question

@Xdmon However the other panel which I would prefer has a Voc of 41v and Vmpp of 34v.

A 60 cell panel?? Probably a marginal Vmp to charge a 24v (29v @ absorp?) battery. Even more marginal when you figure in that at panel temps above 25c, the Vmp drops.

I'm concerned that on overcast days or early morning/late evening the latter panel would struggle to provide enough voltage.

Panel Vmp does not vary much under varying solar insolation (maybe 10% volt drop at 20% insolation). Panel Imp is almost directly proportional to solar insolation though.

A real world Vmp & Imp plot from my old 190w, 72 cell panel.

The Vmp initially bounces around due to shade, but settles to near rated specs once in full sun. Notice the Imp climbs up proportional to the sun angle (insolation).

You should be looking for a 72 cell panel to charge a 24v battery (that's what Vicrtron recommends).

Also factor in voltage drop between panel > mppt, and voltage drop due to higher than rated (25c) panel temps.

Thanks for the reply, I appreciate you taking the time to write one.

That's interesting about the panel voltage not varying too much, I think I'm just assumed that it would vary in proportion to solar isolation but it looks to move up and down in a band once the sun is on the panel as opposed to the current which rises steady.

Yes the panel I was looking at was a 54 cell panel. The alternative is 144 cell (half cut so I assume equivalent to 72 - I'm not 100% with solar panel technology) and has a higher voltage.

It makes sense then that 34v Vmpp whilst it might work is probably marginal and therefore not a sensible choice if it can be avoided especially as you mention there are other factors which effect the voltage.

I will definitely go with the higher voltage panel.

I think I'll also go and do some reading on the basics of solar panels!

Once again thanks I appreciate

the help.