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Subject: More words about battery charging - Part Two
(Posted on Dec 8, 2009 at 04:30PM )

Following up on the November 24 Post -

After a bit of research we find this formula:
    T   =    AH X K
        ---------
              CR

T is the time required to recharge the batteries in hours

AH is the Amp/hours we have taken out of the batteries

K is a constant that makes up for the fact that chargers are not 100% efficient, this factor can vary from 1.1 to 1.4. We will grab 1.2 for our exercise

CR is the charging rate, in our case our charger puts out 40 amps and we will assume that it will put out this rate until the batteries are completely charged.

Whipping out our handy pocket calculator we find the time to recharge the batteries is a whopping 4 hours and 30 minutes.

If we left the fridge and the furnace both on; which may draw up to 10 amps we now have an effective charging rate of 30 amps. The time to now recharge the batteries is approximately 6 hours. Throw in a few lights and you can see where this will lead.

Remember the old adage "There is no such thing as a free lunch"