Automotive battery charging/jumping question

I have a motorcycle that has been sitting unridden for about 4 months, and I haven't been keeping a charge on it.

I trickle charged it last night and found it still dead (lights come on but relay just buzzes when I tried to crank it). I did find that the old trickle charger was messed up because it was only putting out about 10 volts.

I got out my jumper cables and attached them to my truck and the bike. No luck. I cranked the truck for more juice and it still only buzzes the relay. I got out my DMM and noticed that I have 14 volts across the cables whenever it is not connected to my motorcycle battery, but I have only 10v or so when I connect it to the motorcycle battery. It is steadily rising.

What gives here?

Everytime I've jumped off a car with a dead battery it just jumped right up.

Thanks

Sounds like a high contact resistance in the jumper cables.

OK, some theory. Automobile batteries have short plate separation distances. Deep discharge batteries have large plate separation distances. As the electrolyte gets depleted whiskers develop and short the plates.

The Effective Series Resistance determines whether you have enough current to start the starter. This is bundled into the spec "Cold cranking amps".

I've jumped vehicles that would not jump because of a dead battery. For a few reasons it always makes sense to connect to the frame of the jumped vehicle last and remove the frame connection first. This lowers the series ressitance. The battery cabke from neg to the frame isn't counted.

I did, once, and it's not recommended. I loosened the battery cable on the vehicle and jumped the vehicle with the battery mostly out of the circuit. I was then able to tighten the cable.

Measuring the specific gravity and seeing if all the cells are the same is one first test. It's not the same as a battery test.