Re: (ET) Batteries

["David Roden (Akron OH USA)" <etpost drmm net>]

On 8 Jan 2014 at 16:17, Robert wrote:

> [Valve regulated batteries make] No mess and [are] safe in enclosed
> spaces. 

Not to sound like a Nervous Nellie, but nobody should get the idea from 
this 
that you can safely just lay VRR batteries on your cellar floor.    

"Sealed" batteries aren't, even though you (usually) can't remove the cell 
caps.  You don't have to water them because they have platinum to 
catalytically recombine hydrogen and oxygen (that's the second R in VRR).  
They also have safety valves to regulate the pressure in the cells (the V 
and first R).*  If they're overcharged - for example, by a defective or 
improperly configured charger - the hydrogen evolved can be more than the 
catalyst can handle.  The valves pop open and release the hydrogen 
pressure 
so the cells don't burst.   

Now you have hydrogen in your basement.  How about that standing pilot on 
the water heater?  The sparking switch on your water pump or sump pump?  
You 
really don't want hydrogen around.  So, even VRR batteries should still be 
enclosed and properly vented to the outside.

The other hazard (and reason to enclose them) is steam explosion.  If a 
battery cell is reversed at high current, it can cause drastic 
overheating. 
With flooded batteries, a friend of mine used to call these "Trojan 
Teakettles," but they can also happen any brand, with AGMs, and even with 
gel batteries.

VRR batteries are a lot less messy, absolutely true; but they still need 
to 
be properly enclosed and ventilated.  I haven't looked at them for a 
while, 
but IIRC there are codes about this, at least in most US cities.

*Trivia: "valve regulated" actually refers to an early attempt to regulate 
the charging of these batteries by sensing hydrogen pressure in them.  
That's uncommon today, and now "valve regulated" mostly just means the 
battery has release valves to vent excess hydrogen.  

Nontrivial: If your charger's too enthusiastic, you may hear these valves 
ticking or hissing.  This not only means hydrogen is escaping, it also 
means 
the battery is losing water that can't be replaced.  Even if the battery 
doesn't dry out from this, the higher electrolyte concentration will cause 
positive grid corrosion and shorten its life.