[RE-wrenches] AGM battery charging, more details

[Hugh]

Hi Bill,
>
>Hugh, .25 x C20 would be a C80 rate

Sorry I did not mean that, and I do not think that is what the 
manufacturers instructions mean either.  They mean 0.25 times the C20 
capacity.  That is closer to the C4 rate!  (And they say 'up to 0.35 
x capacity' ).

>  All controllers that I've ever worked with make adjustments in 
>current to meet the transitions between bulk-absorption-float.

Again we are not speaking about the same thing.  The manufacturers 
ask for a transition to float voltage when the charging current drops 
to a certain level.  This is very different from the PWM control of 
current to maintain a given voltage (absorb or float).  It's a 
criterion for changing from the one to the other.

>  I've generally steered clear of sealed batteries, believing that 
>the trade-off between maintenance and the fragility of plates made 
>with calcium instead of antimony favors adding water occasionally.

Me too.  However in some cases a sealed battery is required.  And I 
am learning.

It seems that in my situation I do not need to worry too much about 
the transition point so long as I observe the correct temp 
compensated absorb voltage and try to sustain it until the current 
virtually disappears, after which it does not too much matter if it 
floats or goes on at that current and voltage for several hours more.

thanks for the comments.
-- 
Hugh Piggott

Scoraig
http://www.scoraigwind.co.uk