On 01/06/15 15:58, Tom wrote:
Hi Gents

Sorry for offtopic question in your forum, but you folks know more about
marine batteries than any of the boating newsgroups, for my purpose anyway.

I have a half dozen marine deep cycle batteries. I get about 8 years
usefullness from them when I store them properly, I slow charge them
once per month while in my garage for winter storage and I try and never
leave them sitting without being charge. I try to never drain them
completely, I keep them filled with RO water and don't over boil them.
Etc etc etc.

My question is I am coming up on the 8th year and might have neglected
this winter's long storage time. I have two that are my concern. Two
Nautalis 12v Deep Cycle, they are the bigger ones. One only holds the
12v charge for about an hour. Battery charger "intelligent automatic
charger" Will charge them both, and shut off automatically when fully
charged, then a week later one is still 12v, the other is 10v. I needed
to fill about 15% or 20% of the fluid with RO water.

My question is about de-sulfating. I bought the one for $20.00 bucks
that connects and blinks the red light while it is desulfating with an
electronic pulse (reverse) and while I did this for about 2 months now
on the batteries, one shows very very good response but one still only
holds the 12v charge for a week then goes down to 10v.

What I want to try is replacing the sulfuric acid. I think that could
super charge the lead acid reaction. The auto stores in Ontario no
longer sell the replacement battery acid (sulfuric acid) but just over
the border in NY state they all do. Very cheap. So I want to know what
you folks think about doing a 2 month de-sulfation then replacing the
very grey and thick old acid with some very clear and new sulfuric acid.

Replacement batteries would run me about $300.00. The Sulfuric Acid is
about $12.00 per gallon.

The folks at the Auto Supply Stores say it is good idea to do, but some
say not good idea. I am happy to hear you folks opinion of the matter.
Feel free to fling the mud. Just give me lots of advice.


In my less affluent days, I tried all kinds of ways to recover
batteries, mainly lead acid ones. Success was, at best 'limited' and
invariably short lived, even with TLC. I wasn't using the batteries in
situations where, if they let me down, it would be more than a matter of
not being able to 'play radio' etc.

I now have what you call an RV, which has a couple of Leisure/Marine
Batteries in addition to the main Battery. Based on my experience of
recovering batteries, I'd not use a recovered battery in that even
though it remains safely on dry land.

8 years seems good service, I'd expect maybe 5. Having said that, I
replaced the battery in my MX5 after about 13 years and it hadn't
failed, I just decided I'd pushed it too far (my luck, not the car). The
battery is still good, I use it for odd things out of interest more than
anything. It is a 'glass mat' battery, made by National Panasonic.