dead batteries
A spark when connecting battery cables is not uncommon. Vehicle alternators will always bleed a little current backwards through the diodes. When new, this is a low enough drain that starting batteries will go a considerable time before discharging to the point of not starting the vehicle. As the diodes age through use, this drain typically increases. Occasionally, one of the diodes will fail, draining the battery fairly quickly when the engine is not operating. Frequently, the other diodes will operate correctly and the system will charge the starting battery while driving, masking the fact that the alternator is bad. It is not unusual for a starting battery in an alternator car to go flat in a couple of months if it is not charged. I assume your Newell has a larger starting battery and that should last longer against diode drain. As a rule of thumb I consider replacing alternator diodes when I find drains beyond 0.2 amps.
Sometimes there are condensors, coils or the like that will cause a spark while they "charge" up. If you connect and notice a spark and then disconnect and re-connect quickly the lack of a spark the second time will tell you that something was charging up and a short is not likely.
I have found our 93 Newell has things like a digital L.E.D. clock and other 12 volt accessories that run all the time. These are not huge drains, but over time, they will run the house batteries down. Our House Battery master switch actually powers a solenoid so the swithch it self and things like the clock continue to have power even though the lights and other major items are shut down.
Shortened capacities are sometimes the result of low battery acid and or sulfated battery plates.
Let me know what you find.
Bob
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