Easy battery load tester?

[conachair]

Originally Posted by Maine Sail

I have spent many hours on the phone with Midtronics etc. and unfortunately there simply is no such beast.

Taking the battery to 10.5V is not as harmful as the general boating public assumes, if recharged immediately there after. What is damaging is taking a battery to 10.5V and letting it sit there...

Any thoughts on doing a "half test" and overlaying graphs? A full test might not be OK as far as the batteries go but not always easy to recharge from flat when off the grid.

For instance, something like below but with added circuitry to keep the current flat. Do that once or twice when plugged in then would a "half test" tell you much of use when overlaying the graphs?
I would imaging differing temperatures might be a bit of a hurdle.
Any thoughts?