Hello,
I noticed that you offer the 100/20 as a 48V-Version, although that product isn't promoted on the VE-website?
The advantage is that this controller is a very cheap solution as the 150/35 is almost twice the price. But it's also a niche because there come a lot of problems with the 100V limit. I will explain my thoughts.
At normal conditions it will be possible to use both, two 60-cell and two 72-cell panels in a row.
But when it is getting hotter there is a problem when using two 60-cell panels combined with a lead-acid battery. The cell temperature entails the MPP-Voltage to be at the same level as the battery charging voltage, so the charge controller has to set its operating point above the MPP of the PV. That means losing energy. If an equalize-charge is neccessary that could even be a problem. Probably a solution would be to use Pylontech LiFePO4 and such batterys, as they operate at lower voltages. But in an off-grid-system these aren't allowed?
When it is getting colder two 72-cell panels are a problem, too. The open circuit voltage rises above the 100V limit. I don't know how much tolerance there is until the charge controller gets broken, but in winter it would definitely exceed its specs. So there are a few questions I have:
1. Does this charge controller have a PV-overvoltage-protection?
2. When using ESS with feed-in the MPPT normally works at the MPP of the PV. Is it getting more careful when it works near the limit and avoids to get over 100V if that is possible (feed in enabled, batterys empty) or does it still try to find its MPP no matter if that would be above 100V?
3. The bigger 150V models don't work above 145V. How does the 100V-Version? Does it still work at 101V or will it shut down and show an error? At which voltage that error appears?
4. Do you think that the charge controller can be used with 144cells when reaching 102V in the winter (with losing warrenty) without getting broken soon?
5. Who is this controller designed for? In Western Europe it's not an optimal solution. Neither with 120cells nor 144cells. Probably 144cells in Africa would work great.
Thank you!
regards,
porcini