Thanks, Bill. I agree with what you say.
With my 60 Amp PD9160, I have no question: Plug the 120 V shore power cord into the generator. Mine will start at 20 to 30 Amps into the battery depending how low the battery is and drop to maybe 8 to 10 Amp in half an hour. Meantime, I have 120 VAC in the camper to charge cell phones, model planes, shaver, run the microwave, vacuum cleaner, etc., etc.
If he has the old Magnatek unit, it is not clear which is best. The Magnatek will take about 2 days to charge the battery and will have it bubbling to do it. The direct connection will probably start out at 8 amp (generator rating) but soon drop to 4 or 2 Amps. Trouble is, you won't know what is happening. It is indeed a murkey issue.
To really know, you need to use a hydrometer to read the specific gravity of the fluid. That's messy. And don't get the mess on your clothes or it will look like you were attacked by starving moths!
Next best is to read the voltage after a 20 minute no-current rest. That isn't very easy to do when charging, either. It is the method I used before the upgrades. You will eventually get a rough idea how long to charge after a days battery use. This forum posted links to some battery sites that gave the voltage vs % charge. Trouble is, I found 2 charts that were quite different. One would say 50% remains, the other said 10% remains. Probably something to do with deep cycle vs normal batteries or some other parameter. Just another murkey answer.
This situation bothered me to the extent that I installed a 'battery meter', the Xantrex Link-10. Now I know all about the battery. This solution isn't going to fit everyone, either. It is the meter used in homes that use solar or wind to generate their own power and costs about $200.
I hope that helped. It seems like a murkey answer.
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