely coming from the batteries and it only occurs when the charger is running. So, at first I wasn't sure if it was a dying battery or overcharging cooking them. I am concerned at this point that it is indeed overcharging, but here are some facts to see if there are any thoughts on what to do from here:

1. Starts smelling about 5 minutes after turning battery charger on.

2. I have 3 batteries : a small starter battery for the generator, and 2 4DDC one for the port engine, and one for starboard/house battery.

3. When I first smelled the H2S, I checked the batteries and the port 4DDC had one of the vents popped off. Only a tiny amount of liquid. Replaced, left the battery charger overnight and next day smelled H2S. Vents all still on.

4. Voltage check on both 4DDCs show 12.85 volts when the charger is off. So does not seem like they are dead. I did not check the generator battery...perhaps I should but with the vent popped on the port 4DDC I was thinking that is where the H2S was coming from.

5. Hard to see liquid levels in those batteries, but the water seems to be well over the internal plates.

6. After checking the voltage and each showing 12.85v, I put the battery charger on and it went into full charge mode and never moved to float before I could smell the H2S.

7. Battery Charger is a Xantrex Truecharge 2

Thoughts? My initial thought is that at this point things seem to indicate perhaps the Battery Charger is failing and overcharging? Anything else I should look at before spending money on a new battery charger to find that's not the issue?

Thanks!!
-Dan

[Bleemus]

Flooded Lead Acid batteries off gas when charging. Quite normal. Make sure your water levels are always correct and charge away as long as your charger profile is set correctly for your battery type.

[boatpoker]

Yes, FLA batteries off-gas when charging but if you can smell it (Hydrogen and sulfuric acid) you could be very close to a melt down. Believe me this is not something you want to experience ...... ask me how I know !

Charging with exposed plates is dangerous ...... PERIOD. Enough pressure to pop a cap ..... dangerous.

Disconnect those batteries immediately until you can have someone who knows what they are doing look at them

[R1Guy]

To clarify, this may have been misleading:


3. When I first smelled the H2S, I checked the batteries and the port 4DDC had one of the vents popped off. Only a tiny amount of liquid. Replaced, left the battery charger overnight and next day smelled H2S. Vents all still on.


By only tiny amount of liquid, I meant that only a few drops of acid was seen on top of the battery near the vent cap that had popped off. That reads like I meant no water in the battery. While its hard to see in those batteries, there seems to be plenty of water covering all of the plates.


The H2S smell only occurs when the charger runs within 5 mins.

[EngNate]

Check the voltage of any connected battery with the charger on, it should not be over 14.5. If it is the charger is faulty. More likely though is that there is/are one or more cells of one or more batteries shorted internally (failed battery). With a cell shorted the charger voltage is now divided between fewer cells, so those get overcharged and will draw excessive current and produce excessive gas. If you noticed any of the batteries getting hot compared to the others, that one is bad. It is very likely that the cell with the popped cap is the one shorted. You're probably observing the charger's output bargraph going all the way up. With the charger off, disconnect the suspected bad battery. Turn the charger on. If the output is way down, the disconnected battery is bad. Check with one battery at a time connected to the charger.

[R1Guy]

Thanks EngNate!


Ill check to see what the voltages are with the charger on and disconnect the suspect battery. You are correct, charger output was indeed all the way up.



Out of curiosity, what can cause a cell to short in a battery other than age? I purchased the boat 3 months ago and was told (may not be true) that the port battery was new. I know the starboard is as I replaced it in late October.

[DeepFrz]

Batteries usually have a date stamp on them on the side near the top, although the stamp could be on the post or other position.

[senormechanico]

If the voltage isn't over mid 14's and one or more stink, you very likely have replacement battery [s] in your future.

[Madehn]

if you have an infared thermometer (cheap at harbour freight) you can zap each battery at the top of each cell and usually spot a bad one. Also if you let the batteries settle after charging then impose a small load ( a few lights) then check their indiv voltages the weak battery will usually show up as being lower than the others.

[EngNate]

When I see one shorted cell in a battery I think manufacturing defect, otherwise the prime suspect is excessive charge or discharge current for extended periods. A high power alternator with a relatively small battery is potential trouble. Lead acid batteries more or less self regulate their charging current when the voltage is right, but not under all conditions. A deeply discharged battery can draw more than what is good for it if the amps are available and the voltage is in the high end of the range. Continuous current should be limited to not much over 15% of capacity for long periods, and not over 25% at all. That means that 80% recovery from a full discharge is going to take some 5 or 6 hours. This is a situation not favorable for sailors, and often begs to be improved, and when an alternator upgrade is selected its often the biggest that can fit the engine or budget. Unfortunately there's no setup I know of that ties an alternator regulator in with a battery monitor or current limiting. There once was the Link 2000R but it's long gone.

[mvmojo]

Originally Posted by boatpoker

Yes, FLA batteries off-gas when charging but if you can smell it (Hydrogen and sulfuric acid) you could be very close to a melt down. Believe me this is not something you want to experience ...... ask me how I know !

Charging with exposed plates is dangerous ...... PERIOD. Enough pressure to pop a cap ..... dangerous.

Disconnect those batteries immediately until you can have someone who knows what they are doing look at them

^^^ THIS! ^^^^
A shorted battery cell is very dangerous. If you have a battery fire, it will in all likelihood burn through your hull! It will probably also set the boat on fire, but since the boat will be sinking the fire will go out pretty quickly. If you can smell hydrogen sulfide something bad is going on.

[CharlieJ]

To summarize:
The rotten egg smell when the charger is turned on indicates either:
1. There is one or more failed cell in the battery/batteries being charged or;
2. One or more cells have very, very low water and significant plate area is exposed to air. (In this case, the battery has become a very inefficient space heater.) or:
3. The charger has lost control of its output voltage and is applying excessive voltage to the battery/batteries being charged.

Hope this helps.

[Harlequin]

I may have missed it, Dan, but you don't appear to have mentioned what voltage you are seeing with the charger on - probably the most important detail, as you almost certainly have a duff charger which is not reverting to float.

Be very careful, as the next event may be thermal runaway resulting in explosion and/or fire, neither being much fun on a boat.

We experienced something similar in Whangarei marina last Xmas after having been out for the day, plugged into shore power. We remarked on the 'heads' smell before departing the boat, but put it down to harbour water and just put the plugs in the sinks.

Returning late, the sulphur smell was really bad and the 4 x 150 Ah sealed AGM house batts had risen like baked loaves and were spitting gas out of the popped seals. We turned off the shore power (from the dock) to kill the charger, opened all hatches and immediately called the Fire Department. Surrounded by other yachts, the risk was extreme - not only to us, but to our neighbours!

Long story short, the Firemen (there in minutes with 2 trucks) used an IR thermometer and read 85 degs C on the two inner batts and 45 degs on the two outers. They were very, very close to popping off. (I'll try to post a pic...)

Another learning point, amongst many that night: the off-gassing is not only flammable & explosive, it is heavier than air (so accumulates in the bilge), is very toxic, and you can no longer smell it after a few minutes' exposure. ie, you think it has dissipated when it actually hasn't!

This is definitely a problem to be taken VERY seriously.

Best of Luck!

Jim
SY Harlequin
Whangarei, NZ

[sailorboy1]

My batteries always have the rotten smell if I charge with battery charger at 14.8v. They don’t do it if I charge at 14.6v. Now this is with my battery charger, the solar and alternator never produce the smell.

[Harlequin]

Originally Posted by Harlequin

They were very, very close to popping off. (I'll try to post a pic...)

OK, let's see if this works...