"Jim Wilkins" wrote in message
news

As batteries age they may require more than the normal vehicle
charging voltage....

Here is a good explanation:
http://support.rollsbattery.com/supp...n-instructions
" Eventually, the sulfate will cause a resistance to charge and a
"false high voltage" reading will occur. The "false high voltage" is
measured by the charge controller, which further lowers the charging
current to maintain the voltage set point. This further increases the
undercharge condition."

"6. Once the specific gravity begins to rise, the bank voltage will
most likely drop, or the charging current will increase."

I've seen this on a battery that required 17V to initially force 50mA
of current. As the battery recovered and its voltage fell below 15V
the current rose to the limit of the LM350. It didn't harm my circuit
but it needs to be considered.

-jsw