wrote:

On Mon, 21 Jul 2008 08:47:05 -0400, Rosalie B.
wrote:

wrote:

On Mon, 21 Jul 2008 03:24:50 +0000, Larry wrote:

"Roger Long" wrote in
:

1.13. Do NOT use wet lead-acid batteries around salt water. If salt
water is mixed with the battery's electrolyte, deadly chlorine gas is
produced. Only use sealed AGM (Ca/Ca) or Gel Cell (Ca/Ca) VRLA
batteries around salt water.

Good advice I think.

Not really so much

The advice is Ca/Ca, allright. AGM and Gellcell batteries ARE lead acid
batteries, just like wetcells.

Wetcells PROPERLY SECURED INTO THE BATTERY BOX are just as safe as the
other batteries for thousands more because they have gas vent caps on
them that seal out the seawater and seal in the electrolyte in case you
pitch pole the boat doing something stupid or a rogue wave hits.


When you crack the case of an AGM, however, it does not leak acid like a flooded
battery. Even batteries that are tied down sometimes break free in a capsize, or
rough conditions. And if something else is thrown against them hard enough, that
may also release the contents.

If you are going to power something with gasoline, that's a whole lot
more hazardous - as in more likely to cause a problem - than having
batteries thrown around and release their contents. If you are in
rough enough conditions that your batteries are going to be thrown
around even if they are tied down, then you have big problem, and just
changing the type of battery you have won't help you much.

Yeah, my car has seatbelts, so why worry about having airbags. :')

We have old cars and they don't have airbags. g

Ask anyone who has ever had battery acid flung around in a boat, and
then get back to me about whether it's an important issue.

How many people are there who have had battery acid flung around the
boat?

Gasoline is a completely different discussion, as is the one
concerning having a 50 foot tall metal pole mounted on your boat.
There are lots of potential dangers on a boat. It makes sense to
mitigate as many as you can - within reason.

When we used to have to assess penalties for violations of the health
and safety standards we had to use four factors and two of them were
hazardousness (a one level hazard was a cut or rash and a four level
hazard was death or permanent physical disability) and one of them was
likelihood of something happening. I would rate:

Fire from gasoline - hazard 3 and likelihood 2
Tall metal pole - hazard 1 or 2 and likelihood about a 2, and
Danger of battery acid being flung around a boat - hazard 2, and
likelihood 1

You may disagree.

wrote

Now that I see all of this, I wonder if perhaps in the long term, AGM
batteries are really about the same cost as the more dangerous and
unreliable flooded batteries.

You may disagree.

The electrical system specialists who did the final design and engineering
for my 81 foot research vessel do agree and said pretty much just what you
did. They do both land based emergency power systems for things like phone
company switching centers and sophisticated vessel systems. Pretty
knowledgeable guys.

According to them, you didn't even need to factor in the safety of AGM's to
justify their use.

--
Roger Long

"Roger Long" wrote:

wrote

Now that I see all of this, I wonder if perhaps in the long term, AGM
batteries are really about the same cost as the more dangerous and
unreliable flooded batteries.

You may disagree.

The electrical system specialists who did the final design and engineering
for my 81 foot research vessel do agree and said pretty much just what you
did. They do both land based emergency power systems for things like phone
company switching centers and sophisticated vessel systems. Pretty
knowledgeable guys.

According to them, you didn't even need to factor in the safety of AGM's to
justify their use.

Bob converted a car to run on batteries. He had 18 of them. AGMs
were significantly more expensive and didn't last any longer Same
with the boat - I think we have two battery banks - 96 amp hours or
something like that. And the AGM batteries (I have heard) have much
more tricky charging requirements. Now maybe that has changed in the
past 10 years - probably so. And if we were setting up the system
now, we might do it with AGM batteries. But we are not, so we won't.

If they had special charging requirments and this was 10 years ago, they
were probably gel cells with are different and often confused with AGM's.

--
Roger Long

"Roger Long" wrote:

If they had special charging requirments and this was 10 years ago, they
were probably gel cells with are different and often confused with AGM's.

Whatever. When Bob was converting his car to electric power, he did
the research and since he's an electrical engineer I don't have any
reason to second guess him, as I am definitely NOT a physical science
type person.

I used to do forklift (powered industrial truck) inspections and they
had all kinds of rules for charging the batteries, but we had no way
to check whether there was enough ventilation or not. I was also told
by someone that I needed an airtight ventilated box for our batteries.
Which is just silly. So I tend to discount a lot of what is written
about electrical stuff and just go with what Bob wants to do.