How long should it take to charge a dead John Deere 150 battery using a trickle charger?

Hi,
That depends on the state of the battery, the CCA of the battery, the actual amperage of the "trickle" and in some cases the charger itself since some will charge similarly to a capacitor charging.
I gather this a LT150, probably.
Peace,
Clarke

OK, more specifically. The mower started with no problems a week prior. It is an LT 150. The cca is 160. The trickle charger is a two amp. Also, I have both cables from the charger connected to the battery. Is that correct? Finally, would it make sense just to charge it from my car battery? I don't know if that's too much power. You can see how ignorant I am of these matters. Your advice is most welcome.

Hi,
Well, the CCA is below recommended; I think 190 - 225 is that. Still it should workThe best thing to do is just disconnect the battery and charge it. If you charger has an analog meter, it could show little movement and move more as the charged state changes. If it has only lights like most these days, the lights will tell you if the battery is drawing current.
The math will tell you that a fully discharged but healthy battery would take about 80 hours to charge. Reality would be less since full discharge invariably leaves an unhealthy battery.
Car battery is not a good choice, and especially if the car is running; and even worse connecting and then cranking the car.
Peace,
Clarke