[Asterisk-Users] Re: Terrible TICKING sound

[tmpm]

Yes, you are absolutely right...forgot to mention this. (And I should know 
better, having serviced telco baterys for years) I have the battery in the 
basement, so any H2 is widely dispersed, but if youre going thru deep 
discharges this would be a safety factor.

At 13:57 5/13/2004, you wrote:
>tmpm wrote:
>
><snip>
>>>Buy a cheap one that exceeds the wattage you need for every device or 
>>>cluster them, and remove the little tiny gell-cell and tie it to a truck 
>>>battery kept on float at about 70-100ma and youre golden.
><snip>
>
>Do be careful here. There was a time when Lead-Acid battery banks were 
>somewhat common - and so were the explosions from accumulated hydrogen. 
>You see, once a battery is fully charged, all the energy run through the 
>battery (i.e., the trickle charge) just heats the cell and splits water 
>into hydrogen and oxygen, which is a really dangerous combination. (If you 
>don't believe this, note that it's used as rocket fuel.) Gel cells are 
>specially designed to not emit any hydrogen/oxygen and are considered 
>relatively safe when used indoors. Car and truck batteries, since they are 
>designed to be used outside, where the gas can't accumulate, have no such 
>provision.  If you decide to use one of them, just make sure that you 
>provide plenty of ventilation to the outside. And, use a fan motor which 
>has no brushes (this would be almost all commercially available blowers 
>and fans).
>
>Also, if you really want to do this, you may find that, depending upon the 
>battery's capacity, 70-100ma may not be enough to exceed the minimum 
>current required to charge the battery - the first bit of current just 
>heats up the cell and produces gas.  Generally, lead acid batteries should 
>be charged at a current just great enough to exceed the theoretical cell 
>potential of 2.2V per cell (13.2V for a standard 12V car battery at 25 
>degrees C). Typically, the optimum charge voltage would be about 13.8V for 
>a 12V battery.
>
>
>Stephen R. Besch
>
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