Hi.. I'm a lady with a problem.. wondered if I could get some ideas....
​​​​​​
I have a 2004 Ford E250 cargo van

It's been sitting since October because I'm not ready to use it yet.

Ive periodically been idling the engine when I've been working inside it to run the blower and to keep things running as best I can. (I don't have a garage)

Recently the temperature where I live dropped to -22C (-7.6F).

When I tried to start the van, I got a humming sound but no start, no crank.

I charged the battery at 12v for 15 minutes. Van started no problem.

I then put it onto a trickle charge for 5 hours.

The next day, same no start. Charger indicator light says its fully charged. But no start.

Any ideas?

 

When the weather warms up some you might consider having the battery checked out.
if it checks OK, then you might go after the battery cables and connections both at the battery and where the other end of those cables are connected. When you remove the battery if that is what you decide to do, you will better be able to see the condition of the cable connections. Some cables can look good , but be corroded internally and voltage drop testing can confirm if there is a problem with them.