Thanks for the suggestion.
I just looked at the batteries. There are three in all, one on the panel and two on an aux power supply, all warm and dry in the house. The main panel battery is 13.9 vdc and the other two are 13.5 and 13.6. All good but one of the battery terminals on the aux supply had a good amount of corrosion on it, enough I think to cause a problem. I cleaned it up but it will be hard to say if it helps because the restart occurs so seldom.
I know that in an automobile corrosion on a lead acid battery post can be caused by over-charging and maybe that is happening here. It is an Altronix power supply and I do not know of any way to manually activate the charger to test it's output so I have no way to test it.
Mike.