we say that last line as; "an 'ex' is a has been (like ex-husband) and a spurt is 'a drip under lots of pressure'.
I use a '10% rule' as to how much is acceptable drop under load, if it looses 10% of it's voltage, you need to charge it and check it again. so if it was at 37.7 at rest it could drop to 34.0 volts under hydraulic stall before I called it 'bad' and not just discharged, but if it dropped to 33.5 i would want to be sure it had an equalize charge before I tested it again.