I have a Chinese one here that draws a couple of mA from the battery under charge when the panel is dark. If the panel was left disconnected for several weeks, it would discharge the battery.
Did you mean
connected Mike?
Nothing is perfect in electronics, or life in general, Chinese or otherwise.
7weeks * 24 hours per day * 2mA= 336mA/hours, although undesirable, is hardly discharging the battery.
I haven't worked it out, because we do not know the A/H capacity of the battery, but that loss of charge is probably less than self-discharge of the lead/acid battery itself (5% per month). Assuming an 18A/H lead/acid battery, the self discharge over seven weeks would be 1.58 A/H, at 25 Deg C plate temperature. **broken link removed**
I haven't measured the reverse leakage of modern automobile alternator rectifier diodes but, certainly, the earlier rectifier diodes were quite leaky, especially at elevated temperatures.
And Schottky diodes, in general, are quite leaky, especially high current types.
Anyway, the OP's main concerned is damage to the system while driving.
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