Two hopefully easy questions

[Grandad]

First question for me.
1. What is the difference between Polycrystalline and Monocrystalline solar panels please?

And the second to try to help my neighbour....again.
2. How does one test a wet-cell battery (Gel) for its ability to hold a charge?

Jim

[Newcastle George]

Jim, Re question 2: Here is a link re amp hours https://www.instructables.com/id/AmpHourTest/

George

[T1 Terry]

OK, Polycrystalline panels have that well known square module with two silver lines running through each module as well as smaller lines running across each module, as the technology improved, the lines going across became both smaller and closer together. Monocrystalline also have a number of generations. The very early ones were near hexagon shaped divided in the middle. Some smaller panels had each half segment facing the same way, one long side and the other four side about the same length.
The next generation had smaller cut offs on the corners of the hexagon and much finer silver threads across the modules. The latest generation have virtually no cut offs on the corners and micro thin silver lines across each module and very close together.
Polycrystalline panels work well in the heat but are bigger in area for the same output as a Monocrystalline panel. The latest generation Monocrystalline panels can put out up to twice if not more output for the same size area a Polycrystalline panel can. There are still many generations of Polycrystalline as well, the panel size for a 70w panel back in the 60's is around 120w these days.
There is a claim the Monocrystalline panels work in partial shade, but so do Polycrystalline and mono are no better at this than poly, so that claim is misleading. Poly panels seem to have the longest life span, but then mono panels might have been poor quality in the early days. The Poly 70w panels I have are from the 60's and still work fine, they just take up a lot of real-estate so less output for the same area of roof cover.

To test the capacity of a gel deep cycle battery is the same as any other lead acid battery. Connect a 5 amp load for every 100Ah claimed, the voltage should remain above 12v at the 10hr mark if it is as good as new. For each hr less than 10 hrs, deduct 10Ah from the capacity. If it runs for 1 hr before dropping to 12v or less, you now have a very heavy 20Ah battery. If it runs for 20 hrs before dropping below 12v, you have roughly a 70Ah lithium battery. If it will deliver 50 amps for 2 hrs, you have a quality 100Ah lithium battery, no idea how many hrs you could get with the 5 amp load used to test lead acid batteries.

T1 Terry

[T1 Terry]

Jim, Re question 2: Here is a link re amp hours https://www.instructables.com/id/AmpHourTest/

George

I won't recommend that test on a deep cycle battery. They are not designed for high current discharge, genuine Gel cell batteries will be destroyed doing this type of high current discharge and doing this sort of testing on an AGM battery will quickly wreck it and a flooded cell deep cycle that is not at its best will possibly explode.
These type of tests are for thin plate starter batteries, not deep cycle batteries.

T1 Terry

[Grandad]

Thank you Terry,

All that's left to do now I guess is to try and find something with a known 5A draw.

Jim

[Grandad]

Scratch my last comment. Apparently, with all the lamps, TV etc turned on, his Battery Management thing indicates a 5A draw.
Problem solved.

Jim