[aprssig] battery charging

[WB4GQK at aol.com]

Hi Wes,

Deep Cycle settings will NORMALLY bring a wet cell  to 14.45 +/-.05V  due to 
temperature/ AC input voltage/condition of battery. Generally the current will 
be stabilized near 25-35% of maximum charging capability. When the charging 
voltage reaches 14.45,  it will automatically shift over to a float charge, 
generally 2 -4% of the charger's current capability. The voltage will generally 
settle out at 13.35 V. Again depending on the factors listed above.

Normal charging is accomplished by setting the charging voltage to 14.45 V 
and keeping it there until the charging current slowly drops to around 4 amps 
when it switches over to a float charge. 

You can look at it as a constant CURRENT charging with varying voltage 
compared to a constant VOLTAGE charge with varying current. The primary difference 
is the amount of time required to bring a battery up to 85% of full charge. 
Very obviously the constant current will charge a battery much faster than the 
fixed voltage technique. It is somewhat controversial, regards the effect on 
battery life being shortened when deep cycle techniques are used. 

Finally some chargers such as my XANTREX 40Amp has a 21 day automatic reset 
feature that applies an equalization charge of 15.55V that raises the battery 
charge to it's highest level and PRESUMABLY dissolves some of the lead sulfate 
that has accumulated on the plates. This is supposed to extend the life of the 
battery.  The key point here is the battery cannot be "physically hot" when 
this extended voltage is applied. Otherwise the over temperature will 
definitely shorten the battery life.

De Jim wb4gqk