Overcharging is definitely a concern, even with a new trickle charger. They are not all created equal. I do not have a specific brand to recommend however. I think it is fair to say that once it is in trickle mode that you wouldn't want to see the voltage above 13.2 for long term trickle charging. Does anyone else have a specific answer on this? Is your battery a gel-cell type? This might effect the charging recommendations somewhat.

Mike

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra