[ausev] Batteries not getting up to charging voltage?

[Brian Lasseter]

My batteries have been losing range for a while now...  i.e. The
voltage sags more under high current load limiting my effective
electric vehicle range.  However now I'm starting to see a new issue,
which I presume is also related to my batteries being past their
prime.  The batteries are not really getting up to the charging or
acceptance voltage, so the PFC charger just keeps charging them all
night.  This happens about once a month, that I get an unplanned
equalization charge for my car.

At 80F the US8VGC batteries that I have should be charging at 186V
(2.583V * 72 cells as per http://www.usbattery.com/usb_faqs.html ).
At the end of March, I dropped the charge voltage to 184V (the 90F
charging voltage, since it was not reliably hitting 186V).  At the end
of April I dropped it to 181V (the 100F charging voltage, since it was
not hitting 184V).  Now at the end of May, it seems that my batteries
will not get much above 175V.

At first I thought it was temp or water issues (which it may have
been), but I have been checking the water fairly often through this
process.  I last refilled the water a month ago, and at the end of
April the 18 batteries and 72 cells only needed 3 gallons of water
(from the previous 6 weeks of car usage).  I actually have noticed
that as the effective range of the vehicle has been dropping (so I
charge it more often, and can not discharge the batteries as far) the
water used by the batteries has decreased from the amount of water
that I used to use in my batteries.  I spot checked a few batteries
last weekend for their water and they seemed pretty high, and the
batteries have always been very consistent in their water usage (from
cell to cell, and battery to battery).  I'll be watering them again
this coming weekend.

Anyways, I guess my main question was if not getting up to the
charging voltage was a known issue as batteries age.  Mine are at
about 300 cycles now.  I was also curious what other signs would crop
up as the batteries age further.


-- 
TTFN,
Brian "Lasso" Lasseter

"No Sane man will dance."   -Cicero (106-43 B.C.)