Last time it failed was nearly month ago. Had been sitting from Monday until Saturday. temp -5C. Remote engaged the starter, and stopped. Tried the key. Only a clicking noise.

Battery voltage 11.6. Dropped to 9.6 with the door open. Dropped to 7.6 with the starter engaged. Only a clicking noise.

Attached a big charger set to "START" . Started taking 10-12 amps. Turned key, started right up.

Battery voltage at an idle, 14.8.

Similar symptoms as last month.

Trying to understand, if the battery is no good, why doesn't it fail all the time.

 

Cold will drain a battery sometimes if it's moist out. Do you have terminal protectors over your battery posts? Or a battery blanket? And is it the size specified by your year of truck?

 

Battery is probably on its way out

 

Already replaced once by Ford,

There only ever was a protector over the positive terminal.

Cold can be problem but not until it is well below -30C.

The day after it faield the first time, it worked at -31C . Now -5

It is usually pretty dry here in winter.

 

Did they put the right one in? I know that should be a no brainer, but ummm, some techs don't think. Lol. My personal rule is put a slightly bigger CCA battery than required. Comes from working on military diesels. We had "775 CCA" batteries that never load tested below 900. They worked great in the winters.

 

Need more CCA’s... and a block heater.