Smell from battery

Hi,
I was driving my patrol today and a smell like rotten egg was coming through the vents. I have a dual battery system. The normal starting battery has white on top of it. (It's also not starting well after a few hours of not driving it.)

I am going to take the battery out to clean it and check the fluid levels. If one cell has dried out does that mean the battery has had it? Or could I fix it my topping it up?

Also the rotten egg smell would be from the battery acid wouldn't it?

Thanks

Could be A/C?

Oh right I didn't think of the A/C. I'm not sure how to check that.

If you have one dry cell, I dont think topping it up will help.
Check your charging rate as well could be your alternator over charging the battery.
are they square to look at??.
Either way you're up for a battery I feel

Thanks 3 dogs. I'll check the charge rate now. If the alternator is over charging would I be up for a new alternator?

I only bought the battery a year ago from supercheap so that's a bit disappointing.

I would suggest that either the battery has boiled or the battery has a crack and it has allowed the sulphuric acid to leak (rotten egg smell)

If it has leaked I would be getting the battery out immediately (stop acid attack on metal) and neutralising the area with a solution of Bicarbonate of Soda and water - if there is battery acid around the sod bicarb solution with fizz/bubble vigorously.

Continue to apply sod bicarb solution until all bubbling ceases and then thoroughly wash down all areas that the sodbicarb/battery acid might have got to.

If only one year old it would still have warranty wouldnt it?
You'll need to re-co the alternator,

What Kiwi said ^^^^^

Won't be the A/C, well, 99% it won't be the A/C unless someone put a egg down your vent.

If you have a real good smart charger you may get the battery back but in this day and age the plates etc are so thin that if you boil a cell it usually warps the bejesus out of them.

Take it out, wash out the tray as suggested, check the cells and top up as req'd and put it on a smart charger in "recondition" mode.
If it comes good awesome but check what the Alternator voltage is when you put a battery back in the Car.
Should be 13.8 min to 14.7 max, usually you will see around 14.0 to 14.5 ish

Thanks KiwiAngler.

I have just had a good look and found the deep cycle battery was making a sizzling noise with some fluid on top. I have now taken it out. I'm hoping this might also be the reason the patrol hasn't been starting well but it's not the main battery.

make sure you place the battery in a well ventilated area
Petrol or diesel motor?
What dual battery charging system do you have, just thinking its only charging the Aux and not the main