Van battery question

[sternwake]

......................  I have read a few places that its ok to put a 10 watt panel (uncontrolled) onto a 100 amp hour battery, so a dash mounted 10 watt panel should be ok given the 40% power factor due to the windshield (don't know what the amp hr rating of the new battery is but likely in the 50’s).

 The amount of amperage/wattage required to bring a battery to too high a voltage, depends on teh battery. it is not always safe.
Here is a Mainesail video showing how a 12 watt unregulated panel can overvoltage  220Ah of AGM.



A new small healthy battery should be able to achieve full charge at 13.8v given enough time.An unhealthy battery will likely not be able to achieve full charge at 13.8 and higher voltages are likely required.