Kevin, are you using a charge controller between the solar panel, rpt, and batteries? Does your controller provide any kind of monitoring of current or voltage or state of charge? The op-amp circuits can also be extended in range beyond the VCC by using a voltage divider on each side of the input voltage. 1k 1% resistors are my fave for this divider type of app. Keeps the impedance low enough you can get good gain on the op amp with reasonable component values. You might want to consider some sort of outboard microcontroller based data logger. It could tell you how many "charge hours" you are getting, and peak amps, total amps, and at what time of day your batteries reach full charge and when the charge controller begins to dump excess voltage. This can let you know your batteries are doing through the days / nights.
I built an APRS digipeater some years back that ran solar. Low power short burst tx, It would fail in late December due to lack of sunlight, and be fine otherwise throughout the year. Enjoy tinkering! Ed N3SDO <http://geo.yahoo.com/serv?s=97359714/grpId=104168/grpspId=1705063108/ms gId=90412/stime=1238701456/nc1=5349272/nc2=4836040/nc3=5191955>
