Here is a
Trojan document that may help.
Look at the self discharge rates for 86F and 42F, or .0075/wk and .0015/wk respectively.
Note that when the temperature was halved, the discharge rate was 1/5. If you halve the temp again to say 21F, doesn't it stand to reason the discharge would be reduced by 1/5th again?
That gives 1/25th of the 86F rate of .0075, or .0003/wk.
Given 28 weeks in Nov-May x .0003 is a drop is SG of .0084SG, and a drop to 1.28 - .0084 = 1.276.
The fully charged table allows that 1.250 is freeze proof down to -62F.
Think about an AGM that starts at 1.3SG and has a much lower self discharge rate. How many years?
HTH;
John
