Healthy Bats [RE-wrenches]

[sunwise at cheqnet.net]

Greetings group,

While we're are on the topic of battery charging (sorta), I have a
question on which I would really appreciate any thoughts.

I have a client with a stand-alone system that will not even consider
adding a generator (actually not the only client).  I'd welcome any
input on charge control set-points for such systems as well as
recommended practices for attempting to EQ from the PV's.  

The 12 volt system's array is about 30 amps peak with a 1,050 AH battery
(C/33).  The relay based charge controller is a Bobier product and I
have it cranked up all the way to about 15.5.  I also installed an EQ
switch to by-pass the CC.  

I have told them to never take their battery below a 50% discharge, and
they claim they have never had it down that low (Emeter).  After a very
lengthy cloudy period (2-1/2 months), we got four days of good sun on
snow (saw peaks of 40A).  They had the battery up around 16V three days
in a row and probably boiled them each day for four hours.  Of course
amps vary as the day proceeds.  

I am wondering at what point one should consider more frequent
overcharges a problem (instead of occasional EQ's).   It seems like over
the past ten years or so we are taking battery voltage higher and higher
in the name of healthy batteries.  The clients claim the bats never get
noticably warm to the touch and they don't seem to be going through a
lot of water.  I understand Richard's C/20 for 5 to 6 hrs past fully
charged for an EQ, but if one can't quite pull that off, how bout some
other guidelines.  I'm also wondering if the series CC isn't actually a
better choice in this instance (over PWM), as it seems like it can be
set higher, cycling/pulsing the battery up to 15.5, but letting it drop
to about 13.5 on each control cycle?

Thanks in advance -- Kurt Nelson

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